for the 2 pilot
The project No.2018-1-0137 “EU-WATERRES: EU-integrated management system of
cross-border groundwater resources and anthropogenic hazards” benefits from a €
2.447.761 grant from Iceland, Liechtenstein and Norway through the EEA and Norway
Grants Fund for Regional Cooperation. The aim of the project is to promote coordinated
management and integrated protection of transboundary groundwater by creating a
WP3- Harmonization of transboundary groundwater monitoring
Title of document:
Assessment of the resources of transboundary groundwater
reservoirs for the 2 pilot areas
Output 1. Assessment of the resources of transboundary
groundwater reservoirs for the 2 pilot areas
Solovey Tetyana, Janica Rafał, Przychodzka Małgorzata, Vasyl
Harasymchuk, Halyna Medvid, Andriy Poberezhskyy, Michał
Janik, Oksana Stupka, Olga Teleguz, Dmytro Panov, Natalia
Pavliuk, Liubov Yanush, Yurii Kharchyshin, Dāvis Borozdins, Ieva
Bukovska, Jekaterina Demidko, Krišjānis Valters, Jānis Bikše, Aija
Dēliņa, Konrāds Popovs, Andres Marandi, Magdaleena Männik,
Maile Polikarpus, Sławomir Filar, Magdalena Nidental, Agnieszka
The aim of the document is to create a conceptual understanding of the hydrogeological
processes and flow dynamics across the national borders in two different pilot territories -
Polish-Ukrainian and Latvian-Estonian border area. Within the framework of this report,
assessment of transboundary groundwater resources, as well as the determination of
groundwater flow volumes across the state borders has been carried out. The report has been
developed by seven project partners: Polish Geological Institute - National Research Institute,
Latvian Environment, Geology and Meteorology Centre, University of Latvia, State Enterprise
"Ukrainian Geological Company", Geological Survey of Estonia, The Institute of Geology and
Geochemistry of Combustible Minerals of National Academy of Sciences of Ukraine and DC of
NJSC "NADRA UKRAJYNY" "Zahidukrgeologiya".
The project No.2018-1-0137 “EU-WATERRES: EU-integrated management system of cross-border
groundwater resources and anthropogenic hazards” benefits from a € 2.447.761 grant from Iceland,
Liechtenstein and Norway through the EEA and Norway Grants Fund for Regional Cooperation.
Scientific work published as part of an international project co-financed by the program of the Minister of
Science and Higher Education entitled "PMW" in the years 2020-2023; agreement No. 5152 / RF-
COOPERATION / 2020/2.
Abbreviations ............................................................................................................................. 7
Preface ....................................................................................................................................... 8
Introduction ................................................................................................................................ 9
Basic concepts and definitions ................................................................................................. 11
PART I. Assessment of the resources of transboundary groundwater reservoirs for the Polish-
Ukrainian borderland ................................................................................................................ 13
Summary .................................................................................................................................. 13
1 Legal systematics of transboundary groundwater reservoirs ................................................. 14
1.1 Transboundary groundwater reservoirs in international law ............................................ 14
1.2 Transboundary groundwater reservoirs in Poland's water/geological law and their status
of recognition ........................................................................................................................ 20
1.3 Transboundary groundwater reservoirs in Ukraine's water/geological law and their status
of recognition ........................................................................................................................ 23
2 Criteria for the identification of hydrogeological units of a transboundary character ............... 26
3 Geological and hydrogeological conditions of the PL-UA borderland ..................................... 28
3.1 Geological and hydrogeological conditions of the TGR Bug ............................................ 28
3.2 Geological and hydrogeological conditions of the TGR San ............................................ 31
3.3 Geological and hydrogeological conditions of the TGR Dniester ..................................... 35
4 Conceptual model of transboundary groundwater aquifers with significant potential of
groundwater transfer between Poland and Ukraine .................................................................. 37
5 Numerical model of the transboundary aquifer ...................................................................... 47
6 Assessment of transboundary groundwater flows by hydrodynamic modeling ....................... 56
References ............................................................................................................................... 61
PART II. Assessment of the resources of transboundary groundwater reservoirs for the
Latvian-Estonian borderland ..................................................................................................... 63
1 Legal systematics of transboundary groundwater reservoirs ................................................. 64
1.1 Transboundary groundwater reservoirs in Estonia's water/geological law and their status
of recognition ........................................................................................................................ 64
1.2 Transboundary groundwater reservoirs in Latvian water/geological law and their status
of recognition ........................................................................................................................ 65
2 Requirements for a uniform form of parametrization of hydrogeological units ........................ 66
3 Criteria for the identification of hydrogeological units of a transboundary character ............... 69
4 Conceptual model of a transboundary aquifer ....................................................................... 75
4.1 Geological and hydrogeological conditions of the Latvian-Estonian pilot area ................. 75
4.2 Conceptual model structure ............................................................................................ 79
5 Numerical model of the transboundary aquifer of the Estonian-Latvian border ...................... 82
6 Assessment of transboundary groundwater flows by hydrodynamic modeling ....................... 89
6.1 Methodology and materials ............................................................................................. 89
6.2 Results ............................................................................................................................ 92
6.3 Conclusions .................................................................................................................... 95
References ............................................................................................................................... 97
List of Figures
Figure 1 Polish-Ukrainian transboundary groundwater reservoirs within the Bug, San and
Dniester River catchment areas ............................................................................................... 26
Figure 2 Physical environment map of TGR Bug ...................................................................... 28
Figure 3 Geological map of TGR Bug ....................................................................................... 30
Figure 4 Physical environment map of TGR San ...................................................................... 31
Figure 5 Geological map of TGR San ....................................................................................... 33
Figure 6 Physical environment map of TGR Dniester ............................................................... 35
Figure 7 Lines of hydrogeological cross-sections in the Polish-Ukrainian border area .............. 39
Figure 8 Hydrogeological section of AA" ................................................................................... 40
Figure 9 Hydrogeological section of BB" ................................................................................... 40
Figure 10 Hydrogeological section of CC" ................................................................................ 41
Figure 11 Hydrogeological section of DD” ................................................................................ 41
Figure 12 The spatial extent of the boundary of the hydrodynamic model ................................ 42
Figure 13 Geological map of the model area ............................................................................ 43
Figure 14 Model boundary conditions in the first and second modeled layers. Green color
marks blocks with condition III (river) Dark gray color marks blocks with condition II (Q = 0) .... 48
Figure 15 Filtration coefficient distribution in layer I after taring ................................................ 50
Figure 16 Filtration coefficient distribution in layer II after taring ............................................... 51
Figure 17 Spatial distribution of recharge [m3/24h/m2] .............................................................. 52
Figure 18 Summary of the observed values of the ordinate of the groundwater table with the
calculated values and a statistical summary of the model calibration process .......................... 53
Figure 19 Model balance .......................................................................................................... 55
Figure 20 Hydroisohps calculated for layers I of the aquifers of the model ............................... 56
Figure 21 Hydroisohips calculated for layers II of the aquifers of the model.............................. 57
Figure 22 Hydrodynamic zones in the model area .................................................................... 59
Figure 23 Initially selected cross-border territory of Latvia and Estonia .................................... 66
Figure 24 River Basin Districts within project area .................................................................... 69
Figure 25 Groundwater flow maps ............................................................................................ 70
Figure 26 Total abstraction within Latvian-Estonian cross-border area in the period from 2010
to 2019 ..................................................................................................................................... 71
Figure 27 The distribution of abstraction sites and their average abstraction rates in the pilot
area (2010-2019) ...................................................................................................................... 72
Figure 28 Groundwater abstraction from exploited aquifer systems, thousand m3/d (2010-
2019) ........................................................................................................................................ 73
Figure 29 Quaternary deposits in Latvian-Estonian pilot territory .............................................. 75
Figure 30 Pre-Quaternary deposits in Latvian-Estonian pilot territory ....................................... 77
Figure 31 Geological cross-section A-A’ ................................................................................... 78
Figure 32 Geological cross-section B-B’ ................................................................................... 78
Figure 33 Geological cross-section C-C’ .................................................................................. 79
Figure 34 Geological cross-section D-D’ .................................................................................. 79
Figure 35 Boreholes used for conceptual model development.................................................. 80
Figure 36 DEM for Baltic artesian basin ................................................................................... 84
Figure 37 The spatial distribution of PUMA model triangle mesh elements within Estonian-
Latvian transboundary pilot area (red line; blue line indicates terrestrial borderlines) ............... 85
Figure 38 Distribution of sizes of meshes within Estonian-Latvian transboundary pilot area ..... 85
Figure 39 Boreholes used in the PUMA model geological structure development (gray points)
and new boreholes since 2010 in Latvian (blue points) and Estonian (red points) side of
transboundary area .................................................................................................................. 86
Figure 40 Groundwater level observation wells used in the PUMA model (gray points) and new
observations since 2010 in Latvian (blue points) and Estonian (red points) side of
transboundary area .................................................................................................................. 87
Figure 41 Groundwater level observations by the year of measurement used in the PUMA
model ....................................................................................................................................... 87
Figure 42 Hydrographic network in the transboundary pilot area of the PUMA model .............. 88
Figure 43 Groundwater abstraction rates in Latvian-Estonian transboundary pilot area............ 88
Figure 44 Schematic presentation of total discharge of groundwater in confined aquifer (Kresic,
2007) ........................................................................................................................................ 90
Figure 45 Example view on prepared mesh elements along the Estonian-Latvian borderline ... 91
Figure 46 Principal components of calculation of groundwater flow direction and gradient in
an example mesh element. Points 1-3 are mesh nodes that have piezometric head values from
the PUMA model results ........................................................................................................... 92
Figure 47 Estimated transboundary groundwater flows across Estonian-Latvian borderline in
Pļaviņas-Ogre aquifer system (blue borderline sections - no aquifer system present) .............. 94
Figure 48 Estimated transboundary groundwater flows across Estonian-Latvian borderline in
Aruküla-Amata aquifer system .................................................................................................. 95
Figure 49 Estimated transboundary groundwater flows across Estonian-Latvian borderline in
Lower-Middle Devonian aquifer system .................................................................................... 95
List of Tables
Table 1 Hydrogeological characteristics of aquifers included in the hydrodynamic model ......... 45
Table 2 Cross-border groundwater flow between Poland and Ukraine within the main usable
aquifer ...................................................................................................................................... 58
Table 3 Stratigraphy of hydrogeological section in the Latvian-Estonian cross-border territory . 68
Table 4 Characteristics of the aquifers based on PUMA model ................................................ 81
Table 5 Transboundary groundwater flow in Pļaviņas-Ogre aquifer system .............................. 93
Table 6 Transboundary groundwater flow in Aruküla-Amata aquifer system ............................. 93
Table 7 Transboundary groundwater flow in Lower-Middle Devonian aquifer system ............... 94
BAB – Baltic Artesian Basin
DEM – Digital elevation model
EEA - European Economic Area
EU – European Union
GWB – Groundwater Body
IGRAC – International Groundwater Resources Assessment Center
IHF – International Hydrological Programme
INPIRE – Infrastructure for spatial information in Europe
ISARM – Internationally Aquifer Resources Management
RBD – River basin district
RBMP – River basin management plans
TBA – Transboundary aquifer
TGR – Transboundary Groundwater Reservoirs
UNECE – United Nations Economic Commission for Europe
UNESCO – United Nations Educational, Scientific and Cultural Organization
UN/FAO – The Food and Agriculture Organization of the United Nations
WFD – Water Framework Directive (2000/60/EC)
This report has been prepared as part of the EU-WATERRES (EU-integrated management
system of cross-border groundwater resources and anthropogenic hazards; www.eu-
waterres.eu) project, funded by the EEA and Norway Grants Fund for Regional Cooperation. The
project aims to increase the capacity of public institutions to manage transboundary groundwater
resources by creating an integrated information platform, introducing new data analysis tools and
solutions for coordinated management and integrated groundwater protection. The
recommendations are aimed at a wide range of target groups - geological institutes and surveys,
water management authorities, geological sector companies, regional and local authorities -
concerned with environmental protection.
EU-WATERRES project promotes international harmonized data collection, monitoring and
assessment of TBAs. A thorough and comprehensive assessment of groundwater resources in
these layers will let to avoid possible international disputes and maximize the rational and justified
use of common TBAs.
This report synthesizes the knowledge of international law in the management of TBAs and
bilateral agreements between neighboring countries for two pilot regions representing: the Baltic
and Eastern Europe, i.e. the Latvian-Estonian border and the Polish-Ukrainian border. As part of
the assessment of the resources of transboundary groundwater reservoirs, an analysis of
hydrogeological conditions in the entire border section was presented on the basis of integrated
data between neighboring countries. As a result, target areas of detailed modeling studies with
significant transboundary flow in usable aquifers were identified and the first conceptual
hydrogeological model of TBAs was developed. This concept of the TBAs structure was the basis
for the creation of a numerical hydrodynamic model and the assessment of transboundary flows
on its basis. In addition, this model in further work will be necessary to simulate the transboundary
effects of groundwater abstraction and other anthropogenic factors on the quantitative and
qualitative state of TBAs.
As part of the assessment of transboundary groundwater flows, the extent of the area particularly
sensitive to transboundary impacts on groundwater was presented. The structure of TBAs and
the spatial distribution of its basic hydrogeological parameters were visualized - the coefficient of
filtration, alimentation, piezometric surfaces. The developed maps, calculation and simulation
results will ultimately be used to solve problems related to the ownership, use, access and
protection of transboundary groundwater resources in the pilot border areas.
Professor, Polish Geological Institute –
National Research Institute
Coordinated management of TBAs is increasingly desirable around the world to minimize adverse
transboundary impacts. In addition, due to the increasing global trend of groundwater
consumption, the exceeding of sustainable groundwater abstraction in many parts of the world,
and to avoid future international disputes and maximize the rational and equitable use of common
TBAs, there is a need for an accurate and comprehensive assessment of the development
potential of groundwater resources in these layers.
The global identification of TBAs began in 2000 under the coordination of the ISARM Committee
under the UNESCO-IHP. According to the results of this assessment, presented by IGRAC, it is
estimated that there is a total of 591 TBAs in the world, including 72 in Africa, 73 in the Americas,
129 in Asia and Oceania and 317 in Europe (in including 226 Transboundary GWB as defined in
the WFD. The conducted project aroused wide interest of the international community in the
issues of managing the TBAs. As a result of the active activities of a team of experts from three
international organizations: ISARM, UN/FAO, and the International Association of
Hydrogeologists (IAH), work was initiated on the development of the main principles of
international water law in the field of TBAs. In international law, this issue was formalized in 2008
by the United Nations International Law Commission in the form of draft Articles on the law on
transboundary aquifers (Resolution, 2008).
Within the framework of the EU-WATERRES project, the assessment of transboundary
groundwater resources was performed in two pilot areas - Polish-Ukrainian and Latvian-Estonian
borderland. Both territories are different from natural conditions (terrain, geological and
hydrogeological conditions) and from a socio-economic point of view (land use, perspective, water
management, etc.), thus achieving project goals is even more challenging and requires for close
cooperation between countries. However, sustainable transboundary groundwater management,
to ensure good quality and quantity status of groundwater resources for future generations is of
great importance in both areas.
In the Polish-Ukrainian borderland, only the transboundary groundwater reservoir within the Bug
river basin has been qualified to the world list of TBAs (IGRAC, 2015). On the other hand, scientific
publications present the premises allowing to justify the hypothesis of the existence of
transboundary flows within other catchments apart from the Bug River. With this in mind and the
problems related to the intensive intake of groundwater in the Polish-Ukrainian border zone as a
result of mining drainage in the region of Lublin and the Lviv-Volyn Coal Basin, as part of the
international EU-WATERRES project, the development of the concept of coordinated
management and harmonized monitoring of TBAs was initiated. The first stage of the work,
presented in this report, is to assess the transboundary groundwater flows and identify the areas
of TBAs with significant potential for groundwater exchange between Poland and Ukraine. A
reliable calculation in this respect was possible only with the use of numerical hydrodynamic
models. The basis of these numerical models was a conceptual hydrogeological model as a
description of the structure and natural and anthropogenic factors that shape the groundwater
The conducted research has been focused on characterizing the hydrogeological conditions in
the entire border section on the basis of integrated data between Poland and Ukraine, with the
aim of identifying the target area where there is significant transboundary flow in the usable
aquifers. The created numerical hydrodynamic model for this area will provide the most detailed
assessment of TBAs resources between Poland and Ukraine so far, and will estimate the
transboundary groundwater flows. It will also show where the TBAs are supplied and drained, and
how groundwater abstraction will affect flows.
A great challenge in this project was the consolidation of hydrogeological data between Poland
and Ukraine, including the continuity of the TBAs. The key to success was not only integrating
scientific assumptions, but also connecting people.
The hydrodynamic model and the assessment of cross-border flows on its basis should lead to
more effective joint management of TBAs between Poland and Ukraine. It can also help lay the
foundations for a formal international agreement between two countries on the rational and fair
use of joint TBAs under the Agreement on Cooperation in the field of water management in border
waters (Agreement, 1996).
Similar to the Polish-Ukrainian case, the assessment of transboundary groundwater resources
was also performed in the second pilot area - on the Latvian-Estonian borderland. Already at the
initial stage of the assessment of the two pilot areas, it became clear that the two pilot areas are
very different in nature. In contrast to the Polish-Ukrainian border, where there is a mountainous
relief, significant anthropogenic impact due to groundwater extraction and mining, the Latvian-
Estonian border is relatively flat, sparsely populated, there are no significant water abstraction
and anthropogenic pressures.
So far, no common transboundary groundwater bodies have been delineated on the Latvian-
Estonian border area. According to the World List of Transboundary Aquifers (ISARM, 2015),
several groundwater bodies on the Latvian-Estonian border on the Latvian side have been
identified as transboundary, however, on the Estonian side, transboundary aquifers with Latvia
have not been officially delineated before. This situation clearly demonstrates the need for
cooperation between the two countries in the assessment and management of transboundary
groundwater, which is directly implemented within the framework of the EU-WATERRES project.
A bilateral agreement on co-operation in transboundary water management was concluded
between Latvia and Estonia in 2003, however, no real actions for the assessment of
transboundary groundwater were implemented. Only in 2018, cooperation between the two
countries in the field of transboundary groundwater management was launched through the
GroundECO project. Within this framework, groundwater resources were assessed in the
common international river basin - Gauja river basin district, which includes the Gauja (Latvia)
and Koiva (Estonia) river basins.
The pilot area selected within the framework of the EU-WATERRES project includes the entire
Latvian-Estonian land border in order to be able to more fully assess the common groundwater
resources. Initially, both countries exchanged information data, followed by a harmonization
process. Combining the available information and existing knowledge, a conceptual picture of the
pilot area was created. The hydrogeological model was used to determine the geological,
hydrogeological conditions and groundwater flow directions. A semi-analytical method was also
developed to identify significant transboundary groundwater flows and to quantify transboundary
The performed assessment of groundwater resources will serve as a basis for future
transboundary project activities - identification of representative transboundary monitoring points,
as well as assessment of anthropogenic impact on groundwater.
Basic concepts and definitions
For the identification and assessment of transboundary groundwater resources, it is important to
have a common understanding of the hydrogeological terms and definitions used to achieve the
project outputs. At the beginning of the project, a database of basic terms and definitions used by
project partners was developed, where a list of the most commonly used basic hydrogeological
terms and definitions for transboundary groundwater characterization was created. The
definitions of terms used in the national legislation and practice of each country were summarized.
From the compiled definitions, it can be concluded that groundwater terminology (especially for
transboundary groundwater) in countries is poorly defined in national legislation and most of the
terminology for practical use has been taken over from available literature, binding guidelines and
In Latvia, Estonia and Ukraine, only the definitions of the aquifer and groundwater body have
been covered by national legislation and all other terms are interpreted from relevant guidelines
and directives. In Poland, terms are mainly derived from two publications: 1) Instructions for
sharing, updating, verifying and developing the Hydrogeological Map of Poland (Instructions,
2004); 2) The Hydrogeological Dictionary (Dowgiałło et al. 2002).
Nevertheless, the common understanding of the terms among the participating countries is quite
similar and there are no conceptual differences.
Conclusions on concepts between partners: (1) list of terms which are similar: Aquifer, Aquitard,
Unconfined aquifer, Confined aquifer, Transboundary aquifer, Groundwater level, Groundwater
table, Groundwater body; (2) there are no terms that differ significantly, only a few that are not
practically used on in countries; (3) terms covered by legislation: Aquifer and Groundwater body.
The definitions provided by the partner countries correspond to the glossary compiled by the
IGRAC and INSPIRE which provides definitions for groundwater-related terms. According to
previously mentioned, the glossary of this report is mainly based on IGRAC and INSPIRE
definitions. Also, there are some additional terms, like groundwater reservoir, subsurface waters,
main useful aquifers, available groundwater resources, which are used in Poland. As these terms
are included in the content of the report, they are also added to the glossary.
Aquifer – (water bearing horizon) - a hydraulically continuous body of relatively permeable
unconsolidated porous sediments or porous or fissured rocks containing groundwater. It is
capable of yielding exploitable quantities of groundwater (IGRAC, n.d.);
Aquitard – groundwater-filled body of poorly permeable formations, through which still significant
volumes of groundwater may move, although at low flow rates (IGRAC, n.d.);
Aquiclude – groundwater-filled bodies of poorly permeable formations, through which no or
almost no flow of groundwater passes (IGRAC, n.d.);
Artesian aquifer – An aquifer containing water between two relatively impermeable boundaries.
The water level in a well tapping a confined aquifer stands above the top of the confined aquifer
and can be higher or lower than the water table that may be present in the material above. The
water level rises above the ground surface, yielding a flowing well (INSPIRE, 2014);
Available Groundwater Resources (AGR) – the multiannual average amount of the total supply
of a defined groundwater body, reduced by the multiannual average amount of the flow required
to achieve the ecological quality objectives set for surface waters, so as not to allow a significant
deterioration of the ecological status of such waters and to avoid any significant damage to
associated terrestrial ecosystems (Zasady, 2005);
Confined aquifer – fully saturated aquifer (i.e. pressure everywhere greater than atmospheric
pressure) directly overlain by an impermeable or almost impermeable formation (confining bed).
The confining bed prevents the aquifer from interacting directly with the atmosphere and with
surface water bodies (except for surface water bodies that intersect the aquifer) (IGRAC, n.d.);
First Water Bearing Horizon (FWBH) – the first aquifer or group of aquifers from the surface
having good hydraulic contact with each other (Instructions, 2004);
Groundwater body – distinct volume of groundwater within an aquifer or aquifers (INSPIRE,
Groundwater level – elevation to which groundwater will or does rise in a piezometer connected
to a point in the groundwater domain. It is a time-dependent variable, varies from point to point
within the groundwater domain, and indicates the potential energy of groundwater in any point
considered (in meters of water column relative to a selected topographic reference level) (IGRAC,
Groundwater Reservoir (GR) – complex of permeable aquifers of utility importance, the
boundaries of which are determined by hydrogeological parameters or hydrodynamic conditions
and the conditions of formation of groundwater resources (Dowgiałło et al. 2002);
Groundwater table – surface defined by the phreatic levels in an aquifer (i.e. surface of
atmospheric pressure within an unconfined aquifer) (IGRAC, n.d.);
Hydrogeological unit – a part of the lithosphere with distinctive parameters for water storage
and conduction (INSPIRE, 2014);
Main Useful Aquifer (MUA) – the first usable aquifer or usable level from the ground surface,
constituting the main source of supply with a predominant range and abundance in the area of a
separate hydrogeological unit (Instructions, 2004);
Subsurface Waters (SW) – waters of the aeration zone occurring above the groundwater table,
also known as suspended waters: bound waters, capillary waters (some of them are soil waters),
as well as free gravitational waters moving/flowing through the aeration zone to the groundwater
table, to reach the free groundwater. The near-surface waters also include suspended
groundwater levels and very shallow groundwater (low-thickness aeration zone) (Instructions,
Transboundary aquifer – an aquifer that spans two or more political entities, separated by
political boundaries (IGRAC, n.d.);
Transboundary groundwater flow – groundwater flow over two or more political entities,
separated by political boundaries;
Unconfined aquifer – an aquifer containing water that is not under pressure. The water level in
a well is the same as the water table outside the well (INSPIRE, 2014);
Useful aquifer – a layer or set of aquifers showing good hydraulic contact, with the parameters
of the quantity and quality of water qualifying for municipal use: thickness of aquifers over 5 m,
water conductivity over 50 m2/24 hours, potential well over 5 m3/hour (Instructions, 2004).
PART I. Assessment of the resources of
transboundary groundwater reservoirs for
the Polish-Ukrainian borderland
The research carried out in the Polish-Ukrainian borderland has shown the usefulness of the
numerical hydrodynamic model in the assessment of TBAs resources and transboundary
groundwater flows. In the computational process, it was necessary to create a cross-border
conceptual model of the structure of the aquifer TBAs. The merging of hydrogeological data
between Poland and Ukraine has contributed to the continuity of the TBAs. The assumption was
made that the model area will be limited to the area where the cross-border connectivity of the
main usable aquifers is not disturbed by tight barriers to the flow of groundwater, such as drainage
rivers. The area identified this way covers the area of approximately 7,150 km2 and in the
catchment division it includes fragments of the catchment areas of the San and Bug rivers in their
upper parts. The transboundary groundwater flow occurs in the following layers: 1) Quaternary
with an unconfined groundwater table - in alluvia in the valleys of large rivers and in fluvioglacial
sands - on postglacial plains, 2) Upper Cretaceous with a partially confined groundwater table -
in Polesie and the Volyn Uplands, 3) Neogene with a confined groundwater table in Roztocze and
Przedkarpackie Foredeep. The analysis of the individual parameters of the model results showed
that more than 1.5 times more groundwater flows from the main usable layer from Poland to
Ukraine than from Ukraine to Poland. From the territory of Poland to Ukraine, groundwater outflow
is 42,350 m3 / 24h, and broken down into the catchment areas of the Bug and San - 32,981 m3/24h
and 9,369 m3/24h, respectively. On the other hand, only 27,924 m3/24h is transported to Poland
from Ukraine (broken down into the catchment areas of the Bug and San - 11,632 m3/24h and
16,292 m3/24h, respectively).
In the Bug basin, the transboundary groundwater flow is directed mainly to Ukraine, while in the
San basin - to Poland. Therefore, it can be reasonably assumed that in the identified area
particularly sensitive to transboundary impacts on groundwater in the Bug catchment basin,
Ukraine is at a disadvantage as the "Recipient" party. On the other hand, in the San catchment
area, Poland is in a similar situation.
The system of piezometric surfaces defined in this report also proves that in Poland the area of
special attention due to the possible negative transboundary impact on underground waters of
Ukraine is located in the Bug catchment area and has an area of approx. 936 km2, including
Uniform Parts of Surface Waters numbered: RW20000626714189, RW200006267141718,
RW20000626714163, RW2000062671414839, RW2000062671414591, RW20000626714125.
In Ukraine, the relevant area is in the San catchment area and covers an area of approximately
2,334 km2, including the Uniform Parts of Surface Waters with the numbers: RW200009225645,
RW200011225699, RW200009225629, RW200011225499, RW2000092254529, RW20000922
5249, RW2000092252329, RW200011225299, RW200010225269, RW20000622499.
1 Legal systematics of transboundary groundwater reservoirs
1.1 Transboundary groundwater reservoirs in international law
In the legislation of the EU on the protection and management of groundwater, the problem of
transboundary groundwater resources is poorly addressed, despite their high socio-economic
importance. The term "transboundary groundwater bodies" appeared in 2005 as part of the
publication on guidelines for the identification of Groundwater Units. Transboundary Groundwater
Units - these are groundwater reservoirs that are shared by two or more countries. An aquifer that
crosses the administrative boundaries of countries and thus has the potential to exchange
groundwater between neighboring countries is defined as transboundary.
In international law, the development of this issue can be traced back to 2008, when the main
principles of international water law on transboundary aquifers were developed by the United
Nations International Law Commission in the form of draft Articles on the law on transboundary
aquifers (Resolution, 2008; Resolution, 2011). The proposals developed by a team of experts
from three international organizations: UNESCO-IHP ISARM, UN/FAO, and the International
Association of Hydrogeologists (IAH) had the greatest impact on the scope of the Articles project.
Moreover, ISARM was the first to gain international community interest in the management of
transboundary aquifers. In 2001-2010, the organization initiated research on a global scale for
the identification and mapping of transboundary aquifers. In this way, ISARM created a set of
unified data that accelerated international cooperation and was the basis for generating guidelines
essential for the development of international water law. Overall, ISARM has made a significant
contribution to the international management of transboundary aquifers.
The draft Articles were discussed four times by the United Nations General Assembly (UNGA)
Committee over the next 12 years. The last discussion took place on October 22, 2019, followed
by a three-year break for another discussion on this topic and in this format. The 2019 debate
showed a certain degree of agreement on the legal nature of the draft Articles. This document
was considered an optional legal framework and is treated as legally non-binding guidance that
can be adapted to the specific circumstances of countries when developing bilateral agreements
or interstate arrangements for the management and conservation of transboundary aquifers. The
overarching goal of the Articles project is to support effective transboundary cooperation in the
field of groundwater and to strengthen integrated management of transboundary groundwater
Currently, 366 transboundary aquifers and 226 transboundary Groundwater Units (IGRAC and
UNESCO-IHP2015) have been identified around the world according to uniform criteria. In
addition to the hydrogeological conditions of the transboundary groundwater bodies, social,
institutional, legal and economic aspects were also defined, with the most progress being made
in the ISARM-Americas group (UNESCO-IHP) in the Northern Hemisphere. A team of ISARM-
Americas experts developed the "Regional Strategy for the Assessment and Management of
Transboundary Aquifer Systems in the Americas" (Rivera, 2015). The overarching goal of this
strategy is to achieve, sustainably manage and protect transboundary aquifers through:
1. Generating knowledge about the condition, protection and use of TGR resources.
2. Development of guidelines for the management of transboundary aquifers, including the
assessment of the aquifer's sensitivity to pollution and hydraulic connectivity with surface
waters in transboundary catchments.
3. Promoting the exchange of information and scientific knowledge, cooperation between
countries using transboundary aquifers.
4. Development of common standards, methodologies and procedures for assessment, as
well as of hydrodynamic models for the management of the TGR.
5. Development and establishment of ad hoc legal and institutional frameworks related to
the management of the TGR with the use of international legal instruments.
There is a large disproportion between the number of Transboundary Aquifers and
Transboundary Uniform Waters in the world and the number of ratified international treaties that
have been signed. According to data from Burshi (Burshi, 2018), only seven transboundary
groundwater agreements have been signed at the international level and several other
transboundary agreements, including:
1. Agreement on transboundary groundwater between France and Switzerland (1977 and
2. Agreement on the Strategic Action Program for a Transboundary Aquifer between Chad,
Egypt, Libya and Sudan (1992 and 2000).
3. Agreement on transboundary groundwater between Argentina, Brazil, Paraguay and
4. Agreement on Transboundary Groundwater between Jordan and Saudi Arabia (2015).
5. Agreement on the Transboundary Groundwater of the North-West Sahara between
Algeria, Libya and Tunisia (2002, 2008).
6. Agreement on transboundary groundwater between Mali, Niger and Nigeria (2009).
The agreement between France and Switzerland should be seen as a positive example of cross-
border water cooperation between an EU Member State (France) and a non-EU country
(Switzerland). It also sets a precedent that the agreement can be concluded successfully without
full EU status and can be used as a model for cooperation between Poland and Ukraine.
The main principles of international water law regarding transboundary aquifers contained in the
draft Articles document are:
1. Countries recognize the need for joint management of a transboundary aquifer and are
interested in identifying relevant international rules and practices that can shed light on
how the aquifer can be used and protected in a mutually beneficial way.
2. Countries sharing or exerting an anthropogenic impact on transboundary groundwater
shall take all appropriate measures to prevent and limit any adverse transboundary
3. Countries declare the use of transboundary groundwater in a sustainable manner in order
to increase the resulting long-term benefits and to protect groundwater-dependent
ecosystems. To this end, Countries should take into account all the functions of
transboundary groundwater resources, their size and quality, and the rate of renewal, with
a view to avoiding their decline to a critical level.
4. Countries collaborate to identify, parameterize and characterize transboundary
groundwater. They are also working to develop conceptual models whose level of detail
depends on the complexity and impact of the hydrogeological system.
5. Countries shall develop a program of joint monitoring and assessment of the quantitative
and qualitative status of transboundary groundwater. For this purpose, countries, inter alia:
a) use common or agreed standards and methods;
b) agree on evaluation criteria and key parameters to be monitored, taking into
account the specificities of transboundary groundwater occurrence;
c) design a groundwater monitoring network combined with the monitoring of surface
water, where appropriate;
d) develop integrated hydrogeological maps, including groundwater vulnerability
maps and, where appropriate, hydrodynamic numerical models.
6. Countries work together for the integrated management of transboundary groundwater
resources. Countries will take appropriate measures to prevent, limit and reduce pollution
of transboundary groundwater, in particular usable aquifers. Therefore, they follow the
precautionary principle due to the vulnerability of groundwater to pollution, especially in
the case of poorly identified transboundary aquifers. Such measures include, but are not
a) the establishment of protection zones, particularly in the most sensitive parts of
the groundwater recharge area;
b) taking measures to prevent or limit the migration of pollutants into groundwater;
c) implementation of agri-environmental programs and protection of groundwater
against pollution by nitrates and plant protection products;
d) establishing appropriate types of groundwater quality indicators and agreeing on
their criteria values.
7. Countries shall undertake activities to exchange information and data on the state of
transboundary groundwater and the volume of its exploitation and other types of
8. Countries shall develop and implement a joint or agreed program for the integrated
management of transboundary groundwater resources. This program includes, but is not
a) the sharing of transboundary groundwater resources among users, including
b) fixing of abstraction permits for transboundary groundwater;
c) setting limits to the total annual abstraction of transboundary groundwater, its
distribution among users and establishing criteria for the location of new intakes;
d) develop a program to protect and restore good quality and adequate quantity of
9. Planned activities that may have a significant negative impact on transboundary
groundwater, and thus have a detrimental effect on another Party, shall be subject to the
procedure of transboundary environmental impact assessment.
10. Countries take measures to raise public awareness and ensure access to information on
the state of transboundary groundwater.
11. For the implementation of international rules and practices in the field of transboundary
groundwater and for the coordination of cooperation, the Countries shall establish a joint
In conclusion, the main thrust of the transboundary groundwater management strategy governed
by international law is to achieve "good status" of transboundary groundwater through its
sustainable use while ensuring strict control of the qualitative and quantitative status of
groundwater. To this end, a system of joint monitoring of the status of transboundary groundwater
should be implemented.
On January 24, 1994, the Government of the Republic of Poland and the Government of Ukraine
signed an agreement on cooperation in the field of environmental protection, solving ecological
problems and rational use of natural resources in accordance with the concept of sustainable
development (Agreement, 1994). The agreement was concluded on, inter alia:
• treaty between the Republic of Poland and Ukraine on good neighborhood, friendly
relations and cooperation (Treaty between the Republic of Poland and Ukraine, 1992);
• the Rio Declaration on Environment and Development;
• "Agenda 21";
• Convention on Climate Protection,
• Convention on the Protection of Biological Diversity,
which were adopted and signed at the United Nations Conference on Environment and
Development in Rio de Janeiro in 1992.
The aim of the cooperation is to improve the condition of the environment and increase ecological
safety in both countries and to prevent environmental pollution, inter alia by (Agreement, 1994):
• strengthening the control of sources of transboundary pollution and taking the necessary
steps to reduce them continuously, and
• increasing the effectiveness of water, atmosphere and earth surface protection.
The subject of cooperation is primarily the following environmental protection issues (Agreement,
• exchange of experience in the field of improving management and legal regulations in the
field of environmental protection,
• protection of surface and underground inland waters against pollution,
• creating a system of rational use of natural resources, including at the regional level,
• environmental monitoring, primarily in border areas.
Basing on the provisions of the Article 5, in order to implement the agreement, parties have
established a Joint Commission for cooperation in the field of environmental protection.
Two years after signing the agreement on cooperation in the field of environmental protection
(…), on October 10th, 1996 in Kiev both parties signed an agreement on cooperation in the field
of water management in border waters (Agreement, 1996). As a strategic goal of the cooperation,
the parties indicated ensuring rational management of border waters and improvement of their
quality, as well as ensuring the preservation of ecosystems. In concluding the Agreement, the
parties were convinced that the protection and use of border waters and protection against
damage caused by border waters are important tasks, the effective solution of which can only be
ensured through close cooperation in the field of water management. In the Agreement, the
parties referred to the Treaty between the Republic of Poland and Ukraine (1992).
Within the meaning of the Polish-Ukrainian Agreement, border waters mean rivers and other
surface waters along the border, as well as surface and underground waters crossed by the state
border. Polish-Ukrainian cooperation covers a significant part of the cross-border catchment area
of the Bug and San, rivers that are part of the international Vistula river basin. The Bug is approx.
772 km long, and its catchment area is located in Poland, Ukraine and Belarus. The sources of
the Bug are in Ukraine, and the estuary to the Narew River, on the territory of Poland. The average
flow in the lower course is 154 m³/s, which makes the Bug the fourth largest river in Poland. The
San is a right-bank tributary of the Vistula River, its sources are in Ukraine. The length of the river
is 457.76 km. According to the border documentation, the water section of the Polish-Ukrainian
border is 287.97 km in total and runs along the rivers: Bug - 227.77 km, San - 59.21 km and the
Zawadówka Canal - 0.99 km. The rivers Wiar, Wisznia, Szkło and Lubaczówka, which cross the
state border, also have a cross-border character.
The cooperation platform is the Polish-Ukrainian Commission for Border Waters
(https://www.gov.pl/web/infrastruktura/wspolpraca-polsko---ukrainska). The Committee is
composed of Delegations of the Parties composed of Government Plenipotentiaries, their
Deputies, Secretaries, Members and Working Group Managers, who are selected from among
the relevant water management bodies. The function of the Government Plenipotentiary for
Cooperation with Ukraine is performed by a representative in the rank of Deputy Minister
responsible for water management. The functions of the Deputy and Secretary are also performed
by representatives of the ministry responsible for water management. The members of the Polish
delegation are representatives of the State Water Holding "Polish Waters", including the Regional
Water Management Boards in Lublin and Rzeszów, the Management of the Basin in Przemyśl,
the Institute of Meteorology and Water Management - National Research Institute, the Chief
Inspectorate for Environmental Protection and the Border Guard Headquarters. The
plenipotentiary of the Council of Ministers of Ukraine for cooperation with Poland is a
representative of the State Agency for Water Resources of Ukraine in the rank of president or his
deputy. The task of the Plenipotentiaries and their Deputies is to care for the fulfillment of the
parties' obligations under the Agreement. They contact directly, appoint experts as needed and
convene meetings. The secretaries are responsible for drawing up protocols and other
cooperation documents. Once a year, a Commission meeting is held to assess the
implementation of the work, hear the reports of the working groups and approve the work plans.
The cooperation is divided into four areas and is carried out throughout the year within the Polish-
Ukrainian Working Groups, which operate on the basis of the statute of the Commission,
mandates and regulations, and work plans approved during the meetings of the Commission
• The HH group conducts research, observations and data exchange in the field of
hydrometeorology and hydrogeology of boundary waters.
On the Polish side, the tasks of the HH Group are the responsibility of the Institute of Meteorology
and Water Management - National Research Institute with its seat in Warsaw. The Hydrological
and Meteorological Station in Lublin-Radawiec and the Polish Geological Institute - National
Research Institute PGI-NRI, Carpathian Division also cooperate within the HH Group. On the
Ukrainian side, the Ukrainian Hydrological and Meteorological Center is responsible for
cooperation with the help of the Regional Hydrological and Meteorological Center in Lviv and the
Regional Hydrological and Meteorological Center of the Volyn Oblast in Lutsk
As part of the work of the HH group, daily exchange of operational hydrological and
meteorological data for the preparation of hydrological forecasts takes place.
Hydrometeorological and hydrogeological data for the needs of water balances are exchanged
on a quarterly basis. The parties also perform joint flow measurements and joint geodetic cross-
sections in selected Bug profiles. On the basis of agreed data, annual hydrological characteristics
of the established profiles are compiled.
Current information from water gauges and rainfall stations enables the assessment of the
hydrological and meteorological situation in the Ukrainian part of the Bug catchment area.
Forecasts for the daily hydrological cover are also analyzed on an ongoing basis. Forecasts from
the meteorological model are obtained three days in advance and contain data on the daily sum
of precipitation and the average daily air temperature. The results of these forecasts are entered
into a hydrological model that calculates the ratio of rainfall / thaw to runoff, then transferred to
the hydrological forecasting offices and used to formulate hydrometeorological messages and
• OW Working Group for the protection of border waters against pollution
The tasks of the OW Group include monitoring of the state of border waters. On the Polish side,
the tasks of the group are the responsibility of the Chief Inspectorate of Environmental Protection
- Regional Environmental Monitoring Departments in Lublin and Rzeszów. The analysis of the
samples is the responsibility of the Central Research Laboratories of the Chief Inspectorate of
Environmental Protection, branches in Lublin and Rzeszów. On the Ukrainian side, the
Department of Water Resources in Lviv, subordinated to the State Agency for Water Resources
of Ukraine, the Regional Office of Water Resources of the Volyn Oblast, the Lviv Regional Center
of Hydrometeorology and the Volyn District Hydrometeorology Center are responsible for
The regular tasks of the OW Group include testing the quality of water in the Bug and San
catchments. In the Bug catchment area, each side has four measurement and control points, the
Polish side: Kryłów, Zosin, Horodło, Dorohusk, the Ukrainian side: Litowież, Ambuków, Uściług,
Zabuże. In the San catchment area, measurement and control points are located on the Wisznia
and Szkło rivers. On the Polish side: on Wisznia in Gaje, on the Szkło in Budzyń, on the Ukrainian
side: on the Vishnia in Czerwoniewo, on the Szkło in Krakowiec. The analysis of 9 indicators is
performed from the collected samples, i.e.: total suspended solids, BOD5, dissolved oxygen,
ammonium nitrogen, nitrite nitrogen, phosphates, chlorides and sulphates. Samples are taken 6
times a year. The quality and comparability of research is ensured by experts in the field of
analysis quality, who develop measurement programs and standardize research methods. A joint
sampling is carried out once a year by both parties at the same time. On the Bug, the sampling
takes place at the measurement and control point located at the border crossing Zosin-Uściług,
in the catchment of the San river, the sampling takes place at the measurement and control points
in Wisznia and Szkło, simultaneously on both sides of the border. Joint sampling allows the
verification of the measurement methods used on both sides. The results of tests and
observations are used to prepare the annual assessment of the quality of border waters. This
assessment concerns the waters of the Bug and rivers in the San catchment area. The OW Group
also deals with the identification of potential sources of contamination of border waters.
Moreover, the OW Group undertakes actions in the event of extraordinary contamination of border
waters. These activities include the exchange of information and warnings as well as the
elimination of the consequences of an accident. Crisis management is the responsibility of the
competent authorities of both parties. On the Polish side, the National Center for Rescue
Coordination and Population Protection of the Main State Fire Service, Provincial Environmental
Protection Inspectorates, provincial offices, marshal offices and the State Center for Crisis
Management are notified. On the Ukrainian side, the Ministry of Environment and Natural
Resources, the State Agency for Water Resources, the State Service for Emergency Situations
and the State Inspectorate for Environmental Protection cooperate at the state level.
• PL Working Group for Border Water Planning
The PL group is responsible for planning the management of border waters in terms of their use
for utility purposes and the implementation of EU water regulations in the Bug and San river
basins. On the Polish side, the tasks of the group are the responsibility of the State Water
Management Authority (Polish Waters), in particular the Regional Water Management Boards in
Rzeszów and Lublin. The Marshal's Office of the Lubelskie Voivodeship and the Regional
Directorate for Environmental Protection in Lublin also cooperate. On the Ukrainian side, the
Catchment Water Resource Authority in Lviv, which is subordinated to the State Agency for Water
Resources of Ukraine, is responsible for cooperation. The newly established river basin boards
also cooperate (https://www.gov.pl/web/infrastruktura/wspolpraca-polsko---ukrainska).
The role of the PL Group is to exchange information on the directions of water policy, planning
and management of water resources, as well as to inform each other about changes in the
regulations and institutional structure. Equally important is the group's role in implementing EU
water directives. Ukraine currently has the status of an associated country with the EU and is
undergoing an administrative reform in the field of water resources management. In the context
of the above, the parties exchange data for the purposes of developing water management plans
and other planning documents resulting from the provisions of the WFD. The water resource
management plans that the parties have carried out in the cooperation so far are helpful in the
implementation of this task. As regards the economic planning of border waters, the parties carry
out an analysis and exchange of information on water abstraction and wastewater discharge in
the catchments of the Bug and San rivers. With this task, an inventory of water supply and sewage
networks as well as sewage treatment plants in the border area is carried out
The PL group coordinates the cooperation with the other working groups within the Commission
as well with local government administration and bodies managing water resources. To this end,
the group monitors Polish-Ukrainian-Belarusian water management projects implemented in the
Bug catchment area, as well as bilateral cooperation between regional water management units.
On the basis of a cooperation agreement in the Bug catchment area, the regional boards of the
parties exchange information on the water and meteorological situation. A constant analysis of
water levels and consumption is carried out for the purposes of flood forecasting and water quality
assessment on the border section of the Bug. These activities support the state protection system
against the risk of flooding and extraordinary pollution.
• OP Working Group on flood protection, regulation and drainage
The main task of the OP Group is to maintain the patency of watercourses and secure border
areas in order to protect them against flooding. On the Polish side, the tasks of the group are the
responsibility of the State Water Management of Polish Waters, in particular the Regional Water
Management Boards in Lublin and Rzeszów. On the Ukrainian side, the Catchment Water
Resource Authority in Lviv, which is subordinate to the State Agency for Water Resources of
Ukraine, is responsible for cooperation, and the newly established boards of river basins
The OP Group makes detours of border waters, during which problems are identified and
necessary maintenance works within the border waters and water facilities are located. Smaller
works, which do not require a lot of time and money, are performed by the field team on their own.
Larger repairs and renovations requiring investments are carried out according to the schedule
or reported to the relevant water authorities. The catalog of works and works of the OP group
includes: repair and restoration correction of the bed and strengthening of eroded banks, cleaning
the lumen of openings under bridges from contaminants deposited by water, maintenance of
hydrotechnical structures, mowing of bushes and grasses on the banks of rivers, liquidation of
illegal landfills and others (https://www.gov.pl/web/infrastruktura/wspolpraca-polsko---ukrainska).
1.2 Transboundary groundwater reservoirs in Poland's water/geological law and
their status of recognition
Water management, use and protection issues have been regulated by the Water Act dated on
July 20th, 2017. The Act regulates water management in accordance with the principle of
sustainable development, in particular - shaping and protection of water resources, the use of
reservoirs and management of water resources. The Act, in terms of its regulation, implements
(Prawo wodne, 2017):
• Council Directive 91/271/EEC of 21 May 1991 concerning urban waste-water treatment;
• Council Directive 91/676/EEC of 12 December 1991 concerning the protection of waters
against pollution caused by nitrates from agricultural sources;
• Directive 2000/60/EC of the European Parliament and of the Council establishing a
framework for Community action in the field of water policy;
• Directive 2006/7/EC of the European Parliament and of the Council of 15 February 2006
concerning the management of bathing water quality and repealing Directive 76/160/EEC;
• Directive 2006/118/EC of the European Parliament and of the Council of 12 December
2006 on the protection of groundwater against pollution and deterioration;
• Directive 2007/60/EC of the European Parliament and of the Council of 23 October 2007
on the assessment and management of flood risks;
• Directive 2008/56/EC of the European Parliament and of the Council of 17 June 2008
establishing a framework for community action in the field of marine environmental policy
(Marine Strategy Framework Directive);
• Directive 2008/105/EC of the European Parliament and of the Council of 16 December
2008 on environmental quality standards in the field of water policy, amending and
subsequently repealing Council Directives 82/176/EEC, 83/513/EEC, 84/156/EEC,
84/491/EEC, 86/280/EEC and amending Directive 2000/60/EC of the European
Parliament and of the Council.
The Water Act, together with the Geological Law and other environmental acts regulate all
environmental and economic issues of water management in the country.
Chapter 1 of the Act defines the general rules and issues to which the Act does not apply like
water services in the field of storage, treatment or distribution of surface water and groundwater,
and sewage collection.
Article 13, point 1 defines the river basin districts including parts of international river basins
located on the territory of the Republic of Poland. The river basins are as follows:
1. The area of the Vistula river basin, including – apart from the Vistula river basin – the
basins of Słupia, Łupawa, Łeba, Reda and other rivers flowing directly into the Balti Sea
and the Vistula Lagoon.
2. The Odra river basin, including – apart from the part of the Odra river basin located in
Poland – the basins of Rega, Parsęta, Wieprz, Ücker and other rivers flowing directly into
the Baltic Sea west of the mouth of Słupia and also to the Szczecińska Lagoon.
3. River basins of: (a) the Dniester, (b) the Danube, (c) Banówka, (d) the Łaba, (e) the
Nemunas, (f) Pregoła, (g) Świeża – covering parts of international river basins located on
the territory of the Republic of Poland.
In Section I (General Rules), chapter 2 - Explanation of statutory terms, article 16, point 67 defines
the term “border waters” as waters through which the state border runs, or waters in places where
they are crossed by the state border.
Section II - Use of water has been divided into two chapters: Chapter 1 defines the issues
connected with water use and water services while Chapter 2 defines issues connected to water
used for recreation.
Section III - Water protection – has been divided into seven sections dedicated to principles of
protection, treatment of wastes, protection against pollution from agricultural sources, listing of
contaminants, protection of water intakes and inland waters, protection of marine waters and flood
risk management and counteracting of drought.
Section IV – Flood risk management – defines the scope of responsibility of public administration
for preparation of flood hazard maps. Article 171 defines the State Water Holding “Polish Waters”
as being responsible for the task.
Section IV – Flood risk management and counteracting the effects of drought, specifies in article
171, point 6 that the preparation of flood hazard maps and flood risk maps for the areas located
in river basin districts, parts of which are located on the territory of other Member States of the
EU, shall be preceded by activities aimed at the exchange of information with the competent
authorities of these countries. The following point (no. 7) defines that in case of the areas located
in river basin districts, parts of which are located on the territory of countries outside the EU
preparation of flood hazard maps and flood risk maps is preceded by actions aimed at establishing
cooperation with the competent authorities of these countries in this respect.
In Article 173, point 10 of the Article, defines that for the river basin district, part of which is located
on the territory of other Member States of the EU, the minister responsible for water management
shall cooperate with the competent authorities of these countries in order to prepare for the
international river basin district one international flood risk management plan or a set of flood risk
management plans coordinated at the level of international river basin district or ensuring
coordination to the greatest extent possible at the international river basin district level of a flood
risk management plan covering the river basin district within the territory of the Republic of Poland.
Point 11 of the Article states that for the river basin district, part of which is located on the territory
of countries outside the EU, the minister responsible for water management takes steps to
establish cooperation with the competent authorities of these countries in order to prepare one
international flood risk management plan or a set of plans for the international river basin district.
flood risk management coordinated at the international river basin district level or ensuring
coordination as far as possible at the international river basin district level of a flood risk
management plan covering the river basin district within the territory of the Republic of Poland.
In order to supplement the flood risk management plans in the international river basin districts,
more detailed flood risk management plans coordinated at the level of the international catchment,
part of which is located in other countries, the minister competent for water management may
cooperate with the competent authorities of these countries. For this purpose, the minister
responsible for water management may use the existing structures resulting from international
Actions aimed at achieving the objectives of flood risk management included in the flood risk
management plans may not significantly increase the flood risk in the territory of other countries,
except for cases in which these actions have been agreed in the framework of the cooperation.
In Section VII – Water management, Chapter 1 – Planning, Article 320 specifies that for a river
basin district, part of which is located on the territory of other Member States of the EU, the
minister responsible for water management shall cooperate with the competent authorities of
these countries in order to prepare a single international water management plan or to ensure
coordination, as far as possible, at the level of the international river basin district management
plan. For this purpose, the minister responsible for water management may use the existing
structures resulting from international agreements.
Point 3. of the Article 320 stresses that for the river basin district, part of which is located on the
territory of countries outside the borders of the EU, the minister responsible for water
management takes steps to establish cooperation with the competent authorities of these
countries in order to prepare one international water management plan or to ensure coordination,
to the greatest extent, at the international level, of the river basin district located on the territory
of the Republic of Poland, in particular in scope of the activities in this river basin district aimed at
achieving the environmental objectives. If the development of the plan referred to in this point, or
ensuring the coordination, is not possible, the provisions of paragraphs 1 and 2 shall apply to the
part of the international territory belonging to the territory of the EU.
In order to supplement the water management plans in the international river basin, more detailed
water management plans coordinated at the level of the international catchment, part of which is
located on the territory of other countries, the minister competent for water management may
cooperate with the competent authorities of these countries.
Based on point 5 of the Article 320, complementary measures may also be adopted to ensure
additional protection or improvement of water status or for the implementation of international
agreements aimed at water protection, including protection and prevention against the pollution
of the marine environment.
Article 335 defines the State Water Holding “Polish Waters” and Directors of Maritime Offices as
the entities responsible for the control of water management. In case of transboundary waters,
the control is performed in cooperation with the Border Guards.
In Section VIII – Water Management Authorities, Chapter I - The minister competent for water
management, Article 353, states that the minister responsible for water management is the
supreme government administration body responsible for water management.
The Minister submits to the Sejm of the Republic of Poland every 2 years, not later than by August
31, information on water management regarding, among others, water management regarding
international cooperation in border waters and the performance of contracts in this regard.
Article 354 defines that the minister competent for water management coordinates the
implementation of public tasks in water management, in particular performs the obligations arising
from international agreements regarding water management to which the Republic of Poland is a
In Section VIII – Water Authorities – Chapter I – Minister responsible for water management,
Article 354 specifies that the minister responsible for water management performs information
and reporting obligations towards the European Commission in the scope specified in the
provisions of the Act. Moreover, the minister responsible for water management shall perform the
duties resulting from international agreements relating to water management to which the
Republic of Poland is a party.
1.3 Transboundary groundwater reservoirs in Ukraine's water/geological law and
their status of recognition
Water relations in Ukraine are regulated by the Water Code, the Law of Ukraine "On
Environmental Protection" and other legislation.
The Water Code, in combination with measures of organizational, legal, economic and
educational impact, will contribute to the formation of water and environmental law and order and
environmental safety of the population of Ukraine, as well as more efficient, scientifically sound
use of water and protection from pollution, clogging and depletion.
Thus, Article 1 provides a definition of the 74 basic terms used in this Code.
Article 83 states that the use of border waters is carried out in the manner prescribed by the
legislation of Ukraine and interstate agreements.
Article 112 establishes the procedure for the application of international treaties: if an international
treaty in which Ukraine participates establishes norms other than those provided for by the water
legislation of Ukraine, the norms of the international treaty shall apply.
The signing of the Association Agreement between Ukraine and the EU and its Member States
in 2014 obliges Ukraine to implement European standards in various spheres of public life,
including the management of water resources, their protection and the fight against water pollution
(Association Agreement, 2014).
The central body of executive power that ensures the formation of state policy in the field of
environmental protection (including the protection of water resources) is the Ministry of Ecology
and Natural Resources of Ukraine (Ministry of Environment of Ukraine). The implementation of
the state policy in the field of management, use and reproduction of surface water resources is
supervised by the State Agency of Water Resources of Ukraine (State Water Agency of Ukraine).
The signing of the Association Agreement between Ukraine and the EU and its Member States
in 2014 obliges Ukraine to implement European standards in various spheres of public life,
including the management of water resources, their protection and combating water pollution, in
particular to synchronize in accordance with Directive 2000/60 / EC of the European Parliament
and of the Council on the establishment of a Community framework for water policy of 23 October
2000 (Association Agreement, 2014).
With the adoption of the Law of Ukraine "On Amendments to Certain Legislative Acts of Ukraine
on the Implementation of Integrated Approaches to Water Resources Management on the Basin
Principle", (adopted by the Verkhovna Rada of Ukraine on October 4, 2016, № 1641-VIII), the
implementation of the provisions of the WFD in the Water Code of Ukraine and, in general, in the
practice of water resources management in Ukraine has begun.
Schedule of achieving the goals in Ukraine on the WFD (since the signing of the Association
1. 3 years - for the adoption of national legislation and the definition of the authorized body,
the consolidation at the legislative level of the unit of hydrographic zoning of the country,
the development of regulations on basin management with the assignment of relevant
2. 6 years - to determine the areas of river basins and create mechanisms for managing
international rivers, lakes and coastal waters, analysis of the characteristics of river basin
districts, introduction of water quality monitoring programs.
3. 10 years - to prepare river basin management plans, hold public consultations and publish
In addition to the WFD, Ukraine has ratified two more main documents in the field of international
law on transboundary surface waters.
The use of transboundary watercourses is regulated in accordance with the Convention on the
Protection and Use of Transboundary Watercourses and International Lakes, adopted on 17
March 1992, in Helsinki, Finland. The Convention aims to strengthen national measures for the
protection and Ukraine acceded to the Convention on July 1, 1999, and its provisions came into
force on January 6, 2000. The Convention aims to strengthen national measures for the protection
and environmentally sound management of transboundary surface and groundwater.
On 17 June 1999, the Protocol on Water and Health to the Convention on the Protection and Use
of Transboundary Watercourses and International Lakes, London, United Kingdom, was adopted
(Protocol on Water and Health, 1999). Ukraine acceded to this Protocol on July 9, 2003, and
entered into force in Ukraine on August 4, 2005. The purpose of the Protocol is to promote, at all
relevant levels, both nationally and in transboundary and international contexts, the health and
well-being of people on an individual and collective basis in accordance with the principles of
sustainable development by improving water management, including protection of aquatic
ecosystems, as well as by preventing, controlling and reducing the spread of water-related
diseases (Protocol on Water and Health, 1999).
In addition to being a party to a number of international global and regional environmental
agreements, Ukraine has concluded a number of bilateral agreements with other countries. Such
agreements are framework or special, concluded at the governmental or ministerial level.
The largest group consists of agreements concluded at the intergovernmental level and have a
framework character - agreements on cooperation in the field of environmental protection.
Intergovernmental agreements define the main areas of cooperation between the parties.
Sometimes, depending on the geographical location of the country with which the agreement is
signed or the interest in a common issue, the agreement may contain specific areas of
cooperation, such as mutual information, impact assessment and coordination of measures that
could potentially have a negative impact on the environment. on the territory of another state
Intergovernmental agreements determine the agencies responsible for implementing the
agreement. On the Ukrainian side, it is the Ministry of Environmental Protection of Ukraine. For
example, in pursuance of intergovernmental agreements, an Agreement was signed between the
Ministry of Environmental Protection of Ukraine and the Ministry of Environmental Protection,
Natural Resources and Forestry of the Republic of Poland on cooperation in the field of
2 Criteria for the identification of hydrogeological units of a
The results of the research on the transboundary groundwater reservoirs of the Polish-Ukrainian
borderland to date are related to the identification of the TGR carried out by IGRAC and UNESCO-
IHP (2015) on a global scale. In the Polish-Ukrainian borderland, one transboundary groundwater
reservoir was identified, limited by the watershed of the Bug river basin. In Ukraine, the river Bug
is defined as Western Bug. Using the numerical terrain model in a given project, the line of the
Bug River catchment basin was determined (Figure 1).
In addition, in the Polish-Ukrainian borderland, two more transboundary groundwater reservoirs
catchments were identified in the project - the San and Dniester (Figure 1).
Figure 1 Polish-Ukrainian transboundary groundwater reservoirs within the Bug, San and Dniester
River catchment areas
According to our data, the area of the TGR "Bug" is 15,575 km2. Within the boundaries of the
TGR "Bug", on the Polish side, Uniform Groundwater Body (UGB) No. 91 and 121 and partially
No. 67 were located. Currently, there is no division into UGB on the Ukrainian side.
The area of the TGR "San" is 4,569 km2. Within the boundaries of the "San" TGR, on the Polish
side, there are partially UGB No. 136, 154 and 168.
The area of the TGR "Dniester" is 5.929 km2. Within the boundaries of the TGR "Dniester" on the
Polish side, GWB No. 169 was located in its entirety.
The approach to separating hydrogeological units in Poland and Ukraine is similar and consists
of zoning the first usable aquifer. Therefore, uniform rules for the separation of hydrogeological
units within the TGR with regard to the first usable aquifer have been developed.
In order to distinguish the main hydrogeostructural forms of FUA occurrence within the TGR Bug,
San and Dniester the criteria used in the schematization of hydrogeological conditions were
recognized for the need to develop a Hydrogeological Map of Poland in the scale 1: 50,000.
Consequently, it is assumed that the FUA meeting the following criteria will be identified on the
unified hydrogeological map of the TGR Bug, San and Dniester:
• achieves water conductivity over 50 m2/24h;
• total thickness M5m (with an average state of retention);
• shows continuity of occurrence (with the accuracy of hydrogeological schematization
appropriate for a map in the scale of 1: 50,000) in the area A > 20 km2 (in conditions of
good identification and clear spatial differentiation of hydrogeological conditions, A > 5 km2
• enable the execution of a drilled well with a recharge of over 5 m3/h.
Carrying out hydrogeological identification and defining transboundary aquifers begins with
harmonization of hydrogeological spatial data between neighboring countries. The key data are
the spatial diversification of the development and hydrogeological properties of the usable
aquifers, the mapping of the hydroisohypses surface and the thickness of the aquifers with an
accuracy at least appropriate for a 1: 50,000 scale maps. Creation of integrated maps of the
distribution of the above hydrogeological characteristics and maps supporting the analysis -
lithostratigraphic, hydrographic geomorphology is the basis for identifying transboundary aquifers.
The definition of the transboundary nature of an aquifer is carried out on the basis of the criterion
of the potential for groundwater exchange between neighboring countries. In this regard, it is
proposed to consider the division of the groundwater exchange potential determined based on
the water conductivity parameter of the aquifer into:
• significant - water conductivity 50 m2/24h;
• average - water conductivity 20 m2/24h;
• negligible - water conductivity <20 m2/24h.
Lack of groundwater exchange is stated in the case of identifying a "tight" boundary for the
groundwater flow, which is formed by the watercourses draining a specific aquifer and
Stages of identification of the conditions of the occurrence of transboundary aquifers constituting
the basis for the implementation of hydrogeological regionalization are:
1. Determining the type and extent of basic geomorphological forms (hydrodynamic zones)
within the areas of transboundary aquifers.
2. Elucidation of the main hydrological parameters of catchment basins.
3. Identification of common large tectonic structures of the transboundary territory.
4. Stratigraphic and lithological identification of transboundary geological formations.
5. Identification of useful transboundary aquifers that meet the criterion of significant and
average potential for groundwater exchange between neighboring countries.
6. Investigation of spatial (lateral and vertical) characteristics of aquifers.
7. Initial studies of hydrodynamic and hydrochemical parameters of these useful aquifers.
8. Determining the boundaries of transboundary aquifers.
3 Geological and hydrogeological conditions of the PL-UA borderland
The region of the Polish-Ukrainian borderland is located in the south-eastern part of Poland and
the north-western part of Ukraine. Its geographical coordinates are:
• Longitude from 22°25'N to 25°09'N;
• Latitude from 51°54′E to 48°59′E.
According to the physical and geographical division, the research area is located on the border
of two megaregions - the East European Lowlands and the Carpathian Region.
3.1 Geological and hydrogeological conditions of the TGR Bug
TGR Bug is located in the East European Lowlands. In the northern part of the TGR Bug, which
is within Western Polessye, denudation or accumulation plains with a slight slope dominate here.
There are many peat bogs, wetlands and lakes here. The southern part of the TGR Bug is located
in the area of the Volyn Upland, in Ukraine – Volyn-Podillia Upland (Figure 2). Its characteristic
feature is the alternating occurrence of elevated areas and extensive depressions and valleys.
The largest geomorphological structure in the TGR Bug region is the upper and middle part of the
Bug river valley, up to 4 km wide and 20-30 m deep with distinct terraced levels. Annual
precipitation sums in the last forty years ranged from 500 mm in Polessye to 600-700 mm in the
area of the Volyn Uplands. In this period, field evaporation ranged from 450 mm/year to 470
Figure 2 Physical environment map of TGR Bug
The TGR Bug area lies within the East European Platform and is characterized by a significant
diversity of the Paleozoic tectonics. The lowland part of Polessye falls within the Kumów elevation,
while the upland part - into the Włodawa-Lviv basin. Within the elevation, on the Proterozoic rocks
there are Jurassic and Cretaceous rocks and a thin Cenozoic cover. In the depression part, the
platform cover is formed by Ediacaran, Cambrian, Silurian and Devonian deposits, on which the
Carboniferous deposits lie inconsistently. They are covered with Jurassic and Upper Cretaceous
sediments, and on them Neogene and Paleogene in the form of patches of varying thickness are
locally deposited. The Upper Cretaceous formations on the surface are usually exposed on hills
and are formed of carbonate (writing chalk and marl) and carbonate-silica-clay formations of the
Upper Maastrichtian. The thickness of the Upper Cretaceous carbonate complex reaches 500-
700 m. In most of the TGR Bug area, there is a Quaternary cover on the surface. In the drainage
depressions, it is formed of organic formations, in watershed areas, glacial sediments as well as
limnic and limnoglacial glacial muds dominate, in river valleys - sands, gravel, and flooding silts.
The thickness of the Quaternary cover is usually 2-10 m, only in the valleys of larger rivers the
series of limnic and fluvioglacial sediments reaches 30 m (Figure 3).
In the area of the TGR Bug, the usable aquifer is mainly associated with Upper Cretaceous
formations. The aquifer consists mainly of cracked marls and writing chalk. Circulation of
groundwater is carried out by a system of interconnected fractures. The fractures network is
relatively regular and, together with the almost horizontal gaps between the aquifer, forms the
most common fractures in the massif, which determine its water capacity. Bundles of vertical
fractures of increased width and large extent are much less common, creating strongly water-
bearing zones of tectonic loosening of the massif.
Figure 3 Geological map of TGR Bug
The best hydrogeological conditions are found within tectonic zones constituting routes of
concentrated, underground horizontal flow, and near river valleys, buried valleys and valley edge
zones. The thickness of the Cretaceous formations may be up to several hundred meters,
however, the depth of the active exchange zone, due to the increasing pressure of the rock mass,
decreases with depth, and is estimated at 100 to 150 m from the surface.
In most of the area, the Upper Cretaceous formations are covered with loess and clay loam, and
partly covered with silt and clay formations. The thickness of this cover of poorly permeable
formations varies - from a couple to several or even several dozen meters. Sometimes, Upper
Cretaceous aquifer occurs from the ground surface.
The Upper Cretaceous aquifer is recharged by direct infiltration of surface waters. The recharge
takes place especially in the elevated areas of Upper Cretaceous sediments outcrops. The main
drainage base is the Bug River and its tributaries.
The preliminary hydrogeological studies in Ukraine have shown the possibility of water inflows
into the Upper Cretaceous aquifer from the lower aquifers by tectonic faults. Such areas are
characterized by local halos of increased total dissolved solid in waters and specific geochemical
features. Excessive water pumping at water intakes can lead to the mixtures of such waters
reaching consumers. One of the tasks of this project will be to confirm or refute this theory.
Within Poland, the aquifer is usually unconfined, although when covered with low-permeable
Quaternary formations, there are also areas with a confined water table. However, in Ukraine the
Upper Cretaceous aquifer has mainly confined water table. The depth of the groundwater table is
set at 1.5-10 m in river valleys, up to 20-40 m - in watersheds. The discharge of the intakes ranges
from 0.09 to 11 dm3/s.
Most often, in river valleys, there is one shallow, 15-20 m thick, Quaternary aquifer with an
unconfined groundwater table. This reservoir is characterized by high groundwater resources.
Waters of this aquifer usually remain in a hydraulic contact with the Upper Cretaceous aquifer. In
the Polessye part of the Bug River Basin, in the watershed area, the subsurface aquifer is formed
by fluvioglacial sandy formations with a thickness of 5-10 m. The water table is unconfined, the
depth of occurrence is 0-15 m. The Quaternary aquifer is characterized by a very high variability
of hydrogeological parameters. The water conductivity is usually in the range of 10-100 m2/day,
although locally it is 500 m2/day.
3.2 Geological and hydrogeological conditions of the TGR San
TGR San is located in Roztochia in the northern part and in the vast majority of the Carpathian
Region - the central and southern parts (Figure 4).
Figure 4 Physical environment map of TGR San
It is an area belonging to three geological and tectonic units. The Roztochia part of the TGR San
belongs to the margin basin, the Podkarpacie region - to the Carpathian basin, and only the
southern part - the Eastern Beskids is associated with the Outer Flysch Carpathians. This fact is
reflected in the geological structure (Figure 5).
The Badenian sediments of the Roztochia hills are formed by quartz sands and limestones.
Detritic limestones are most widespread in the study area.
In the area of the Carpathian Foredeep, the Miocene limestone sediments are of other geological
origin and are thrown down by faults to a considerable depth. A thick layer of Sarmatian deposits
in the form of the so-called "Kraków loams" is composed of loams, silts and fine-grained sands.
In the near-edge zone, they also include sandstones, mudstones and marls. The thickness of the
Sarmatian deposits is varied and reaches up to 3,000 m. On the surface, the Kraków loams are
exposed only on the hills.
The southern part of the TGR San belonging to the Outer Carpathians is characterized by its
distribution of flysch deposits on the surface. These formations are formed as alternately
deposited Cretaceous and Tertiary sandstones and shales, which has a significant influence on
the hydrogeological conditions. The ratio of schist to sandstone varies. Krosno layers have the
largest share of schist in the structure of flysch, therefore the worst hydrogeological features.
Figure 5 Geological map of TGR San
The vast majority of the TGR San area (over 90%) is covered by Quaternary sediments. These
are sediments of variable thickness (up to several dozen meters in the buried valleys) and of
various types of development. River valleys are filled with alluvial sediments - sand, gravel,
pebbles. These sediments are generally well permeable, and the thickness of the aquifer is varied,
usually not exceeding 5 m. Apart from the river valleys in Roztochia and the Carpathian Foredeep,
the Quaternary formations are represented by glacial residues, limnoglacial hydro-glacial silts and
aeolian sediments. In the Carpathians flysch, Quaternary formations are represented by
weathered clays with a relatively small thickness, usually up to several meters.
In the area of the TGR San, there are aquifers in the Cretaceous, Neogene and Quaternary
The useable Upper Cretaceous aquifer in Roztochia is mainly in the Polish part of the area. It is
associated primarily with the carbonate formations of the Upper Cretaceous. Thus, it is a fractured
reservoir, most often with a unconfined or lightly confined water table. The average thickness of
waterlogged deposits is 100 m. The averaged filtration coefficient is 3.7 m/d. The water
conductivity of the aquifer ranges from <100 to 1500 m2/d, and the potential intake discharge from
<10 to 120 m3/h.
Within the Polish part, the Neogene aquifer is of local importance, because most of the basin is
filled with thick series of Kraków clays. Within the Ukrainian part, this aquifer is useful. It is the
main aquifer of the western water intakes of Lviv.
The Neogene aquifer is common in sandy sediments, sandstones, gypsum and calcareous-
The average thickness of these sediments is up to 30.0 m. These formations lie at a depth
of 16.0 – 21.0 m and sink towards the south-west. The Neogene aquifer is mainly confined –
drilled at a depth of 11.0 - 46.0 m, the potentiometric surface was at a depth of 5.0-13.0 m below
the surface. The discharge of the wells ranges from 13.3 to 45.7 m3/h. This aquifer is also
associated with the presence of sulphate medicinal waters. The Neogene aquifer recharges in
the Roztochia region and discharges in the San River. The waters of the Neogene and
Cretaceous aquifers are often in hydraulic contact.
The useful aquifer in the Quaternary alluvial formations is widely spread in the area of the TGR
San. Actually, it does not occur only in places where there are tills covers directly on the Miocene
loams. The quaternary aquifer is built of river sediments of the San valley and its tributaries, as
well as hydro-glacial formations and sediments of old buried structures (e.g. the San and
Lubaczówka proglacial valleys). They are made of gravel and sand. The thickness of the
Quaternary formations in the San valley is up to 20.0 meters. Outside this region, the thickness
of the Quaternary formations usually does not exceed several meters. The best conditions for
infiltration occur within the Holocene terraces of San, Szkło and Lubaczówka, i.e. where there are
deposits with high permeability. The aquifer is generally up to 1-5 m below the ground level. The
Quaternary aquifer is unconfined (usually in river valleys) or pressurized. The pressure may be
up to 20 m. The filtration coefficient is usually in the range of 10 - 30 m/d. The capacity of wells is
30 m3/h on average.
Due to the presence of flysch on the surface, the southern part of the TGR San outside the river
valleys was treated as a waterless area in terms of the presence of usable aquifers. However, it
is believed that in areas separated as anhydrous, there may be places where even more than
5 m3/h can be obtained from a single intake. These places are conditioned by the occurrence of
fractures in the sandstone.
3.3 Geological and hydrogeological conditions of the TGR Dniester
TGR Dniester is mostly located in Ukraine. It is an area belonging to three geological and tectonic
units (Figure 6):
1. Northern part - the Roztochia - belongs to the Volyn-Podillia Upland.
2. Central parts - the Podkarpacie region - to the Carpathian Foredeep.
3. Southern part - the Eastern Beskids is associated with the Outer Flysch Carpathians.
Figure 6 Physical environment map of TGR Dniester
In the Roztochia Miocene limestone is the most widespread. In the Carpathian Foredeep, the
Miocene limestone sediments are thrown down by faults to a considerable depth. Here they
appear on the surface of the ground the Sarmatian deposits in the form of the so-called "Kraków
loams" is composed of loams, silts and fine-grained sands.
The southern part of the TGR San belonging to the Outer Carpathians is characterized by its
distribution of flysch deposits on the surface. These formations are formed as alternately
deposited Cretaceous and Tertiary sandstones and shales. Flysch formations are covered with
quaternary weathered clays with an admixture of sandstone. Their thickness is generally 1–3 m.
There are two aquifers in the TGR Dniester area: Quaternary and flysch (i.e. Paleogene-
Cretaceous). The flysch aquifer occurs almost in the entire area, while the Quaternary - only
locally in river valleys, in a very small area in total.
The Paleogene-Cretaceous (flysch) layer represents the Upper Cretaceous, Paleogene and
Lower Miocene layers. The flysch aquifer of a rift character is a near-surface zone built of fractured
sandstones containing clay-marly shale inserts with a thickness of 40-80 m. The flow of
groundwater in the flysch formations takes place in the cracked and fractured zone, accordingly
to the morphology of the terrain towards the river valleys. The water table of this level is
fragmented, not continuous and its shape cannot be reproduced in the form of hydroisohypses.
On the Polish side, the Paleogene-Cretaceous horizon has a poor hydrogeological recognition
based on ca. 70 wells reaching a maximum depth of 100 m (most often 30–50 m). The well
discharge of flysch aquifer ranges from 0.3 to 14 m3/h. The flysch aquifer is drained by the Strwiąż
and Mszanka rivers with their tributaries, and by numerous springs of various discharges, usually
not exceeding 1 dm3/s.
The Quaternary useful aquifer occurs in gravel-sandy, partially clayey alluvial sediments of
Strwiąż and Mszanka. The supply of the Quaternary aquifer takes place through direct infiltration
of atmospheric precipitation, infiltration of surface waters and lateral inflow of waters from flysch
formations, which is favored by full hydraulic connectivity of both aquifers. The best conditions for
infiltration exist within the Holocene terraces of the Strwiąż River, i.e. where there are deposits
with high permeability.
The Quaternary aquifer is drained by Strwiąż and Mszanka. The water table is generally up to
5 m below the ground level and is most often unconfined. Only in regions where the Quaternary
formations are characterized by high lithological variability in the vertical profile and in horizontal
spread, and where they are covered with a layer of silty and loess formations, the waters may be
characterized by low pressure. Moreover, it was found that the alluvials of Strwiąż and Mszanka
are often muddy. The thickness of the Quaternary formations in the Strwiąż and Mszanka valleys
reaches a maximum of 7.0 meters. The filtration coefficient is usually in the range 5 - 10 m/24h.
The discharge of the wells is 10 m3/h on average.
4 Conceptual model of transboundary groundwater aquifers with
significant potential of groundwater transfer between Poland and
The conceptual hydrogeological model (conceptual model of an aquifer) is a descriptive and
graphical representation of the structure and processes occurring in the hydrogeological system.
The model is a set of hypotheses as to how the real hydrogeological system is structured and
behaves, how it is related to the environment (supply, contact with surface water) and how it
responds to recharge. These hypotheses are verified in the next, more detailed, stages of
hydrogeological research (e.g. mathematical modeling).
The concept of the functioning of the hydrogeological system on the PL-UA pilot site was
developed on the basis of analyzes of archival materials, including:
• observation of the position of the groundwater table in ok. 57 monitoring wells;
• 2 926 hydrogeological data and profiles of boreholes;
• hydrological measurements from 20 hydrometric sites;
• meteorological data form 10 meteorological observation sites;
• documentation of ca. 200 groundwater intakes;
• GIS databases "Detailed geological map of Poland in the scale 1: 50,000" (Geological
• GIS databases "Geological map of Ukraine in the scale 1: 50,000";
• GIS databases "Hydrogeological map of Poland - Main Useful Aquifer in the scale
• GIS databases "Hydrogeological map of Ukraine - Main Useful Aquifer in the scale
• GIS databases "Hydrogeological map of Poland - First Aquifer in the scale 1: 50,000";
• GIS CORINE Land Cover CLC 2018 Database - Land Cover (The Copernicus
• digital terrain model based on SRTM data;
• topographic maps in scales from 1: 10,000 to 1: 50,000 (geoportal.gov.pl);
• hydrographic data available in the MPWP information layer.
Stages of creating of a conceptual hydrodynamic model are:
• concept of the structure (structure) of the hydrogeological system;
• concept of the structural processes taking place in the hydrogeological system;
• structure of spatial variability - schematization of hydrogeological conditions.
The model structure concept defines and justifies:
• spatial extent of the layers forming the analyzed hydrogeological system,
• division of the hydrogeological system into aquifers and poorly permeable layers;
• hydrodynamic barriers to groundwater flow (rivers draining useful aquifers, watersheds,
significant intakes and drainage systems);
• the amount of infiltration recharge (including evapotranspiration);
• directions and quantity of the aquifers flow.
In the assessment of the transboundary groundwater flows between Poland and Ukraine based
on the numerical hydrodynamic model, an assumption was made that the modeling area would
be limited to the area of the first cross-border usable aquifer with significant groundwater
exchange potential. According to the indicator adopted in this regard - water conductivity of the
aquifer, the selection of the relevant transboundary aquifers is carried out on the basis of the
water conductivity criterion 50 m2/24h.
Correct determination of the spatial extent of the model and preparation of a conceptual model of
the aquifer system structure is not possible without a detailed analysis of the geological structure
and hydrogeological conditions of the area. Hydrogeological maps and sections are the basis for
determining the concept of the model structure. Already at this stage, the preliminary
schematization of the aquifer is carried out. This is due to incomplete (discrete) knowledge of the
geological space, which in turn makes it necessary to interpret the spread and lithology of rock
layers. Reliable interpretation of geological data requires the widest possible use of the available
geological information and knowledge about the possible course of processes that determine
sedimentation and erosion.
The development of the conceptual model began with the preparation of five hydrogeological
sections cutting the studied area parallel (section AA”) and perpendicular (sections BB”, CC”,
DD”) to the Polish-Ukrainian border (Figure 7).
Figure 7 Lines of hydrogeological cross-sections in the Polish-Ukrainian border area
This made it possible to trace the nature and distribution of the aquifers on a regional scale and
their variability. The regional approach made it possible to identify regularities that would be
difficult to notice on a local scale. The profiles of exploitation and research holes were used to
prepare the cross-sections. Additionally, data from the Geological Map of Poland and Ukraine in
the scale 1: 50,000 were used. The cross-sections provide information on the lateral and vertical
distribution of successive aquifers and impermeable layers (Figures 8-11). The levels of
groundwater tables and potentiometric surfaces of individual wells was also marked, which,
combined with the image of the hydroisohypses taken from the hydrogeological map, allowed for
the interpretation of the directions of groundwater flow and the directions of infiltration through
hardly permeable layers.
Figure 8 Hydrogeological section of AA"
Figure 9 Hydrogeological section of BB"
Figure 10 Hydrogeological section of CC"
Figure 11 Hydrogeological section of DD”
Hydrogeological sections were the basis for determining the model boundaries.
In hydrogeological modeling, the most correct models are those in which the model area boundaries
are surface water courses. In the developed model, in the vast majority of cases, the boundaries
have been based on rivers draining the first aquifer, but also often on watersheds (Figure 12). As
shown in Figure 12, the model covers only the southern part of the TGR Bug - from the place where
the Bug ceases to be a border river and turns towards Ukraine, which means it ceases to be an
obstacle to the transboundary flow of groundwater. Moreover, it has been decided not to include the
eastern extremities of the TGR Bug - the right-bank part of the catchment area of the Bug in the
model, because groundwater from these areas ends up in the Bug and does not cross the state
border. According to analogous assumptions, the western extremities of the TGR San were not
included. On the other hand, the exclusion from the modeling area of the TGR Dniester and the
southern part of the TGR San is related to the failure to meet the criterion of significant groundwater
exchange potential. In this area, the potential for cross-border groundwater exchange is below
50 m2/24h according to water conductivity.
Figure 12 The spatial extent of the boundary of the hydrodynamic model
Hydrogeological sections were the basis for the development of a conceptual model diagram. This
diagram provides an idea of the structure, functioning and relationship with the surroundings of the
aquifer. The development of a conceptual model requires further schematization of the system. This
is mainly due to incomplete (discrete) knowledge about the individual elements of the model. Thus,
the image of the aquifer can be treated as a preliminary hypothesis that requires verification. The
means of verification is a mathematical model of the aquifer. This means that the methodology of
model development should follow the requirements of the mathematical model. It makes it necessary
to apply simplifications consisting in aggregation of aquifers.
The structure of the conceptual model was developed based on the following criteria:
• the separated aggregate aquifers had to be common in the study area or at least widely
• aquifers could be aggregated only when their hydraulic connectivity was found to be common,
and the separating layers were discontinuous and of limited thickness;
• when aggregating aquifers, the nature of the aquifer and its water permeability were first taken
into account, and only then the stratigraphy of sediments;
• the separated isolating (separating) horizons had to be of considerable thickness and
Within the conceptual model of the research area, two layers were distinguished (Figure 13):
• 1st layer - alluvial aquifer in the valleys of large rivers;
• 2nd layer is spatially heterogeneous. In the north it is the Upper Cretaceous fissure aquifer,
in the central part - the Neogene fissure-pore aquifer, and in the south - the Quaternary pore
Figure 13 Geological map of the model area
1st layer - alluvial aquifer in the valleys of large rivers
It consists of various types of alluvial sands, gravel, pebbles, and therefore the layer has good
permeability. As a rule, these are pieces not covered with any cover of impervious rocks, so this
aquifer is unconfined. The layer occurs in the valleys of the main rivers of the study area and their
larger tributaries. The thickness of the aquifer rarely exceeds 30 meters. It is recharged mainly due
• Within the Upper Cretaceous sediments of the lowland unit within the borders of the East
This aquifer is built mainly of marls, chalk, sandy marls, marly limestones, gaize. It occurs over the
entire lowland part of the model area.
Upper Cretaceous aquifer is one of the most useful aquifers of the study area. It is an aquifer of the
fissure type of water-bearing rock. It is mainly confined (artesian) aquifer. The type of water is mainly
HCO3-Ca. The filtration coefficient of the aquifer is in the range of 0.01 - 1.8 m/h. The water
permeability of the aquifer depends on its fracture. In the upper part of the massif, the network of
tectonic fractures overlaps with airborne cracks, which facilitate the flow of groundwater. As the depth
increases, the fractures are gradually tightened by the pressure of the rock mass. The conducted
research has shown that the bottom of the active water exchange zone is located at a depth of
100 - 50 m, and the rocks deeper than 200 m below the surface are practically impermeable. The
depth of occurrence of the base of the active exchange zone is determined by the mechanical
properties of the rocks. In hard marls and limestones it is greater than in soft marls or writing chalk.
Locally it may occur deeper. It takes place in dislocation zones, where the flow of groundwater
through numerous fissures is facilitated. These fragmented zones of tectonic faults can be ways of
penetration into the Upper Cretaceous aquifer of waters from the lower horizons.
• Within the Neogene sediments of the upland area
Despite the small distribution of the Neogene aquifer, it was decided to single out this layer because
of the very large role it plays in transboundary flows. It is located in the central part of the model area
within the uplands of Roztochia region.
Neogene aquifer is common in fissure-porous formations. Often water-bearing rocks are karst. It
combines water-bearing layers of sandstones, limestones, gypsum. Therefore, type of water is
HCO3-Ca and SO4-Ca. The aquifer is mostly confined, the potentiometric surface is at a depth of 5 to
50 m below ground level. The water-bearing capacity and capacity of the deep wells of this aquifer
are considerable. The thickness of the connected aquifer is several dozen meters. The waters of the
Neogene aquifer are often weakly isolated from the surface. The recharge is carried out by the
infiltration of precipitation directly into the layers or through the permeable sands of the Quaternary
• Within the Quaternary deposits of postglacial areas
Quaternary fluvioglacial aquifer was separated in the southern part of the modelling area within the
Within the Carpathian Foredeep, only the Quaternary formations play the role of aquifer, because
below the deposits of the Neogene Age are represented by a complex of practically impermeable
clay. The Quaternary cover in this area is postglacial. This area, as well as the above, underwent
glaciation once (southern Poland, after which there were remaining thick layers of tills), and twice
during the Central and North Polish glaciations, periglacial conditions prevailed here. During the
Mazovian interglacial period, the area was elevated, and strong erosion caused the cutting of the
glacial sediment covers and the formation of deep valleys, which were then filled, during the Central
Polish glaciation, with sand and silt sediments of large river backwaters. Aeolian sediments are
among the sediments that are represented in this area and remain a remnant of the North Polish
The Quaternary aquifer includes all fluvioglacial layers, mainly various types of sand and gravel. As
a rule, these areas are not covered by any cover of impervious rocks, so aquifer is unconfined. The
thickness of the aquifer rarely exceeds 20 meters. It is recharged mainly due to precipitation.
Within Ukraine, this aquifer is locally spread, mainly within river valleys. Here it is characterized by
weak water saturation.
The hydrogeological characteristics of the separated aquifers are presented in Table 1.
Table 1 Hydrogeological characteristics of aquifers included in the hydrodynamic model
The depth of the top of
aquifer (from – to) [m]
The nature of the
aquifer (confined /
The ordinate of the
surface (m above sea
160 - 300
Characteristics of the
of the aquifer
The nature of the
contact with the
Apart from the aquifers, the model structure distinguishes also the separating layers that were
aggregated with respect to their poor permeability and stratigraphy. The following separation layers
• QG - it is a discontinuous layer of tills and other sediments with poor permeability, mainly silt,
which is common and constitutes interfacing in the Quaternary layer or underlying this level.
In some areas, it occurs above the ground, especially in areas with no usable aquifers. The
thickness of the level is varied, up to 40 m.
• Tr - a layer covering a stratigraphic range of practically impermeable Paleogene-Neogene
formations, especially the Kraków loams belonging to the Miocene. It is the most common
layer in the Carpathian Foredeep, whose thickness varies but reaches up to 3,000 m. Within
it, there are interfaces carrying highly mineralized waters, but well insulated from the usable
5 Numerical model of the transboundary aquifer
Hydrogeological model studies of the transboundary groundwater flow in the border region of Poland
and Ukraine were carried out on the basis of the conceptual model described above. Archival data
and geological information, in particular, such as: profiles of hydrogeological holes, geological maps,
cross-sections, numerical terrain model (SRTM) were used to construct the mathematical model.
The structure of the model and the workflow were adapted to the main objective of the model study,
i.e. the preparation and calibration of the model reflecting the hydrodynamic state of the groundwater
flow, enabling the balance of groundwater flowing across the state border and the design of an
effective monitoring network in the future.
The model study concerned the first and the main usable aquifer in the study area.
Software tools used for research
The Groundwater Vistas 6.2 program (MODFLOW, PEST counting modules) was used for
mathematical modeling. ArcGIS 10.3 and QGIS 3.10 were used to manage archival hydrogeological
data and conduct spatial and statistical analyzes.
In order to conduct model calculations, the research area was discretized, the model boundaries
were determined, its boundary conditions were defined, the hydrogeological conditions were
schematized, an appropriate calculation algorithm was selected and the model was calibrated to
determine the effective values of the water-bearing filtration coefficient and conductance of the river
Discretization of the area of model study
The groundwater circulation system was modeled on a two-layer hydrodynamic model (the
separating layer is not a model layer). The research area was digitized with a square grid with a step
of 500 m. The basic size of the discretization grid is 264 columns and 280 rows. The total area of the
discretized area is 18,480 km2. The z-axis discretization of the surface of the research area was
based on dividing the space into two layers of variable thickness. Within this area, the active area of
the model in layers I and II is 5,582.75 km2. The model was made in the PUWG-1992 coordinate
system. The initial model coordinates (lower left corner) are x = 745,500 y = 190000.
Model boundaries, boundary conditions
The boundaries of the model research area were defined to minimize the impact of boundary
conditions on the results of the calculations in the cross-border region. The authors decided to model
the area limited by the natural conditions of the 2nd type Q = 0 based on watersheds and the 3rd
type - based on the course of surface watercourses. In practice, the model covers a large area of the
San and Bug catchment areas limited by lower-order watersheds. The current groundwater
abstraction is presented in the form of the type II condition (Q<0). Water ordinates in surface
watercourses were adopted on the basis of topographic data (10k) and a numerical terrain surface
model. Hydrological data (MPHP) were used to determine the parameters of the river beds. The
parameters determining the hydraulic contact between groundwater and surface waters were
determined by the method of solving the inverse problem in the process of taring the model.
The distribution of the boundary conditions in the model blocks is presented in the Figure 14.
Figure 14 Model boundary conditions in the first and second modeled layers. Green color marks
blocks with condition III (river) Dark gray color marks blocks with condition II (Q = 0)
In the process of hydrogeological schematization, it was determined that there are two aquifers in
the study area with an unconfined and confined groundwater table remaining in hydraulic contact
through semi-permeable formations. The first layer from the surface is in direct contact with surface
waters mapped with the 3rd type condition. In areas without layer I, layer II has hydraulic contact with
surface waters. The aquifers within the model are recharged mainly by percolation, locally by
infiltration of surface waters. The constructed flow model is therefore a two-layer model. Groundwater
generally moves towards the San and Bug rivers, which are the main drainage base, and locally
towards their more important tributaries. The so-defined hydrogeological diagram was supplemented
with the following assumptions:
• aquifers are separated by a low-permeable layer, which is not a physical layer of the model,
mapped by the filtration coefficient (T '= k/m, where k - separation layer filtration coefficient;
m - separation layer thickness);
• bottom of the second aquifer is impermeable;
• groundwater velocity field is constant over time;
• vertical component of the groundwater flow velocity is negligible in relation to the horizontal
Mathematical model of water flow
The mathematical model used for the steady-state groundwater flow is the following equation:
H(x,y) – position of the groundwater table at the point (x, y) [L]
m(x,y) – the thickness of the aquifer at the point (x, y) [L]
k(x,y) – filtration coefficient at point (x, y) [L/T]
Qinf(x,y) - infiltration intensity at point (x, y) [L3/T]
Qst(x,y) - well discharge at point (x, y) [L3/T]
The presented equation is solved by the finite difference method using a rectangular discretization
grid with a constant step.
The ordinates of the top and bottom of the modeled layers were adopted on the basis of data from
boreholes, cross-sections and geological cartographic studies. The spatial distribution of the filtration
coefficient (Figures 15-16) in all layers in the entire domain of the model was interpreted on the basis
of auto-matching values using the PEST module using the pilot points method, distributed by
triangulation between points with a known value of the water table position (targets). The input values
were the mean values of the filtration coefficient in the individual lithostratigraphic extracts. This is a
classic example of using the inverse task method.
Figure 15 Filtration coefficient distribution in layer I after taring
Figure 16 Filtration coefficient distribution in layer II after taring
Recharge of the model was adopted using the constant volume method. It is based on using the
value of the underground runoff (Hp) to calculate the amount of infiltrating water within the catchment
area (Figure 17). The long-term average value for the part of the Bug catchment area covered by the
research is approx. Hp = 60 mm/year, while for the San catchment area Hp = 120 mm/year and such
values were adopted as the basis for calculating the infiltration value in individual blocks. The
calculated amount of infiltrating water on the model's surface was distributed on the basis of
geological conditions (effective infiltration coefficient) identified with use of geological surface maps
and GIS information layers showing the presence of wetlands and peatlands (evapotranspiration).
Figure 17 Spatial distribution of recharge [m3/24h/m2]
The basic criterion for model calibration was the compliance of the hydrodynamic state of the
groundwater flow recorded during the drilling of hydrogeological wells, monitoring tests and
hydroisohypses resulting from maps with the state obtained as a result of computer simulation. Both,
the hydroisohypses image and the location of the groundwater table at 883 research points were
analyzed, where data on the level of the groundwater table was obtained. In the model calibration
procedure, the conductance of the river beds and the value of the filtration coefficient were modified.
After each simulation, the calculated groundwater levels were analyzed.
After initial adjustment of the conductance of surface watercourses (by the method of successive
approximations to obtain infiltration not exceeding 20% of the runoff), the values of the filtration
coefficient were adjusted using the PEST module.
It is assumed that the standard deviation of the differences between field measurements and the
values calculated on the model should not exceed 15% of the measurement range. In the analyzed
case, this value is 2.8% (Figure 18). The standard deviation is 8.7 m and the maximum deviation
exceeds 40 m, which is most likely caused by incorrect determination of the water table elevation in
individual wells. It should be noted here that the difference between the minimum and maximum
terrain elevation in individual blocks can be as high as 125 m (average 14.5 m). This is mainly due
to large differences in the mountainous area of the model. It should also be noted that for a very large
range of the ordinates of the measured water table at the test points (ΔH = 311.4 m), such a deviation
constitutes only about 13% of the amplitude. Based on the above data, it can therefore be concluded
that the model has been calibrated to a satisfactory degree.
Figure 18 Summary of the observed values of the ordinate of the groundwater table with the
calculated values and a statistical summary of the model calibration process
Model credibility assessment
The mathematical model is always a simplification of the actual hydrogeological conditions.
Therefore, the results of model simulations are burdened with a certain error, which is the result of
always incomplete hydrogeological identification of the investigated aquifer and the necessary
simplifications made during the schematization. In the case of the model prepared for the analysis of
groundwater flows, the factors limiting the accuracy of the model forecasts and those contributing to
the reliability of the results can be mentioned.
Factors limiting credibility:
• limited recognition of the structure and hydrogeological parameters of the first aquifer;
• uneven distribution of hydrogeological boreholes;
• no simultaneous hydrogeological measurements at all benchmarks;
• large terrain height differences within the model;
• a very large area covered by model studies and irregular ranges of aquifers, in particular
• significant errors in determining the ordinates in archived borehole data.
Factors increasing credibility:
• simple geological structure and hydrogeological conditions, in particular, the presence of only
two main aquifers with a regional range;
• good, regional identification of hydrogeological conditions in the second layer - the main
aquifer in the study area;
• model area limited by natural boundary conditions - no participation of uncontrolled
inflow/outflow from artificial boundary conditions in the balance of the model;
• no significant anthropogenic factors changing the groundwater flow regime.
Taking into account the above conditions, both those indicating deficiencies in the diagnosis and
showing elements increasing the credibility, the model made can be considered sufficient to be used
to assess the amount and directions of transboundary water flows. It is certainly much more reliable
forecasting tool than analytical or graphical calculation methods. It should be mentioned that to
assess the conditions at specific points (e.g. to be drilled for testing wells), detailed taring can be
performed locally, e.g. using the results of parametric pumping of nearby groundwater intakes.
The identification and taring of the model was performed in the conditions of the current exploitation
of the intakes (average for 2018-2020). The summary balance of the model is presented below in
tabular and graphic form (Figure 19).
Figure 19 Model balance
The total balance includes only infiltration supply (from precipitation and river) on the positive side,
and river outflow and groundwater intake on the negative side. Evapotranspiration of peatland areas
was included in the infiltration supply (negative value). A good fit and a negligible percentage error
indicate that the selected boundaries are tight and the area can be considered as a balanced one. It
should be noted that the authors' assumption was to avoid the use of artificial boundary conditions,
the impact of which on the model balance is difficult, and in the case of such an extent of the model,
even impossible to control.
6 Assessment of transboundary groundwater flows by hydrodynamic
The results of the modeling allowed, among others, for the determination of piezometric surfaces for
both aquifers, the hydrodynamic relationship between them and the identification of the zones of
transboundary groundwater flow.
Illustrative maps of the calculated hydroisohips of the groundwater table for both aquifers of the model
are presented below (Figures 20-21).
Figure 20 Hydroisohps calculated for layers I of the aquifers of the model
Figure 21 Hydroisohips calculated for layers II of the aquifers of the model
It should be noted that some of the blocks of layer I are dry - dark gray. This is natural because the
ranges of layer I were determined on the basis of the extent of lithogenetic separations (sandy alluvial
formations), often devoid of any hydrogeological recognition. The general dependence of the water
table in the first layer on the morphology of the terrain and the decline of surface watercourses as
well as its "mosaic" nature is visible. This is especially evident in the San catchment area.
In layer II, the hydroisohypses system confirms the regional continuity of the aquifer, despite the
changing lithogenetic formation and stratigraphy of the sediments that build it.
The layout of piezometric surfaces in Figures 20 and 21 shows the groundwater circulation system
in the transboundary parts of the Bug and San catchment areas. The distribution of the water table
in layers I and II is determined by the river network. These figures show that the groundwater
circulation system consists of a number of local systems related to the catchments of watercourses
of a lower order than the Bug and San.
In the model area, the watershed zone between the basins of the Bug and San underground waters
is the Roztochia region. In this area, the piezometric surface of the main usable aquifer (layer II of
the model) reaches its highest elevation - 290 m a.s.l. From Roztochia, groundwater outflow takes
place in two opposite directions - to the north-east in the Bug catchment area and to the west and
south-west in the San catchment area. Thus, there is a general separation of the directions of cross-
border flows. In the Bug basin, the transboundary groundwater flow is directed mainly to Ukraine,
while from the San basin - to Poland.
For individual catchments, on the basis of calculations of the piezometric surface, the spatial extent
of the main hydrodynamic zones - supply, transit and drainage - was determined (Figure 22). These
figures show that the main drainage base for both model layers is Bug and San respectively. At the
same time, the Sołokija and Rata rivers in the Bug basin and the Lubaczówka, Szkło, Wisznia and
Wiar rivers in the San basin play a minor drainage role. The elevation of the water table in the
drainage zones of the Bug and San are at the same level - 180-210 m a.s.l.
Based on the developed numerical model of the Polish-Ukrainian border zone, as a result of a
detailed analysis, the values of cross-border flows were calculated for the main usable aquifer, which
in larger river valleys also takes into account the alluvial aquifer. A detailed zonal balance is presented
below, showing the cross-border flows divided into individual catchments (Bug and San), which was
the main purpose of the research described above (Tab. 2). The zones were separated by dividing
the studied catchments - San and Bug river into Polish (Zone 1 and Zone 3) and Ukrainian (Zone 2
and Zone 4) parts.
Table 2 Cross-border groundwater flow between Poland and Ukraine within the main usable aquifer
Summary of Flows for Zone
Zone 1 1 Inflow
Zone 2 Inflow
Zone 2 Outflow
Zone 3 Inflow
Zone 3 Outflow
Zone 4 Inflow
Zone 4 Outflow
Figure 22 Hydrodynamic zones in the model area
In general, the transboundary groundwater flow in the main usable aquifer between Poland and
Ukraine occurs not along the entire length of the border, but is concentrated on a specific section
discussed in detail in the presented model study (Figure 22). The location of this section can be
marked with two extreme points: starting from the place where the Bug River ceases to be a border
river and turns towards Ukraine to the border point marked No. 430A on the watershed between the
rivers Wyrwa and Łopuszanka.
With regard to the main usable level, the total amount of groundwater runoff from Poland to Ukraine
is 42,350 m3/24h, and broken down by the Bug and San basins - 32,981 m3/24h and 9,369 m3/24h,
respectively. On the other hand, the inflow to Poland from Ukraine amounts to 27,924 m3/24h, and
broken down into the catchment areas of the Bug and San - 11,632 m3/24h and 16,292 m3/24h,
respectively. The highest flow intensity is observed within the transit zone shown in Figure 22.
The amount of groundwater outflow from Ukraine to Poland is 27,924 m3/24h, and broken down into
the catchment areas of the Bug and San - 11,632 m3/24h and 16,292 m3/24h, respectively. On the
other hand, the inflow to Ukraine from Poland amounts to 42,350 m3/24h, and broken down into the
Bug and San basins - 32,981 m3/24h and 9,369 m3/24h, respectively.
As a result of the balance calculations, it was unequivocally proved that the inflow of groundwater
from Poland to Ukraine is more than 1.5 times greater from the main usable layer than from Ukraine
to Poland. This finding is of particular importance for the further interpretation of possible
transboundary impacts on a common useable aquifer.
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Government of Ukraine on cooperation in the field of environmental protection, 1994
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and post-ISARM experience. J. Hydrol.: Reg. Stud.: 2015–2020
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PART II. Assessment of the resources of
transboundary groundwater reservoirs for the
The Latvian-Estonian pilot area is part of the BAB. The boundaries of the pilot area were determined
taking into account the existing Latvian-Estonian border groundwater bodies along the state border,
previously identified transboundary surface water bodies, Baltic sea coastline, as well as groundwater
flows from the existing hydrogeological model. The defined pilot area covers an area of approximately
8000 km2 and mainly includes Gauja-Koiva and Salaca-Salatsi transboundary river basins that are
located in the territories of Gauja RBD and Daugava RBD in Latvia, as well as three RBDs in Estonia
- Koiva, West Estonia and East Estonia.
Existing knowledge shared between Estonia and Latvia and the formerly developed hydrogeological
model for the entire BAB were used to assess hydrogeological conditions and geological structure
for the Latvian-Estonian pilot area. Also, the model was used to develop a conceptual understanding
of transboundary groundwater resources dynamics.
In pilot area, for detailed characterization on transboundary area, aquifers were combined into
appropriate aquifer systems. As a result, the aquifers were divided into four groups: 1) Quaternary
aquifer system, 2) Pļaviņas-Ogre aquifer system, 3) Aruküla-Amata aquifer system, 4) Lower-Middle
Devonian aquifer system. The deepest aquifer systems were not considered further as they were not
considered aquifers according to WFD requirements.
For the assessment of transboundary groundwater flow, the project partner - University of Latvia,
within the framework of the project, developed a semi-analytical method, which was used for the
assessment of transboundary groundwater flow volumes across the Latvian-Estonian pilot area. The
obtained results showed that the majority of transboundary groundwater flow across the Estonian-
Latvian pilot area occurs in the Aruküla-Amata aquifer system with a total flow from Latvia to Estonia
of 9488.5 m3/d, a total flow from Estonia to Latvia of 5807.2 m3/d and a total net flow of 3681.3 m3/d
that contributes to the flow from Latvia to Estonia. The majority of transboundary groundwater flow
occurs in the Eastern part of the pilot territory.
1 Legal systematics of transboundary groundwater reservoirs
Even before joining the EU, international legislation in transboundary water management was
incorporated into national law. In 1992, both countries signed the Convention on the Protection and
Use of Transboundary Watercourses and International Lakes (UNECE Water Convention), which
was adopted in 1992 in Helsinki, Finland. It was ratified in national legislation in Estonia in 1995, and
in Latvian legislation in 1996. The purpose of the Convention is to strengthen national and
international action to protect transboundary waters and ensure ecological balance. The Water
Convention requires Parties to prevent, control and reduce transboundary impact, use transboundary
waters in a reasonable and equitable way and ensure their sustainable management. Parties
bordering the same transboundary waters have to cooperate by entering into specific agreements
and establishing joint bodies. As a framework agreement, the Convention does not replace bilateral
and multilateral agreements for specific basins or aquifers; instead, it fosters their establishment and
implementation, as well as further development. The convention also defined concepts such as
“Transboundary waters” and “Transboundary impact (UNECE Water Convention, 1992).
Latvia and Estonia are two member states of the EU (since 2004), with similar historical
developments in the field of groundwater management. Both countries have adopted the
requirements of the WFD and incorporated it into their legislation, for the protection of groundwater,
the conservation of good quality water and the sustainable use of groundwater resources.
In 2003, a bilateral agreement was signed between the Ministry of the Environment of the Republic
of Latvia and the Ministry of the Environment of the Republic of Estonia on co-operation in the
protection and sustainable use of transboundary watercourses. Despite the agreement, by 2018 no
systematic exchange of information has taken place between both countries and no joint research
has been carried out in the assessment of groundwater resources. There has been closer co-
operation in transboundary surface water management.
In 2018, a joint project (GroundECO project) between Estonian and Latvian institutions was launched
on the assessment of Latvian-Estonian transboundary groundwater, with the aim to promote the
sustainable management of common groundwater resources and related ecosystems in the
transboundary Gauja-Koiva river basin.
1.1 Transboundary groundwater reservoirs in Estonia's water/geological law and their
status of recognition
To comply with WFD requirements and to coordinate the management of water resources in Estonia,
the territory of Estonia is divided into 3 river basins: East-Estonia river basin, West-Estonia river
basin, and Koiva river basin. RBMP for each river basin are established for six years and are then
updated. County governments, local authorities, citizens located on the territory of the river basins
and other interested parties will be included in the process of establishing the RBMP. The
Environmental Board is responsible for the inclusion of parties. The current valid RBMPs have been
drawn up from 2009 through 2015.
To reach the environmental goals of protecting the areas stated in the RBMP and areas in need of
protection, a programme of measures will be developed where measures of water usage and
protection shall be stated to be taken into account in establishing, reviewing and amending the
general and detailed zoning plans and public water supply and sewerage system development plans
of local authorities. The implementation of the programme is organised by the Commission for River
Basin Management. To ensure the implementation of the programme of measures, the
Environmental Board will establish an action plan for the implementation of the programme of
measures for each river basin.
According to RBMP, Estonia has delineated no transboundary groundwater bodies.
1.2 Transboundary groundwater reservoirs in Latvian water/geological law and their
status of recognition
In Latvia, the main legal act regulating the management and protection of water resources (including
– groundwaters) is the Water Management Law, as well as the Cabinet Regulations issued on the
basis of this law. Although the Water Management Law contains clear definitions of terms such as
“groundwater” and “groundwater body”, so far, the law has not provided a definition of the term
“transboundary groundwater body”. The law is largely based on the requirements of the EU in the
field of water protection and management, including WFD.
It is worth noting, however, that Cabinet Regulation No.92 (adopted on February 17, 2004)
“Requirements for the Monitoring of Surface Water, Groundwater and Protected Areas and the
Development of Monitoring Programs” issued on the basis of the Water Management Law stipulate
activities such as insuring monitoring network, which allows the evaluation of the direction, rate and
changes in the chemical quality of transboundary groundwater flow, as well as the determination of
the cause of changes; as well as performing monitoring in groundwater bodies crossing the State
border of Latvia, which allow the determination of the risk of transboundary impact and the evaluation
of transboundary impact.
To comply with WFD requirements and to coordinate the management of water resources in Latvia,
the territory of Latvia is divided into 4 river basins: Daugava river basin, Gauja river basin, Lielupe
river basin and Venta river basin. RBMP for each river basin are established for six years and are
then updated. County governments, local authorities, citizens located on the territory of the river
basins and other interested parties will be included in the process of establishing the RBMP. Latvian
Environment, Geology and Meteorology Centre is responsible for the inclusion of parties. The current
valid RBMPs have been drawn up from 2009 through 2015.
According to RBMP, Latvia has delineated transboundary groundwater bodies with Lithuania. In
2019, the project B-solution was completed, within the framework of which Latvian-Lithuanian
transboundary groundwater assessment was performed. During project implementation it has been
agreed that there are 14 GWBs (7 in Latvia and 7 in Lithuania). As delineation of GWBs is a matter
of each Member State and accompanied with many political decisions and national level planning
principles, the boundaries of GWBs have not been changed.
2 Requirements for a uniform form of parametrization of
In order to get a better picture of the Estonian-Latvian transboundary territory and the common
aquifers, a larger area was initially selected, based mainly on the distribution boundaries of the
existing groundwater bodies (hereinafter - GWBs). All GWBs adjacent to the borders of both countries
were taken into account - in the territory of Estonia they are GWBs 21, 22, 23, 24, 25, 26 and in the
territory of Latvia - GWBs D6, D8, A8, A10, P. The initially selected area is shown in Figure 23.
Figure 23 Initially selected cross-border territory of Latvia and Estonia
In accordance with the requirements of the WFD, GWBs in both countries (Latvia and Estonia) have
been delineated mainly on the basis of the existing hydrogeological classification, and in addition to
assessing the compliance of groundwater with drinking water quality requirements. As well as
determining groundwater watersheds - using the existing information on groundwater levels in
aquifers, which allows the identification of regional recharge and discharge areas, as well as
groundwater flow directions. In Estonia, the boundary of this watershed is determined by the
boundaries of the largest river basins (East-Estonian river basin and West-Estonian river basin), while
in Latvia the groundwater watersheds were delineated mainly on the basis of modeled water levels
in the aquifer systems.
Accordingly, the existing knowledge base was used to identify, characterize and determine the
common hydrogeological parameters between the two countries:
1. On the boundaries of the distribution of aquifers and the stratification of the existing
hydrogeological section (Quaternary sediment maps at the scale of 1: 200 000, pre-
Quaternary sediment maps at the scale of 1: 200 000, and geological sections of existing
2. On hydrogeological and geological conditions in the cross-border area, based on the results
obtained from the PUMA model of the BAB.
3. On delineated GWBs in each country.
4. Regarding the compliance of the composition of groundwater with the quality requirements
for drinking water (maps of the chemical composition of aquifers existing in the country, as
well as data of existing water extraction and monitoring wells have been used).
5. On the volumes of groundwater abstraction, the density and number of water supply wells.
Initially, based on the available knowledge base on the lithology and permeability of sediments in the
study area, water-containing and water-poor permeable layers were identified, mainly by sectioning
regional aquitards (Middle Devonian Narva regional stage, Ordovician and Silurian sediments).
Based on water permeability of the sediments and the lithological composition, homogeneous strata,
separated from each other by weakly permeable layers, were combined in aquifers. In turn, the
adjacent and hydraulically interconnected aquifers with relatively similar characteristics were
combined in aquifer systems.
In addition to the above conditions, the compliance of groundwater with drinking water quality
requirements was assessed, as the WFD gives priority to the protection of water that is or may be
used for human consumption. After collecting the relevant data, aquifers were identified that can be
used for water supply and groundwater quality meets drinking water standards (SO42- and Cl-
concentrations do not exceed the norm - 250 mg/l, water mineralization (TDS) < 1 g/l). The role of
the identified aquifers in the water supply was also taken into account when compiling data on water
abstraction volumes and density of water supply wells in the identified aquifer or aquifer system. If
the significance of groundwater abstraction was relatively low, then the aquifer was not identified as
a separate groundwater body and a detailed data analysis for this aquifer was not performed.
Aquifers and aquifer systems where 1) water quality did not meet drinking water quality requirements
and 2) there was no information on existing water supply wells or their density was low and there
were no groundwater well fields, were not considered aquifers in the context of WFD. The
summarized information on the determination of common hydrogeological parameters is given in
Table 3, adapting it to the delineated GWBS in both countries.
For further characterization of the cross-border area, the division of aquifers into aquifer systems was
mainly used. As a result, the aquifers were divided into four groups: 1) Quaternary aquifer system,
2) Pļaviņas-Stipinai aquifer system, 3) Aruküla-Amata aquifer system, 4) Lower-Middle Devonian
aquifer system. The deepest aquifer systems were not considered further as they were not
considered aquifers according to WFD requirements.
Table 3 Stratigraphy of hydrogeological section in the Latvian-Estonian cross-border territory
Distribution / Aquifer in the context of the WFD
(attached to each
Whole territory. Considered as aquifer in the context of
the WFD, as aquifer consists of freshwaters that are widely
used for small household needs due to shallow occurrence
and ease of access; aquifer is also crucial for groundwater
dependent ecosystems and surface bodies. Quaternary
aquifer is attached to the first embedded groundwater body
(Upper-Middle Devonian aquifer system).
(LV GWBs D6 and
EE GWB 26)
In the south-eastern part. Considered as aquifers in the
context of the WFD, as the aquifer system consists mainly
of freshwaters that are and can be used for drinking water
(LV GWBs A8 and
A10, EE GWBs 23,
24 and 25)
Whole territory. Considered as aquifers in the context of
the WFD, as the aquifer system consists mainly of
freshwaters that are and can be used for drinking water
Narva reģional aquitard D2nr
Devonian (LV GWB
P, EE GWBs 21
Whole territory. Only in the western part of the territory
were considered as aquifers in the context of WFD, in the
rest of the territory they were not considered as aquifers,
because saline waters that are not used as drinking water
are distributed in the aquifer system.
Ordovician and Silurian regional
Marl, solid limestone
Whole territory. Were not considered as aquifers in the
context of WFD, as chloride-sodium brines not used as
drinking water are distributed in the aquifer system.
Archean and Proterozoic crystalline
3 Criteria for the identification of hydrogeological units of a
Transboundary area mainly includes Gauja-Koiva and Salaca-Salatsi transboundary river basins that
are located in the territories of Gauja and Salaca RBDs in Latvia and in three RBDs in Estonia -
Koiva, West Estonia and East Estonia. The Latvian side includes only the part of the Gauja river
basin with direct transboundary water bodies and their tributaries, which may affect the water quality
in transboundary water bodies. In addition, in order to fully view the entire transboundary area, the
Estonian and Latvian sides have been supplemented with water bodies at the border that extend
beyond the Gauja-Koiva and Salaca-Salatsi cross-border river basin districts. This approach would
secure consideration of anthropogenic pressures in all of the Latvian-Estonian border area when
devising solutions suitable for meeting the environmental objectives (Figure 24).
Figure 24 River Basin Districts within project area
Based on the existing knowledge base, aquifers carrying groundwater across the boundary line were
identified. Figure 25 shows that groundwater flows in the Middle and Upper Devonian aquifer systems
(active water exchange zone) are similar and generally follow the land surface terrain and coincide
with the boundaries of river basins. The recharge of these aquifers takes place mainly in the uplands,
while the valleys and the lowlands serve as discharge zones. Groundwater flow in the Lower-Middle
Devonian aquifer system (slowed water exchange zone) is more homogeneous and there is no
significant connection with the higher existing systems, as well as surface water catchment areas.
This deepest groundwater recharge area is considered to be the south-eastern part of the territory,
the groundwater flow is directed mainly in the north-western, western direction and the groundwater
discharge takes place in the Baltic Sea.
The transboundary flow is mainly found in the eastern part of the territory in the upland areas, where
the feeding area of all identified aquifers (except the Lower-Middle Devonian aquifer system) is
detected, and in the central part, where the possible groundwater flow from Estonia to Latvia is also
identified (Figure 25). In order to identify the "significance" of groundwater flow between boundaries,
it is planned to determine the balance using the semi-analytical method.
Figure 25 Groundwater flow maps
Based on the types of land use in the Latvian-Estonian pilot area (The Copernicus Programme,
2018), the largest part is covered by forest areas - 63%, followed by agricultural lands (32%) and
wetlands (3%). The main pressure-causing factors that can affect the quantity of groundwater
resources and influence changes in groundwater flow are water abstraction, amelioration, drainage
from quarries, as well as fluctuations in groundwater levels caused by hydroelectric power plant
reservoirs. It is known that drainage systems and drainage from quarries mainly significantly reduce
the resources of shallow aquifers in some areas. In addition, the impact of shallow aquifers on total
water resources is negligible, therefore, these factors have not been taken into account when
assessing transboundary groundwater resources. In the areas affected by the reservoirs, the
groundwater level is rising - i.e. the reservoir replenishes rather than decreases the groundwater
resources. However, the infiltration of surface water into the groundwater in the vicinity of reservoirs
increases the concentration of organic matter in groundwater, as well as slows down the exchange
of groundwater. These processes can lead to the accumulation of pollutants in certain aquifers.
These processes are generally poorly studied, but they are known to take place in the immediate
vicinity of reservoirs and only in shallow aquifers. Therefore, similarly to the pressure caused by
amelioration, the impact of water reservoirs was not taken into account when assessing
transboundary groundwater resources. Thus, it was considered that in the Latvian-Estonian cross-
border hydrogeological conditions, only groundwater abstraction could pose a real risk. Groundwater
is abstracted mainly for the supply of drinking water.
In order to understand the water abstraction pressure and its possible impact on changes in
groundwater flow, a more detailed data analysis of groundwater abstraction volumes over a longer
period of time was performed in the Latvian-Estonian cross-border area identified below. The
collected data show that intensive water abstraction is not marked in the cross-border area. In the
period from 2010 to 2019, it mainly fluctuated from 6.3 thousand m3/d to 7.8 thousand m3/d, on
average - 7.0 thousand m3/d (Figure 26).
Figure 26 Total abstraction within Latvian-Estonian cross-border area in the period from 2010 to 2019
In the cross-border territory of Latvia, water abstraction volumes in the respective period ranged from
3.3 to 4.2 thousand m3/d, in the last 5 years water abstraction volumes decreased, and on average
did not exceed 3.5 thousand m3/d. In turn, in the part of the cross-border territory in Estonia there is
a slight increase in water extraction and in the period from 2010 to 2019 has been fluctuating from
2.7 to 3.6 thousand m3/d. In the Latvian-Estonian cross-border area, water abstraction sites are
distributed unevenly, the densest number of water abstraction wells is observed around populated
areas (cities), for example, in Latvian territory around cities - Valka, Rūjiena, Salacgrīva and Ainaži,
while in Estonian territory around cities - Valga, Tõrva and Karksi-Nuia. Outside populated areas,
groundwater abstraction is more dispersed and groundwater is mainly extracted from individual wells
Figure 27 The distribution of abstraction sites and their average abstraction rates in the pilot area
The collected data show that higher groundwater abstraction was identified from the Aruküla-Amata
aquifer system, which is distributed throughout the cross-border area, water abstraction ranged from
4.6 to 6.3 thousand m3/d during the respective period, which is on average about 80% of total water
abstraction (Figure 28). Groundwater abstraction from this aquifer system mainly takes place from
individual wells with abstraction volumes not exceeding 100 m3/d (mainly ranging from 1 m3/d to
50 m3/d) and only in urban areas inside groundwater well fields water abstraction increases to 119-
789 m3/d. The largest groundwater abstraction in Latvian territory is marked in the groundwater well
field “Valka”, which ensures the centralized water supply of the city of Valka. In Estonian territory, the
largest abstraction sites are also in the city of Valga, which