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Evaluation of the remaining hydro potential in Italy

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Abstract

A methodology is described to evaluate the residual hydropower potential in Italy, taking into account the current demands on water resources (irrigation, drinking water, existing hydropower). The model applied uses a numerical technique coupled with a CIS, the hydrological and physiographic characteristics of nearly 1500 interconnected sub-basins, and rainfall maps. Maps of water resources availability and the related maximum hydropower potential have been produced and are found to be quite helpful tools to support power authorities, decision makers and other stakeholders in creating energy masterplans, and in implementing small hydro plants.
The aim of the work described here was to devel-
op a methodology for the creation of maps to
show the maximum and the residual hydro -
power potential of Italy, as a tool that can highlight
areas in which hydro potential is still available, or has
not been fully exploited [Alterach, et al, 20061;
20072].
The assessment of the hydropower potential in a sin-
gle sub-basin is based on two elements: the water
availability, assessed from the historical rainfall data,
and the physiographic characteristics of the sub-basin
itself. These basic components are useful to compute
the maximum potential hydropower, since they can be
provided by both the Italian maps of the water
resources availability (that is, the discharge profiles of
each river) and the geodetic heads.
The next step is the evaluation of the human impacts
on the water availability, and consequently on the
hydropower potential. That means, flow withdrawals
determined by different human activities (irrigation,
industry, drinking water treatment, and so on), which
diminish the water volumes in the rivers. As a result,
the water availability is different from the natural
flow, and the maximum hydro potential varies from
the residual potential.
Besides the water exploitation, there is another con-
straint that decreases power production, and that is the
so called ‘minimum instream flow’ MIF. The role of
the MIF is to prevent excessive river exploitation.
Consequently every water withdrawal must take into
account that the river flow cannot reach a lower level
than this particular threshold.
The ‘Maximum Potential Hydropower’ methodolo-
gy has been applied to the entire Italian territory,
divided into almost 1500 sub-basins, and its results are
shown in a maximum potential hydropower map. The
‘Residual Potential Hydropower’ methodology was
also applied on a GIS model relating to the whole
Italian territory; a specific application to the Basilicata
region is proposed, with almost 80 interconnected
sub-basins model results shown.
1. Evaluation of the hydro potential
The methodology is divided in two main parts, as
shown below:
Physiographic and hydrologic data processing:
elementary watershed shape definition;
mean annual rainfall assessment;
evaluation of the mean rainfall - runoff coefficient
for each basin; and,
ranking of elementary basins
Calculation of the maximum and residual hydro potential:
characteristic parameters of each basin;
simplified evaluation of the MIF (minimum
instream flow);
evaluation of the withdrawal scheme of the water;
natural flow and residual flow assessment; and,
maximum and residual hydropower potential.
1.1 Land and hydrology: basic data
elaboration
The macro-basin borders are obtained from Italian
Digital Elevation Model (DEM 90 ×90 m definition
grid), through an ArcGIS tool called ‘Hydrology
Modelling’. Each macro-basin is then divided into
several elementary sub-basins, defined according to
the river ranking order and other parameters, such as
the basin size and the presence of important tribu-
taries.
The rainfall distribution over each elementary basin
is the main parameter used to determine the natural
flow, and consequently to calculate the potential
hydropower. The input data are from the mean rainfall
map, from 1950 until 2004, processed by the so-called
‘spline’ interpolation method.
It is thus possible to couple each basin with the mean
annual rainfall, taking into account not only the rain-
fall measured in the station within the basin itself, but
also the measurements in the neighbouring basins.
Effective natural discharge is obtained using the
rainfall and the runoff coefficient [19563]. In some
particular cases, the runoff coefficients have been
updated and calibrated based on a water volume bal-
ance of the reservoirs.
Multiplying the rainfall, the basin surface and the
runoff coefficient determines the mean river discharge
available at the basin closure point.
The elementary basin ranking completes the data-set
for evaluation of the hydrological profile, which
makes it possible to identify the relationships and con-
tribution of the upstream basins. The importance of
the ranking is clear as the total potential hydropower
is a function not only of the flow ‘produced’ in the
basin itself, but also relates to the water that comes
from the upstream basins.
1.2 Evaluation method
Two definitions are used:
maximum potential hydropower: this represents
the watershed potential, taking into account the natur-
al available hydrological profile and the topography of
the watershed; and,
56 Hydropower & Dams Issue Five, 2009
Evaluation of the remaining
hydro potential in Italy
J. Alterach, M. Peviani, A. Davitti, M. Vergata, ERSA SpA, Italy
G. Ciaccia, AEEG and Sapienza University of Rome, Italy
F. Fontini, University of Padova, Italy
A methodology is described to evaluate the residual hydropower potential in Italy, taking into account the
current demands on water resources (irrigation, drinking water, existing hydropower). The model applied uses a
numerical technique coupled with a GIS, the hydrological and physiographic characteristics of nearly 1500
interconnected sub-basins, and rainfall maps. Maps of water resources availability and the related maximum
hydropower potential have been produced and are found to be quite helpful tools to support power authorities,
decision makers and other stakeholders in creating energy masterplans, and in implementing small hydro plants.
res idual potential hydropower: this means the
watershed potential taking into account the flow with-
drawal scheme and the minimum instream flow con-
straint.
The methodology relating to the evaluation of the
residual potential calculates the hydro potential avail-
able from ‘usable river flow’, which means the natur-
al river flow, but subtracting:
• the annual average water withdrawals discharge;
and,
the minimum instream flow (MIF), assumed to be
equal to 10 per cent of the mean hydrological river
discharge.
1.2 Pilot case study
The residual hydro potential method was applied to a
pilot case, which was the Basilicata region in Italy.
1.2.1 Characterization of the actual water uses
The actual uses of water can be considered as ‘energy
withdrawals’, that is, the annual volume which is
taken off from the system and it is not available for
power generation purposes. In a similar way, water
restitution measures represent supplementary hydro -
power potential, from the point of view of the water-
shed system.
Types of water withdrawals considered in the model
are:
Irrigation: There are normally no restitution mea-
sures, so the whole water volume is consumed.
Potable water: it is assumed that there is usually a
restitution, even if the volume returned is less than the
withdrawal volume.
Industrial: like drinking water withdrawals, indus-
trial water use generally has some restitution volume,
but less than the withdrawal volume.
Hydroelectric generation: all the water volume
drawn for hydr generation purposes is restored to the
river downstream.
Some different scenarios can be identified as regards
the withdrawal/restitution points in a particular river
reach:
• water withdrawn from one basin and discharged
back into another, outside the study area;
water withdrawn from a basin and not replenished;
water withdrawn from a basin and discharged back
into the same basin, but at a different elevation;
water withdrawn from a basin and discharged back
into another basin within the same study area;
water discharged back into a basin from a point out-
side of the study area;
• water discharged back into a basin from another
basin within the study area.
1.2.2 Basin ranking hydrologic and anthropical discharges
Fig. 1 shows a typical example of basin ranking. The
current basin is included between points A and B.
There are also three upstream basins, named
UPSTREAM_1, UPSTREAM_2 and UPSTREAM_3.
The rivers in the three upstream basins converge in the
basin studied, and merge at point A, called the
‘upstream closure point’ (the ground elevation of
which is known as Hupstream_clos). In a similar way,
the basin studied is down-edged from point B, called
‘closure point’ (the ground elevation of which is called
Hclosure).
For the basin under study, three kinds of discharge
can be defined:
Afferent discharge: Qaff = A×p×cd
That is the natural hydrological river discharge, with-
out any water use consideration. The afferent dis-
charge is obtained by multiplying the basin area (A),
the annual mean rainfall (p) and the rainfall-runoff
coefficient (cd).
Hydrological discharge: Qhyd = Qaff + Qup_hyd
This represents the total natural discharge evaluated at
the closure point of the basin, taking into account the
afferent discharge in the basin itself (Qaff) and the dis-
charge coming from the upstream basins (Qup_hyd).
Anthropical discharge: Qant = Qaff + Qup_ant - Σjqj.
This is the discharge in the closure point of current
basin, taking into account the upstream flow and the
human impact on the natural flow (withdrawal +qor
restitution –q).
1.2.3 Calculation of the maximum and residual hydro
potential
The determination of maximum total hydropower
potential is obtained from the sum of the two kinds of
potential:
• upstream potential (sub-indexup): which considers
the potential hydropower derived by the flow coming
from the upstream watersheds;
own potential (sub-index own): which considers only
the potential hydropower of the single watershed stud-
ied; and, as a result:
total potential (sub-indextot): total of the own
and upstream contributions.
Each of these three terms can be classified as:
maximum potential (sub-indexmax), that is, the total
hydropower potential without taking into account either
the minimum instream flow or water withdrawals;
residual potential (sub-indexres), that is, the poten-
tial energy with the effectively usable flow, taking into
account the minimum instream flow constraint and the
withdrawals/restitutions.
There is a further term, which is ‘energy extracted’
(sub-indexprel) relating to a particular river basin. This
is proportional to the sum of the products between the
value of the discharge withdrawal and the existing
head between the withdrawal elevation and the water-
shed closure elevation.
Hydropower & Dams Issue Five, 2009 57
Fig. 1. Basin
ranking.
The upstream energy is calculated based on the flow
arriving from upstream and the geodetic head avail-
able inside the basin. This head is the difference
between the elevation of the upstream flow entry point
elevation (Hupstream_clos) and the watershed closure
elevation (Hclosure).
The watershed’s own energy is calculated based on
simplified hypotheses. In fact the potential hydropow-
er at a generic point inside of the river basin, with ref-
erence to the closure basin section, is equal to:
Eown_maxi= Conv ×g ×η×Ai ×pi×cdi×(HiHclosure) =
Conv ×g ×η×Qaffi ×(Hi – Hclosure)
where Qaffi and Hiare the basin’s own discharge (Qaffi
= Ai×pi×cdi) and the elevation of a generic elemen-
tary area i. The potential of the entire watershed is
obtained from the summation of the contributions of N
elementary areas which make up the river basin itself:
Eown_max = Conv ×g ×η×Σi [Ai×pi×cdi×(Hi – Hclosure)]
where the sub-index i indicates each elementary basin,
and varies from 1 to N.
If considering the river basin as a physical entity, it
can be assumed that each has its own unique precipi-
tation (p) and rainfall-runoff coefficient (cd) values
uniformly distributed between the elementary areas.
That means pi= p = constant, cdi= cd = constant. The
above formula is expressed in terms of the medium
watershed elevation (Hmean).
Eown_max = Conv ×g ×η×p ×cd ×Σ
iAi×cdi×(Hi– Hclosure)
or:
Eown_max = Conv ×g ×η×Qaff ×(Hmean – Hclosure)
1.2.4 Formulation used to calculate the maximum and the
residual hydro potential
After the introduction of the relevant data into an
ARCGIS database, appropriately structured, the pro-
cedure developed makes it possible to determine the
various kinds of potential hydropower, according to
the following formulae:
Eown_max = Conv . g.η. Qaff . (Hmean – Hclosure)
Eown_mif = Conv . g. η. (Qaff – MIFaff).(Hmean – Hclosure)
Eprel = Conv . g. h . Σj q j.(h j – Hclosure)
Eown_res = Eown_mif – Eprel
Eup_max = Conv . g. η . Qup_hyd . ( Hupstream_clos –
Hclosure)
Eup_res = Conv . g. η . (Qup_ant – MIFups).(
Hupstream_clos – Hclosure)
58 Hydropower & Dams Issue Five, 2009
Annotations
Eown_max = maximum annual potential hydropower
relating to the current watershed without
considering upstream flow contributions,
calculated with the total theoretically
available flow in the basin itself (GWh/year)
Eown_mif = maximum annual potential hydropower
relating to the current watershed, without
considering upstream flow contributions,
calculated taking into account the
minimum instream flow respect (GWh/year)
Eprel = annual potential hydropower relating to the
actual withdrawals in the current watershed
(GWh/year)
Eown_res = residual annual potential hydropower
relating to the current watershed, without
considering upstream flow contributions,
calculated taking into account the minimum
instream flow and the planned actual
withdrawals (GWh/year)
Eup_max = maximum annual hydropower potential
relating to the flow coming from the
upstream watersheds, and calculated with
the total theoretically available flow
(GWh/year)
Eup_res = maximum annual hydropower potential
relating to the flow coming from the
upstream watersheds, calculated taking into
account minimum instream flow and the
actual withdrawals scheme (GWh/year)
Etot_max = maximum total annual potential hydropower
relating to the current watershed,
considering also the energy associated to
upstream flow contributions, calculated with
total theoretically available flow(GWh/year)
Etot_res = maximum total annual potential
hydropower relating to the current
watershed, considering also the energy
related to upstream flow contributions,
calculated taking into account the minimum
instream flow and the planned actual
withdrawals (GWh/year)
Esp_max = maximum total annual hydropower potential
specific to each unit length, calculated with
the total theoretically available flow
(GWh/year/km)
Esp_res = maximum total annual hydropower potential
specific to each unit length, taking into
account also the energy associated with the
upstream flow contributions, and calculated
taking into account the minimum instream
flow and the actual planned withdrawals
(GWh/year/km)
Per_tot = loss of hydropower potential, that is the
portion of energy which is not usable
because of the minimum instream flow and
the actual withdrawals
Conv = unit transformation coefficient 24 ×365 ×10-6
(= 0.00876) to obtain the potential
hydropower in terms of GWh/year;
Hmean = mean elevation of the current watershed,
calculated as the integral weighted
elevations of the ipsographic curves (el.);
Hclosure = elevation of the watershed closure point (el.)
Hupstream_clos =elevation of the upstream watershed closure
point (el.);
A= area of the current watershed (m2);
L= distance between the upstream watersheds
closure points and the current watershed
closure point (km);
g = gravity acceleration (9.81 m/s2);
η= energy efficiency of the system (0.8);
q j = mean annual withdrawals from the current
watershed (+ positive )
or restored flows to the current watershed (-
negative) in a particular point ‘j’ (m3/s)
hj = elevation over the see level of the ‘j’ points
where the flows are taken or restored (el.);
MIFaff = minimum instream flow Qaff ×0.1 (m3/s);
MIFups = minimum instream flow Qup_ant ×0.1
(m3/s).
Fig. 2. Maximum
potential hydropower
in Italy.
Hydropower & Dams Issue Five, 2009 59
Etot_max = Eown_max + Eup_max
Etot_res = Eown_res + Eup_res
Esp_max = 103. Eown_max / A0.5 + Eup_max / L
Esp_res = 103 . Eown_res / A0.5 + Eup_res / L
Per_tot = (Esp_max - Esp_res) / Esp_max
See Table of annotations, for definitions.
2. Application of the methodology and
conclusions
The maximum potential hydropower calculated for
Italy, using the procedure which has been described, is
shown in Fig. 2 using a colour range scale.
A large amount of potential can be observed along
the Alpine range and in some of the river basins in the
Appennins, where there are high geodetic heads and
local climatic conditions characterized by intensive
precipitation. The total value of the maximum
hydropower potential, obtained with this methodolo-
gy, is approximately 190 000 GWh/year. This value
assumes an 80 per cent total efficiency, and does not
take into account the effects of the actual uses of
water.
The procedure for the appraisal of the residual
hydropower potential described in the present work,
was applied to the case of the Basilicata region in
Italy. A sub-model with 78 structured watersheds was
built. The value of the minimum instream flow (MIF)
was defined as a function of the annual mean flow,
and withdrawals were taken into account.
On the basis of these data and the method desdribed,
two maps of hydropower potential for the Basilicata
region could be created. In Fig. 3, a comparison
between the maximum (natural) and the residual
potential hydropower (considering MIF and with-
drawals) is shown.
Some basins in the central and southern part of the
region have been found to be interesting from the
point of view of a more extensive hydropower study in
a watercourse scale (particularly those from the Sinni
and Basento river).
The method was found to be a quite useful tool to
produce maps, at a national or regional scale, which
gives a first approach for the identification of interest
areas with a residual hydropower potential. These
maps may provide the support to administrations,
decision makers and stakeholders, to make Energy
Master Plans, or assess and implement small scale
hydropower plants ◊.
References
1. Alterach, J., Brasi, O., Flamini, B., Peviani, M., Gilli L.,
and Quaglia, G., “Valutazione della disponibilità idrica e
del potenziale di producibilit‡ idroelettrica a scala nazionale
e di bacino” Report 7000597; 2006.
2. Alterach, J., Davitti, A., Elli, A, Garofalo, E., Grasso, F.,
Peviani, M., and Menga, R., “Mappe di potenziale
idroelettrico e metodi di caratterizzazione di nuovi siti”.
Report 08001022; 2007.
3. Commission Economique pour l'Europe, Comite de
l'Energie Electrique, Délégation Italienne“Potentiel brut
hydroelectrique des cours d’eau italiens”; 1956.
Acknowledgement
This article is based on a paper presented at Hidroenergia 08,
organized by The European Hydropower Association, which
took placed in Bled, Slovenia in 2008.
The work described was financed by the Ministry of Economic
Development with the Research Fund for the Italian Electrical
System under the Contract Agreement established with the
Ministry Decree of March 23, 2006.
All the opinions reported in this paper are expressed from a
personal point of view and they do not represent in any way the
Italian Authority for Electricity and Gas.
Fig. 3. Maximum and
residual potential
hydropower in the
Basilicata region.
Julio Alberto Alterach is Expert Engineer of the
Environment and Sustainable Development Department
(TMI) of ERSE, based in Milan, Italy. He is a specialist in
resolving problems related to the numerical optimization of
the hydropower generation and hydropower potential. He
has been responsible for developing tools and guidelines for
better planning and distribution of the small hydro plants.He
has been involved in projects relating to diagnostics and the
modelling of river basins, water and plant management
studies considering the flood safety of dams and developed,
calibrated and hydrologic, hydraulic, statistical and
simulations. He has authored a number of papers in the field
of sustainable reservoir management and the evaluation of
hydropower potential.
Prof Dr Maximo A. Peviani is an expert scientist working
at ERSE SpA (Milan, Italy) and he is also a Professor at the
University of La Tuscia (Viterbo, Italy) and at UNESCO-
IHE (Delft, The Netherlands). He has been leading multi-
disciplinary groups both for research and applied
engineering in hydropower and reservoir management
related projects. He acts as Coordinator of the SEE
HYDROPOWER project (funded by the SEE Transnational
Cooperation Programme - EU)
Alessandro Davitti has a BSc in Civil Engineering (2004),
and a Master’s degree in Hydraulic Engineering (2007),
both from the Politecnico of Milan, Italy. In 2007 he joined
CESI Ricerca as a Hydro Developer Engineer. One of his
main activities was developing software for the evaluation
of the technical and economic feasibility of small hydro
plants. He then worked (2008 until April 2009) as an
Assistant Civil Engineer with Techint, Italy.
Milena Vergata qualified with a degree in Accountancy
Programming from the Technical High School of Milan.
Since 1988 she has worked for ERSE SpA (formerly CESI
Ricerca), specializing in the development of database
applications, visual basic applications, and geographic
information systems. She then studied territorial analysis
and modelling techniques using ArcView, a dedicated
software package developed by the Environmental System
Research Institute.
ERSE SpA, Via R. Rubattino 54, 20134 Milano, Italy.
Ing. Gervasio Ciaccia received his MSc degree in
Mechanical Engineering from the Polytechnic of Turin,
Italy, and took postgraduate studies specializing in
Management of Energy and Environment at the University
of Rome ‘Sapienza’. He then worked in ST Microelectronics
and at the University of Rome ‘Sapienza’. He has also been
a consultant to GSE responsible for the regional energy plan
in Basilicata. At present he is an official at the Italian
Regulatory Authority for Electricity and Gas (AEEG).
AEEG - Autorità per l’Energia Elettrica e il Gas, Piazza
Cavour 5, 20121 Milan, Italy.
Prof. Fulvio Fontini was awarded his MSc degree from
University College, London and his PhD from the
University of Siena, Italy Has been teaching at the
Universities of Siena and Florence, Italy, and has been a
visiting researcher at the University of Saarbruecken,
Germany. At present he is Professor of Economics at the
University of Padua, Italy.
Università degli Studi di Padova, via 8 Febbraio 2, 35122
Padova, Italy.
J. Alterach
G. Ciaccia
A. Davitti
M. Vergata
M. Peviani
F. Fontini
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... In another study, a GIS study was conducted to determine the amount and size of various potential microhydro projects in an exemplary region in order to accurately understand hydro resources at both regional and local scale (Alterach et al., 2009;Forrest, 2009;Jorgensen, 2009;Kusrea, Baruah, Bordoloi, & Patra, 2010;Monk, Joyce, & Homenuke, 2009;Rojanamon, Chaisomphob, & Bureekul, 2009;Stadler et al., 2009;Yi, Lee, & Shim, 2010). Due to India's enormous energy demand, the geographic information system's spatial characteristics and using relevant hydrological models, hydroelectric potentials of a region are automatically scanned and determined (Kusrea et al., 2010). ...
... A methodology was proposed to assess the residual hydropower potential in Italy, which took into consideration the present utilization (ie. irrigation usage and drinking water), and it had a numerical technique coupled with GIS [12]. In order to completely comprehend the potential existing for SHP (50 kW-10 MW), there was an innovative method developed by Norwegian Water and Energy Directorate (NVE) which was used for resource mapping using GIS technology between the years of 2002-2004 ([14]). ...
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Some of the first outcomes of a project aiming at mapping the renewable energy potential in Lesotho are hereby presented. In particular, the present paper deals with the task of the project devoted to produce a digital hydrographic map of Lesotho and an associated geographic database. Different geographical, meteorological and hydrological data were collected in the first steps of the project. The hydrographic network was derived in vector format from a digital elevation model of Lesotho using geoprocessing tools in GIS environment. Results were compared with existing cartography and satellite images. Moreover, a methodology proposed in literature for the assessment of the theoretical maximum hydroelectric producibility at watershed level in Italy was applied to one of the main catchment areas of Lesotho. The activities planned to fulfil the objectives of the project are finally outlined.
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Hydroelectric power (HEP) sites in Balephi River valley, Nepal, were identified using remote sensing and ancillary data. Historical discharge data were used to identify 50% (2004–05) and 90% (2003–04) dependable years. Temporal snow cover, temperature and precipitation for dependable years were assessed using MODIS snow cover, LST and NOAA-CPC data, respectively. Snowmelt runoff model was used to estimate discharge with Nash–Sutcliffe model efficiency coefficient obtained as 0.86 and 0.89 for 50% and 90% dependable years, respectively. While combining design discharge corresponding to 50th percentile flow with hydraulic head determined from digital elevation model, the power potential was computed for dependable years. Five HEP sites were identified with power potential varying from 7.49 to 13.48 MW (50% dependable year) and 4.81 to 8.37 MW (90% dependable year). Sensitivity analysis of assessed potential was analyzed, and up to 31% variation in discharge and consequent changes in power potential were observed.
Article
Currently large-scale studies of water-power potential of minor and mean rivers are being conducted to identify location of prospective hydropower plants and estimate their manufacture and economic efficiency. Because of tight schedule, large study area and large number of criteria involved in choosing prospective hydropower plants, it is necessary to use modern methods and technologies to solve the problem. This paper reviews the methodology that allows performing multi-criteria analysis to find locations on plain rivers suitable for hydropower development. All estimations were performed using geographic information systems (GIS). Traditional way to find location for prospective hydropower plants consists in comparing several variants of location for hydropower development and several marks of normal pond level. Unlike traditional method, developed methodology and GIS-based tools allow analyzing large number of locations and considerably automating calculations.
  • J Alterach
  • O Brasi
  • B Flamini
  • M Peviani
  • L Gilli
  • G Quaglia
Alterach, J., Brasi, O., Flamini, B., Peviani, M., Gilli L., and Quaglia, G., "Valutazione della disponibilità idrica e del potenziale di producibilit ‡ idroelettrica a scala nazionale e di bacino" Report 7000597; 2006.
Mappe di potenziale idroelettrico e metodi di caratterizzazione di nuovi siti
  • J Alterach
  • A Davitti
  • A Elli
  • E Garofalo
  • F Grasso
  • M Peviani
  • R Menga
Alterach, J., Davitti, A., Elli, A, Garofalo, E., Grasso, F., Peviani, M., and Menga, R., "Mappe di potenziale idroelettrico e metodi di caratterizzazione di nuovi siti". Report 08001022; 2007.