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Citation: Alexakis D. Μanagement Options of a Brackish Water Spring. Case Study: Almyros Spring (Heraklion,
Greece). Austin J Hydrol. 2016; 3(1): 1017.
Austin J Hydrol - Volume 3 Issue 1 - 2016
ISSN : 2380-0763 | www.austinpublishinggroup.com
Alexakis. © All rights are reserved
Austin Journal of Hydrology
Open Access
Abstract
Management options of brackish water springs seemed to attract many
researchers the last decades. The unsuitable quality of the brackish water
resources is generally considered as a great barrier to their application for
irrigation or human consumption. The main goal of the development of brackish
spring water is to obtain a good quality status for water body. This goal can be
achieved by taking measures against seawater intrusion (controlled withdrawals,
increase fresh water head by dam construction) or by applying desalination
methods (e.g. reverse οsmosis, ε lectrodialysis). A simplied owchart has been
presented to develop the brackish spring water in coastal aquifers. The example
of the Almyros Heraklion spring water (Crete, Greece) is discussed.
Keywords: Brackish water; Water quality; Karstic spring; Almyros spring;
Crete
Introduction
Among the possible solutions to combat water scarcity problems
in Mediterranean Region, the rst priority is usually given to the
sustainable use of existing water resources. According to many
scientists [1-4], among the main pillars of water management
strategies are: (a) to apply measures for ecient use of fresh water,
and (b) to develop management of non-conventional water resources
(e.g. rainwater harvesting, recycled water and brackish water).
Brackish water use can be a possible solution to the water scarcity
problems [4-6].
e karstic aquifers in many Mediterranean coasts are the main
source of freshwater while they exhibit a very fragile behavior because
these systems are prone to seawater intrusion and consequently to
the deterioration of freshwater quality. Moreover, issues dealing
with karstic springs seem to attract many scientists worldwide [6-8].
It is noteworthy to mention that a water mixture composed of only
5% seawater and 95% freshwater exceeds the parametric values and
criteria for drinking and irrigation uses [4,6,9]. Needless to say that
management problem of a brackish spring is not an exclusive matter
of quantity but also of water quality.
Brackish water management options
e goals of the European Water Framework Directive [10]
include, among others, the attainment of good chemical and
ecological status for surface water bodies and of good quantitative and
chemical status for groundwater bodies. e computation of water
balances, the denition of the status of water body, the designing of
monitoring networks as well as the management of exploitation plans
are quite dicult tasks to be carried out in karstic coastal aquifers due
to possibility of seawater intrusion.
Hydrogeological science has advanced the state of the art on
seawater intrusion, but has not found a solution yet. e main goal of
the management of brackish spring water is to obtain a good quality
status for water body.
Case Report
Μanagement Options of a Brackish Water Spring. Case
Study: Almyros Spring (Heraklion, Greece)
Alexakis D*
Laboratory of Reclamation Works and Water Resources
Management, National and Technical University of
Athens, Greece
*Corresponding author: Alexakis D, Laboratory of
Reclamation Works and Water Resources Management,
School of Rural and Surveying Engineering, National and
Technical University of Athens, 9 Heroon Polytechniou,
15780 Zografou, Athens, Greece
Received: October 05, 2015; Accepted: January 19,
2016; Published: January 22, 2016
e main factors controlling the selection of a particular
development method are: (a) geological conditions, (b) economic
factors, and (c) water needs of the area. e main actions comprising
a management plan of brackish water may be summarized as follows
(Figure 1 & Table 1): (a) to prevent the water contamination by taking
measures against seawater intrusion (upraise the fresh water hydraulic
head by a dam construction at the spring mouth, to block entirely or
at least partly the seawater intrusion by a special marine dam), (b) to
treat the brackish water by selecting the most suitable desalination
method (e.g. distillation, reverse osmosis, electrodialysis), and (c)
to estimate the useful water potential of sources with varying water
Brackish spring water
Is the water
quality
acceptable?
STORAGE
YES
Is it feasible
to prevent
water
contaminaon?
NO
Is it feasible to
treat
water?
NO
YES YES
NO
NO USE
TAKE MEASURES
TREATMENT
(Desalinaon)
USE
-Drinking purposes
Figure 1: Proposed simplied owchart for the development of a brackish
water spring.
Austin J Hydrol 3(1): id1017 (2016) - Page - 02
Alexakis D Austin Publishing Group
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quality which is based on the identication of the period at which all
quality parameters are within the acceptable limits which are dictated
by the quality requirements of the use.
A variety of technologies for treating brackish water has been
developed over the years, including primarily reverse osmosis, vapor
compression and distillation. Desalination systems can be categorized
in the following types: (a) those powered by renewable energy sources
(solar, wind, etc), and (b) those powered by conventional energy
sources (gas, oil, electricity). Spain has the largest in Europe and the
world’s h largest desalination capacity at 800 km3 per day from
facilities at Almeria (5), Alicante (7), Barcelona (1), Murcia (5), Malaga
(2) and Girona (1) which allow the Spanish regions to maintain their
hydro-independence [11]. e price of desalinated water has been
expensive in comparison with conventional water supplies. Since
desalination plants consume vast quantities of power, water prices
and drinking water availability are inuenced from fossil fuel prices.
Karagiannis and Soldatos [12] reported that desalination is still not
a desirable option due to the large amounts of the required energy
(Table 2). e desalination facility in Lastovo (Croatia) produces
high costly water ($2.05 per m3) as a result of a high investment costs,
especially civil works [13].
Many researchers have performed cost analysis of desalinated
water [12,14,15]. According to these studies, the price of desalinated
water in 2010 varied between $0.2-1.2/m3 for brackish water and $
0.3-3.2/m3 for seawater. Other researchers [16,17] reported that the
prices for water abstracted from wells, lakes or rivers are at least two
or three times lower than prices for desalinated water.
Case Study
Description of the almyros spring
e spring of Almyros is located about 8 km from Heraklion city
(Crete Island, Greece). e average annual volume of water discharged
at the spring is about 240 million m3 [18]. It is a periodically brackish
spring, its discharge range from 4 m3 s-1 in dry period to 70-80 m3 s-1 in
the wet period [19]; while the electric conductivity value of Almyros
spring water ranges from 331 to 18430 µS cm-1 [20]. Regarding the
mechanism of seawater intrusion of the Almyros karstic system,
most geologists, following Breznik [21], assumes that fresh water is
becoming brackish at a mixing reservoir.
Development of the almyros spring
e development of the spring is of prominent socio-economical
importance for both the irrigation and drinking demands of
Heraklion-Crete. Obtaining water of suitable quality from Almyros
brackish spring is a challenging issue that requires interdisciplinary
scientic cooperation. Development of this spring seemed to
attract many researchers [3,4,6,21-31] in order to better understand
the function mechanism of the Almyros karstic system, but still,
successfully realized solutions of coastal karstic springs protection
from sea water intrusion were not achieved. e scope of the Almyros
experiment conducted in 1987 [32] was to articially raise the fresh
water level in the Almyros spring reservoir up to 10 m a.s.l. and nally
to increase the hydraulic head in the karstic conduit aiming to block,
at least partly, the intrusion of seawater. e experiment results were
not negative, since it is outlined that a dam with a height of 6 m can
improve the water quality of the spring only by a magnitude of about
500 mg L-1. Maramathas et al. [19] applied a model for the simulation
of the periodically brackish spring of Almyros and concluded that an
upraising of the outlet point of Almyros spring up to the elevation
of 26 m will block totally the seawater intrusion. Panagopoulos and
Lambrakis [8] presented that the Almyros karstic system presents a
bimodal character: (a) the rst component presents a decorrelation
time of the rst 6 days which is attributed to the quick drainage of the
aquifer by the karstic conduits, and (b) the second component shows
Main goalMethod of development Technology Advantages Disadvantages
Preventing water
contamination
Interception of fresh water
inland of the seawater
inuence
Construction of
boreholes or tunnels
No further water treatment
is required
• Difculties to locate the fresh water
• Difculties in the determination of the
amount of fresh water that could be
taken from the aquifer without sea water
intrusion going further inland
Upraise the fresh water
hydraulic head and block the
seawater intrusion
Construction of a dam
in front of the karstic
spring
Many possibilities to block
seawater intrusion
• Difculties in the determination of the
sufcient upraising
• Difculties in the estimation of the
freshwater loss to the sea
Block at least partly the lower
conduit
Construction of a
special marine dam
Many possibilities to block
seawater intrusion
• Difculties in locating the saturated karstic
conduit
Treating water Desalination
Reverse osmosis,
vapour compression,
distillation
The last years desalination
methods have been
technically improved
• High economic cost of basic overhead
• High requirements of energy amounts
which is costly both in environmental
pollution and in money terms
• Concentrate disposal (NaSO4, NaCl, etc)
Estimation of useful
water potential Assessing the water potential Apply fuzzy sets
No further water treatment
is required
Low economic cost
• Strong quality seasonality
• The estimated suitable water quantities
are a small proportion of the annual water
volumes discharged
Table 1: Development technologies matrix for a brackish water spring.
Desalination Technology Short Description Size of unit (m3/day) Cost
(Euro per m3)Source of Information
Reverse osmosis (RO) Membrane method
< 20
20-1200
40000-46000
4.50 – 10.32
0.62 – 1.06
0.21 – 0.43 [12, 34]
vapour compression (VC) Thermal method 1000-1200 1.61 - 2.13 [12,35]
Table 2: Cost of water produced (per m3) and thermal methods.
Austin J Hydrol 3(1): id1017 (2016) - Page - 03
Alexakis D Austin Publishing Group
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a decorrelation time of 55 days, which is explained by the presence
of a dominant base ow. Arb et al. [20] concluded that the distance
between the Almyros spring and the zone where the seawater intrudes
into the conduit can be calculated by using the salinity variations
as a tracer and that the volume of the karstic conduit between the
spring and the mixing zone was calculated to be constant. Tsakiris
et al. [31] have applied two fuzzy methodologies in order to assess
the water quantity of the spring which is suitable for various uses.
e min intersection rule is more appropriate for the appraisal of the
water potential for drinking purpose; while the multicriteria ltering
method is a exible method for classifying annual water quantities
into quality categories in respect to European Union directives and
irrigation guidelines. Alexakis and Tsakiris [4] reported that the
statistical analysis test identied signicant trends for the determined
quantity parameters (annual discharge) and the determined quality
parameter (chloride concentration). Moreover, they concluded that
climate change is most likely to provoke the seawater intrusion
in Almyros karstic system which will be caused by the reduction
of freshwater hydraulic head. Concerning desalination option,
Karagiannis and Soldatos [12] reported that the cost of a desalination
system with capacity of 60000 m3 per day, which is comparable with
the water demands of the city of Heraklion, is in the range of 0.26-0.54
$. According to Mohsen [33], the cost of a major desalination plant
with a capacity of 250 million m3 per year, is about $ 1 billion (about
$250 million for required operating expenses for een years and $
600-700 million for basic overhead). For a major desalination unit
with capacity of 250 million m3, which is comparable to the average
annual volume of Almyros spring water, the cost of brackish water
desalination is about 4$/m3. Consequently, desalination of Almyros
spring water is still an expensive solution to obtain acceptable water
quality (Table 2).
A study conducted by Tsakiris and Alexakis [6] indicated that a
signicant impact on the water quality and quantity of the Almyros
spring can be attributed even to the abstraction of a relatively small
quantity of groundwater, in other words, Almyros karstic system
exhibits a very fragile behavior. According to Tsakiris and Alexakis
[6], the detected changes in the water quality of the Almyros spring
during the dry period could be attributed to the withdrawal of
groundwater from the recharge area.
Investigation of innovative methods for the mapping of
almyros karstic system
e karstic conduits and large voids that present in karstic aquifers
are dicult, even impossible to be localized from the surface by any
method, geophysical as well as geological investigation. Sinkholes and
paleo-karstic conduits in karstic environments can be a nightmare
or a dream [36]. Geophysics can help to investigate a karstic aquifer
but the geophysical method and parameters that may be best suited
for the problem at hand are a less certain choice. A karst mapping
by using the new geophysical methods could investigate the karstic
conduits that hydraulically connect the sea with the brackish springs.
e method of MRS (Magnetic Resonance Sounding) has been
applied to Hortus karst area (Lamalou spring, France). According to
Vouillamoz et al. [37] the MRS proved a useful tool for karst mapping
because it can identify the spatial variations of transmissivity and
permeability that delineate karstic structures bearing water (as caves
and conduits). Consequently, the objective of the Almyros karst
mapping using the new method of MRS is to localize the saturated
karstic aquifer and delineate the spring function mechanism. e
localization of the karstic conduit is a very important parameter in
order to better develop and manage the brackish springs and combat
the water scarcity problems.
Conclusion
e spring function mechanism of coastal karstic springs has not
been yet fully understood. e localization of the saturated karstic
aquifer, the knowledge of the geometry and position of the main
karstic conduit should be used successfully for the implementation
of the necessary measures for the management of the spring water.
e detailed exploration of the Almyros karstic conduit is necessary
in order to delineate the hydraulic connection between the sea and
the spring. e proposed management and development scenario of
Almyros karstic spring has the following steps: (a) to prevent water
contamination by taking measures (e.g. raising up articially the fresh
hydraulic head, constructing a dam, controlled withdrawals), and (b)
to apply fuzzy methodologies for evaluating the water potential with
varying water quality and store suitable water. e high economic
cost of basic overhead as well as the high operating expenses of a
desalination plant should be considered. e desalination is already
an important water management option in energy-rich and water
scarce regions of the world.
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Citation: Alexakis D. Μanagement Options of a Brackish Water Spring. Case Study: Almyros Spring (Heraklion,
Greece). Austin J Hydrol. 2016; 3(1): 1017.
Austin J Hydrol - Volume 3 Issue 1 - 2016
ISSN : 2380-0763 | www.austinpublishinggroup.com
Alexakis. © All rights are reserved
