Geographical and climatic features

The Akrotiri aquifer, located in the southern most part of Cyprus, in the Eastern Mediterranean, is part of a peninsula situated between two shorelines at elevations ranging from -2 masl to 30 masl. The aquifer exhibits a characteristic semi-arid climate: the ETP is, on average, more than double the precipitation (average 500 mm/year), a situation typical for many Mediterranean coastal areas. It is the most important porous aquifer of Southern Cyprus and extends from Limassol in the east to Episkopi in the west, with an approximate surface area of 45 km² (Fig. 1).

The Kouris River (situated in the west) is the largest river of Cyprus and drains a catchment area of 300 km², extending far up into the Troodos Mountains. The catchment of the Garyllis River (located in the east) is much smaller, only 65 km² (Hydrological Year Book, 1984).

The hydrological and climatic condition of the topographic catchment of the Kouris River, extending up into the Troodos massif, reaching altitudes of 1600 masl within a distance of 30 km, is very different from the situation on the Akrotiri Peninsula. The average precipitation within its catchment (surface area 290km²) is 730 mm for the years between 1951-1980.

Fig. 1: Main physiographic features of the Akrotiri Peninsula, Southern Cyprus, showing the boundary of the Akrotiri aquifer with respect to the main villages, the most important plantations, the Kouris and Garyllis rivers and other features  (dams, salt lake).

Aquifer description and exploitation history

The Akrotiri aquifer consists of unlithified deposits of post-Pliocene age, deposited in two big fan deltas, and intercalated shoreline and shallow marine deposits. The thicknesses of the delta deposits are between 20-40 m in the east, being typical for the smaller Garyllis river system, and reach up to 120 m in the west, in the area of the Kouris River.

The southern boundary of the aquifer runs along the northern edge of a large salt lake. The water table in the salt-lake is always below sea level, due to very intense evaporation. This leads to the special situation of an internal drainage basin, diverting the hydraulic gradients towards the salt-lake, rather than towards the sea.

Shallowly south-dipping carbonate units form the northern aquifer limit. The connection between the bedrock and the porous aquifer is not well known. Data from drilling records show that there are highly confined, water-bearing units within the limestone. Karst-phenomena have not been explicitly described, but Constantinou (1970) mentions the importance of secondary porosity due to dissolution processes in fractured zones in the limestone successions of the Akrotiri area. Drilling records also suggest a major large-scale tectonic fault zone within the bedrock below the aquifer, with an estimated vertical displacement of several 100 meters.

Exploitation of the aquifer started with the development of two big fruit plantations in the late 1930s. These still exist and cover an area of approximately 11km² in the central part of the aquifer. Since 1940, large amounts of water have been extracted for domestic use and irrigation purposes (average 14 mio. m³/year between 1967 and 1977), leading to problems of seawater intrusion since the 1960s. A total of app. 620 wells and boreholes exist in the Akrotiri aquifer, whereas most of these have been abandoned due to the progressive salinization.

Growing water demand caused by agriculture and the booming tourism in the 1970s and 1980s called for a complete reorientation within regional water management. This led to the construction of the Kouris dam in 1987, about 10 km upstream of the Akrotiri aquifer (Fig 1). The construction of the dam led to a drastic decrease in recharge of the alluvial aquifer. This is when the problem of seawater intrusion started to become imminent. The water table sank below mean sea level over large areas, not even recovering during the rainy season. This caused an inland gradient and, thus, landward movement of seawater, now affecting particularly the western part of the peninsula, but also the eastern part in the area of Limassol.

The extraction record of the Akrotiri aquifer after the construction of the Kouris dam in 1987 shows that until 1990 large quantities (up to 18 mio. m³/year) were still extracted, causing rapid propagation of the seawater front into the aquifer. For the past ten years the extraction volumes have been reduced successively from 18 mio. m³/year in 1990 to about 7 mio. m³/year in the period 1997-1999. Recently, the Akrotiri aquifer was declared a conservation area, and now only limited extraction is permitted and water meters are installed in all wells.

Artificial recharge with dam water is done in three infiltration ponds, which were constructed in the area of the fruit farms and in infiltration ponds in the former Kouris riverbed, whenever water excess is recorded either in the Kouris dam or in the smaller Yeramasoya dam, during winter time. Infiltration of water from the Limassol treatment plant was planned in the Kouris riverbed infiltration ponds, but the water was used directly for irrigation due to an increasing water shortage during the past decade.

Aquifer monitoring and existing data

The Akrotiri aquifer has been monitored by the Cyprus Water Development Department since the beginning of exploitation in the 1940s. Intensified monitoring, however, was implemented in the 1960s, when seawater intrusion started to become a serious threat. A report on the hydrogeology of the Akrotiri Peninsula was published in 1970 by the Cyprus Geological Survey (Constantionou 1970). It gives a very good overview of the different stratigraphic units forming the aquifer itself and the underlying bedrock, and describes the evolution of the seawater intrusion. Further information was collected in connection with the Akrotiri Irrigation Project in 1970 (Humphreys and Sons 1972), and the first groundwater model was done in 1973 (Jackovides 1973), for the time period between 1967 and 1972.

Detailed lysimeter investigations were carried out to assess the recharge in the Akrotiri aquifer ( Kitching et al. 1980).

The feasibility study of the Southern Conveyor Belt, which implied the construction of the Kouris dam, gave rise to another study of the Akrotiri aquifer, in which the first pump tests (eleven) were undertaken, with observation wells to determine the storage coefficients. Within this work, a 2-D flow model (SIM) was done for the time period 1967-1977. From this an estimate of the recharge of the Akrotiri aquifer of 15% from precipitation and 65% from the Kouris river infiltration was obtained (Jackovides 1982).

A diploma thesis was carried out a few years ago, compiling data from borelogs, extractions, water tables, salinity distributions and a finite elemnt model was established, reflecting the  large-scale characteristics. Field data, including 30 vertical electrical conductivity logs, radiomagnetotheluric soundings and geochemical sampling was also carried out within the framework of that study, leading to a conceptual model of the area (Milnes 2000)

The following list of data is available from the Water Development Department for this work for the period 1987-present:

• The Water Development Department (WDD) has published river gauging measurements, precipitation data, extraction data and water table measurements as well as chloride distribution maps, until 1984 in Hydrological Year books.
• 220 borehole logs, which were drilled between 1937-1998.
• Water levels from ca.150 wells and boreholes are available on a monthly base.
• Vertical conductivity measurements in ca. 15 boreholes in the critical zone of seawater intrusion have been done for the past ten years, with a gap in the record between 1994 and 1998, on a quarter-yearly basis.
• Precipitation and evaporation data is provided on a twice-daily basis from the Phasouri meteorological station, which is situated in the central area of the Akrotiri aquifer.
• Extraction rates measured on a monthly basis by water meter, the record being complete for the time period since 1987.
• Records on water importation from the Kouris, the Garyllis and Yeramasoya dams as well as from the sewage plant were provided on a yearly basis.
• Artificial recharge data is available on a monthly basis.
• Chemical and in particular chloride analysis are available for ca. 70 boreholes on a twice-yearly bases.

Site specific problem evaluation

The Akrotiri aquifer has been suffering the consequences of seawater intrusion and salinisation for the past two decades. Many wells have been abandoned and a very costly irrigation system, conveying water from the Kouris dam to the agricultural areas have been implemented. The problem of the irrigation system is, that in times of water shortage (during the summer months), freshwater from the dams is provided in a very limited amount. For the past ten years, the aquifer has been declared a conservation area, where groundwater exploitation takes place mainly to compensate the water shortage during summer. Even though the area has been declared a conservation area (no more new well permits and water meter installation in wells), the authorities do not have a decision making tool to allow them to evaluate, where and which quantities can be extracted to preserve or even ameliorate the overall groundwater quality. For the moment decision of extraction quantities are therefore made according to plot-sizes or seamingly randomly.

It will be an important issue to first understand the functioning of the aquifer (geometry, recharge, boundary conditions), investigate the presence and potential impact of other sources of salinity, in particular from agricultural activity but also from dissolution of evaporitic deposits, to obtain an overall understanding of the system before any optimisation of the present exploitation scheme can be suggested.

References

Constantinou C., 1970, Hydrogeology of the Akrotiri Peninsula, Cyprus Geological Survey Department, Nicosia.

Humphreys and Sons, 1972, The Akrotiri Project, Water Resources, Volumes 4., ODA, UK

Hydrological Year Book Of Cyprus, 1983-1984, 1994, Cyprus Water Development Department, Nicosia.

Jackovides J.,1973, Optimisation of Kouris recharge to minimise subsurface losses of groundwater to sea or salt lake from the Akrotiri Aquifer. Cyprus Water Development Department, Report H/17.

Jackovides J., 1982, Southern Conveyor Project, Feasibility study, Groundwater Resources, Vol.3, Cyprus Water Development Department, Nicosia.

Kitching R., 1975, A mathematical model of the Akrotiri Plio-Pleistocene gravel aquifer, Cyprus. IGS, RN 75/2, London.

Milnes E., 2000, Hydrogeological investigation of the Akrotiri porous aquifer, Southern Cyprus: seawater intrusion modelling. Diploma thesis , Cycle postgrade interuniversitaire, EPFL, UNI-Neuchatel, Spécialisation en hydrogéologie, Neuchâtel, November 2000.