The stable isotopes of oxygen and hydrogen in groundwater and precipitation were integrated for the description of groundwater flow in the Kouris catchment (Cyprus). The catchment consists of an ophiolitic complex in the North and sediments in the South. It is characterized by strong heterogeneity of the underground media and steep slopes of the topography.The regression line, constructed from the data of 70 rainfall samples, is described by the equation: dDZ6.6d 18 OC10.9, which shows evaporation during precipitation. The altitude gradients in the precipitation were estimated to be K1.7‰/100 m for dD and -0.27/100 m for d 18O. The stable isotope analysis of 234 groundwater samples reflected fractionation due to evaporation. The origin of groundwaters in the catchment was described based on the regression equation between surface elevations and dD contents for 33 selected springs of the ophiolitic complex. It was found that the groundwaters in the ophiolitic aquifer and in the consolidated sediments originated from local recharge at high and low altitudes, respectively. On the contrary, the groundwater in the alluvium aquifer originates from the high altitudes in the ophiolitic complex. Additionally, dD data were used for the calibration of the recharge rates for a steady state groundwater flow and transport model. The resulting calibrated total steady state recharge rate was 100-130 mm per year.

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The Kouris catchment in Cyprus is currently experiencing a scarcity of water resources due to the semi-arid climate across the southern part of the region, a series of dry years, and recent surface/subsurface water over-extraction. The catchment consists of the upper part of an ophiolitic complex in the North, which is considered a very significant aquifer for Cyprus, and an overlying sedimentary complex in the South, which has low water storage capacity. Water balance calculations are conducted using a steady state groundwater model. The recharge rate was calculated to be between 12 and 16% of the total annual rainfall. This agrees, with an estimate based on the mass balance of chloride. When the rate of extraction was increased to a value close to the present water demand, river baseflow was reduced from 25 to 18 Mm 3 per year. Other negative impacts were extreme drawdowns and drying up of springs.

Abstract:The Kouris catchment is located in the south of the Troodos massif in Cyprus. The hydrology is driven by a Mediterranean climate, a mountainous topography, and a complex distribution of hydrogeological properties resulting from complex geology.To quantify the regional water balance further, a simple method using continuous streamflow records in the River Limnatis (Kouris catchment) was applied to calculate the actual evapotranspiration rate in the dry seasons. It was found that daily cycles of streamflow, recorded by automatic pressure logger, were caused by direct evaporation from the groundwater table and by transpiration of riparian forest. The daily amounts of 'missing' streamflow were calculated for the period 30 October-4 November 2001 and were extrapolated to the entire dry season and to the whole Kouris catchment. The actual evapotranspiration rate from the alluvial aquifer of the region is 2Ð4 š 0Ð5 Mm 3 for April-September 2001. The validity of the assumptions and the uncertainties in the estimates used in the method are discussed.

The Kouris catchment is located in the south of the Troodos massif in Cyprus. It constitutes one of the biggest catchments of the island with important freshwater resources. Geologically, the catchment includes an ophiolitic complex outcropping in the north which is overlaid by sedimentary rocks in the south. The hydrology is driven by a Mediterranean climate, a mountainous topography, and a complex distribution of the hydrogeological properties resulting from the complex geology.To improve the understanding of groundwater hydrology of the Kouris catchment, 176 groundwater and precipitation samples were collected and their 3 H contents were analyzed. The three-dimensional 3 H transport in the groundwater was simulated by the PMPATH code. For numerical modelling, a regional input function of 3 H in precipitation was constructed from a linear regression between data for Cyprus and for neighboring meteorological stations. The calculated residence times for the groundwaters in the sedimentary aquifer and Pillow Lavas were greater than 48 a and were considerably greater than those of the ophiolitic complex (14-30 a). The calibrated aquifer porosities were in a range of 0.05-0.06. The PMPATH model was applied for delineation of spring catchments that were represented by quite narrow zones of lengths up to 5 km.Another contribution resulting from the 3 H analysis was a better understanding of the river-aquifer interactions. In most of the southern part, the lithified sediments received only negligible amounts of water from the rivers, while the alluvial aquifer contained mostly water infiltrated from rivers. The largest springs in the southern part, associated with the alluvial aquifer, also discharged water identical to that in the rivers.