GROUNDWATER RECHARGE ESTIMATION FOR SHAQLAW-HARRIR BASIN IN KURDISTAN REGION, IRAQ

Increasing water demand in Kurdistan region has prompted the need to quantify the available groundwater resources. In semi-arid region, the groundwater recharge estimation is difficult due to the large variability of hydrological events in space and time. Shaqlawa-Harrir basin covered an area about 1150 km2, and rainfall is the main source for replenishment of moisture and recharge of ground water in the area. Groundwater recharge estimated by employing water balance method based on climatic data, water table fluctuation method (WTF), where measured water table rises are correlated to recharge events (rainfall) and estimating the specific yield of the zone of fluctuation of the groundwater level is required, and environmental tracer (CMB) method depending on chloride concentration in rainfall and groundwater. Four temperature-based equations methods were used to estimate the potential evapotranspiration, actual evapotranspiration, water surplus and deficit. Horton’s infiltration capacity was determined by taking twenty points in different locations, and statistics were used to evaluate the relationship between time and infiltration rate. The result of infiltration capacity shows that the type of infiltration rate ranges between moderate-rapid to slow-moderate. Coefficient of permeability determined for these infiltration points by using the Bindeman method ranges between 1.8*10-6 to 1.4*10-4 m/s. The mean monthly potential evapotranspiration is 120, 174, 194, and 219 mm/year determined by Thornthwaite, Blaney-Criddle, Kharrufa, and Romanenko method respectively. Surface runoff is about 209.6 mm/year and groundwater recharge is 50.9 mm/year by water balance method, 144.5 mm/year by WTF method, and 87.4 mm/year by using chloride as environmental tracer. The water budget is about 10.8*107 m3/year based on the average groundwater recharge and area of the basin.