Assessing the impact of dams on groundwater resources

The most sensible effect of dams is altering the hydrologic regiment of the lower area. Also, dams could supply a base debit and change the groundwater table levels. In this research, the Salmaan dam and its effects on the hydrologic system of Qir and Karezin plains and underground water level fluctuations are investigated to estimate the effectiveness of the dam in mitigating the effects of droughts. The methodology is based on literature reviewing, field measurements and statistical analysis for which the data of underground water level of the plain and in observational wells, the Qara Aqaj river debit, wells’ debit and precipitation rate were gathered for the period of 1993 to 2011. Also, in order to process the data the following software were used: ArcGIS, Google Earth, Arc Hydro tools extension, and MS Excel. The results showed that during the study period, 10 years have experienced drought in which the worst effect belonged to the 4 years period drought of 2003 to 2001 as it reduced the debit to zero. Also, the Salmaan dam has changed the hydrologic regiment and caused a sustainable summertime debit. However, due to the insufficient supply of the aquifers of Qir and Karezin, annually, 5 million cubic meters of the aquifer volume is reduced and the water table level in all wells are falling down by different rates. Therefore, it could be said that the Salmaan dam could not be effective in mitigating the effects of the droughts occurred.