Estimation of groundwater recharge using water surface fluctuation (case study: Shyramyn area)

Groundwater recharge rate is a key component in groundwater modeling. A multitude of methods has been used to estimate groundwater recharge. In this research, natural recharge of groundwater was studied using the Cumulative Rainfall Departure (CRD), Water Table Fluctuation (WTF) and Rainfall Infiltration Breakthrough (RIB) models with regards to existing information in the study area. All models are used to estimate the recharge the fraction of precipitation which infiltrates as well as the fraction of irrigation water that recharges the water table. There are 19 observations wells in the study area and groundwater recharge of the aquifer around these wells were estimated by optimization technical. So, study area was divided into 19 zones using Theissen method. Hydrogeological properties were uniformly distributed throughout each sindividual zone, but varied between zones. Simulated water table exhibits good agreement with observed water table for all zones. The results showed that the rate of the recharge from precipitation estimated by WTF and RIB models ranges from a maximum of 25 and 27 percent to a minimum of 3.4 and 1.1 percent, respectively. The results of the CRD model showed that the fraction of precipitation that infiltrates range from a minimum value of 2.9% and a maximum value of 25%. Also, the estimated fraction of irrigation that acts to recharge the water table by WTF, RIB and CRD models were 40, 33 and 32 percent, respectively. The results indicated that the WTF and RIB models show reliable results rather than CRD model.