Estimation of Groundwater Recharge Rate Using a Distributed Model (Case Study of Rafsanjan Aquifer, Kerman Province)

Water balance estimation techniques are one of the main issues in hydrology and the tools to face the important hydrological problems. One of the most important challenges to estimate the groundwater balance components is uncertainty in the proposed inflow and outflow parameters, such as recharge rate. The recharge rate is varied temporally and spatially and it's directly measurement is very difficult. For this purpose, in this study to accurately estimate the recharge rate component of groundwater balance, WetSpass-M distributed model was applied using the meteorological data, landuse map, soil texture map, leaf area index map using Landsat8 images and operation wells data (irrigation of gardens and agricultural lands, industrial and drinking uses) in the study area of Rafsanjan plain, Kerman province. The model was run monthly for 8 years. In order to calibrate and validate the model, monthly surface flow measured data of the hydrometric station was used. Due to the negligible surface flow rates in the study area, actual evapotranspiration data estimated by remote sensing techniques were also used to evaluate and control the reliability of the data and different components of the water balance. According to the previous studies, the mean total precipitation and the average withdrawal from the operation wells during the simulation period are 300 and 683 MCM/year, respectively. The estimated evapotranspiration and groundwater recharge rate were averagely 564.7 and 422.1 MCM/year, respectively. The model results indicated that the two components of recharge and evapotranspiration rates contribute a large portion in the water balance of the plain.