Estimation of Artificial Groundwater Recharge by Flood Water Spreading System in an Arid Region Using Inverse Modeling and SCS Method; A case Study of Mosian Plain

Aims In arid and semi-arid regions, to reduce the impact of infrequent flood, groundwater recharge and decrease flood damages, runoff should be stored through Flood Water Spreading (FWS) systems. The aim of the present study was to estimate of artificial groundwater recharge by flood water spreading system in an arid region using inverse modeling and the Soil- Conservation Service-Curve-Number (SCS-CN) method in Mosian plain. Instruments & Methods The present study is the original research which was done in a computational manner, groundwater recharge by FWS system under arid conditions of west of Iran was estimated using mathematical and empirical methods. The annual component values of the water balance equation were estimated using the mathematical model (MODFLOW). Groundwater recharge by FWS system was estimated using the inverse modeling approach for the study area. Daily rainfall data (1994-2014) was used to estimate the daily runoff from the upland using SCS-CN method. The estimated runoff was used to estimate the groundwater recharge from FWS system. The R-squared statistic test and PMWIM? Software were used. Findings Estimated annual average groundwater recharge by the MODFLOW model and SCS method were 6.55 and 8.47MCM respectively (1994-2014). Comparison between mathematical and empirical models showed minor differences. A minimum of 13mm daily rainfall was required to generate 1mm of recharge from the floodwater spreading system. Conclusion Combination of the mathematical and empirical models can increase the accuracy of the groundwater recharge predictions. Groundwater recharge in FWS system area increase with increasing of rainfall, but after the certain value of precipitation, it is nearly constant due to ponds capacity and infiltration speed limitation.