Estimation of the Recharge spatiotemporal pattern by Distribute PRMS model (Case study: Neishaboor watershed)

In this study, distributed Precipitation-Runoff-Modeling-System (PRMS) was used to estimate the spatiotemporal pattern of recharge in monthly time step. To this regard, first, a sensitivity analysis of PRMS model illustrated that the most effective parameters that control hydrologic budget components in the study area are evapotranspiration, preferential flow density, water-holding capacity of soil zone and contributing area in the runoff. After performing the sensitivity analysis, calibration of the PRMS was done using PEST, regarding runoff in hydrometric stations and actual evapotranspiration (ETEns1.0). the Model Calibration and validation period were 7 years (2002-2009) and 2 years (2009-2011), respectively. PRMS calibration based on the two components of the hydrologic budget (runoff and actual ET) led to increase in reliability of calculated recharge. The results revealed that actual ET which had 87 percent of total rainfall and irrigation volume, was the most important component of the hydrologic budget ) while the second one was recharge, which was 12.5% of total rainfall and irrigation volume. The PRMS simulation showed that annually 295 MCM water enters to the aquifer from the surface as recharge, which most of it occurs in mountain foothill and irrigated areas. This recharge happens from November until the following May. Thus, there is no recharge during warm months due to the high amount of evapotranspiration and soil water deficit.