SWAT application in intensive irrigation systems : model modification , calibration and 1 validation

14 The Soil and Water Assessment Tool (SWAT) is a well established, distributed, eco15 hydrologic model. However, using the study case of an agricultural intensive irrigated 16 watershed, it was shown that all the model versions are not able to appropriately reproduce the 17 total streamflow in such system when the irrigation source is outside the watershed. The 18 objective of this study was to modify the SWAT2005 version for correctly simulating the 19 main hydrological processes. Crop yield, total streamflow, total suspended sediment (TSS) 20 losses and phosphorus load calibration and validation were performed using field survey 21 information and water quantity and quality data recorded during 2008 and 2009 years in Del 22 Reguero irrigated watershed in Spain. The goodness of the calibration and validation results 23 was assessed using five statistical measures, including the Nash-Sutcliffe efficiency (NSE). 24 Results indicated that the average annual crop yield and actual evapotranspiration estimations 25