Hydrological cycle simulation of an irrigation district based on a SWAT model

A distributed hydrological cycle model of an irrigation district was developed based on the SWAT model (Soil and Water Assessment Tool) and an artificial-natural composite of the hydrological cycle was considered. The SWAT model was modified in the aspects of the extraction of ditches, distributed subbasins and hydrologic response units, and the calculation method of the crop’s actual ET  . The applicability of the model was validated in the Fenhe irrigation district. The information on hydrology, weather and water use from 1996 to 2001 in the Fenhe irrigation district was used to simulate and analyze the water balance. The sensitive parameters were estimated by EnsEns, RE   and R2R2. The model was further validated with the monthly flow data from 2002 to 2006. The results showed that the simulated results of two monitoring points meet the estimated requirements. The RE value of the average annual runoff at the Erba Station varied from −7.34% to 19.13% except a low RE value (−30.70%) in 2006. The RE of the average annual runoff at the Yitang station was from −17.21% to 9.86% with an exceptional RE   value (−21.13%) in 2003. From the monthly simulated results, the R2R2 of the monthly runoff at the Erba and Yitang stations was 0.81 and 0.77, respectively. The EnsEns of the monthly runoff was 0.72 and 0.65, respectively. A modified SWAT model was applicable for water balance simulation at the Fenhe irrigation district.