Irrigation plays a significant role in total water use, especially in areas with a large agricultural production. It was reported that irrigation accounts for more than 60% of water use in Hebei Plain, and 90% in northern Texas. In recent years, these two regions were suffering the increasing water demands due to climate change, population growth, and long-term intensive agricultural irrigation. In this study, we estimated the potential crop water demand and overall water resources using the Soil and Water Assessment Tool (SWAT). Some impact factors were applied for the actual irrigation calculation, including the information of the percentage of the irrigation area and a ratio indicating the deficit irrigation strategy. Then the irrigation water of each subbasin were entered back into the SWAT for hydrological evaluation. To better simulate the crop growth and hydrological conditions, the key parameters were calibrated.
Results/Conclusions
Our results indicate the proposed method can be used to estimate the spatiotemporal variation of the amount of actual irrigation use in different regions. The overall R2 is 0.88, and RMSE is 56 million m3 in northern Texas. The total irrigation use fluctuated dramatically in different years, indicating precipitation plays an essential role. In contrast, irrigation strategies influenced the spatial pattern of irrigation at most. Irrigation has an important impact on streamflow and groundwater, while it is more significant in Hebei compared to Texas. The findings about irrigation from this study is of great use to explore the role of irrigation in watershed hydrology for water sustainability.