Modeling the Risk of the Salt for Polluting Groundwater Irrigation with Recycled Water and Ground Water Using HYDRUS-1 D

Abstract

Long-term irrigation with recycled water (RW) that contains high salt may pollute groundwater. The HYDRUS-1D model was texted against soil water content and electrical conductivity (ECe) observed in a summer maize and winter wheat rotational field irrigated with ground water (GW) and RW; then, the risk for polluting groundwater in two regions of Beijing was evaluated. The comparisons indicated that the simulated soil water content and ECe values were generally in agreement with the field observations, indicating the reliability of HYDRUS-1D in soils irrigated with GW and RW. The regional prediction results of the proposed simulation model indicated that the average soil ECe at the bottom of vadose zones ranged from 0.400 to 0.896 dS m−1, and the values in the Tongzhou and Daxing Districts irrigated with RW were 1.40 and 1.09 times, respectively, higher than that irrigated with GW over the next 50 years. Five risk indicators represent salt transporting time and values were used. The results of the proposed evaluation model showed that the risk scores ranged from 3.04 to 9.32. In the Tongzhou and Daxing Districts, the risk scores of RW irrigation for polluting groundwater were 1.06 and 1.08 times, respectively, higher than that GW irrigation. The risk scores of GW or RW irrigation for polluting groundwater in the Tongzhou District were 1.75 or 1.72 times, respectively, higher than that in the Daxing District. Considering the small risk difference between GW and RW irrigations, RW can be used in both regions. Due to the different vadose zone structures, the Daxing District is more suitable for RW irrigation. The long-term use of RW for irrigation should consider the salt content of RW and vadose zone structure.