Assessment model of rainwater resource utilization and influencing factors in arid and semiarid areas

Arid and semiarid areas generally face problems of natural resource degradation. In this paper, two indicators are proposed to characterize the utilization of rainwater: rainwater resource utilization quantity (RRU, mm) and rainwater resource utilization rate (RRUR, dimensionless ratio). A spatiotemporal assessment model (rainwater utilization assessment [RUA] model) for the RRUR and its influencing factors is constructed. The RUA model is based on Soil and Water Assessment Tool and Geographically Temporal Weighted Regression. The Zuli River Basin, located on the Loess Plateau in China, was selected as the study basin. The results show that the annual averages of the RRU and RRUR are 164 mm and 0.44, respectively, in the study basin. The RRU ranged from 71.4 to 243.2 mm, and the RRUR ranged from 0.32 to 0.53 during the evaluation period. Eight explanatory variables were selected, of which the leaf area index (LAI) and rainfall had a significant positive effect on RRUR, but there was spatial and temporal variability in the effects. The forest rehabilitation and crop rotations that can increase the LAI can effectively increase the RRUR, which increased by 0.10 and 0.11, respectively, and the increase in RRU was at least 36.42 mm, with a water volume of 3.85 × 108 m3. The impact of grassland rehabilitation and parallel terracing on the RRUR was small. We found that there is an interval effect and a threshold effect on rainfall utilization in the basin. The interval effect causes the RRUR to fluctuate within a certain range for rainfall intervals of 300–400 or 400–500 mm (Zuli River Basin). Threshold effects can guide the determination of the potential for rainwater utilization in different areas to ensure that the RRUR can be effectively enhanced with management measures.