Research on the optimal allocation of agricultural water and soil resources in the Heihe River Basin based on SWAT and intelligent optimization

Abstract

In the context of global climate change, changes in precipitation and temperature conditions, especially the increasing frequency of extreme climate events, have a severe impact on agricultural production. Predicting climate change and adjusting planting structures over time are critical to sustainable agricultural development. In this study, the Coupled Model Intercomparison Project Phase 6 (CMIP6) and Soil and Water Assessment Tool (SWAT) models were used to simulate the future climate and runoff in the middle reaches of the Heihe River Basin (MHR). Then, the MOPSO and NSGA-II were used to plan future planting structures. The results showed that the temperature and precipitation in the MHR showed an increasing trend. By the 2070 s, the temperature was projected to increase by more than 2 °C under SSP245, while that under SSP585 was more than 4 °C. The annual mean precipitation was projected to increase, but the distribution was uneven, and the increased precipitation was mainly concentrated in spring and autumn. Under the interaction of temperature and precipitation, the runoff of the Heihe River will increase in the future, especially under SSP585, and the runoff of the Heihe River is projected to reach 2.48 billion m³/a in the 2070 s. Crop water demand was projected to increase with temperature, and crop irrigation water demand would increase by 14.4 % in the 2070 s under SSP245. Planting vegetables helps to improve agricultural economic benefits and carbon sinks, but to control soil erosion, the area of vegetables is best kept at approximately 16 %. Fertilizers and agricultural films are the primary carbon sources in agricultural production activities in MHR, accounting for more than 60 % of the total carbon. This study suggests promoting sustainable agricultural development by improving irrigation efficiency, using low-carbon fertilizers, controlling soil erosion, and gradually expanding the vegetable planting area with a considered ecological environment.