Coupling Mechanism and Collaborative Optimization of hydrological processes and Land Space in loess hilly and gully areas

Abstract

In recent years，water resources and water environment have been taken as important constraints for the territorial spatial planning in China. Especially in arid and semi-arid areas, how to reduce the risks related to climate change and meet the sustainable development of human settlements in the future is a topic worthy of in-depth discussion. Therefore, the present study has chosen the Yanhe River Basin, a typical watershed in the loess hilly and gully area that is influenced by the water resources and water environment, as a research subject. Currently, the contradiction between the hydrological process and the territorial space development of the region is prominent in the context of urbanization. Fully understanding the interactions between territorial space change and hydrological process has great significance to the territorial space development of this region. Existing studies are commonly limited to specific considerations, for example, the impact of land use change, climate change, or the policy of returning farmland to forest on the hydrological process. Moreover, the guidance of research on national spatial construction is relatively weak. Therefore, this study presents the following main achievements considering the multi-factor and multi-scale coupling mechanisms: (1) The spatiotemporal evolution of hydrological/meteorological elements in the basin was analyzed, and the future climate change in the Yanhe River basin from 2000 to 2021 was evaluated. (2) The spatiotemporal evolution of territorial space in the Yanhe River Basin was analyzed, and the territorial space pattern in 2035 was predicted. (3) The coupling mechanisms between hydrological processes and territorial space in the Yanhe River Basin was analyzed by SWAT-MODFLOW coupled hydrological simulation and statistical analysis methods. (4) The vulnerability evaluation index system of the hydrological process-territorial spatial coupling system in the Yanhe River Basin for territorial spatial optimization was constructed. (5) The synergistic optimization path of hydrological process and territorial space in the Yanhe River Basin was created. At the macro scale, the main functional areas of each administrative section in the Yanhe River Basin were optimized through the evaluation of territorial spatial suitability. At the meso-scale, the spatial patterns of the territory under the natural development scenario, ecological priority scenario, and agricultural protection scenario were optimized based on the hydrological models. The results indicate that the response of hydrological processes in the basin is in good agreement with the synergy goals of hydrological processes and the territorial space. Whereas, under the priority scenario of cultivated land protection, the peak value of surface runoff is too large, and the groundwater decreases significantly in some areas. Thus, under the premise of increasing precipitation in the future, we should still adhere to the policy of returning farmland to forest and grassland and continue to reduce the area of cultivated land. The results of this study show important reference significance for the territorial spatial planning of the same type of watershed in the loess hilly and gully area.