Impact of Climate Variability and Land Use Change on Surface Hydrological Processes in the Hilly-Gully Region of the Loess Plateau, China

Abstract: Climate and land-use change are the two main driving forces that affect watershed hydrological processes. Separately assessing the impacts of climate and land use change on hydrology is important for water resource management. In this research, the SWAT (Soil and Water Assessment Tool) and statistical methods were employed to evaluate the effects of climate and land-use change on surface hydrology in the hilly-gully region of the Loess Plateau. The results showed that both the temperature and potential evapotranspiration (PET) had significant upward trends (p < 0.05), while the precipitation presented a slightly downward trend in the Yanhe watershed during 1982-2012. The contribution of precipitation to streamflow is concentrated in the flooding periods (from July to September), the average contribution rate of surface runoff on stream flow accounted for 55%, of which the flooding period accounted for 40%. With the 2.17% of slope farmland transformed to the forest and grassland, the average runoff coefficient decreased from 0.36 to 0.15 during 1982-2012. The impact of land use change on soil water content is mainly happened in the upstream stream, while the dominated factor converted to climate from northwest to southeast in the Yanhe watershed. The Evapotranspiration was more sensitive to land-use change than climate variability in all sub-basins, and increased by 209% with vegetation restoration in the Yanhe watershed. Therefore, the impacts of climate variation and land use change on surface hydrological processes were heterogeneity in different geographical regions, climate is the main factor to influence the runoff, while the land use is the dominated factor to evapotranspiration. The quantitative assessment the influence of climate variability and land-use change on hydrology can provide insight into the extent of land use/cover change on regional water balance, and develop appropriate watershed management strategies on the Loess Plateau.

Keywords: climate shift, human activities, hydrological processes, SWAT, the Loess Plateau

Funding: This study was funded by the National Natural Science Foundation of China (No. 41877078, 41371276), Key research and development project of Shaanxi Province (2020ZDLSF06-03-01), National Key Research and Development Program of China (No. 2017YFC0504703) and Knowledge Innovation Program of the Chinese Academy of Sciences (No. A315021615).