Quantitative assessment sustainability of the river-irrigation district-lake system under global climate change

• River-irrigation district-lake system’s sustainability was assessed quantitatively. • Water diversion capacity of the system was fully guaranteed under climate change. • Runoff and pollutants from Hetao Irrigation District were remain unchanged. • Water quality and aquatic organisms in Lake Ulansuhai were monitored and analyzed. • Global climate change has not changed the spatiotemporal distribution of Chl-a. Global climate change (GCC), which alters meteorological factors such as temperature and precipitation, significantly impacts the river-irrigation district-lake system (RILS), affecting both water resources and aquatic ecosystems related to water. A quantitative assessment framework coupled with GCC, downscaling, hydrological, hydrodynamic, water temperature, and eutrophication models at the global, basin, lake, and ecology scales was proposed to predict the impact of GCC on water resources and water ecological environment of RILS and was applied to the Yellow River-Hetao Irrigation District-Lake Ulansuhai system (YR-HID-LUS). Predictions for runoff, pollutants, water temperature, and Chlorophyll a (Chl-a) were made for the baseline year and four GCC scenarios, evaluating the impacts of GCC on the available water intake of the YR, runoff, and pollutant of the HID, and eutrophication of LU. The results showed that the statistical downscaling model (SDSM), the Soil and Water Assessment Tool (SWAT) for the YR and HID, and the MIKE21 and ECOLab models for LU met the accuracy requirements. Under the four GCC scenarios, the YR’s main stem runoff met the system’s water intake demand. Meanwhile, the runoff, the load of total nitrogen (TN) and total phosphorus (TP) of HID remained basically unchanged from the baseline year. The degree of harmful algal blooms (HABs) remains no HABs and no obvious HABs under the GCC scenarios. The impacts of GCC do not radically change the spatiotemporal distribution of HABs. This study addresses the scientific issue of the sustainability of RILS under GCC.