Exacerbating water shortage induced by continuous expansion of surface artificial water bodies in the Yellow River Basin

Aggravated water shortage limits high-quality and sustainable development in the Yellow River Basin (YRB), an important strategic region with a dense population in China. Surface water area (SWA) and terrestrial water storage (TWS) are two crucial indicators of the overall status of water resources in the region, so monitoring their dynamics and drivers is extremely important for sustainable water management under a changing climate and anthropogenic disturbances. Here, we examined the interannual variabilities and trends of SWA and TWS in the YRB during 1990–2021 utilizing all Landsat-5/7/8 surface reflectance observations, Gravity Recovery and Climate Experiment mascon data, a robust water mapping algorithm based on spectral indices and thresholds, and the Google Earth Engine (GEE) cloud computing platform. We found that SWA continuously and substantially expanded (49.67 ± 9.73 km2/yr) in the YRB. The most rapid expansion of SWA occurred in Shandong Province (20.24 ± 1.00 km2/yr), next in the provinces of Henan (15.09 ± 1.16 km2/yr), Shanxi (13.21 ± 1.11 km2/yr), and Shaanxi (4.11 ± 1.07 km2/yr). Quantitative attribution analysis showed that anthropogenic factors, including constructing and extending artificial reservoirs/lakes (42.4 %) and aquaculture ponds (26.5 %), were the major contributors to increased SWA. However, TWS had a significant downward trend (-6.82 ± 0.99 mm/yr) across the entire YRB. Using water evaporation data, we found that evaporation consistently increased (0.07 ± 0.01 km3/yr or 0.16 ± 0.02 mm/yr), which was mainly caused by SWA expansion in Shandong, Henan, Shanxi, Shannxi, Inner Mongolia. We also identified the hotspots with the most rapid increases in evaporative loss, which were in the provinces of Shandong (0.026 ± 0.002 km3/yr) and Henan (0.018 ± 0.001 km3/yr). These losses resulted in a decline of TWS by 1.37 ± 0.11 mm/yr and 0.5 ± 0.05 mm/yr, respectively. Our findings warn that the expanding surface water bodies were not only an illusion of increased freshwater resources in the YRB but also exacerbated the water crisis by accelerating TWS loss through evaporation.