Rapid surface water expansion due to increasing artificial reservoirs and aquaculture ponds in North China Plain

Abstract

Water shortage has severely threatened the North China Plain (NCP), a typical grain bowl and highly populated and urbanized area in China. As surface water body area (SWA) is a critical variable for measuring regional water resources, understanding its changes and driving mechanisms is important for sustainable water management. Here, we examine the interannual variations and trends of SWA in the NCP during 1987–2020 by using all the available Landsat imagery, the water indices- and threshold-based water mapping algorithm, and cloud computing platform Google Earth Engine (GEE). The results show that SWA of the NCP significantly (p < 0.05) expanded by 68.0% (from 4740.0 km2 in 1987 to 7963.7 km2 in 2020) at a rate of 101.9 km2/yr. The most remarkable expansion of SWA happened in Shandong Province (75.0 km2/yr), which is an increasingly important aquaculture production region. We find that the increasing artificial reservoirs/lakes due to the implementation of water projects, together with aquaculture development, are the main drivers for the expansion of SWA in the NCP. The expansion of SWA caused a significant increase in water evaporation (0.09 km3/yr) in the NCP as the shallow nature of these artificial reservoirs/lakes and aquaculture ponds could lead to excess evaporation because of the frequent heating and cooling cycles due to their limited abilities to store energy. Similarly, Shandong Province experienced the most rapid increase in water evaporation (0.03 km3/yr), which could accelerate the loss of water storage at a rate of 8.4–14.4 mm/yr in the regions covered by surface water bodies. Continuous temperature rise (0.02–0.06 °C/yr) in the future, as predicted by the climate models (CMIP5) under the two Representative Concentration Pathway (RCP) scenarios of medium (RCP 4.5) and high (RCP 8.5) greenhouse gas emission, could further increase water evaporation, which may add more pressure to regional water shortage. This study warns that, despite an observed significant SWA expansion, water shortage remains a major concern in the NCP.