A comparative analysis of the impacts of climate change and irrigation on land surface and subsurface hydrology in the North China Plain

Few studies have investigated the similar/different characteristics of regional environmental changes induced by climate change and human activities (e.g., irrigation, groundwater pumping). In this study, three climate change scenarios and one irrigation scenario were simulated using the Community Land Model 4.0 to investigate and compare the water-related environmental changes induced by climate change and irrigation in the North China Plain (NCP). Compared to future change climate scenarios, extensive groundwater-fed irrigation in the NCP could have similar magnitude of effects on land surface fluxes and states, but with much larger effects on subsurface water fluxes/states. For example, it was found that groundwater-fed irrigation has led to the decrease of annual mean water table depth by 1 m in major agricultural areas of the NCP while climate change has negligible impacts on water table depth. That is, human water use tends to dominate the subsurface water balance in the NCP. Moreover, climate change and irrigation exhibited different effects on the vertical profile of soil column. That is, irrigation appears to have much larger effects on the top layer soil moisture (SM) whereas increase in precipitation associated with climate change exerts more influence on lower layer SM. Through indentifying the similar/different characteristics between climate change and irrigation, our results highlight the importance of exactly accounting for the effects of human water use and could provide guidance for determining effective measures for adapting to environmental changes induced by climate change and human water use for this region.