Effects of Yellow River Water Management Policies on Annual Irrigation Water Usage from Canals and Groundwater in Yucheng City, China

The Yellow River Water Allocation Management Method was put into place in 1998 to decrease the Yellow River water amount used by upstream areas and provide more water to downstream regions. Rainfall and Yellow River’s infiltration are the main groundwater supply in the downstream area of Yellow River. The groundwater table in the downstream area has continued to decrease since 1979, and the extracted groundwater for irrigation is the main reason for this. Whether the increased river water amount could improve the decreased groundwater level is uncertain. Therefore, we used remote sensing images, groundwater level observations, meteorological data, and unit mean irrigation rate to identify the irrigation events for river water and groundwater, estimate the annual river water irrigation amount and groundwater irrigation amount, and analyze the effects of river water allocation on the groundwater table. Our analysis showed that the area of double-irrigated farmland (farmland that could be irrigated by both groundwater and river water) tended to decrease, while well-irrigated farmland area (farmland that could only be irrigated by groundwater) remained unchanged during the study period. The number of annual irrigation events tended to increase, and the usage of river water remained consistent throughout this period. The increased number of well irrigation events caused annual groundwater usage for irrigation to increase. However, the usage of river water for irrigation remained stable. The increased usage of groundwater for irrigation led the groundwater table to continually decrease from 1998 to 2019. This indicates that there are shortcomings to the current water allocation policy, and that further improvements are needed to prevent continued decrease in groundwater levels.