The response of river water quality and quantity to the development of irrigated agriculture in the last 4 decades in the Yellow River Basin, China

[1] Irrigation agriculture is a major economic activity throughout the Yellow River Basin and has doubled in area in the last 5 decades. Monitoring data for major ions at 63 monitoring stations in the Yellow River system, ranging from 1960 to 2000, were studied. The concentration of major ions in much of the basin, and especially in downstream of the major irrigation areas of the upper basin, increases significantly between 1960 and 2000. We conclude that this increasing trend is mainly a result of saline irrigation return waters, especially from irrigated lands in arid zones of northern China where sodium increases by 100% and total dissolved solids increases by 29% in the main stem. Since 1972 a critical water quantity issue, "duanliu,'' has appeared, which refers to the drying up of the lower reach of the Yellow River. This phenomenon is due mainly to increasing irrigation water withdrawal, which is officially reported to be 91% of all surface water abstraction from the Yellow River. High rates of evapotranspiration and loss to groundwater, especially in the arid irrigated areas in two large irrigation areas in Ningxia and Inner Mongolia, where abstracted water is some 25-30% of annual main stem flow, creates major water losses. There is a need to develop and enforce more rational water quotas as part of a reform of water management in the basin so that basin-wide management is given at least as much importance as provincial-level benefits.