Response Characteristic and Mechanism of Shallow Groundwater Level on the Successive Years with Less Rainfall in the Agricultural Areas of the Central Hebei Piedmont Plain

Shallow groundwater,which is in over-exploitation,is the main water source of farm irrigation in the agricultural areas of the central Hebei piedmont plain.According to the dynamic monitoring data of shallow groundwater level from long-time observation hole in the different agricultural areas of the central Hebei piedmont plain,variable characteristics of shallow groundwater level response to the successive years with less rainfall were studied.The results show that large-scale and intensive shallow groundwater exploitation during spring irrigation periods of successive years with less rainfall mainly causes the continuous decline of shallow groundwater level in the agricultural areas of the central Hebei piedmont plain;the decline amplitude of shallow groundwater level during spring irrigation period is related closely with the precipitation from January to June of the previous year and the same year;when the annual precipitation is less than the local annual average precipitation(528.4 mm),the effect of agricultural water exploitation on the decline of shallow groundwater increases significantly with the decrease of precipitation;when the annual precipitation is more than the local annual averageprecipitation,even more than 630 mm,the effect of agricultural water exploitation on the decline of shallow groundwater decreases significantly; adjusting and controlling rationally the exploitation intensity of shallow groundwater in the agricultural areas is important for improving the sustainable utilization of shallow groundwater in the agricultural areas of the central Hebei piedmont plain.