Groundwater-table and recharge changes in the Piedmont region of Taihang Mountain in Gaocheng City and its relation to agricultural water use

Rapid groundwater drawdown in Gaocheng City, the alluvial plain of the Taihang Mountain in the North China Plain, has become the biggest threat to agricultural sustainability. In order to determine the factors resulting in the groundwater decline and to develop a practical plan for long-term groundwater use, water-table fluctuation data were collected over a period of 25 years. The analysis showed that although the drawdown of the water-table was mainly due to water used for winter wheat production and other crops, another reason for groundwater level decline was the tremendous decline of upstream groundwater recharge. It was estimated that, compared to the 1970s, decrease in upstream groundwater recharge in the 1990s resulted in about 1.2 m/a of groundwater level decline. Thus, decline of upstream groundwater recharge rather than agricultural water use was the main reason for the recent groundwater drawdown. On the other hand, gradually improved agricultural practices have saved a great deal of water since the 1970s. The analysis also revealed that, although the groundwater level declined during the wheat-growing season, corn-growing season and over the whole year strongly correlated with the amount of precipitation in that period, aside from one year of extremely high precipitation, precipitation did not recharge groundwater directly but affected groundwater levels through a decrease in irrigation water use. Finally, in order to maintain the groundwater balance, agricultural practices have to save about 180 mm/a of irrigation water from their present level. WaterSA Vol.28(2) 2002: 171-17