ZHANG Lei and KENNEDY Christopher Department of Civil Engineering. University of Toronto, Toronto, Canada
As the world’s population becomes increasingly urbanized and many cities rely on local aquifers for water supply, the issue of sustainable groundwater development is critical. But several complicating factors in urban areas increase the difficulty of determining the sustainable yield: infiltration following precipitation is changed by the reduction of evapotranspiration together with the augmentation of runoff, and additional artificial water sources contribute to groundwater recharge. “Safe yield” has long been the principle for groundwater exploitation. However, ignoring the changes in the groundwater regime caused by abstraction, it has limits and often leads to the overexploitation of groundwater. This paper develops a water budget equation for sustainable groundwater systems, taking into consideration the boundary conditions of a city and potential urban recharge and discharge. A case study of Beijing City, China, is presented. Sustainable yield of groundwater resources of urban Beijing is estimated to be 666~1964 Mm3/year in 1990 and 773~2090 Mm3/year in 2000.