Present and future of urban water balance in the rapidly urbanizing Heihe River Basin, Northwest China

Urbanization impacts water availability by increasing water demand due to economic development and population growth; in turn, the availability of water affects the growth rate of urbanization. In addition, urbanization alters the hydrologic, or flow, regime of rivers by increasing impervious surface cover. Utilizing an integrated modeling framework linking urban-land expansion, water-allocation, and hydrological processes, this study examines the combined impacts of the changes in land use-land cover and economic activity due to urbanization and in climatic conditions on water resources in the Heihe River Basin in northwest China over the period of 2010-2050. The redistribution of limited water supplies and the increase in water consumption are identified as to pose the highest pressures on water resources resulting from rapid urbanization. The findings of the study indicate that total water consumption is expected to increase from 21.74 × 108 m3 in 2010 to 24.35 × 108 m3 in 2050. In addition, the runoff in the downstream reach of the basin is forecasted to increase by 9.14% due to combined effects of urban expansion and climatic changes. This indicates that more water can be withdrawn from the Heihe River to meet the increasing water demand due to urbanization in the middle reach if water demand for ecological sustainability and functioning of the downstream reach remains unchanged. The integrated framework developed here can serve as a useful tool to examine the impact of various development scenarios with the aim of successfully allocating water resources and maximizing water use efficiency in the Heihei River Basin as well as other basins elsewhere with similar characteristics.