sponge city

SPONGE CITY: WATER BALANCE OF MEGA-CITY WATER
USE AND WASTEWATER USE IN HYDERABAD, INDI5

Cities are increasingly competing with agriculture for water resources as urbanization unfolds in water-scarce river basins in Asia. This study documents a partial water balance of Hyderbad city, India and Tokyo, Japan. Hyderbad city is located in the Krishna basin and currently the fastest growing city in India, and gives estimates of its impact on both traditional and wastewater irrigated area. Though previous projects have had significant local impacts on irrigated areas, additional water supply from a major reservoir on the Krishna River to Hyderbad is likely to be a relatively small component of total reservoir releases to irrigated agriculture (5.3-10.2% by 2030). Urban storm water runoff generates a volume of water of the same order of magnitude as the domestic wastewater volume, though the fate of this water vis-à-vis irrigated agriculture is not known. Wastewater irrigation compensates for more than half of the traditional irrigated area water lost, so the urban-agriculture conflict also generates significant opportunities that also need to be considered. However, the impact of wastewater use on crop yields, cropping changes, human health and the environment need to be fully addressed.