Title
Cities as tightly coupled social-ecological systems: the water-energy nexus of Bangalore city, India.

Presenters
Vishal K. Mehta and Eric Kemp-Benedict

Venue
SEI Science Forum 2013, Stockholm, Sweden

Abstract
India’s 370 million urban population exceeds the total population of all countries except China. Water supply has not kept up with increasing demand.  No city receiving 24×7 water supply. As utilities reach farther out to increase supply, their energy consumption and costs are increasing, even as private self-supply from groundwater pumping increases apace. These dynamics dramatically impact local hydrology, water availability, energy consumption and emissions.
In this paper, we illustrate the tight coupling of social-ecological systems in Bangalore city, India. Bangalore is one of Asia’s largest urban agglomerations.  In addition to over 900 million liters per day (MLD) of utility-supplied distant river water, residents tap groundwater. We developed a framework to allocate water, energy and carbon emissions associated with domestic water consumption between the 9 million residents of Bangalore. We first analyzed spatial patterns in population growth and utility water supply. Self-supply from groundwater was estimated and used in coupled social-hydrological models of the urban water budget. Results show that despite artificial recharge from leaking pipes and return flows, private groundwater pumping is the largest component of the groundwater balance, leading to an overall groundwater overdraft of 130%. Finally, we estimate energy and emissions spatially, allocating them between utility supply and private self-supply.
We conclude with recommendations, including the importance of systematic collection of groundwater depths, and water extraction data from all sectors and sources. A household survey currently in progress will provide a comprehensive water demand function for the first time, filling in one of the major knowledge gaps.