Ensuring an adequate water supply isn’t only an issue for large urban centers like New York or Los Angeles. It’s also a vital concern of the growing populations of cities in the developing world.
Veena Srinivasan, of the Department of Environmental Earth System Science, Stanford University, shared her work on ‘The integrated water paradigm: a new approach to water supply in the developing cities’ during a Columbia Water Center Seminar April 16.
Her study was based in Chennai (formerly Madras), a city of 4.5 million people in southern India. During dry periods, the public utility can provide residents of the city with only 100 litres of water a day, or less. The goal of the study was to find the best way to ensure that people had access to sufficient water in the future, given the specific local conditions and constraints.
In Chennai there is a public water delivery system, but during dry periods running water may be available only a couple of hours a day, or not at all, and for many people that means filling buckets or pans from an outside water tap or pump, and carrying it home. Other options include drawing water from private wells, which can be poor quality and can also go dry during drought, or purchasing water from tanker trucks. People who are able to install storage tanks and sump pumps are able to weather the dry spells with less inconvenience.
Srinivasan’s work analyzed the cost and benefit factors that go into people’s decisions on how to acquire the water they need, and the prospects for different methods of provision. This, combined with forecasting water availability through 2025 based on past conditions, led her to several conclusions, which will be published in forthcoming journal papers.
There are three basic policy options currently promoted in Chennai. One is to increase the supply of water through desalinization and other methods. The second is to improve the efficiency of the public delivery system by repairing the infrastructure and reducing the water lost to leakage. The third is rainwater harvesting, which bypasses the public water utility and allows people to increase the amount of water they acquire from private sources. Because of rainfall patterns in the area, rainwater harvesting in this context means diverting rainfall into private wells which would recharge the groundwater supply, rather than filling household tanks for direct use.
Based on the results of her models, Srinivasan prefers a forth option, a combination of the efficiency and rainwater harvesting policies, which together provide the greatest benefit at the lowest cost. As part of this solution, the public utility water rates would increase to reflect more of the cost of water provision, encouraging people to use the piped water for drinking and cooking, and the groundwater wells for other things. This would help provide a steady flow of clean public water farther into a dry spell, supplemented by water from the replenished aquifer.
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