Dhaka has a critical water supply problem, one of the worst for a South Asian city. According to a study by the Institute of Water Modeling based in Bangladesh’s capital city, its groundwater level is falling by three meters per year. Groundwater has already receded by fifty meters in the past 40 years, bringing the current level to sixty meters below ground. The supply-demand gap is approximately 500m liters per day. The situation is so problematic that in the summer of 2010, the Government of Bangladesh deployed troops to manage water distribution in Dhaka.

Since 1963, the population of Dhaka has grown by thirteen times. When Bangladesh gained its independence in 1971, Dhaka faced a growing influx of rural-to-urban migration. The city expanded into the low-lying marshlands at its borders. Historically, most of Dhaka’s water supply comes from its two rivers, the Buriganga and the Shitalakkhya. But as population has increased and industry has expanded, river water has become contaminated with industrial waste. Today, groundwater is expected to satisfy over 80% of the city’s water supply.

Infrastructure in Dhaka is not robust enough to sufficiently recharge groundwater. In a recent seminar, international NGO WaterAid and Bangladesh’s Institute of Engineers concluded that rainwater harvesting needs to be included in establishing the country’s bylaws. In 2008, it was recommended that 40-50% of building premises should remain unpaved and that half of that area should be under “green” cover to allow for natural recharge of aquifers. The caveat though is that 65% of Dhaka is already paved and the remaining 35% does not ensure natural recharge of aquifers because top soil in most of these locales consists of clay.

Rainwater harvesting, low-cost systems that collect and store rainwater for year-round use, offers a cost-effective and practical solution to ease Dhaka’s water crisis. It is estimated that rainwater harvesting (RWH) systems could supply more than 15% of Dhaka’s requirements. Since 1997, one thousand RWS have been installed in Bangladesh, mostly in rural areas. The systems’ capacities vary from 500L to 3,200L, at costs in the range of US$50-150. If RWH is undertaken as a serious investment, it could help conserve groundwater and recharge the water table. About 150bn liters of rainwater could be harvested during the monsoon season alone. Water can be stored for four to five months without bacterial contamination – an important fact given that 110,000 children in Bangladesh die of waterborne illnesses every year.

There has been precedence of public-private partnerships working to establish RWH in Bangladesh. In early 2008, Coca-Cola Far East Ltd teamed up with Plan Bangladesh to install RWS in five primary schools in the Mirpur and Borguna Sadar areas of the country to ensure potable drinking water for school students.

In 2009, Coca-Cola became involved in a new partnership with UN-Habitat called The Safe Drinking Water and Sanitation Project. It is a two-year project valued at US$300,000. The goal is to impact six thousand families by demonstrating RWH and other water conservation and storage systems. RWH will be set up at twenty schools while drinking water and sanitation systems will be set up at thirty schools. The commissioned RWH recharge capacity is projected to be 3.25m liters per year.

This story originally appeared in the February 2011 edition of the Searchlight South Asia newsletter created by Intellecap for the Rockefeller Foundation.

The opinions expressed on the Searchlight South Asia site are solely those of the authors and do not necessarily reflect the positions of the Rockefeller Foundation.

Sources:

http://bangladesh2day.com/newsfinance/2010/March/20/Safe-drinking-water-and-sanitation.php

http://www.downtoearth.org.in/node/32915

http://www.eng-consult.com/arsenic/article/rain-water.htm

http://www.irc.nl/page/44854

http://www.unep.or.jp/ietc/publications/urban/urbanenv-2/9.asp