Dhaka turns to rainwater harvesting to ease water crisis

By Mushfique Wadud, AlertNet

Bangladesh plans to begin requiring rooftop water harvesting systems in new buildings in Dhaka in an effort to address the city’s worsening water shortages and curb drops in groundwater levels.

The amendment to the city’s building codes is expected to be in place this year, said Sheikh Abdul Mannan, director of planning for Rajdhani Unnayan Kartipakkha, Bangladesh’s capital development authority.

“In this system, a portion of water would be used for drinking and other household activities and another portion will directly go to underground water reservoirs,” Mannan added.

Water shortages are an annual occurrence in Bangladesh’s largest city during the peak of the dry season in April and May.

Dhaka requires 2.4 billion litres of water a day, but can only produce 2.1 billion, according to the country’s national Water Supply and Sewerage Authority (WASA). Unofficial estimates suggest the supply gap may be even larger.

The shortfall leads to water supplies being turned off in some parts of the city for periods of time, forcing families to purchase drinking water and use pond or river water for their other needs. Regular power cuts, which turn off well pumps, also contribute to the water shortages.

WATER PROTESTS

The shortages in turn are leading to protests. Every year during the dry season, people demonstrate in Dhaka’s streets demanding an uninterrupted supply of water. In 2010, Bangladesh’s government had to deploy troops to guard water pumps following angry protests.

This year, the city also saw protests in August as residents in some parts of the city took to the streets, saying they had no water service.

“We are not getting supply water since last week. Sometimes we get water in the supply line but it is dirty and not drinkable. We are purchasing bottled water for drinking,” said Alamgir Hossain, a resident in Mohammadpur area, a poor sub-district of Dhaka.

WASA officials said that the crisis is due to Dhaka’s dependence on ground water for its water supply. According to officials of the authority, 87 percent of the city’s water supply comes from groundwater, while the remaining 13 percent is treated water taken from two rivers.

But groundwater levels are dropping at an alarming rate in Dhaka as demand for water exceeds natural replenishment of the aquifers.

According to a study by the Institute of Water Modeling in Dhaka in 2009, groundwater levels in the city currently are going down by three metres every year. The study said that, overall, the city’s water table has sunk by 50 metres in the past four decades and the closest underground water is now over 60 meters below ground level.

“In our study, we found that in some parts of the city the ground water level is going down by 3.5 metres every year and on average it is going down two to three metres,” said SM Mahbubur Rahman, director of the water resources planning division at the Institute of Water Modelling.

“This is alarming,” he said. “If the ground water level goes in this way, there will be severe water shortages in the future, and it is also harming the environment. Government must find an alternative to ground water.”

RECHARGING AQUIFERS

Liakath Ali, deputy managing director of Dhaka WASA, said his agency was trying to shift from groundwater to surface water as a supply source. He said rain water harvesting would be a help, particularly if some of the water collected is directed back into aquifers to recharge them, as is happening with some pilot projects.

Collecting rainwater also will help avoid flooding problems in Dhaka during the monsoon season, he said. Roads in Dhaka are regularly flooded during the monsoon as a result of poor drainage systems.

Though rain water harvesting dates back at least to biblical times, it is seeing a recent surge in popularity around the world, in part as a means of addressing growing water shortages brought about by changing climatic conditions and by growing water demand.

The United Nations Environment Programme (UNEP) calls rain water harvesting an environmentally sound approach for sustainable urban water management.

Rooftop rainwater harvesting systems are already mandatory for new buildings in 18 states in neighbouring India. The Karnataka state government has proposed giving a 5 to 10 percent discount on water bills for users that install water harvesting systems.

In 2010, Delhi’s government also directed all its departments, local bodies and public sector undertakings to install rainwater harvesting systems in their buildings.

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