Pits expected to bring back clean water

The Jakarta Post , Jakarta | Wed, 03/12/2008 11:48 AM

The Jakarta Mining Agency has kicked off a campaign to promote the construction of percolation pits throughout Jakarta in a bid to conserve the city's clean water.

Governor Fauzi Bowo said at Tuesday's campaign launch the construction of pits is expected to help resolve the city's clean water shortages.

"The target is to have more than 220,000 pits in the city. It won't be an easy job and I doubt it will be achieved during my five-year term," Fauzi said, adding there are currently around 38,000 percolation pits in the city.

The campaign, dubbed "Let's save Jakarta's underground water", is supported by the School of Engineering at the University of Indonesia and several large national companies, which have already built percolation pits in their compounds.

Most of the city's houses and buildings pump underground water for their daily use. The extensive underground water extraction has led to clean water shortages during the dry season and land subsidence, resulting in more areas being flooded each year.

The city's land surfaces have sunk an average of 1.2 meters during the past 25 years.

Underground water is quickly replaced by seawater. According to a city agency report, salt water intrusion has reached as far as 15 kilometers inland.

Hari Sasongko, head of the Property Management and Control Agency, said for a percolation pit to harvest water efficiently, one square meter hole is required for every 25 square meters of covered land surface.

Pits must reach the land's sand layer, usually between 4 and 8 meters down, to allow the water to be absorbed quickly.

Hari said it had been compulsory since 2001 for all new constructions in the city to include percolation pits.

"For those buildings constructed before 2001, the owners will be required to build a pit as part of their building use permission renewal," he said.

The city will also prohibit developers from dewatering the land in tall building developments. Dewatering is a procedure for drying out land by pumping out underground water, generally used in developments with basements.

The campaign introduces the "5 Rs guide to saving underground water". The "5 Rs" are Reducing water use, Reusing water for other needs such as watering plants, Recycling polluted water, Recharging the land using percolation pits and biopore holes, and Recovering damaged water catchment areas. (dre)