Theresia Sufa and Triwik Kurniasari, THE JAKARTA POST, BOGOR/JAKARTA | Sat, 03/21/2009 10:33 AM
An expert with the Bogor Agricultural Institute (IPB) says Jakarta’s city administration may be able to ease the water crisis in the capital city by using bioretention technology.
Bioretention technology uses the chemical, biological and physical properties of plants, microbes and soils, to slow the rainwater runoff and retain water longer in the soil.
Nana M. Arifjaya, a lecturer at the institute’s School of Forestry, said the city needed to set aside 44 percent of its land area, or around 28,902 of its 64,346 hectares, to retain groundwater with bioretention technology.
“Jakarta needs to set aside specific areas, which can act as a huge sponge absorbing rainwater and retaining it,” Nana said.
He pointed out Senayan, Pasar Minggu, Srengseng, Kebon Jeruk, Meruya, Joglo, Menteng and Pondok Indah as among the key areas the city should use to retain groundwater.
He added since most areas in the city were built-up, residents could convert small spaces across the city, such as backyards, gutters, pavements, parks, parking spaces and small alleys, to build water retention wells using the technology.
With an average precipitation of 2,000 millimeters per year, Jakarta can store up to 578.34 million cubic meters of water per year, or 1,583,655 cubic meters per day, he estimated.
“That will be more than sufficient to cater for the water needs of 7.9 million city residents,” he claimed.
“The implementation of the technology would also slow down land subsidence and seawater intrusion thanks to the well-maintained water table in the ground,” he said.
Experts have warned earlier that many parts of the city would be underwater before the year 2012. Firdaus Ali, an environmental expert at the University of Indonesia, reported land was sinking at around 10 centimeters a year on average. The city environmental management agency also confirmed land subsidence had increased due to pressure from buildings (87.5 percent) and ground water absorption (12.5 percent). More than 21 million cubic meters of groundwater was pumped out every year.
Some other experts also reported seawater intrusion, 11 to 12 kilometers from the coast. Seawater intrusion and subsidence can also cause buildings to collapse.
The city administration teamed up with the IPB last year to introduce bioretention technology to the capital.
“We’ve already built 800 wells,” Governor Fauzi Bowo said Friday.
“We will keep developing the wells throughout the city. The problem is how to involve as many as city residents in this project,” Fauzi said.
Aside from the bioretention technology, the city administration recently introduced biopores, 1-meter-deep holes bored into the ground to collect rainwater. Biopores are made by putting organic waste into soil. Insects and worms then create micropores around the waste, improving the soil’s water absorption.
Nana said Jakarta alone needs more than 125,000 bioretention wells.
If the technology is used to tackle flooding, he said, it should be implemented across Greater Jakarta and include 261,622 wells spread around Bogor, Tangerang, Bekasi and Depok. He estimated the costs of building those wells would reach Rp 1 trillion.