Replenishment of groundwater still low

The Jakarta Post, Jakarta | Wed, 06/16/2010 11:01 AM | City

Awareness among Jakartans to replenish groundwater is still low, whereas water recharge is a key to prevent flooding and land subsidence, experts say.

As long as city dwellers recharge groundwater from shallow wells, a 15- to 20-meter long drilled or hand-dug well, groundwater exploitation will have little impact on land subsidence. “The point is that you need to restore the water you have taken from underground,” Fatchy Muhammad from the Indonesian Water Society told The Jakarta Post recently.

One effective way to prevent flooding and land subsidence is by storing rainwater as much as possible by creating biopores and water reservoirs such as absorption lakes. However, education on the importance of giving back to nature, ensuring that the groundwater extraction does not exceed its recharge, is still lacking. Budiarsih, a tailor who lives in Pondok Cabe, South Jakarta, has an 18-meter shallow well standing in her backyard where she pumps water from underground to meet her household water needs.

“I never knew that using groundwater had an environmental consequence of land subsidence, nor did I know that I have to make a biopore hole to replenish the water I have taken underground,” she said.

With more than a half of Jakarta’s population still lacking access to piped water, groundwater has served as a cheap alternative resource and a solution to meet the water needs of city households. A recent study from the Bandung Institute of Technology found that the exploration of groundwater, along with pressure from high-rise buildings, mainly contributed to land subsidence in Jakarta at a rate of 10 centimeters per year.

“One thing that most people forget or don’t know is that Jakarta laid in a low, flat basin, around 40 percent below sea level in 1973,” Firdaus Ali, a graduate geology from the University of Wisconsin-Madison, the US, told the Post.

He said Jakarta was slowly but surely sinking; the sea would reach Jl. Hayam Wuruk, Central Jakarta, around 5 kilometers inland, making North Jakarta completely submerged within next 50 years.

Firdaus, also a board member of the Jakarta Water Supply Regulatory Body, said that while it was important to empower grassroot communities to participate in conserving and recharging groundwater, it was clearly much more important to restrict business entities from exploiting it.

“I’m worried about the use of deep wells by many business entities, such as malls and hotels as they sometimes over pump deep groundwater without replenishing it,” he said. “Big buildings are the largest contributor to groundwater extraction and land subsidence in the city.”

Many large business establishments in Jakarta dig their own wells, which can be as deep as 200 meters, as an additional water supply that water tap operators cannot meet. But they sometimes use deep groundwater instead of tap water to avoid paying high water rates of Rp 14,650 (US$1.6) per cubic meter, according to Firdaus.

The City Environmental Management Agency (BPLHD) sealed off an illegally drilled deep well in the Bukopin building in South Jakarta last year as part of its bid to enforce a bylaw on groundwater extraction.

A biopore is around a 10-centimeter wide, 1-meter deep infiltration hole that is filled with organic waste to conserve groundwater.

Kamir R. Barata, a groundwater expert from the Bogor Agriculture Institute, said biopores are easy to make, as people just need to drill through watered soil using a standardized measurement.

He said rainwater absorption into soil was an effective way to conserve water and avoid water loss caused by evaporation.

Meanwhile, NGOs such as WatSan Action Tirta Lestari Foundation have emerged to raise awareness about the plight of groundwater exploitation through water-related educational programs, including teaching some city dwellers about how to make rainwater collection systems and biopores.

“We educate them about the danger of exploiting groundwater and how to better preserve it,” the foundation’s water engineer Noni Arkendita said, adding that her team also taught groundwater users in Cilincing, North Jakarta, and Bintaro, South Jakarta, how to construct water trenches to enhance water seepage and help channel water to biopores. (tsy)