Rain Catchers Revive a Wellspring of Life in Semarang
Semarang, Central Java. Rain pours down in Gintungan hamlet, in rural Semarang, Central Java, one afternoon. The local community leader, Suwarno, checks the surrounding yards and appears satisfied; there hasn’t been any flooding around his house since he installed two infiltration ponds in his front yard.
The ponds, essentially two basins of 8,000 liters in volume each, are lined at the bottom in concrete and buried in the ground. They are designed to absorb rainwater from the soil and leach it out underground to replenish the groundwater reserves.
Many of the villagers were initially skeptical about the idea of digging such ponds in their land without any compensation. But after witnessing how Suwarno’s ponds helped keep the area around his house relatively flood-free, they changed their minds and began installing their own basins.
“All residents have recently allotted a space in their yard for pond construction, because they’ve been convinced it will recharge the groundwater [that will keep supplying] their wells during drought, while preventing floods during the rainy season,” Suwarno says.
More than 20 years ago, the village was blessed with abundant groundwater. Villagers could easily reach into their wells with a dipper and scoop out water. Today, they have to go much deeper: the water table has dropped to 11 meters below the ground.
Located on the lower slopes of Mount Merbabu, Gintungan hamlet is part of the rain catchment area for the Senjoyo spring, which supplies clean water for residents of Semarang and the neighboring town of Salatiga, as well as two tapwater companies owned by the municipal administrations.
The spring, situated at 615 meters above sea level, is recharged by four villages in Semarang — Butuh (where Gintungan hamlet is located), Patemon, Karangduren and Bener – and the two Salatiga villages of Noborejo and Randuacir.
The flow of water from Senjoyo, however, has slowed significantly in the past two decades. It had a discharge rate of 1,334 liters per second in 2000, before dwindling to 838 liters per second in 2008. The flow rate shrinks by a further 40 percent during the dry season.
Villagers have now dug infiltration ponds extensively in catchment lands in the upstream areas, which host a growing number of homes and farms. This is being done to replenish the groundwater aquifers that supply the spring, in order to restore Senjoyo’s once-abundant flow.
Each pond is expected to fill up with rainwater a hundred times a year, contributing 800,000 liters each to the groundwater reserves.
“I’ve agreed to make my yard available for an infiltration pond because it has some benefits for the environment, mostly saving water and curbing floods,” says Hardi, a resident of Butuh village.
He says he has not seen any rise in the water level in his own well, but attests to the fact that the pond has helped reduce the excessive rainwater runoff around his house during heavy rains, by quickly absorbing the water.
Rain harvesting
The construction of these ponds is jointly funded by the Coca-Cola Foundation Indonesia and the United States Agency for International Development (USAID), under the latter’s five-year program Indonesia Urban Water, Sanitation and Hygiene (Iuwash) program. The agencies have partnered with a local farmers’ group in Salatiga, the Qoryah Thoyyibah Farmer Association Union (SPPQT), to work on the project.
So far the project has seen the digging of 920 infiltration ponds – 732 of them in Semarang and the rest in Salatiga. In all, the basins are expected to catch at least 600 million liters of rainwater per year and transfer it into the groundwater reserves.
The project is aimed at conserving groundwater through the simple technology of rain harvesting. Besides restoring the flow rate of the Senjoyo, the ponds in Semarang and Salatiga are also expected to revive the smaller Ngablak spring on Mount Ungaran.
A similar project commissioned by USAID’s Environmental Service Program in West Java, in which 51 ponds were dug in cooperation with a local community, successfully more than doubled the discharge of the Cikareo River from 48 liters per second to 110.
“Not only it is easy to build, but an infiltration pond is also effective to increase groundwater reserves as well as to reduce flooding,” says Iuwash’s chief of party, Louis O’Brien.
The pond is designed to resemble a cubical tank to capture rainwater that would otherwise naturally flow into a river and then out to sea. It captures excess water that the ground is unable to naturally absorb. The tank is designed to let the rainwater permeate the ground and fill the aquifers, which is especially useful during the dry season to fill wells and maintain the spring volume.
This method of rain harvesting is also aimed at boosting groundwater supplies for the local tapwater companies, or PDAM, in Salatiga and Semarang, from which thousands of families in the cities’ urban areas get their drinking water.
The Salatiga PDAM currently pumps out 350 liters per second of clean water to some 27,000 families, or 78 percent of the town’s population. It currently draws around 150 liters per second of raw water from the Senjoyo.
The Semarang PDAM, meanwhile, takes 30 liters per second from the Senjoyo. The flow rate from the Ngablak, currently at 10.4 liters per second, is inadequate to supply the PDAM, which distributes piped water to 29,000 families, around 20 percent of the district’s population.
Each infiltration pond costs Rp 2.4 million ($184) to build and install. In Semarang, the cost for installing some of the ponds is borne by local authorities as well as earmarked in a Rp 1.4 billion fund to be disbursed to each village across Indonesia under a national village development scheme, which will also pay for future ponds.
“We have 286 infiltration ponds built by CCFI-USAID, but our target is to have 600 to 700 because our village is always in shortage of water during drought,” says Budiono, a Patemon village official.
Even as it experiences severe water shortages during the dry season, Patemon also sees frequent floods during the rainy season.
“We expect the infiltration ponds built across the village to be an effective solution for our water problem during the dry season, by lifting the water level in our wells,” says Joko Waluyo, a Patemon resident who has two infiltration basins in his yard.
Farming communities have shown the most interest in the project, given that ensuring an adequate supply of water is a crucial element of agriculture. The Senjoyo spring alone supports around 60 farmers’ collectives.
“We hope the ponds will raise water stocks for farming activities along the riverbank,” says Mujab, the coordinator of the local farmer group SPPQT.
Other projects
Since 2011, CCFI has also worked on replenishing groundwater supplies in Mojokerto, East Java, as well as Sibolangit and Pematang Siantar in North Sumatra. With the Semarang and Salatiga projects, as well as an ongoing project in Malang, East Java, the latter of which targets the construction of 800 ponds, the foundation is building a total of 3,300 infiltration basins in six Indonesian municipalities and districts.
“Groundwater conservation is a part of our global sustainability platform to deal with water issues,” says CCFI chairwoman Titi Sadarini. “We’ve set aside $1 million for the infiltration pond project in Indonesia.”
CCFI’s global program of Water Replenish Initiative is the part of the company’s work to become a “water neutral” business by 2020. That means that by that date, it will be returning water to nature, and to the communities living around its bottling plants, at the same rate that it draws water for its beverages.
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