Hulu Sungai Selatan wants Kandangan on mountain water from the Amandit Weir, and the saving starts at the source

Some of the most useful water investments in Indonesia do not involve building a bigger treatment plant. They involve choosing a better source. On Tuesday, 6 October 2026, the Regent of Hulu Sungai Selatan (HSS) in South Kalimantan, H. Syafrudin Noor, inspected the Amandit Weir in Malutu Village, Padang Batung District, and set out a plan to do exactly that for Kandangan, the regency capital.

The plan is to lay a pipe connection from the weir to the Muara Banta intake, which supplies Kandangan and the surrounding area. The regent said the regency wants to begin installing that connection this year. The stated aims are practical: add raw water to the system, reduce the amount of chlorine needed in treatment, lower processing costs over the long term, and improve the quality of the water that households drink. On the same visit, the regent also announced that HSS has secured Rp250 billion in central government funding to normalise the Amandit Lama river, scheduled for 2027.

Together, the two announcements describe a regency that is managing one river system for several purposes at once: drinking water, irrigation, and flood control.

A source that already works

The Amandit Weir is not a new or untested source for drinking water. Since July 2020 it has fed the treatment plant (instalasi pengolahan air, IPA) of the regional water utility's Sungai Raya unit, located in Paharuangan Village, Sungai Raya District. That plant draws raw water from the Amandit River at the weir with a permit from the river basin authority, and its pipeline from source to plant was installed with direct support from the Ministry of Public Works' river basin office.

The regent's description of the result was simple.

"Air ledeng di Kecamatan Sungai Raya yang dari bendung tersebut sangat jernih, karena berasal dari pegunungan langsung." (The tap water in Sungai Raya District that comes from the weir is very clear, because it comes straight from the mountains.) H. Syafrudin Noor, Regent of Hulu Sungai Selatan

This is not a new observation in HSS. When the Sungai Raya plant opened in 2020, then Regent Achmad Fikry made the same point in economic terms. He said the source used by the plant was already clean enough that its production cost was lower, and he contrasted it with the Muara Banta unit, which treats cloudier water taken from the Amandit River further downstream. The 2026 plan therefore extends a proven arrangement to the intake that serves the regency capital.

The numbers behind the Sungai Raya plant

Reporting from the plant's opening in July 2020 gives a clear picture of what the existing investment looks like.

The plant was built in three phases. A water reservoir was constructed in 2016 at a cost of Rp5.1 billion. The treatment plant itself followed in 2018 at Rp9.9 billion. The raw water intake was completed in 2019 at Rp1.8 billion. Together, that is Rp16.8 billion, funded through the regional budget (APBD), the Special Allocation Fund (DAK), and the river basin authority's support for the pipeline.

The plant has a design capacity of 300 litres per second and began operating at 50 litres per second. At that opening rate, the sources describe service in two slightly different ways. Kalselpos reported that about 2,000 customer connections could be served, while Kalimantan Post reported that a 50 litre per second plant has the capacity to serve about 4,000 connections. The two figures are best read as a starting service level and a capacity ceiling for the first stage, rather than as a conflict. At opening, the plant supplied Sungai Raya, Simpur, and parts of Kandangan, with officials already mentioning future distribution to more of Kandangan and possibly to border areas of neighbouring Tapin Regency.

The scale of the remaining headroom is worth stating plainly. Fifty litres per second is about 4,320 cubic metres a day. Three hundred litres per second is about 25,920 cubic metres a day. The system was designed from the start for six times its opening output, and the raw water feeding it is, in the regent's words, very clear.

Why source quality is an economic variable

Raw water quality is often treated as a technical detail. In practice it shapes a utility's cost structure every day. Turbid river water needs more coagulant, more settling time, more filter backwashing, and more disinfectant to reach drinking standard. Clearer water from an upland source needs less of all of these. The difference shows up in chemical purchases, in electricity for pumping and backwashing, in sludge handling, and in the wear on equipment.

That is the logic behind the regency's plan. Muara Banta draws from a stretch of the Amandit River that carries more sediment. Blending in, or substituting, water from the weir would lower the treatment load at that intake. The regency has named chlorine as the specific saving it expects, and it has tied the plan to public health as well. The regent said the aim is for children to have clean and healthy water, to grow up healthy, and to avoid stunting.

There is also a capital efficiency argument. Using the weir as a source for Kandangan builds on a source corridor that the existing Rp16.8 billion investment has already established. As an illustration only, the build cost works out to about Rp56 million per litre per second of design capacity, or about Rp4.2 million per connection at the 4,000 connection capacity reported for the first stage. Each additional litre per second drawn through infrastructure that already exists lowers those unit costs further.

One river, three services

The weir sits at the head of a wider water system. The Amandit irrigation area served from Malutu covers 5,472 hectares, managed by the Kalimantan III River Basin Authority (BWS Kalimantan III). In March 2025, the regency proposed raising the weir so that farmers could irrigate year round rather than depending on rainfall, and it set out a plan for the river basin authority to dredge the Amandit channels, with the regency adding drainage channels, to lift food production in Kalumpang and Simpur districts.

The newly announced Rp250 billion for the Amandit Lama river addresses the third service. The river has become shallow, which causes seasonal flooding in areas that include Simpur, Kalumpang, and Kandangan. Normalisation in 2027 is intended to restore its capacity to carry water through the rainy season.

Seen together, drinking water, irrigation, and flood control are three services drawn from the same catchment. A decision about how much water to send to the Muara Banta intake is also, in a small way, a decision about irrigation flows and river management. That is a good reason to plan the three together and to measure them in comparable terms.

Sirkularium's view

Hulu Sungai Selatan is taking a sound and cost-conscious approach. Rather than expanding treatment to cope with poorer raw water, it is moving to a cleaner source it already knows, through infrastructure it has already built, with a clear public health objective. The central funding for the Amandit Lama river shows that the regency is also able to bring national resources to its water system.

Three steps would help the plan deliver its full value and make it easier to finance. First, the regional water utility could publish a simple baseline for the Muara Banta and Sungai Raya units: raw water turbidity, chemical dosing, and production cost per cubic metre. With that baseline, the chlorine and treatment savings the regency expects can be measured rather than assumed, and the pipeline can be justified on observed returns. Second, the allocation of water at the weir between irrigation and drinking water supply could be agreed formally with BWS Kalimantan III, including dry season scenarios, so that both services are protected as demand grows. Third, the upland catchment that keeps the Amandit clear deserves recognition as an asset. Mapping its forest cover with remote sensing and valuing the water quality it provides would show how much treatment cost the catchment avoids every year, and would give the regency a basis for protecting it.

Sirkularium sees source water quality as one of the most direct and measurable ecosystem services a regency can manage, and the Amandit case shows how it can be valued in plain rupiah per cubic metre. What to watch next: whether the pipe connection to Muara Banta begins before the end of 2026 as the regent intends, how far the Sungai Raya plant moves toward its 300 litre per second design capacity, and how the 2027 river normalisation is coordinated with the irrigation and water supply plans for the same river.