Bart Schultz
By 1998, reclamation had already begun in several locations. At the invitation of the Ministry of Public Works, after two previous visits to the area in 1986 and 1995, I visited some parts of the reclaimed area to review the plans that the project team at the Ministry had drawn up and to discuss them later in Jakarta.
After arriving in Jakarta and having a few meetings at the Ministry, I left for Banjarmasin in South Kalimantan with a few members of the project team. The next morning, we would take a speedboat to the area and spend a few days visiting several relevant locations. We visited the reclaimed areas of Dadahup and Lamunti. Dadahup is located along the west side of the Barito River, and Lamunti is west of Badahup. The speedboat was essentially the only way to visit several places in this vast area in a short time, as roads were virtually non-existent at the time.
Indonesia distinguishes between tidal and riverine lowlands. Water levels in tidal areas are primarily determined by the tides of the adjacent sea and wind upset. In riverine areas, water levels are primarily determined by the wet and dry monsoons. Dadahup and Lamunti lie partly in the transition zone between riverine and tidal areas. Due to the surface level of the land and the expected subsidence resulting from the land reclamation, polder development was necessary.
After the discussions during the trip, we reviewed the plans back in Jakarta. A reasonably good soil map was already available, from which the distinction between clay soils and peat soils could be determined. This is essential for the development of lowland areas in the humid tropics. Clay soils do subside due to land reclamation, but this is a gradual process that comes to an end after a few years. You can predict the expected subsidence fairly well in advance. The situation is different for peat soils. After reclamation, in the humid tropics these soils continue to subside by about 10 to 15 centimetres per year. As a result, they can eventually become so low that excess water must be pumped out. With the high rainfall during the wet monsoon this is unaffordable for agricultural areas.
The area contained approximately 600,000 hectares of peatland and 400,000 hectares of clay soil. Dadahup and Lamunti are situated on good clay soils, so things would likely go well there. However, the development plan had been drawn up for the entire area. We discussed at the time that, given the anticipated problems, the peatlands should not be reclaimed. The project team also reported this at the time. However, the government decided otherwise, because, as they said, a million hectares is a million hectares.
Things quickly went wrong in the reclaimed peat area, causing almost the entire project to fail, including the reclaimed good clay areas. In Dadahup, approximately 25,000 hectares, the system of primary, secondary, and tertiary canals had already been constructed. A dike with eleven inlet and outlet sluices had been built around the entire polder. The outlet sluices were weirs with culverts that could be opened and closed depending on the desired water management. It was actually a perfectly good polder. Unfortunately, this polder, too, had since fallen into disrepair due to a lack of management and maintenance, primarily due to the failure of the culverts, making proper water management impossible.
The current Indonesian government has decided to build a new capital in Kalimantan. Development is now well underway. It has also been decided to increase food production near the new city. The Dadahup polder plays a key role in this. I became involved again in 2021. Due to the coronavirus pandemic, we held zoom meetings with staff in the Ministry of Public Works for about a year. The Dadahup polder is now being renovated. If management, operation and maintenance can be effectively continued, the polder can play a significant role in the food supply of the new capital.
