Trials aimed at raising water levels in peatlands drained by Indonesia’s unsuccessful Mega Rice Project through canal blocking in Central Kalimantan showed only partial success. The constructed dams were unable to fully counteract peatland subsidence along the canal corridors.
During the 1990s, the Indonesian government embarked on an initiative to convert one million hectares of peat swamp forest on Borneo into farmland. Between 1996 and 1998, around 4,475 km of primary, secondary, and tertiary canals were excavated across Kapuas, Pulang Pisau, Barito Selatan, and Palangka Raya. The effort to develop rice paddies failed to meet its objectives and was terminated in 1999.
The Network of Canals Drained Vital Peatland Ecosystems
The constructed canals accelerated surface water runoff, reduced water retention in the peat soils, and lowered groundwater tables in the surrounding peatlands. This excessive drainage led to irreversible drying, peat subsidence, and frequent fires, especially during dry periods.
Most of the canal system in the northern section of the project area (referred to as Block A) remained unused for farming or other activities after the project’s collapse. Furthermore, the drying made ecological restoration more difficult by limiting plant survival.
Deep excavation of canals hastened peat decomposition and risked exposing acid sulphate soils toxic to many plants. The drainage disrupted the naturally waterlogged, acidic conditions essential for tropical peatland ecosystems.
A subsequent Wageningen University and Research investigation highlighted the abandoned region’s vulnerability to forest and peat fires. Restoration typically focuses on elevating the water table and rewetting surfaces to reduce fire risk and encourage reforestation efforts.
Seven Constructed Dams Raised Water Tables Near Blockage Points
The Climate Change, Forests and Peatlands in Indonesia initiative introduced canal-blocking techniques in northern Block A. Organizations Wetlands International Indonesia and Wildlife Habitat Canada built seven dams, termed locally as tabat, composed of wooden stakes, geotextiles, and soil-infused bags.
Surface water, groundwater, and precipitation levels were closely monitored: daily surface water measurements began in December 2004, while groundwater was gauged weekly using monitoring wells. Data spanned from December 2004 to September 2005.
In the dry season, upstream water depth near the first dam was nearly 60 centimetres higher than downstream levels. Upstream water stayed within approximately 30 centimetres of the peat surface, while downstream levels dropped to around 60 centimetres below.
Though the dam retained water during dry spells, its hydrological influence diminished further downstream. Additionally, rainfall rapidly entered the canal network via surface and groundwater flows.
The study did not quantitatively analyze dams’ impacts on vegetation revival, but field reports noted robust growth and high survival of newly planted jelutung, pulai, and belangiran trees around the dams. The authors recommended establishing dedicated monitoring plots for detailed evaluation.
Subsidence Persisted Despite Water Level Improvements
Research in northern Block C also recorded raised water tables following canal blocking. However, these improvements did not fully counterbalance ongoing peatland subsidence near canals.
As peat surfaces sank, canals deepened into depressions that trapped moving water. A 2014 Wageningen University report described the canals as relentlessly “eating” into the peatland, heightening the risk of dam overtopping during heavy rains.
These findings led to revisions in canal-blocking strategies and improvements in dam designs. The study emphasized the necessity for further research into drainage-induced landform changes before refining restoration techniques for degraded Indonesian peatlands.
New Rice Cultivation Plans Reignite Debates Over Environmental Risks
In May 2020, Indonesian authorities announced ambitions to establish 900,000 hectares of rice paddies on peatlands across Borneo. Mongabay reported that Pulang Pisau, site of one of the largest canals from the previous initiative, was among the targeted areas.
Officials asserted that enhanced policies and technologies would avoid the pitfalls of the original Mega Rice Project. Nonetheless, skeptics doubted the feasibility of large-scale rice cultivation on peat without exacerbating drainage and harming the environment.
An 80-hectare government pilot on a former project area yielded under three tonnes of rice per hectare, roughly half the productivity seen on Java and Bali. The initial planting phase spanned 164,000 hectares, requiring at least 300,000 farmers.
Officials stressed that the initiative would focus on previously cleared land, not intact peat forest. By 2020, the Peatland Restoration Agency had identified 60,000 hectares of abandoned project land with shallow peat and outside forest zones as potentially suitable for agriculture.
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