The Ciliwung River Basin is one of the largest river systems in Indonesia, flowing along a 97km narrow corridor from the Tugu Puncak in the mountains near Bogor, through the Jakarta metropolitan area, and terminating in the sea in Jakarta Bay.
The Ciliwung is a major water source for the large municipalities of Bogor and Jakarta, and its waters are also utilised for local transportation, for agricultural irrigation, and for general household uses in many small communities along its banks, including illicit slum-dwellers living next to the river in Jakarta. The river has a recent history of extensive waste dumping and silt build-up; toxic inputs from household and industrial chemicals; congested riverside dwellings; and man-made obstructions such as bridges and dams. These have all resulted in considerable increases of the frequency and volume of wet season flooding in Jakarta, dramatically declining water quality, and loss of biological diversity.
“The Ciliwung is now recognised as one of the most exploited, congested and polluted rivers in the world”
In late 2012, following previous government-sponsored river management efforts (for example, PROKASIH), the governor of Jakarta proposed a new expansion of the Ciliwung river as one solution to these on-going challenges, especially the flooding. However, parts of this US$190 million project will involve building more dykes, dredging canals, and overhauling four reservoirs over the next five years (Jakarta Post, 2013), as well as relocating 30,000 people living in slums along the river’s banks to various regions around Jakarta. This will all amount to more human-induced alteration of what was once a natural river.Figure 2: Dredging in Ciliwung River for channel deepening and expansion
Human alteration of River ecology
Rivers with highly altered and regulated flows lose their ability to support natural processes and native species (N. LeRoy Poff et al, 1997). According to a study conducted by Jakarta’s Biology Research center, from 1953, when research began, to the early 21st Century, the Ciliwung River was home to 18 types of native crustaceans, 187 types of native fish, and 62 reptile species. Today, only 9 crustacean species, 23 fish species, and 14 reptile species survive in the river. Moreover, an analysis was undertaken from 1993 to 2005 by the Department of Environmental Engineering on the water quality of the river. As shown in Table 1, water quality has drastically decreased at all sites tested from the quality originally measured in 1993.
Sustaining Ecological Integrity
“Society’s ability to maintain and restore the integrity of river ecosystems and flowing water systems depends largely on their natural dynamic character”
The plans to dredge areas along the Ciliwung to deepen its channels; to build more dykes across it; and to overhaul four reservoirs along its course to remove silt buildup and increase water storage together can only be short-term solutions to reduce wet season flooding of metropolitan Jakarta.
By contrast, fundamental long-term river conservation and management solutions, as emphasized by N. LeRoy Poff et al (1997), involve coordinated actions to restore the river’s natural flow variability and connectivity. By removing waste swelling, re-connecting rivers to floodplains, and enhancing the quality and capacity of wetlands, river restoration increases natural storage capacity and reduces flood risk as a long term solution (RESTORE). In turn, it will incrementally restore ecological integrity of the river for native species diversity and the needs of local residents.
Alexandra Dunbar | Australian National University