The Indonesian government has identified the development of coastal reservoirs as a potential means of providing water for the public, as a growing population, coupled with threats posed by climate change, could strain the existing water supplies in densely populated areas.
A coastal reservoir is a type of reservoir to store fresh water located on the coastline near a river delta. The Netherlands, Singapore and Hong Kong are among countries and territories that have long used coastal reservoirs to bulk up their freshwater supply.
Minister of National Development Planning Suharso Monoarfa emphasised the importance of improving water security in Java, the country’s most densely populated island, saying that high water demand as a result of a rapidly increasing population “put a lot of stress” on many river basins across Java.
He said on Monday: “Six river basins are experiencing water deficits ranging between 10 and 70 cubic metres per second. Furthermore, five urban agglomerations in northern Java will experience a water deficit of 163 cubic metres per second in 2024.”
Citing a World Research Institute (WRI) projection, he said that Java would face high water stress in 2040, meaning that more water users would compete for a limited supply of water. Suharso also predicted that coastal flooding would occur more frequently and severely because of land subsidence.
He considered developing coastal reservoirs an ideal solution in areas as densely populated as Java given that their development would not use up existing land.
Suharso said: “Increasing water storage capacity is a must in addressing water shortages in Java, but the construction of water storage [facilities] on land is constrained by land availability.
“Therefore, the second generation of coastal reservoirs is expected to be a solution to the water shortage and coastal flooding on the north coast of Java.”
The National Development Planning Agency (Bappenas) has listed northern Java’s integrated coastal development as one of the key priorities in the 2020-2024 National Medium-Term Development Plan (RPJMN).
The programme is intended to tackle land subsidence and coastal flooding, as well as to improve water supply and wastewater processing in Java, home to 56 per cent of the population of the country.
It includes a plan to install 104 devices to monitor land subsidence and to build 100 water quality monitoring stations and domestic wastewater treatment plants, according to Suharso.
He, however, did not elaborate on the cost nor the target date for its completion.
Bappenas director for irrigation Abdul Malik Sadat Idris said increasing water storage capacity was also critical, considering a projection that showed the Greater Jakarta area could face a 355.3 million cubic metre water deficit by 2030.
He said the agency had already planned the development of some coastal reservoirs in the northern coastline of Java that were expected to help improve connectivity on the island.
Abdul said: “We plan to add coastal reservoirs and integrate [them] with the current development in the mainland of Java.
“We hope such a facility will also serve to connect with economic centres or other existing infrastructure, and also to become an area that is water and energy self-sufficient.”
He cited an example of a proposed plan to build a coastal reservoir in Semarang, Central Java, which will also become part of the Semarang-Demak toll road. Bappenas, he said, was still studying the proposal initiated by the toll road operator.
Bappenas has identified six areas across the northern coastline of Java as the potential locations for coastal reservoirs – the estuaries of the Cisadane, Citarum, Sayung, Bengawan Solo and Brantas rivers, as well as Pekalongan, a coastal region in Central Java.
Indratmo Soekarno, civil engineering professor at the Bandung Institute of Technology (ITB), said the government could also learn from past experience in constructing the Duriangkang coastal reservoir in Batam, Riau Islands – the first coastal reservoir the government built in 1995.
“Indonesia has enough experience with Duriangkang,” Indratmo said. “Because of the construction of this reservoir, Batam Island has a supply of good quality fresh water almost 24 hours a day.”
THE JAKARTA POST/ASIA NEWS NETWORK