Weather Modification Operation Conducted to Maintain Citarum Water Availability
Perum Jasa Tirta II (PJT II) has commenced Phase II of its Weather Modification Operation (OMC) as part of mitigation efforts to face the impacts of the dry season and maintain water availability in the Citarum River Basin (DAS). The President Director of Perum Jasa Tirta II, Imam Santoso, stated that the implementation of Phase II, which began on 18 September 2026, at Husein Sastranegara Airbase, is a follow-up to the coordination meeting led by the Director General of Water Resources on 9 September 2026.
“This activity is planned to take place from 18-22 September 2026, with daily execution adjusted based on monitoring results of cloud conditions and potential rain clouds in the West Java region, based on information from BMKG,” Imam said in a written statement in Jakarta on Saturday (19/9/2026).
Imam explained that Phase II of the OMC is being carried out to optimise available rain cloud potential. He hopes this will increase rainfall in catchment areas and provide additional inflow for the Citarum Cascade Reservoirs, which consist of Saguling, Cirata, and Jatiluhur.
Imam noted that for Perum Jasa Tirta II, the Weather Modification Operation is part of a rapid response as the dry season continues.
“This OMC is vital to maintain the resilience of water reserves in the Citarum River Basin so that water services for the community, agricultural sector, industry, and energy needs can continue to operate optimally amidst dry season conditions,” said Imam.
Based on BMKG analysis for the first ten-day period of September 202<0xC2>6, most parts of Indonesia are still experiencing low rainfall, below normal levels. BMKG also noted a very strong El Niño intensity and predicts that Java Island may still experience low rainfall during the second and third ten-day periods of September 2026.
“These conditions must be anticipated as they can impact the reduction of river flow and inflow to reservoirs,” Imam continued.
Imam stated that the impact of the dry season is also visible in the condition of the Jatiluhur Reservoir. As of 18 September 2026, at 07:00 WIB, the water level was recorded at approximately +94.32 metres above sea level (masl). However, this condition remains above the lower operational limit of the Jatiluhur Reservoir, which is +87.50 masl. Based on reservoir management calculations, water availability is still projected to support requirements until the end of 2026.
In addition to the OMC, Imam added that PJT II is conducting reservoir operation adjustments, regular water balance monitoring, water distribution management, and coordination with stakeholders to maintain services for irrigation, public and industrial raw water, and to support power generation.
The Director of Operations and Maintenance of Perum Jasa Tirta II, Anton Mardiyono, said that the Weather Modification Operation provides a positive impact in supporting efforts to maintain water availability, particularly through the optimisation of rainfall potential in catchment areas. Anton noted the additional rainfall generated.
“The hope is that it can help maintain water inflow into the reservoirs and maintain storage conditions, so that the needs for raw water, irrigation, and other water resource services can still be met during the dry period,” said Anton.
Anton stated that this activity is also part of the company’s commitment to integrated, adaptive, and sustainable water resource management through collaboration with the government and all stakeholders. Anton added that PJT II continues to monitor weather developments, hydrological conditions, water levels, inflow, and reservoir outflow regularly as a basis for subsequent operational decision-making.
“With measured management, PJT II strives to ensure that available water can be utilised effectively and equitably to support water, food, and energy security,” said Anton.
In its implementation, PJT II is coordinating with the Ministry of Public Works through the Directorate General of Water Resources and BBWS Citarum, BMKG, cascade reservoir managers, the Indonesian Air Force, PT PLN Nusantara Power, PT PLN Indonesia Power, and PT Rekayasa Atmosphere Indonesia as the cloud seeding executor.