Thailand’s reservoirs 82% full ahead of heavy rain forecast for October 21–24
Water agencies have been told to coordinate reservoir releases ahead of further downpours, with particular attention on the East and West and flood-prone areas including Satun and Chachoengsao.
Thailand’s large and medium-sized reservoirs were holding 82% of their combined storage capacity ahead of heavy to very heavy rain forecast for October 21–24, 2026, prompting instructions to coordinate water releases and limit downstream impacts.
An Office of the National Water Resources (ONWR) update dated October 19 put total storage at 66,728 million cubic metres, according to Nation Thailand. The office instructed agencies to align reservoir operations with expected rainfall, with particular attention to reservoirs in the East and West.
The forecast cited by the ONWR and the Thai Meteorological Department points to increased rainfall across the East, lower Northeast, Central region and upper South during October 21–24, including isolated heavy to very heavy downpours and strong gusts.
Western and eastern reservoirs under scrutiny
Western Thailand had the highest regional storage proportion in the October 19 update, with 27,556 million cubic metres of water, equivalent to 97% of capacity. The East followed at 89%.
Several reservoirs in those regions were more than 80% full, while some exceeded their stated storage capacity. The ONWR said releases needed to be managed to accommodate further rainfall without adversely affecting downstream areas.
Nong Pla Lai Reservoir held 185 million cubic metres, or 113% of its stated capacity, in figures dated October 18. Its reported level requires close monitoring of releases.
The office is monitoring Nong Pla Lai, Prasae and Bang Phra reservoirs because they supply water for households, agriculture and industry in the Eastern Economic Corridor, which covers Chon Buri, Rayong and Chachoengsao.
Flood-prone communities urged to follow alerts
The agencies’ assessment for October 19 identified persistent rain and isolated heavy to very heavy downpours in the East and South, along with heavy rain in parts of the Central region. Residents were advised to watch for heavy rainfall and waterlogging.
Satun recorded 134 millimetres of rain, the highest reading among the regional rainfall maxima listed in the ONWR report. Chachoengsao recorded the highest reading in the East, at 80 millimetres.
The ONWR said heavy rainfall had already caused water to accumulate in low-lying areas. It had coordinated with local agencies to prepare for rivers overflowing their banks and possible flash floods.
People in flood-prone areas, particularly Satun, Chachoengsao and parts of the Central region, were urged to follow official weather and water alerts closely. Farmers and residents facing heavier rain and gusts were also advised to take precautions to protect agricultural produce and vulnerable structures.
Dry-season reserves sufficient, ONWR says
Nationwide usable water stood at 42,600 million cubic metres, equivalent to 75% of usable storage capacity. The ONWR assessed those reserves as sufficient for the coming dry season.
The immediate task is to manage releases while allowing room for additional rainfall, with high storage levels in the East and West remaining a focus of reservoir operations.
