ONWR monitors five Thai reservoirs above maximum storage levels
Rain was reported in every region on Wednesday (June 17, 2026), with Buri Ram recording the country’s highest rainfall at 74 millimetres.
- Thailand's Office of the National Water Resources (ONWR) is monitoring five large reservoirs where water levels have exceeded maximum storage capacity.
- The situation was caused by accumulated rainfall from a monsoon trough, with forecasts predicting more heavy rain.
- The five affected reservoirs are Mae Ngat Somboon Chon, Kiu Lom, and Mae Chang dams in the North, and Nam Phung and Lam Pao dams in the Northeast.
- In addition to the five large reservoirs, 38 medium-sized reservoirs with water volumes above 80% are also under close watch.
The Office of the National Water Resources (ONWR) summarised the nationwide water situation for Wednesday (June 17, 2026), saying rainfall had been scattered across all regions.
The highest rainfall was in Buri Ram province, at 74 millimetres.
It also issued an alert to monitor five large reservoirs where water volumes had exceeded their maximum storage levels, and forecast that Thailand would see more rain and heavy falls in some areas during Thursday (June 18, 2026) and Friday (June 19, 2026).
Weather forecast: monsoon trough passes over Thailand, bringing heavy rain risk
Weather conditions on Wednesday showed the monsoon trough lying across Myanmar, upper northern Thailand and upper Laos, extending into a low-pressure cell over upper Vietnam.
The moderate south-westerly monsoon continued to prevail over the Andaman Sea, Thailand and the Gulf of Thailand.
As a result, Thailand was expected to see more rain, with heavy rainfall in some areas of the North, Northeast, Central region, Bangkok and surrounding provinces, and the East.
During Thursday and Friday, Thailand was forecast to continue seeing more rain, with heavy falls in some areas.
Locations with the highest rainfall by region on Wednesday
- Northeast: Buri Ram province (74 millimetres), the highest in the country
- South: Pattani province (68 millimetres)
- North: Uthai Thani province (62 millimetres)
- Central region: Phra Nakhon Si Ayutthaya province (62 millimetres)
- East: Rayong province (57 millimetres)
- West: Ratchaburi province (45 millimetres)
Reservoir situation nationwide and the four main Chao Phraya River Basin dams
The overall water volume in reservoirs nationwide currently stood at 56% of storage capacity, or 45,077 million cubic metres.
The volume of usable water was 37%, or 20,968 million cubic metres.
A closer look at the four main dams in the Chao Phraya River Basin, Bhumibol, Sirikit, Khwae Noi Bamrungdan and Pa Sak Jolasid, showed the situation as summarised below:
- Bhumibol Dam had 7,589 million cubic metres of water (56%).
- Sirikit Dam had 5,034 million cubic metres of water (53%).
- Khwae Noi Bamrungdan Dam had 241 million cubic metres of water (26%).
- Pa Sak Jolasid Dam had 144 million cubic metres of water (15%).
Summary of reservoir water volumes by region
- The West had the highest water volume, at 18,180 million cubic metres (64%).
- The South had 4,607 million cubic metres of water (60%).
- The North had 15,040 million cubic metres of water (55%).
- The Northeast had 5,580 million cubic metres of water (46%).
- The East had 1,098 million cubic metres of water (35%).
- The Central region had the lowest water volume, at 572 million cubic metres (29%).
Close watch: ONWR orders monitoring of five large water sources and 38 medium-sized reservoirs
As a result of accumulated rainfall, five large water sources required monitoring because of high water volumes or volumes above maximum storage levels.
They were:
- North (three): Mae Ngat Somboon Chon Dam, Kiu Lom Dam and Mae Chang Dam
- Northeast (two): Nam Phung Dam and Lam Pao Dam
In addition, 38 medium-sized water sources nationwide had stored water volumes above 80% and required close monitoring, broken down by region as follows:
- North: 17
- Northeast: 11
- South: 4
- East: 3
- West: 2
- Central region: 1
People living in low-lying areas downstream of dams and in areas forecast to receive heavy rain were advised to closely follow news and warning announcements from ONWR and relevant agencies to prepare for possible runoff.
