The National Water Resources Office (NWRO) has issued an urgent order to accelerate water discharge into the Gulf of Thailand ahead of heavy rains expected from 5 to 7 October. It is also adjusting water discharge plans for major dams nationwide, concerned that early-month sea surges could cause riverbanks to overflow, impacting downstream areas.
Mr. Chayan Muangsong, Secretary-General of the National Water Resources Office (NWRO). He revealed that, based on joint weather monitoring with the Meteorological Department and the Hydro-Informatics Institute (Public Organization), rainfall in Thailand is starting to decrease. The NWRO has integrated efforts across all agencies to rapidly push water towards the Gulf of Thailand through all channels. This is to prepare for a high-pressure cold air mass from China that will cover northern and upper northeastern Thailand, causing increased rainfall and heavy showers in some areas from 5 to 7 October 2026. The rain will begin in the northeast, then spread to the north, central, eastern, and southern regions.
Accelerating water discharge during the rain lull is a proactive approach in critical water management. It helps lower water levels in main rivers and tributaries to create sufficient space to accommodate incoming new water volumes, thereby preventing repeated flooding in low-lying areas.
Regarding the Chao Phraya basin, water flow at Station C.2 in Nakhon Sawan Province is expected to peak at no more than 2,700 cubic meters per second. Additionally, floodwaters from the Sakae Krang River will add about 500–600 cubic meters per second, causing water levels above the Chao Phraya Dam to rise.
According to the Royal Irrigation Department, they are currently maximizing water diversion into irrigation systems on both east and west sides, including diversion into harvested floodplain fields. Nevertheless, the Chao Phraya Dam must gradually increase discharge from 2,300 to 2,400 cubic meters per second, which may cause some riverbank overflow along the Tha Chin River. To delay upper basin water from reaching downstream too quickly, the Bhumibol Dam temporarily stopped discharging water (30 Sept–1 Oct 2026), and the Sirikit Dam reduced discharge to 7 million cubic meters per day.
Outside the Chao Phraya basin, recent rains have caused significant water accumulation in many dams, especially in the Pasak basin. The Pasak Cholasit Dam is at 109% capacity, requiring phased increases in discharge up to 30 million cubic meters per day. This will also necessitate increased discharge from the Phra Ram 6 Dam.
Meanwhile, in the Mae Klong basin, Vajiralongkorn Dam is at 99% capacity. The Electricity Generating Authority of Thailand (EGAT) has set discharge at 42 million cubic meters per day, controlling outflow downstream at 2,200 cubic meters per second without impacting areas below the dam. Additionally, close monitoring is required for Khlong Si Yat Dam (94%), Khun Dan Prakan Chon Dam (97%), and Prasae Dam (105%), adjusting discharge plans appropriately to maintain dam stability.
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