High tide, saltwater intrusion to hit 5 provinces, May 27–June 1
Latest advisory from the Office of the National Water Resources (ONWR). Announcement No. 7/2025: Warning of high tides and seawater intrusion. Applicable period: May 27 – June 1, 2025.
The Office of the National Water Resources (ONWR) has issued a warning regarding anticipated high tides and the risk of seawater intrusion, following ongoing monitoring in coordination with the Hydrographic Department.
During the period from May 27 to June 1 , 2025, elevated sea levels are expected along the Chao Phraya River, particularly around Phra Chulachomklao Fort and nearby areas, between 7pm and midnight.
Forecasts indicate that water levels in this zone may reach 1.70 to 2.00 metres above mean sea level, which is approximately 0.30 metres higher than the critical threshold.
In addition, the strengthening of the south-westerly monsoon and the passage of an active monsoon trough is expected to bring heavy rainfall to several areas. This combination of meteorological factors is likely to cause a further rise in river levels, increasing flood risks in low-lying areas along the Chao Phraya, Tha Chin, and Mae Klong rivers.
Communities outside permanent flood defences or temporary embankments (known as “gaps in the levee”) are particularly at risk of flooding caused by the high tides.
There is also an elevated risk of saline water intrusion, which may affect water quality for domestic use and agriculture, especially in Samut Prakan, Bangkok, Samut Sakhon, Nakhon Pathom, and Samut Songkhram provinces.
To ensure preparedness and effective response, all relevant agencies are requested to:
- Closely monitor the water situation, inspect the stability of riverbank protection structures, and reinforce embankments in flood-prone low-lying areas. Public information campaigns should be launched to inform communities residing outside flood barriers or in vulnerable zones along the rivers.
- Prepare machinery and equipment for immediate deployment to support affected communities and mitigate the impact.
- Monitor high tide patterns throughout the advisory period and adjust water management strategies accordingly, including the operation of reservoirs, dams, and sluice gates, to align with the evolving situation.
