Samui relies on small reservoirs, desalination and an undersea pipeline from the mainland. In 2026 a long dry spell led the PWA to rotate supply by zone from 3 August.
Koh Samui watch
What is known (sources linked below):
Tap water on Samui is run by the PWA (Provincial Waterworks Authority), Ko Samui branch.
Supply comes from the island's small reservoirs, desalination plants and a pipeline from the Surat Thani mainland.
According to the PWA as reported in July 2026, the mainland pipeline supplies about 16,000 m³ per day, against an average island demand of about 34,000 m³ per day.
In late July 2026 a prolonged dry spell, worsened by El Nino, cut clean-water production to about 40% of normal, and the PWA announced supply rotating by zone from 3 August 2026 (Bangkok Post, 29 July 2026). Hotels and businesses bought trucked water.
What the app tracks: PWA Samui interruption notices (from the PWA notice service) and rain vs normal. What it does not track (no machine-readable source): reservoir levels and the rotation schedule. Check PWA Samui announcements directly.
Why it matters for Koh Samui
A system already short in August 2026 enters the 2027 dry season with a very strong El Nino peaking. If the October-December monsoon is weak, shortages in February-April 2027 are likely. This is the single biggest risk for residents who stay.