Getting to know Tonle Sap
Tonle Sap is the largest freshwater lake in Southeast Asia, and its most unusual feature is not its size but its plumbing. A river of the same name connects the lake to the Mekong at Phnom Penh, and for roughly six months of the year, from June to November, the Mekong runs high enough that it pushes water backward up that river and into the lake, more than quadrupling the lake’s surface area at peak flood. Once the rains stop and the Mekong drops, the flow reverses again and Tonle Sap drains back out toward the sea. It is one of the few large-scale flow reversals of its kind anywhere on Earth, and it is the reason this lake has supported such a dense fishing economy for so long.
That system is under real strain. Research published in 2025 found that the volume of water pushed back into the lake each year, measured at the Prek Kdam gauge on the Tonle Sap river, has dropped from an average of 41.5 cubic kilometres a year between 1996 and 2009 to just 29.3 cubic kilometres a year between 2010 and 2024, a fall of close to 29 percent. Peak lake levels have dropped by as much as 1.97 metres, and the maximum flooded area in an average year is down 24.7 percent from historical norms. The leading cause is sand mining in the Mekong itself, which nearly doubled in Cambodia from 32 million tonnes in 2011 to 59 million tonnes in 2020, deepening and reshaping the riverbed in ways that reduce how much water backs up into the lake, compounded by dam operations further upstream.
This matters for a visitor because the lake that supported roughly 500,000 tonnes of fish a year under normal historical conditions is not the same body of water it was two decades ago, and the floating villages you can visit today reflect that shift as much as they reflect tradition. We would rather explain the trend than let a guide gloss over it as ordinary seasonal variation.
Things to see and do
Kampong Khleang
The largest floating settlement on the lake, about 55 km from Siem Reap and the least set up for tourism of the three usual options.
Kampong Phluk
A cluster of stilt-house villages about 35 km out, a middle ground between convenience and authenticity.
Chong Khneas
The closest floating village to Siem Reap at roughly 15 km, quick to reach but the one most associated with pushy boat operators.
Prek Toal bird sanctuary
A protected area on the lake’s northwest edge known for large waterbird colonies, best combined with an early start.
Boat travel on the lake itself
An open-water crossing that shows the scale of the flood pulse directly, striking at high water and far less so in the dry months.
We are direct about the three main villages because the difference between them is not small. Chong Khneas is the easiest to reach and the one where operators most often try to steer visitors into overpriced floating restaurants and souvenir stops before they get near the water. Kampong Phluk sits further out and includes both Khmer stilt houses and a Vietnamese floating community with its own school and clinic, a reasonable middle option on a tight schedule. Kampong Khleang, the furthest at about 55 km, is both the largest village on the lake and the one that runs least around tour groups; its Community First tour, roughly 35 USD per person for about two and a half hours, puts its profits toward a local school. If you have the extra hour of driving, this is the one to choose.
Good to know
| What | Detail |
|---|---|
| Flow reversal | Roughly June to November, driven by high Mekong water at Phnom Penh |
| Reverse-flow volume, 1996-2009 average | 41.5 cubic kilometres per year, measured at Prek Kdam |
| Reverse-flow volume, 2010-2024 average | 29.3 cubic kilometres per year, a drop of about 29 percent |
| Peak lake level | Down by as much as 1.97 metres versus historical norms |
| Best month to visit | November, when the lake is near its highest and boats can reach every part of the villages |
| Weakest month to visit | The driest part of the dry season, when low water can keep boats from reaching parts of Kampong Khleang |
| Which village to choose | Kampong Khleang for the least touristed option; Kampong Phluk as a shorter middle ground; Chong Khneas only if time is very tight |
Trips that include Tonle Sap
A Tonle Sap village visit can be added to almost any Siem Reap itinerary as a half-day excursion. Tell us how much time you have and whether you would rather trade a longer drive for a quieter village, and we will build it into your schedule.