Which lake expands dramatically during Cambodia’s rainy season?

Tonle Sap is the Cambodian lake that expands dramatically during the rainy season.

Tonle Sap is a combined lake and river system in Cambodia. During the dry season, water flows out through the Tonle Sap River toward the Mekong. During the Southwest Monsoon, the Mekong rises and reverses the river’s flow, sending water into the lake.

This annual reversal can multiply the lake’s area and greatly increase its depth. The changing water levels support highly productive fisheries and sustain floating and stilt-house communities around the lake.

Tonle Sap is often described as Southeast Asia’s largest freshwater lake, although its exact size changes substantially through the year. It should not be confused with the Tonlé Sap River, the channel connecting the lake with the Mekong.