Lesson 65: The Tonle Sap: A Unique Lake System

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Fact & Info Desk

Lesson 65: Cambodian Geography & Nature (B1)

Research Mission: Read this article about the Tonle Sap lake. Pay close attention to the unique "flow reversal" phenomenon and why the lake is so important for food in Cambodia. Hover over the underlined words for definitions.

Geographical Brief: The Tonle Sap Ecosystem

The Tonle Sap is not just the largest freshwater lake in Southeast Asia; it is a unique and vital ecosystem that is often called the "beating heart" of Cambodia. Its most remarkable feature is a rare natural phenomenon involving its river system.

Most of the year, the Tonle Sap River flows south from the lake into the Mekong River at Phnom Penh. However, during the rainy season (monsoon) from June to October, the huge volume of water coming down the Mekong River causes the Tonle Sap River to reverse its flow. Water is pushed *back up* into the lake. This makes the lake expand enormously, growing up to five times its dry-season size.

This annual flooding is crucial. It carries nutrient-rich soil into the surrounding forests and fields, creating perfect breeding grounds for fish. As the water recedes in the dry season, it leaves behind an abundant supply of fish. This lake provides more than half of all the fish caught in Cambodia, making it essential for the nation's food supply.

Academic Comprehension Check (B1)

1. When does water flow *from* the Mekong River *into* the Tonle Sap lake?

2. Why is the annual flooding of the lake important?

3. Why is the Tonle Sap called the "beating heart" of Cambodia?