Tonle Sap Lake (aka Boeung Tonle Sap) is a large freshwater lake in Cambodia's Siem Reap Province (Lower Mekong Basin). The lake is attached to the 120-km (75-mi) long Tonle Sap River connecting it to Mekong River. By surface area (approx 2700 km2 / 1000 mi2) it is ranked Southeast Asia's largest freshwater lake. When inundated seasonally (during the annual monsoon rains) lake's surface area reaches approx 16000 km2 (6200 mi2). Tonle Sap has max-length 250 km (160 mi), max-width 100 km (62 mi), max-depth 10 m (33 ft) and max water volume approx 80 km3 (19 mi3).
Inflow starts in early summer (May or June, with max rates ~10,000 m3/s) and ends in the autumn (October or November). As the Mekong River is at its minimum flow in October-November, its water level falls deeper than the lake. During this period, the lake drains (via Tonle Sap River) into Mekong. The result is that Tonle Sap River flows for 6 months northbound (southeast to northwest) and for 6 months southbound (in the reverse direction). Lake's annual reverse flow is approx 30 km3 (7,2 mi3) or ~1/2 of its maximum volume. Another 10% enter the lake by overland flow from Mekong.
In 2001, the Cambodian government officially designated the lake and its surrounding 9 provinces as Biosphere Reserve. The reserve is divided into 3 zones - core (Prek Toal), buffer (Boeng Chhmar) and transition (Stung Sen).
Tonle Sap Lake cruises
On the lake's northern shores is located Siem Reap - homeport for river cruise ships and among Cambodia's best-known resort towns. Siem Reap is also the gateway to Angkor Wat - Khmer Empire's capital city. Boat cruises on the lake are usually inclusive of roundtrip bus transportation (from/to Siem Reap), lunch and plenty of opportunities for handmade souvenir shopping. These boat tours vary by length and visit the following most-popular floating villages - Chong Khneas, Kampong Khleang ~2-hour boat ride from Siem Reap), Kompong Luong, Kampong Phluk, Prek Toal.
Best time to cruise Tonle Sap Lake is during the monsoon season (June-October), during which the lake becomes 5 times larger than in the dry season (November-May) and the surrounding wetlands and forests are inundated. Boat tours visiting lake's bird sanctuaries are usually booked during the dry season (December-April).
Among the largest river cruise companies with ships passing through Boeung Tonle Sap are CroisiEurope, Avalon Waterways, Emerald Waterways, Scenic, Lindblad-National Geographic, Nicko-Mystic. The one-way itineraries are between homeports Siem Reap and Phnom Penh, while longer itineraries connect to Saigon (Vietnam) and feature cruising the Mekong Delta.
Tonle Sap Lake fishing
During lake's flooding fishing is forbidden. It is allowed only at the end of the monsoon season (when lake's levels drop). During the following (dry) period fishermen construct floating houses and cluster them into villages on Tonle Sap River - along 1/2 of the river, as the other half is used for navigation.
Fishing is via cone-shaped nets dropped into the water for a very short time. The technique allows them to catch 2-3 tons of fish each time the net is dropped and lifted. Because of the Buddhist prescriptions against killing, Cambodians don't physically kill the fish. After taking it out of the water they wait for it to die naturally.
Fishers (mostly women) then cut off the fish heads, clean the fish in the river, remove the fat then salt the fish for preservation. Fish heads are collected, dried in the sun and used as fertilizer. The fat is also collected and used for making soap. Fishermen exchange fish for rice, and the excess rice is sold.