Belize River is a 180-mile (290 km) river in Belize that drains more than one-quarter of the country as it winds along the northern edge of the Maya Mountains across the center of the country to the sea just north of Belize City . However, the Belize River/Mopan River Catchment contains over 45 percent of the population of Belize. Also known as the Old River, the Belize River is navigable up to the Guatemalan border and served as the main artery of commerce and communication between the interior and the coast until well into the twentieth century.
The Belize River begins where the Mopan River and Macal River join just east of San Ignacio (Cayo), Belize . It flows through the Belize river valley which is largely tropical rain forest. The river has long been associated with forestry, particularly of mahogany, some small stands of which still occur.
The Belize River is a vital source of drinking water and other domestic use for local people living along the river; however, water quality is degraded from sediment, nutrient loading, pesticides and other toxins. The major source of degradation is the extensive deforestation in the upper reaches of the Mopan River and non-sustainable agriculture. Karper and Boles have asserted: "The greater Mopan/Belize River Catchment provides a prime example of a watershed under stress from extensive non-sustainable agricultural practices that have occurred within the region over the past three decades." Slash-and-burn agricultural practices by native peoples are contributing to such watershed degradation in an ongoing way.