rivers

Rivers are natural flowing watercourses that drain an area of land known as a drainage basin or watershed. They originate from sources such as springs, ice melt, or rainfall collected in headwaters and flow through a network of channels until they reach an ocean, sea, lake, or another river. The main stem and tributaries form a river system.

Along their courses rivers transport water, sediment, and energy. Discharge varies seasonally and with weather; rivers erode their beds and banks through processes such as hydraulic action, abrasion, and solution, while transporting sediment (bed load, suspended load, and dissolved load). Bedrock rivers tend to carve steep valleys; alluvial rivers form broad valleys and rich floodplains. Meandering and braiding are common channel patterns; oxbow lakes can form when bends are cut off. Deposition creates features such as deltas at mouths and point bars along bends.

Rivers shape landscapes and ecosystems. Floodplains, wetlands, and riparian vegetation support diverse communities. Inhabitants rely on rivers for drinking water, irrigation, hydroelectric power, navigation, and industry, yet rivers are vulnerable to pollution, damming, over-extraction, and climate change.

Rivers are often classified by size, discharge, and permanence. Perennial rivers flow year-round; seasonal or intermittent rivers may stop during dry periods. Many rivers cross political boundaries and require transboundary management. Conservation and restoration efforts aim to maintain water quality, ecological integrity, and flood resilience.