Flodsystemet

A flodsystemet, or river system, is the network of rivers and streams that drain a landscape. It includes the main river, its tributaries, as well as connected lakes, wetlands and groundwater that contribute to the flow. The boundary of a river system is the watershed or drainage basin, the area from which all precipitation drains toward the river.

Key components include the drainage basin, the river network, floodplains, and estuaries. The flow is governed by precipitation, evaporation, infiltration, and runoff. Sediment and nutrients are transported downstream by the river, shaping morphology by erosion, transport, and deposition. Groundwater exchange can sustain flow during dry periods.

River systems exhibit dynamic morphologies such as straight or braided channels, meanders, and oxbow lakes. Seasonal and long-term changes in discharge drive floods, droughts, and shifts in channel planform. Human modifications such as damming, channelization, and water withdrawals alter natural regimes and sediment delivery.

River systems are central to ecosystems and human societies. They provide freshwater for consumption and agriculture, support habitats for diverse organisms, and offer hydropower, navigation, and recreation. Integrated river basin management seeks to balance water use, ecological integrity, and flood risk, often involving pollution control, restoration projects, and stakeholder cooperation.

Global river systems show wide variation in size and regime, from small mountain streams to large basins such as the Amazon or Congo. They are vulnerable to climate change, land-use change, and pollution, which can reduce flows, degrade habitats, and alter sediment transport.