tidevatten

Tidevatten, or tidal water, refers to coastal and estuarine waters whose level and, to some extent, salinity are shaped by tides. These waters are typically brackish to marine, with freshwater input from rivers and rainfall affecting gradients along the estuary or coastal plain. The term is used to describe a range of environments, from open-coast bays to extensive tidal flats and salt marshes.

Tides are driven by the gravitational forces of the Moon and the Sun. Their interaction creates regular sea-level rises and falls, which in many places occur twice daily (semidiurnal) or once daily with varying amplitudes (diurnal). Spring tides, occurring during full and new moons, feature higher highs and lower lows, whereas neap tides, around quarter moons, have smaller tidal ranges. The exact tidal regime depends on coastline shape, water depth, bathymetry, and wind and weather conditions.

Ecologically, tidevatten host diverse communities. Intertidal zones are exposed during low tide and submerged at high tide, creating dynamic habitats such as mudflats, salt marshes, mangroves, and seagrass beds. These areas support a wide range of species and act as nurseries for many fish and invertebrates. Tidal mixing transfers nutrients between marine and freshwater systems and influences sediment transport and chemistry.

Human activities intersect with tidevatten in navigation, fisheries, coastal infrastructure, and energy production. Estuaries often serve as ports and fisheries hubs, while tidal energy schemes exploit the regular flow of water through turbines or barrages. Ongoing climate change and sea-level rise pose challenges for coastal management and habitat conservation.

Examples of notable tidal systems include the Bay of Fundy, the Severn Estuary, and other large estuarine regions worldwide.