Water science news, explainers, and statistics covering freshwater, hydrology, lakes, rivers, groundwater, ice, and Earth’s connected water systems.
A tide is the long-period rise and fall of ocean water produced mainly by the gravity of the Moon and Sun. A current is horizontal water movement from one place to another. Tides can generate currents, but wind, water-density differences and the shape of coasts also drive currents. The distinction separates water level from water…
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Stream order is a system for ranking channels within a river network. On a map, the smallest channels at the tips of the network receive the lowest number. Their ranks increase only when channels of the same order meet, so the number describes a stream’s position in the branching network rather than its width on…
A drainage divide is the boundary between neighboring areas of surface drainage. Rain falling on one side flows toward one outlet, while water on the other side follows a different stream system. The divide usually follows ridges or local high ground, but it can be subtle across flat terrain. Every watershed has a divide, from…
Watershed, drainage basin and catchment usually describe the same core feature: an area of land whose surface water drains to a common outlet. The preferred word changes by country, profession and mapping system. Scale and the chosen outlet matter more than the label. In some older geographic usage, “watershed” means the high boundary separating basins.…
