útstreymis

útstreymis is the Icelandic term for outflow, the process or amount of material that leaves a defined system. In hydrology and related fields it commonly refers to the discharge of water from a body of water, such as a lake, reservoir, river reach, or groundwater aquifer. Outflow is usually expressed as discharge (Q) in units of cubic meters per second (m3/s) and is a central component of water budgets, along with inflow, precipitation, evaporation, and changes in storage.

Outflow is governed by the continuity of mass and can vary with weather, season, topography, and human management. In lakes, for example, outflow through a river or outlet dam controls water level and residence time. In groundwater systems, discharge to springs or streams represents the lower boundary of the aquifer and can influence baseflow in rivers and nutrient transport.

The ecological and environmental significance of útstreymis lies in the transport of nutrients, sediments, and pollutants. The rate and composition of outflow affect habitat quality, salinity in estuarine zones, and downstream ecosystem functioning. In many regions, managing outflow is essential for flood control, water supply, and evaporation losses.

Etymology: útstreymis derives from út- meaning out and streymi related to streaming or flow, reflecting its meaning as the outflow from a system.