Väljavoolu

Väljavoolu is the Estonian term for outflow, the movement of fluids, gases, or energy out of a system through a boundary or outlet. It is a general concept used in hydrology, engineering, biology, and environmental science. Outflow is typically described by a flow rate (Q), expressed in units such as cubic meters per second (m3/s) or liters per second (L/s).

In hydrology and water resources, väljavoolu refers to discharge from basins, lakes, or reservoirs. Examples include a lake’s outflow through a river, groundwater outflow from an aquifer, or drainage effluent from a watershed. The balance of inflow and outflow determines changes in storage and water level; at steady state, inflow equals outflow.

Outflow is measured at gauging stations, weirs, flumes, or with flow meters. In hydrological modeling, the continuity equation relates inflow, outflow, and storage change: storage change equals inflow minus outflow. Managing outflow is essential for flood control, water supply, and ecosystem health, because the timing and quality of outflow affect downstream areas.

In biology and pharmacology, outflow can refer to the efflux of ions or metabolites from cells, often mediated by membrane transporters called efflux pumps. Cellular efflux influences drug accumulation and resistance. Exocytosis and other vesicle-mediated processes are also forms of outward transport.