closedbasin

A closed basin, commonly referred to as an endorheic basin, is a drainage basin that retains water and has no natural outlet to rivers, seas, or oceans. Inflows come from precipitation, snowmelt, and runoff, but the water cannot escape through an outflow; it leaves mainly by evaporation or infiltration. This creates conditions in which dissolved salts and minerals accumulate over time, often producing saline or alkaline lakes, playas, and evaporite deposits.

Geography and hydrology of closed basins are strongly influenced by climate and regional geology. They are most common in arid and semi-arid regions, where high evaporation rates coupled with limited rainfall promote salt buildup. The interior drainage and lack of external outlets mean that even modest changes in input or losses can cause large fluctuations in lake levels and water chemistry, leading to ecological shifts and land surface changes inside the basin.

Examples and distribution: well-known endorheic basins include the Great Basin in western North America, the Tarim and Qaidam basins in China, and the Caspian Sea basin, which is the largest endorheic system by area. The Lake Eyre Basin in Australia and the Dead Sea region are other notable examples. Historically, some basins have seen dramatic changes in water balance due to natural climate variation or human water use.

Ecological and human considerations: endorheic systems host specialized organisms adapted to brackish or hypersaline conditions but are particularly vulnerable to climate change and water management practices that alter inflows, potentially causing lake shrinkage, salinization, and habitat loss.