Most saline lake basins are found between about 400 and 1500 m above sea level (masl) and were formed by tectonic action. Some were formed during volcanic activity (maars and craters) while others were created during recent glacial activity.
True saline lakes (athalassic) occur mainly in arid (precipitation 25-200 mm) and semi-arid (precipitation 200-500 mm) climatic zones (between 53° N and 30° N in the Northern Hemisphere and 3° N and 42°S in the Southern Hemisphere; and south of 77° S in Antarctica) where net evaporation exceeds precipitation. They are usually located in hydrologically closed (endorheic) basins and consequently are the termini of inland drainage basins (inflows but no outflows).
Some saline lakes (thalassic), however, due to their proximity to marine environments, exhibit features (ionic composition and biology) closer to marine environments than inland saline lakes.
Sources of incoming water include precipitation, groundwater seepage, underwater springs (mostly in karst environments), creeks, and rivers. Approximately 1/10 of the Earth's surface area is made up of such closed or endorheic drainage basins (Figure 2). The location of saline lakes within semiarid and arid climatic zones and endorheic drainage basins means that saline lakes are extremely responsive to climate, both within and between years. During times of decreased precipitation and/or drought, or changes in land use patterns within the basin, water levels and volumes can decrease markedly with concomitant increases in salinity. For example, from 1904 to the 1990s, water levels in Redberry Lake, a MgSO4 dominated lake in south central Saskatchewan, dropped from 737 to 728 masl. At the same time total dissolved solids (TDS) rose from 12 000 to 19 000mg l-1 (12-19%) (Figure 3). These changes are thought to be a direct result of land use changes in the basin as well as periods of drought. Small shallow North American prairie wetlands can show this kind of decrease in water level and increase in salinity within one season (Figure 4). Because small climatic changes can be amplified in saline lakes and wetlands, they are very sensitive to climate change.
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