# What Are Saltwater Lakes and How Do They Form? > Saltwater lakes, more precisely called saline lakes, are inland bodies of water containing elevated concentrations of dissolved salts. Most form in closed drainage basins where streams carry dissolved minerals into a lake but no river carries them onward to the ocean. Water... Canonical URL: https://www.argo.net/what-are-saltwater-lakes-and-how-do-they-form/ Byline: ARGO.net Editorial Team Published: 2026-08-22T10:09:47+00:00 Updated: 2026-08-23T23:28:00+00:00 Categories: Explainer, Water ![Aerial view of the Great Salt Lake in Utah](https://www.argo.net/wp-content/uploads/2026/08/verified_featured_52429.jpg) **Saltwater lakes**, more precisely called saline lakes, are inland bodies of water containing elevated concentrations of dissolved salts. Most form in closed drainage basins where streams carry dissolved minerals into a lake but no river carries them onward to the ocean. Water leaves mainly through evaporation, while salts remain and become concentrated. Yes, saltwater lakes occur on every continent and their chemistry varies widely. Some are only mildly saline; others are several times saltier than seawater. Names can be misleading: the Dead Sea and Caspian Sea are lakes because they are enclosed inland waters, while an ocean sea is connected to the global ocean. ## What makes lake water saline? Rain and snow contain little dissolved mineral matter, but water acquires ions as it moves across soil and weathers rock. Rivers and groundwater deliver sodium, chloride, carbonate, sulfate, calcium, magnesium and other dissolved substances to lakes. The particular rock types and geothermal inputs in a watershed influence the final chemical mixture. In an open lake, an outlet river exports water and dissolved material. In a **closed basin**, also called an endorheic basin, surface drainage ends inland. The [USGS water-cycle glossary](https://www.usgs.gov/glossary/glossary-water-cycle-terms) defines saline lakes through the buildup of salts as evaporation removes water, noting that most lack an outlet river. Evaporation transfers water molecules into the atmosphere but leaves most dissolved ions behind. Repeated inflow and evaporation can therefore raise salinity over thousands of years. If a lake shrinks enough, some minerals precipitate as crystals, creating salt flats or layered evaporite deposits. ## Closed basins and dry climates Most perennial saline lakes lie in arid or semiarid regions where evaporation is strong relative to precipitation. Mountains can create internal drainage by enclosing a basin or casting a rain shadow. Water flows downhill into the lowest depression, but no channel crosses the basin rim. A classic [USGS study of closed lakes](https://pubs.usgs.gov/publication/pp412) found that their levels and areas fluctuate more than those of open lakes because changes in inflow cannot be balanced by river outflow. Shallow terminal lakes may expand across broad flats during wet years and retreat sharply during drought. Closed drainage alone does not guarantee very salty surface water. Some lakes lose dissolved salts through groundwater seepage, while others are geologically young or receive enough fresh inflow to remain dilute. Climate, basin permeability, water residence time and mineral supply act together. ## Saline, brackish and hypersaline water Salinity is the concentration of dissolved salts, measured in units such as grams per liter or parts per thousand. Ocean water averages roughly 35 parts per thousand, although it varies by place. The [USGS salinity overview](https://www.usgs.gov/water-science-school/science/saline-water-and-salinity) uses broad freshwater, slightly saline, moderately saline and highly saline categories based on dissolved-solids concentration. **Brackish water** lies between fresh water and seawater in salinity. It commonly occurs where rivers mix with the ocean in estuaries, but a lake can also be brackish. "Saltwater lake" has no single universal numerical cutoff in everyday use, so a reported salinity and measurement date are more informative than the label alone. Hypersaline water is saltier than typical seawater. Even then, equal total salinity does not mean equal chemistry. Mono Lake is alkaline and rich in carbonate, while Great Salt Lake brine contains a different balance of major ions. Mineral composition affects pH, density, organisms and which salts crystallize first. ## Why salinity changes over time Lake salinity rises when water volume falls while the dissolved salt mass stays similar. Wet periods can dilute a lake; drought and water diversions can concentrate it. Salts may also be removed when crystals form, brine seeps underground, wind carries salty dust away, or people extract minerals. Shallow lakes respond especially quickly because a modest vertical change exposes a large area of gently sloping lakebed. Salinity can differ within the same lake when a causeway or natural sill restricts mixing. USGS satellite observations show that [Great Salt Lake's north arm is more saline](https://www.usgs.gov/centers/utah-water-science-center/science/great-salt-lake-fifty-years-change-through-satellite) than its southern arm because of restricted exchange and the location of freshwater inflows. A salinity figure without a date, location and method can therefore mislead. Seasonal inflow and evaporation alter concentrations, while long-term climate and water use shift the whole lake. Measurements from separate arms or depths may not be directly comparable. ## Great Salt Lake Utah's Great Salt Lake is the largest saline lake in North America and a remnant of prehistoric Lake Bonneville. Rivers deliver water to the terminal basin and evaporation provides the main exit. A [USGS geochemical study](https://www.usgs.gov/publications/geochemical-evolution-great-salt-lake-utah-usa) links its brine chemistry to rock weathering across the drainage basin and to repeated mineral precipitation and redissolution. Salinity varies greatly with lake level and between arms divided by the railroad causeway. Brine shrimp, brine flies, algae and microbes support huge numbers of birds despite the limited fish habitat in the saltier open lake. The ecosystem is biologically rich in a specialized way rather than lifeless. Great Salt Lake illustrates the dependence of a terminal lake on its entire watershed. Water consumed upstream does not reach the lake, so human diversions combine with drought and warming to affect level, exposed lakebed, salinity, wetlands and industries. ## Mono Lake California's Mono Lake occupies a closed basin east of the Sierra Nevada. It is saline and alkaline, with no fish in the lake, yet it supports abundant brine shrimp and alkali flies that feed migratory birds. Freshwater streams entering the basin create important wetland and delta habitats. The lake is a remnant of a much larger Pleistocene water body known as Lake Russell. According to the [USGS history of the Mono Lake volcanic field](https://www.usgs.gov/volcanoes/mono-lake-volcanic-field/science/geology-and-history-mono-lake-volcanic-field), the ancient lake reached about 130 meters above the modern level. Volcanic features and uplifted lake sediment further distinguish the basin. Mono Lake's tufa towers form when calcium-rich freshwater enters carbonate-rich lake water and calcium carbonate precipitates. Many towers developed underwater and became exposed as the level fell. They record chemistry and hydrology, not piles of ordinary table salt. ## The Dead Sea The Dead Sea is a hypersaline lake in a closed watershed between Jordan and Israel and the West Bank. Its traditional "sea" name does not change its geographic classification. Water primarily arrives through the Jordan River system and leaves by evaporation. High salinity and dissolved-mineral content make the water unusually dense. Fish and aquatic plants cannot live in its open water, although salt-tolerant microbes can persist under some conditions. Broad claims that it supports absolutely no life overlook microbial biology. The lake level has declined as tributary water has been diverted and mineral industries use evaporation ponds. [USGS Landsat records](https://eros.usgs.gov/earthshots/dead-sea-israel-jordan-west-bank) show the retreat and the separation of the former southern basin from the northern water body. The modern southern pools are industrial evaporation ponds, a distinction often lost on maps. ## The Caspian Sea and other examples The Caspian Sea is the world's largest inland water body by surface area and is legally and historically called a sea, yet geographically it is an enclosed lake. Its water is brackish overall rather than uniformly ocean-salty and salinity varies from the fresher north to saltier southern areas. It has no natural connection to the ocean. Other saline lakes include Lake Urmia in Iran, Lake Van in Türkiye, Lake Eyre or Kati Thanda in Australia and many lakes in East Africa's Rift Valley. The Aral Sea was once one of the world's largest lakes, but river diversion caused extreme shrinkage and large changes in salinity. Each basin has a distinct water budget and geologic history. Some saline waters have marine-sounding names, while some freshwater bodies are called seas. Classification depends on physical connection and drainage rather than the word on a map. Argo's [lake-versus-pond comparison](https://www.argo.net/lake-vs-pond-key-differences/) explains why common names and scientific definitions do not always align neatly. ## Life in salty lakes Rising salinity excludes organisms that cannot maintain water and ion balance, but it creates habitat for specialists called halophiles. Microbes, algae, brine shrimp and brine flies can flourish where fish predators are absent. Their high productivity may support migratory waterbirds at continental scales. Food webs can be simple and vulnerable. If salinity moves beyond the tolerance of a key alga or invertebrate, birds may lose a major food supply. Freshwater wetlands around a saline lake add habitat diversity and can be damaged when inflow or lake level changes. Color sometimes reveals biology. Dense microbial communities may give brines pink or red hues, while algae influence green tones. Color alone cannot determine salinity, because suspended sediment, depth and sunlight also affect appearance. ## Saline lakes as resources and records People extract sodium chloride, potash, magnesium compounds, lithium-bearing brines and other materials from saline lakes and their deposits. Evaporation ponds concentrate brine until minerals precipitate. Extraction can support local economies but also changes water and salt budgets, so quantities and effects must be assessed basin by basin. Lake sediments preserve pollen, fossils, volcanic ash, mineral layers and chemical indicators of earlier conditions. Alternating wet and dry periods can leave distinct deposits. Geologists use cores and old shorelines to reconstruct climate, inflow and lake-level history. Conservation requires treating the lake and watershed as one system. Upstream withdrawals, groundwater pumping, climate and land management determine how much water reaches the basin. Comparisons with [salinity among oceans](https://www.argo.net/the-saltiest-ocean-in-the-world/) provide useful scale, while Argo's account of [Earth's freshwater](https://www.argo.net/where-is-most-of-earths-freshwater/) shows why these saline lakes occupy a separate part of the water inventory. The [Dead Sea’s position below sea level](https://www.argo.net/is-the-dead-sea-the-lowest-place-on-earth/) shows how elevation, evaporation and a closed basin can combine.