The Sea of Galilee is a freshwater lake. Despite its name, it carries roughly 600 milligrams of total dissolved solids per liter, well within the range that limnologists classify as fresh water. The “sea” label is a holdover from ancient naming conventions, not a description of its chemistry. That said, the lake has an unusually complicated relationship with salt, fed by hidden saline springs beneath its bed and shaped by the same tectonic rift that produced the hypersaline Dead Sea just 105 kilometers downstream.
Why It Is Called a Sea
In the ancient world, any large, landlocked body of water could earn the title “sea.” The Hebrew name Yam Kinneret, used in the Old Testament, follows that convention. Greek and Latin texts added more names: the Sea of Tiberias, the Lake of Gennesaret. The Arabic name, Buhayrat Tabariyya, translates closer to “Lake Tiberias.” Modern hydrology settled the matter long ago. The lake sits in northern Israel, measures about 21 kilometers long and 13 kilometers wide at its broadest, and holds approximately 4 cubic kilometers of water. By any scientific standard it is a lake, and a freshwater one at that.
How Fresh the Water Actually Is
Freshwater is generally defined as having fewer than 1,000 milligrams per liter of total dissolved solids. The Sea of Galilee sits at around 600 milligrams per liter, placing it firmly in the freshwater category but noticeably saltier than many well-known lakes around the world.1Chemical Geology. Lake Kinneret (The Sea of Galilee): the effects of diversion of external salinity sources and the probable chemical composition of the internal salinity sources For comparison, large North American or European lakes typically measure well under 300 milligrams per liter. So while the Sea of Galilee is unambiguously fresh, its water has a slightly mineral quality that residents and visitors sometimes notice. This mineral character has real consequences: the lake serves as a major source of drinking and irrigation water for Israel, providing roughly a quarter to a third of the country’s drinking supply in some years, and its salinity is monitored closely by water authorities.2Elsevier. Evaporation from Lake Kinneret, Israel, during hot summer days
Where the Salt Comes From
The elevated mineral content is not a mystery. A significant share of the salt entering the Sea of Galilee comes from saline springs that discharge directly through the lake bed, many of them unmonitored and difficult to measure because they sit beneath the water surface.3Limnology and Oceanography. Chemical tracing of salinity sources in Lake Kinneret (Sea of Galilee), Israel These submarine springs carry water that is far saltier than the lake itself, a mixture of ancient brines from deep aquifers and fresh groundwater from shallow ones. Along the western shore, hot saline springs emerge where these two groundwater systems meet on their way to the surface.4Water Resources Research. Hydrogeological modeling of the saline hot springs at the Sea of Galilee, Israel
The most studied of these springs are the Fuliya springs (sometimes spelled Tabgha), which sit along the lake’s northwestern shore. Geochemical analyses of the lake’s internal salt sources show ionic ratios that closely match those measured at the Fuliya springs and at a deep observation well north of the lake, suggesting that a connected brine system feeds salt into the lake from below.1Chemical Geology. Lake Kinneret (The Sea of Galilee): the effects of diversion of external salinity sources and the probable chemical composition of the internal salinity sources So the lake receives a slow, constant injection of dissolved minerals from underground, which is why its salinity sits higher than you would expect from surface runoff alone.
The Ancient Brine Beneath the Lake
The brines feeding into the Sea of Galilee have an origin story stretching back tens of thousands of years. The lake occupies a topographic depression within the Dead Sea Rift, the same tectonic fault system that produced the Jordan Valley and the Dead Sea basin. During the late Pleistocene, roughly 26,000 to 24,000 years ago, a massive ancient lake called Lake Lisan filled much of this rift, merging the basins that would later become the Sea of Galilee and the Dead Sea into a single water body. Lake levels reached around 170 meters below mean sea level at their peak, high enough to drown what is now the Sea of Galilee basin.5Quaternary Research. The late Quaternary limnological history of Lake Kinneret (Sea of Galilee), Israel
During this period, the dense, salty water of Lake Lisan likely percolated into the sediments beneath the northern basin. When the ancient lake receded and a freshwater lake formed in its place, those trapped solutes began slowly leaking back upward into the overlying water. Modeling work supports this hypothesis: the saline groundwater currently discharging into the Sea of Galilee appears to include remnants of this ancient Lake Lisan brine, still working its way out of the sediment thousands of years later.6Water Resources Research. Transient salt transport modeling of shallow brine beneath a freshwater lake, the Sea of Galilee, Israel
What makes this geological history remarkable is that despite the Pleistocene merger, the Sea of Galilee never became saline itself. Sediment records show that the lake has deposited calcite continuously for at least 40,000 years, while the Dead Sea basin deposited aragonite, a mineral that forms only in water saturated with the kind of concentrated brine the Dead Sea is known for. The calcite record proves that the hypersaline Dead Sea brine never actually invaded the northern basin, even when the two lakes briefly shared a surface connection.5Quaternary Research. The late Quaternary limnological history of Lake Kinneret (Sea of Galilee), Israel The freshwater character of the Sea of Galilee is not a recent development. It has persisted through dramatic climate swings and lake-level changes spanning tens of millennia.
Two Brine Origins Under One Lake
The underground salt sources are not uniform across the lake bed. Analysis of pore water from sediment cores reveals that the brines beneath the central and northern parts of the lake are chemically distinct from those beneath the southeastern shore. The central-northern brines appear to be residual evaporative brines belonging to the same family of ancient rift-valley brines found elsewhere in the Dead Sea system.7Chemical Geology. The origin of brines underlying Lake Kinneret The southeastern brines have a different chemical signature, suggesting a separate source or a different geological pathway. This patchwork of brine origins means that the lake’s salt input is not evenly distributed; some areas of the lake bed contribute more dissolved minerals than others, creating localized plumes of slightly saltier water near the bottom.
How Israel Manages the Lake’s Salinity
Because the Sea of Galilee doubles as a national water reservoir, Israel has gone to considerable lengths to control its salt balance. Starting in the 1960s, engineers constructed the Saline Water Diversion Canal, a channel designed to intercept several of the most concentrated saline springs before their water could reach the lake. The canal collects this salty discharge and routes it southward, bypassing the lake entirely.
The diversion had a measurable effect. After the canal began operating, the concentrations of chloride, sodium, magnesium, potassium, calcium, sulfate, and bromide in the lake all declined over the long term.1Chemical Geology. Lake Kinneret (The Sea of Galilee): the effects of diversion of external salinity sources and the probable chemical composition of the internal salinity sources At the same time, certain ionic ratios shifted, reflecting the removal of those specific spring inputs from the lake’s chemical budget. The diversion did not eliminate the salt problem entirely, because many of the submarine springs that discharge through the lake floor are too deep or diffuse to intercept. But it brought the lake’s salinity down meaningfully and improved its suitability as a drinking water source.
The Role of Evaporation
Salt management is not only about what flows in. Water that leaves the lake through evaporation takes no salt with it, so every liter that evaporates concentrates the minerals left behind. In the Sea of Galilee’s semi-arid climate, evaporation is substantial. It accounts for roughly 35 to 50 percent of the lake’s total water loss in any given year.2Elsevier. Evaporation from Lake Kinneret, Israel, during hot summer days During hot summers, when temperatures around the lake can exceed 40°C, evaporative losses spike. Over time, changes in evaporation rates directly affect salinity; a run of drought years with low inflow and high evaporation can nudge the lake’s mineral content upward even without any change in the saline spring input.
This makes the lake’s freshwater status something that requires active maintenance rather than something that simply takes care of itself. If the Jordan River’s inflow drops due to drought or upstream diversions, and evaporation stays high, the balance tips toward saltier water. Israeli water managers track this carefully, and it is one reason the country has invested heavily in desalination plants along its Mediterranean coast in recent decades, reducing the pressure on the Sea of Galilee as a sole water source.
How the Lake Mixes Through the Year
The Sea of Galilee is a warm monomictic lake, which means it undergoes one major mixing event per year. From roughly March or April through December or January, the water column is thermally stratified: a warm upper layer floats on top of a cooler, denser layer below.8Frontiers in Microbiology. Particle-Associated Microbial Community in a Subtropical Lake During Thermal Mixing and Phytoplankton Succession During winter, cooling air temperatures reduce the surface temperature until the density difference disappears and the entire water column turns over, mixing thoroughly from top to bottom.
This annual mixing cycle matters for the lake’s chemistry. During stratification, saline groundwater seeping up from the lake bed accumulates in the bottom layer, where it can create a slightly saltier, oxygen-poor environment. When the lake mixes in winter, that bottom water and its dissolved salts get redistributed throughout the entire volume, diluting the salt plumes but also exposing the surface layer to nutrients and minerals that had been trapped below. The mixing event resets the lake’s chemistry and plays a major role in driving the following spring’s plankton bloom, which in turn supports the lake’s fish populations, including the commercially and culturally important species sometimes called “St. Peter’s fish” (a tilapia).
From the Sea of Galilee to the Dead Sea
The Sea of Galilee sits at about 209 meters below sea level, making it one of the lowest freshwater lakes on Earth. Water exits the lake at its southern end and flows into the Lower Jordan River, which meanders roughly 220 kilometers southward before emptying into the Dead Sea, which sits at around 430 meters below sea level and has salt concentrations roughly ten times that of the ocean.9Elsevier. Water quality and discharge of the Lower Jordan River
This downstream relationship has been profoundly altered over the past several decades. Both the Sea of Galilee and the Yarmouk River, the two main tributaries of the Lower Jordan, were dammed during the 1960s to meet the growing water needs of Israel, Jordan, and Syria.9Elsevier. Water quality and discharge of the Lower Jordan River The result is that far less fresh water now reaches the Dead Sea than did historically, and the Dead Sea has been shrinking dramatically as a consequence, dropping roughly a meter per year. The water that does reach the Lower Jordan today is a much smaller flow with poorer quality, partly because the diverted saline springs from the Sea of Galilee’s canal system are routed into the river’s lower reaches instead of being fully treated.
The irony is that managing the Sea of Galilee’s freshness has contributed, at least modestly, to the Dead Sea’s decline. The salt removed from the lake to protect drinking water quality is transferred downstream into a river system that is already stressed. The ecological and geopolitical complications of water allocation in this region are difficult to overstate, but the basic physical fact remains: fresh water starts at the Sea of Galilee and salt accumulates as you move south along the rift.
The Lake’s Ecology in Fresh Water
The freshwater status of the Sea of Galilee supports a diverse ecosystem that would not survive in saline conditions. The lake harbors several species of tilapia, catfish, and other freshwater fish, along with rich phytoplankton and zooplankton communities. The annual stratification cycle drives a predictable succession of algal blooms, with spring dominated by dinoflagellates and summer by cyanobacteria, a pattern typical of warm, nutrient-rich freshwater lakes.
This ecology is sensitive to salinity shifts. Even modest increases in dissolved minerals can alter which algal species dominate, change nutrient cycling, and affect fish reproduction. The lake’s status as a meso-eutrophic system, meaning it has moderate to high nutrient levels, makes it productive but also vulnerable to water-quality changes. Maintaining its freshwater character is not just a matter of taste or chemistry; it is an ecological imperative for the species that depend on it and for the fisheries that have operated on the lake for thousands of years.
Why the Confusion Persists
The name is the main culprit. English speakers encounter “Sea of Galilee” in religious texts, travel guides, and news reports, and the word “sea” implies saltwater. People familiar with the region sometimes add to the confusion by noting its proximity to the Dead Sea and its location along the same geological fault, leading to the reasonable but incorrect assumption that the two bodies of water share similar chemistry. The presence of hot saline springs near the lake’s shore, which have been known since antiquity and were used as thermal baths in the Roman period, further muddies the picture.
In reality, the Sea of Galilee is one of the more carefully studied freshwater lakes in the world, partly because of its importance to the Israeli water supply and partly because of its cultural significance. Its salinity has been tracked for decades, its underground salt sources have been mapped with isotopic tracers, and its geological history has been reconstructed from sediment cores going back 40,000 years. The science is clear: this is a freshwater lake with a salt problem that is well understood and actively managed, not a salt lake in disguise.