Chemical tracing of salinity sources in Lake Kinneret (Sea of Galilee), Israel

Lake Kinneret is a freshwater lake in northern Israel that receives a major part of its salt input from unmonitored springs that discharge through the lake's bottom. We attempt to characterize the nature of these springs by e stimating their chemical composition. While the springs around Lake Kinnere t are subject to wide spatial and temporal variations in their ionic concen trations, specific sodium (Na), potassium, magnesium (Mg), strontium, bromi ne, and lithium to chlorine (Cl) ion ratios are almost constant within indi vidual springs and spring groups. The radium:Cl ratio and the delta(18)O-Cl relationship confirm the notion that the spring waters result from recent mixing between saline brines and freshwater. Available compositional data f rom past years along with new analyses of the lake and its known springs al low identification of the salinity source that causes the observed deficit in the lake's salt budget (e.g., 91-93% chloride). The relative contributio ns from these saline springs are different for different ions; this contrib ution is highest for bromide (95%), decreases to 84% for Na, and is less th an 50% for Mg. Two independent approaches have been used for balancing the salts in the la ke, and they are as follows: (1) an annual mass balance between salt remova l and supply of the different ions, assuming a steady-state lake; and (2) s imulation of the lake's evolution from 1964 (the beginning of salt removal from the lake via the Salinity Diversion Channel) until the present. Both m ethods predict very similar ionic ratios for the (yet unknown) average sali ne spring(s), testifying to the reliability of both approaches. The ionic r atios so obtained closely resemble Fuliya (+/- Tabgha)-type waters, excludi ng the Tiberias and eastern shore springs as significant salt sources. This inferred composition of the average unmonitored springs depends strongly o n present-day diversion of saline springs (this diversion thus prevents the ir flow into the lake). The different ionic ratios that identify the variou s spring groups reflect the respective compositions of the brine pockets th at feed them. Our simulation also shows that the layered structure of Lake Kinneret enhanced the evolution rate of the lake after the implementation o f the salt diversion program in 1964.