Lake Kinneret (The Sea of Galilee): the effects of diversion of external salinity sources and the probable chemical composition of the internal salinity sources

Abstract

This paper investigates the chemical variations and evolution of Lake Kinneret (LK), the Sea of Galilee after the diversion of onshore saline springs through the Salinity Diversion Channel (SDC) which reduced the salinity of the lake water. The mass-balance approach enables to determine the average chemical composition of the unknown internal lake sources of salinity that in addition to other known sources, contribute salts and control the chemistry of the lake water. This study reveals, for the first time, the average chemical composition of the internal lake salinity sources. Mass balances show that the water discharge of the lake internal sources is 61×106 m3 year−1 and that these sources contribute 72,000 tons of chloride, annually. The SDC operation caused a long term decrease in the concentrations of Cl, Mg, Na, K, Ca, SO4 and Br in lake water. Concomitantly, the ionic ratios of Na/Cl, Mg/Cl. Ca/Cl, K/Cl and SO4/Cl have increased and Br/Cl ratio has decreased. The average chemical composition of the lake internal sources, is characterized by Na/Cl and Mg/Cl ionic ratios which closely resemble those measured in the two well known submerged saline springs, of Fulyia a and Fulyia b, and in water of a deep observation well, located north of the lake (referred to as KIN-8). The decrease in Br/Cl ionic ratio from ≥3.58×10−3 prior to the SDC operation, to 3.29(±0.11)×10−3 in mid 1990s implies that the major internal sources of Cl and Br to the lake are characterized by Br/Cl ratios ≤3.29×10−3. Br/Cl ionic ratios somewhat lower than 3.29×10−3 were found only in Fulyia a and Fulyia b springs and in KIN-8 water. It is therefore suggested that Fulyia like water is the internal saline source which supplies most of the Na, Cl and Br to the lake. Sulphate, however, is contributed to the lake mainly (over 80%) through freshwater streams. Calcium and alkalinity originate mainly from freshwater sources, including internal lake flow of groundwater, lower in salinity but saturated with CaCO3. Thus, internal sources of solutes are mostly composed of the saline end member of Fulyia like water and of fresher groundwater. These conclusions have practical implications for lake water management.