Water quality and discharge of the Lower Jordan River

The fresh surface water of the Lower Jordan River (LJR) has been limited in the past several decades due to damming of its main tributaries, which reduced the annual flow by 90%, leaving a mixed flow of polluted and saline sources. A monitoring and sampling hydrometric station was installed on the southern LJR to track the temporal variations of its discharge (Q) and hydrochemistry. In addition to manual water sampling, the station includes an automatic water sampler and cellular transmitting pressure and EC sensors, allowing real time observation. All samples were analyzed for major ions (Na⁺, Ca²⁺, Mg²⁺, K⁺, Cl^-, SO₄^2-, NO₃^-, Br^-) and several samples were analyzed for selected isotopes (³⁴S_sulfate, ¹⁸O_sulfate, ¹⁵N_nitrate, ¹⁸O_nitrate, ²H_water, ¹⁸O_water) as tracers. A general inverse seasonal trend was found between EC and water level although extreme values relate to flood events during the wet period. High values of EC (up to 40.3mS/cm), high concentration of major ions, and flood events characterized by clockwise EC-Q hysteretic relations likely relate to the dissolution of precipitated salts in the basin. Isotope analyses reveal lithology and sewage as the respective major contributors of salinity; they were used to identify events unrelated to runoff (i.e., to precipitation in the area). The continuous monitoring is an essential tool for understanding long term changes of such a dynamic system but is critical for identifying extreme events occurring rarely and rapidly, possibly having a drastic effect on fauna and flora.