QUANTIFYING THE GROUNDWATER IMPACT ON THE DISCHARGE AND CHEMISTRY OF THE LOWER JORDAN RIVER ALONG THE BORDER BETWEEN JORDAN AND ISRAEL

The peace treaty between Israel and Jordan that was signed in 1994 consists of a detailed section on water issues. Among other things, this section addresses water allocation and pumping rights along the Lower Jordan River. Although more than a decade has passed, many of its water related decisions were never implemented. One of the reasons is the environmental risks that may danger the future sustainability of the river if these decisions would have been implemented.

This presentation discusses some of the results of a collaborating project, led by researchers from Israel, Jordan and Palestine. The objective was to provide the hydrogeochemical understanding needed before these treaty decisions could be implemented. We demonstrated the chemical trends along its flow-path and quantified, for the first time, the interaction between the river and surrounding groundwater system.

The variations of ions such as chloride and sulfate are characterized by different trends. While sulfate concentration is constantly increasing from the Sea of Galilee to its end at the Dead Sea, chloride concentration is initially decreasing, then keeps a nearly constant value, and finally increases sharply along the last 40 km of the river.

Following an intensive sampling effort, we hypothesized that the reason for these variations is the river interaction with the shallow aquifer on both Jordanian and Israeli sides. Therefore, piezometers were installed on the banks of the river together with reference points inside the river itself. It was found that there are two distinct groundwater systems that affect the river chemistry. Low salinity groundwater fluxes add large volumes of water along the north section of the river while extremely high salinity water is added to the river at very low flow rates along the south part. The hydraulic gradients and the chemical characteristics of these two end members were quantified and the effective length of active interaction between the river and the groundwater was estimated by numerical modeling.

Finally, following the Jordan River project, continuation studies have emerged covering issues such as the development of a modified isotope pairing technique to study denitrification inside the river sediments and vegetated flow modeling to study the mixing mechanisms that takes place in the river.