Quantifying ground water inputs along the Lower Jordan River.

Area of Science:

• Hydrology
• Geochemistry
• Environmental Science

Background:

• The Lower Jordan River's flow rate decreased dramatically in the late 20th century due to water diversion.
• Drought years (2000-2001) caused severe low flow events, increasing the impact of external water sources.

Purpose of the Study:

• To quantify the contribution of groundwater inflow to the river's flow rate and chemical composition.
• To identify the characteristics of the external water sources influencing the river.

Main Methods:

• Mass-balance calculations using detailed flow rate measurements.
• Water sampling and chemical analyses along the northern river section.
• Comparison of river water chemistry with potential end-member sources.

Main Results:

• River base-flow during 2000-2001 was 40 times lower than historical rates (500-1100 L s⁻¹).
• Groundwater contributed 20-80% of the river's flow and 20-50% of its solute mass.
• Identified groundwater end-members with high sulfate, similar to agricultural drains and the Yarmouk River.

Conclusions:

• Groundwater inflow is a major factor influencing the diminished Lower Jordan River's flow and chemistry.
• External sources, particularly groundwater, significantly alter the river's chemical composition.
• Regional development must consider river-groundwater interactions for sustainable water management.