Use of a high-resolution pore-water gel profiler to measure groundwater fluxes at an underwater saline seepage site in Lake Kinneret, Israel

We have used new gel pore-water profilers and conventional seepage meters to determine the advective flux of water from an underwater saline seep into Lake Kinneret. The gel probes sampled pore waters from medium to coarse sands that could not be sampled by conventional coring methods. The anions Cl, Br, and SO₄ were constant at levels just above those for the lake for 3-5 cm into the sediment due to wave action or other turbulent mixing processes. There was then a sharp increase in concentration to values of approximately 8,000 mg Cl liter^-1, 370 mg SO₄ liter^-1, and 120 mg Br liter^-1 at a depth of ~8.5 cm. Using an advection-diffusion model, the linear interstitial advection velocity (LIV) of the groundwater into the lake was calculated to vary between 140 and 275 cm yr^-1. The LIV values from conventional seepage flux meters at the same site were 30 and 164 cm yr^-1. Differences between the LIV measurements of these two methods may be due to a number of possible factors, including groundwater flux heterogeneity.