Effect of Physical Factors on Bacterial Distribution in the Jordan River Mouth Area in Israel

Abstract

The Jordan River mouth is an area of complicated hydrography and variable and vulnerable ecology. It has changeable water and sediment regimes, for example, large spatial gradients of biological, chemical, physical, and hydrological characteristics. The Jordan River enters Lake Kinneret in the north and carries with it sewage from the Upper Galilee; thus the river is the major source of enteric bacteria in the lake. This research is based on theoretical analysis as well as on biological-hydrodynamical measurements along a discharging free, turbulent jet flow. Three components of velocities were recorded downstream from the exit cross-section for a distance of 700 m, and the mean streamwise velocity turbulence intensity and the turbulence scale were calculated. The measuring devices were an original three-dimensional velocity-fluctuation meter. Results of these measurements show that the Jordan River flows through the whole transect until it reaches the crest of a bar. After this, there is a separated exponential flow from the bottom and upper layers for ~100m after the bar. Fecal coliforms, Escherichia coli, and Klebsiella spp. were enumerated as colony-forming units from samples taken along the Jordan River path as it entered Lake Kinneret. Bacterial numbers were similar in surface and bottom waters in front of the bar. Behind the bar, however, there was a sharp decrease of bacterial numbers in the surface water, probably because of photooxidative stress. Despite the more protective environment of the bottom waters, the numbers here also decreased, indicating that the bar is a physical barrier for bacterial distribution. Furthermore, we found a significant effect of the flow velocity of Jordan River water on the bacterial distribution in Lake Kinneret. When the velocity is high, bacteria are distributed over a longer distance, regardless of their numbers in Jordan River mouth.

Keywords:

• Distribution Enteric Bacteria Flow Velocity Hydrodynamic Conditions Lake Kinneret