Effect of physical factors on bacterial distribution in the Jordan River mouth area in Israel

The Jordan River mouth is an area of complicated hydrography and,variable a nd vulnerable ecology it has changeable water and sediment regimes,for exam ple, large spa tial gradients of biological, chemical, physical, and hydrol ogical characteristics. The Jordan River enters Lake Kinneret in the north and carries with it sewage from the Upper Galilee; thus the river is the ma jor source of enteric bacteria in the lake. This research is based on theor etical 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, a nd the mean streamwise velocity turbulence intensity and the turbulence sca le Ir cre calculated The measuring devices were an original three-dimension al 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 a nd upper layers for similar to 100 m after the bar Fecal coliforms, Escheri chia coil, and Klebsiella spp. were enumerated as colony-forming units from samples taken along the Jordan River path as it entered Lake Kinneret. Bac terial numbers were similar in surface and bottom waters in front of the ba r. Behind the bar however there was a sharp decrease of bacterial numbers i n the surface water, probably because of photooxidative stress. Despite the more protective environment of the bottom waters, the numbers here also de creased, indicating that the bar is a physical barrier for bacterial distri bution. 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, regardl ess of their numbers in Jordan River mouth.