The potential impact of pesticides on the Kinneret and its watershed, over the period 1980–1984

Abstract

Over the period 1980–1984, water and fish samples have been routinely analysed for pesticide residues as part of a more general lake and watershed monitoring programme. Water samples were taken from 14 sites in the Hula Valley, close to the main farming areas. Initially, concentrations of various pesticides (such as Parathion and Endosulphan) were high, especially at certain sites, but later, only traces of these chemicals were found even though there has been little reduction in the quantities of pesticides used. During the rainy season some residual pesticides remaining in the soil were washed into the drainage canals at the beginning of the winter floods, but concentrations dropped rapidly, suggesting that either quantities of pesticides in the fields were low, or that they were bound strongly to soil particles. Fish analyses largely comprised cases of deliberate poisoning of Sarotherodon galileaus (St Peter's fish), by Endosulphan and/or Lindane, for illegal fishing purposes. In the past few years, however, the numbers of both suspected fish poisonings and poisoned fish have significantly declined, and analyses now mostly involve spot checks of catches. ‘Baseline’ studies of fish, zooplankton, algae and benthic mussels, as well as water samples, from the lake were also carried out. Pesticide residues were not found in any of these samples. These results suggest that the potential threat to the Kinneret from pesticide residues is at present relatively low. The Kinneret Limnological Laboratory pesticide monitoring programme has been, at least partially, instrumental in reducing pesticide contamination (accidental or otherwise) of water or fish, in the lake and watershed. In the light of possible changes in agricultural practices and water management policies in the north of Israel, however, this programme will be continually updated to avoid any deterioration in the current situation.