In November 2011 a new project for protecting groundwater in the Mediterranean Basin was established. The “Protecting Groundwater” project aims to promote sustainable management of water resources and alleviate pollution of groundwater in Mediterranean Basins. Groundwater is a very important constituent of Israel´s water supply and so it needs to be preserved and hazards evaluated. One of those hazards are “Pesticides”, which is a general term for substances which are used to poison pests, such as weeds, insects, molds, and rodents. Pesticides are bioaccumulative and relatively stable, as well as toxic and carcinogenic. The major sources of pesticide pollution are industries, agriculture, forestry and domestic activities. The dust particles in the air adsorbed the pesticides (due to pesticides spray in agriculture, forestry and domestic use) and contaminate water bodies, sediments and soil through rain water. There are several factors which influence a pesticides’ potential to contaminate water:
First, it is the ability of the pesticide to dissolve in water (solubility). Other are environmental factors, such as, soil, weather, season, and distance to water sources. And last but not least, application methods and other practices associated with the pesticide.
The “Israel Union for Environmental Defense” has found high levels of 105 different pesticides in fruits and vegetables, a third of which are banned in Europe. According to a survey, every dunam of land used for agricultural purposes in Israel absorbs, on average, 0.72 kilos of toxic substances per year. This amounts to an average of 8,300 tons of pesticides used each year for agricultural purposes.
In Israel, about 60% of supplied drinking water are from surface and ground water near or below agriculture lands and, therefore, it is very important to check the purity of groundwater before it is supplied to the public.
When weighing management decisions for protection of groundwater quality, it is important to consider the time lag between application of pesticides and fertilizers to the land and arrival of the chemicals at a well. This time lag generally decreases with increasing aquifer permeability and with decreasing depth to water. In response to reductions in chemical applications to the land, the quality of shallow groundwater will improve before the quality of deep groundwater, which could take decades.
Also, the effect of combining more than one pesticide in drinking water might be different than the effects of each individual pesticide alone. Very little monitoring of water pesticides has been done in Israel. For many years, FoEME has been developing experience and best practices related to ground water issues. To name two of the outcomes of this project is a spatial hydrological model calculating the excepted risk to groundwater from different hazards in watershed and a hazard Reduction and Prevention Guidelines.
This blog was contributed by FoEME’s research intern Scalet Pesch, with contributions from FoEME’s PGW team. Scalet is based in our Tel Aviv office.