Groundwater Vulnerability to Pesticides: An Overview of Approaches and Methods of Evaluation
Groundwater is the most important source of drinking water supply in many countries especially in plainlands, often amounting to over 90% of total tapped water. Groundwater vulnerability is a general concept that identifies the natural susceptibility of underground water bodies to be affected, to some extent, by contaminating substances migrating from a pollutant load imposed on land surface. The long-accepted hypothesis that soil and the deeper unsaturated layers could always constitute an effective defense against penetration by pesticides is thus questionable. The important structural defense of groundwater against penetrating pesticides represented by the soil zone always occurs in situations of diffuse agricultural pollution. A completely different approach to the problem of vulnerability evaluation integrates the unsaturated and saturated zones into a unitary or systemic view. Empirical procedures or classification schemes may be used to combine the effects of the parameters for the evaluation of vulnerability of soils to penetrating pollutants.