Mapping water ressources exposure of agricultural pesticides in the Lake of Guiers basin and environs (Senegal)

Water is essential for human life and for the socio-economic development of countries. However, it is a limited resource and highly vulnerable because of global changes. The high pressure on the Lake of Guiers basin requires a continuous assessment of water quality for the adequate management of the resource. The aim of this publication is to identify the potential sites of exposure of water resources to agricultural pesticides in the lake of Guiers basin by aggregating thematic layers in a GIS. For weighting the layers, the hierarchical analysis process (AHP) was used: Leaching (L), Sedimentation (S), Soil Storage and Infiltration Capacity (SS&FC), Surface Runoff-Generation (SR-G), Surface Runoff-Transfer (SR-T) and Surface Runoff-Accumulation (SR-A). The weights were assigned and normalized for each layer according to their spatial characteristics and their relationship with the exposure of the hydrological system being studied. According to this method, the surface waters are highly exposed to agricultural pesticides for 57%, moderate for 25% and low for 18% of the area of the Lake of Guiers basin. The groundwater is highly exposed to agricultural pesticides for 53%, moderate for 46% and low for 1% of the total basin surface. The results of the research are most relevant for the planning of the basin management, as they indicate the potential areas of exposure of water resources. The methodology based on logical conditions and generic data can be tested in all watersheds with appropriate adaptations