Determination of protection zones in drinking water basins: a case study from Turkey, Sapanca Lake Basin

To prepare specific protection and policies for drinking water basins is important for providing sustainable drinking water management. In this study, a decision support system composed of hydrogeological, hydrogeochemical, soil type and topological parameters was applied to define the protection zones. Littoral zone and slope parameters in topology, the grain size in soil media, hydraulic conductivity, aquifer type and well parameters in hydrogeology, hydrogeochemical and isotopic assessment were used to create protection zones in the decision support system based on the Geographic Information System. Identifying hydrological resource areas, and determination of residence time and recharge altitude in groundwater were done using hydrogeochemical parameters and isotopic tracers. The GIS platform was used to evaluate the maps generated from the parameters and to apply reclassification and overlapping methods. The proposed methodology was applied to the Sapanca Lake Basin in Turkey since the lake is one of the most crucial drinking water lakes in Turkey. According to the proposed methodology, green belt, wellhead, absolute, short-range groundwater protection, short and medium-range protection zones were defined in the basin. The absolute protection zones in the basin are distinctively the areas covered with karst structures which are dolines and swallow holes.