Wellhead protection zones for sustainable groundwater supply

摘要

Wellhead protection zones (WPZs) and groundwater supply protection areas are strategies to minimize contamination hazards and ensure a safe groundwater supply. Their implementation may require land use restrictions, industrial process changes and/or waste and effluent treatment changes, service adaptations, systematic controls of groundwater levels and groundwater quality and detailed well inspections. The aim of this paper is to present a scheme to ensure the protection of drinking water sources comprising the new pumping field supplying Esperanza and Rafaela cities in Santa Fe Province, Argentina. A 5-10-m radius was adopted for delineating the wellhead operational zones. To define the microbiological and surveillance zones, the fixed radius and Wys-sling methods were applied, taking into account the groundwater travel time of 50 and 100 days, respectively. The land activities were inventoried and categorized according to their potential for generating a subsurface contaminant load. A sanitary survey and assessment of pumping wells was made using a checklist. The results have shown that appropriate radii might be 70 m for the microbiological protection zone and 100 m for the surveillance zone. These values were obtained taking into account a pumping rate of approximately 60-70 m3/h. This abstraction rate should be regulated and maintained because it not only affects the validity of the defined zones but also, when it is exceeded, induces an influx of water of different quality to the semi-confined aquifer.