Groundwater protection in fractured media: a vulnerability-based approach for delineating protection zones in Switzerland

Pochon, Alain; Tripet, Jean-Pierre; Kozel, Ronald; Meylan, Benjamin; Sinreich, Michael; Zwahlen, François

Groundwater protection in fractured media: a vulnerability-based approach for delineating protection zones in Switzerland | Protection des eaux souterraines en milieu fissuré: Approche basée sur le concept de vulnérabilité pour la délimitation des zones de protection en Suisse Grundwasserschutz in Kluftgesteinen: Ein Vulnerabilitätsansatz zur Bemessung von Schutzzonen in der Schweiz Protección del agua subterránea en medios fracturados: una aproximación basada en la vulnerabilidad para definirzonas de protección en Suiza Protezione delle acque sotterranee negli acquiferi fessurati: approccio basato sulla valutazione della vulnerabilità per la delimitazione delle zone di protezione in Svizzera Protecção da água subterrânea em meios fracturados: abordagem baseada na vulnerabilidade para a delimitação de zonas de protecção na Suiça

2008

A vulnerability-based approach for delineating groundwater protection zones around springs in fractured media has been developed to implement Swiss water-protection regulations. It takes into consideration the diversity of hydrogeological conditions observed in fractured aquifers and provides individual solutions for each type of setting. A decision process allows for selecting one of three methods, depending on the spring vulnerability and the heterogeneity of the aquifer. At the first stage, an evaluation of spring vulnerability is required, which is essentially based on spring hydrographs and groundwater quality monitoring. In case of a low vulnerability of the spring, a simplified method using a fixed radius approach (“distance method”) is applied. For vulnerable springs, additional investigations must be completed during a second stage to better characterize the aquifer properties, especially in terms of heterogeneity. This second stage includes a detailed hydrogeological survey and tracer testing. If the aquifer is assessed as slightly heterogeneous, the delineation of protection zones is performed using a calculated radius approach based on tracer test results (“isochrone method”). If the heterogeneity is high, a groundwater vulnerability mapping method is applied (“DISCO method”), based on evaluating discontinuities, protective cover and runoff parameters. Each method is illustrated by a case study.

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