Sampling strategy for karst waters

To optimize sampling strategy in a small water supply in Northwestern Switzerland, event-specific sampling of turbidity and microorganisms was conducted. These data were compared with previously performed tracer tests and water quality data from routine drinking water sampling 1 to 4 times a year. Whereas the data from routine sampling only give information on the general behaviour of karst springs, event-specific sampling gives specific information of the karst system and residence times of microorganisms. In addition, previously conducted tracer test gave partly wrong evidence on the input locations of microorganisms. Furthermore, the present sampling strategy can not account for microbial risk. Therefore, karst systems with short response times on precipitation in the order of hours should be equipped for automatic sampling. After the transgression of defined tolerance values of e.g. turbidity, a sample device should be activated to take several samples and send a signal to the local authorities who should collect the bottles from the sampling device and take them to the laboratory for analysis.