Percolation and particle transport in the unsaturated zone of a karst aquifer.

Recharge and contamination of karst aquifers often occur via the unsaturated zone, but the functioning of this zone has not yet been fully understood. Therefore, irrigation and tracer experiments, along with monitoring of rainfall events, were used to examine water percolation and the transport of solutes, particles, and fecal bacteria between the land surface and a water outlet into a shallow cave. Monitored parameters included discharge, electrical conductivity, temperature, organic carbon, turbidity, particle-size distribution (PSD), fecal indicator bacteria, chloride, bromide, and uranine.

Particle-size distribution as indicator for fecal bacteria contamination of drinking water from karst springs.

Continuous monitoring of particle-size distribution (PSD), total organic carbon (TOC), turbidity, discharge and physicochemical parameters, together with analyses of fecal indicator bacteria, particularly Escherichia coli, made it possible to better understand the processes governing pathogen transport in karst groundwater and to establish PSD as indicator for possible microbial contamination of drinking water from karst springs. In the study area near Yverdon-les-Bains, Switzerland, tracer tests proved connection between a sinking stream draining agricultural land and several springs, 4.8-6.