Worthington Groundwater
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Carbonate aquifers
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Spring monitoring
Walkerton

spring at Walkerton Spring monitoring

The presence of springs in carbonate aquifers is a simple and powerful demonstration that the aquifer is not behaving like a porous medium. Continuous water level and electrical conductivity are useful to investigate transient aquifer characteristics. The capture zone for the spring can be calculated from discharge measurements. Where springs are present they are far more useful than wells in monitoring contaminant plumes since springs integrate groundwater discharge from large areas. Springs are also commonly used as monitoring points for tracer tests.

The photo shows a spring close to Municipal Well 7 at Walkerton, Ontario. A datalogger recorded water level and electrical conductivity every ten minutes. Water levels and water chemistry change in response to pumping at Well 7 (seen in the background), demonstrating a hydraulic link between the well and the spring. Our discharge measurements showed that the capture zone for the spring is more than 500 hectares (2 square miles). A tracer test from Municipal Well 6 arrived at this spring after 21 hours (240 m/day) and at Well 7 after 30 hours (280 m/day). These rapid groundwater velocities implicate a large potential source area for the bacterial contamination of the Walkerton wells which resulted in seven fatalities.