Groundwater seepage can exacerbate environmental pollution through contaminant transport, pose a threat to dam safety and can also be associated with valuable mineral deposits.
Dam safety, environmental remedial works and mineral location normally involve comparatively expensive techniques, but, if the extent and location of groundwater seepage can be accurately predicted, then the amount of work, and thus costs, can be dramatically reduced.
THE SAMANALAWEWA DAM
Numerous challenges complicate the effort to identify the source and character of groundwater seepage. Traditional investigative techniques, which involve the chance intersection of drilled bore holes and seepage paths, can become very expensive when required to cover large areas. The Willowstick diagnostic method, detailed in this paper, significantly mitigates these problems. By charging the subsurface with a low-voltage, low-frequency electric current, and mapping the resulting magnetic field, this method effectively and efficiently charts groundwater flow in complex environments, at significant depths, and over large areas.
This method was recently used at the Samanalawewa Dam, a large and important hydroelectric power project on Sri Lanka’s Walawe River. The Samanalawewa Dam is a 105 meter high rockfill dam surrounded by karstic geology, which has long complicated the effort to account for and remediate seepage through the dam. The Willowstick method proved effective at mitigating the particular challenges associated with groundwater seepage at this site. The results represent an important advancement in the ongoing quest for better ways to monitor and remediate seepage. This paper discusses the Willowstick diagnostic tool, which allows individual seepage points to be mapped at depths of more than 100 meters to an accuracy of less than 100 millimeters.
The Use Of Innovative Groundwater Seepage Detection Techniques - Case Study