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New Technologies Help Communities Protect Drinking Water Wells in Karst Terrain
Posted: 04/26/2012
CEDAR FALLS — The aquifers underlying Cedar Falls have long been an excellent source of drinking water –both in quality and quantity – for the northeast Iowa community. Yet, the terrain that creates these aquifers can also pose threats to their waters, allowing water and the contamination it picks up from above ground to seep in. New technologies are helping Cedar Falls and other communities protect these valuable resources.

Cedar Falls, working with the DNR’s Source Water Program, launched an investigation to better understand its groundwater resources and how they connect to the land above. Depending on the area, the Silurian-Devonian aquifer below Cedar Falls can be within a few feet of the surface or buried more than 100 feet. Over thousands of years, the terrain saw extensive erosion and weathering from flowing water and glaciers, fracturing the shallow bedrock and forming large open channels where water can move through quickly. Known as “karst” terrain, its trademarks include sinkholes, cave openings and low-lying wet areas above ground.

While making sure the way land is managed prevents contamination from seeping in to drinking water sources is not new, emerging technology can better define karst topography and how water moves through it. In the past, drinking water protection areas were arbitrarily defined as a 1-mile radius around wells. Now, new mapping methods allow communities to better understand how groundwater moves and its risks for contamination. Highly accurate LiDAR elevation mapping data, paired with digital soil layer information, easily defines protection areas. For Cedar Falls, it showed those areas could be smaller than before, allowing the city to focus resources.

“With new technology, especially LiDAR, we can more efficiently locate drinking water protection areas for karst communities and at a lower cost,” said Chad Fields with the DNR’s Source Water Program. “These areas are typically much smaller than our previous size, so it greatly helps a city better spend its resources for protection. In Cedar Falls’ case, it let the city focus on an area less than a quarter of the initial size.”

Using results from the investigation, the DNR plans to develop standard practices to assist 22 other Iowa communities that pull drinking water from karst areas to proactively protect their water supplies. Those water systems serve more than 140,000 Iowans.

“Cedar Falls was a unique opportunity for this investigation,” Fields said. “In addition to having wells in karst terrain, they also had a previous groundwater investigation and various groundwater research projects done by the University of Northern Iowa. This gave us the benefit of both checking our assumptions and conclusions and to build on the previous research.”

The full report for the Cedar Falls investigation can be found at:
http://www.iowadnr.gov/Portals/idnr/uploads/geology/CedarFallsReportTIS55.pdf
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