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Field verification of stable perched groundwater in layered bedrock uplands

January 1, 2011

Data substantiating perched conditions in layered bedrock uplands are rare and have not been widely reported. Field observations in layered sedimentary bedrock in southwestern Wisconsin, USA, provide evidence of a stable, laterally extensive perched aquifer. Data from a densely instrumented field site show a perched aquifer in shallow dolomite, underlain by a shale‐and‐dolomite aquitard approximately 25 m thick, which is in turn underlain by sandstone containing a 30‐m‐thick unsaturated zone above a regional aquifer. Heads in water supply wells indicate that perched conditions extend at least several kilometers into hillsides, which is consistent with published modeling studies. Observations of unsaturated conditions in the sandstone over a 4‐year period, historical development of the perched aquifer, and perennial flow from upland springs emanating from the shallow dolomite suggest that perched groundwater is a stable hydrogeologic feature under current climate conditions. Water‐table hydrographs exhibit apparent differences in the amount and timing of recharge to the perched and regional flow systems; steep hydraulic gradients and tritium and chloride concentrations suggest there is limited hydraulic connection between the two. Recognition and characterization of perched flow systems have practical importance because their groundwater flow and transport pathways may differ significantly from those in underlying flow systems. Construction of multi‐aquifer wells and groundwater withdrawal in perched systems can further alter such pathways.

Publication Year 2011
Title Field verification of stable perched groundwater in layered bedrock uplands
DOI 10.1111/j.1745-6584.2010.00736.x
Authors J.T. Carter, M.B. Gotkowitz, M.P. Anderson
Publication Type Article
Publication Subtype Journal Article
Series Title Ground Water
Index ID 70035270
Record Source USGS Publications Warehouse