Abstract

Springs are groundwater discharge points that serve as vital coldwater sources for streams in southeast Minnesota. The springs generally emanate from Paleozoic carbonate and siliciclastic bedrock aquifers. Use of systematic dye tracing began in the 1970s and continues through the present as a standard method for investigating karst hydrology and to map springsheds,. The work was accelerated in 2007 because of increased funding from the State of Minnesota’s Environment and Natural Resources Trust Fund. A compilation springshed map of dye traces conducted over the last several decades has been assembled for the region. In southeast Minnesota, the springs are the outlets of conduit flow systems in both carbonate and siliciclastic bedrock aquifers. Conduit flow dominates groundwater transport in carbonate aquifers and is an important component of groundwater flow in siliciclastic aquifers. Conduit flow in aquifers occurs independently of the presence or absence of surface karst features. The springsheds of these springs have three interacting components: Groundwater Springsheds (analogous to classic karst autogenic recharge areas), Surface Water Springsheds (analogous to classic karst allogenic surface runoff areas), and Regional Groundwater Springsheds. Surface Water Springsheds can be up to several orders-of-magnitude larger than the Groundwater Springsheds to which they contribute water. Surface Water Springsheds can feed surface flow into one or several stream sinks. Those multiple stream sinks may be in one or more Groundwater Springsheds. The leading edges of dye tracing breakthrough curves typically show groundwater flow velocities in the hundreds-of-meters to kilometers-per-day range in all of the bedrock aquifers tested. The width and duration of tails of breakthrough curves in these conduit flow systems vary with the bedrock aquifers. The Galena Group has Full Widths at Half Maximums (FWHMs) of a few hours and tails that are down to background in a few days. The Prairie du Chien Group also has FWHMs of hours but has tails that continue for weeks. The St. Lawrence and Lone Rock Formations have FWHMs of months to years.

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DOI

http://dx.doi.org/10.5038/9780991000951.1024

 

Creation of a Map of Paleozoic Bedrock Springsheds in Southeast Minnesota

Springs are groundwater discharge points that serve as vital coldwater sources for streams in southeast Minnesota. The springs generally emanate from Paleozoic carbonate and siliciclastic bedrock aquifers. Use of systematic dye tracing began in the 1970s and continues through the present as a standard method for investigating karst hydrology and to map springsheds,. The work was accelerated in 2007 because of increased funding from the State of Minnesota’s Environment and Natural Resources Trust Fund. A compilation springshed map of dye traces conducted over the last several decades has been assembled for the region. In southeast Minnesota, the springs are the outlets of conduit flow systems in both carbonate and siliciclastic bedrock aquifers. Conduit flow dominates groundwater transport in carbonate aquifers and is an important component of groundwater flow in siliciclastic aquifers. Conduit flow in aquifers occurs independently of the presence or absence of surface karst features. The springsheds of these springs have three interacting components: Groundwater Springsheds (analogous to classic karst autogenic recharge areas), Surface Water Springsheds (analogous to classic karst allogenic surface runoff areas), and Regional Groundwater Springsheds. Surface Water Springsheds can be up to several orders-of-magnitude larger than the Groundwater Springsheds to which they contribute water. Surface Water Springsheds can feed surface flow into one or several stream sinks. Those multiple stream sinks may be in one or more Groundwater Springsheds. The leading edges of dye tracing breakthrough curves typically show groundwater flow velocities in the hundreds-of-meters to kilometers-per-day range in all of the bedrock aquifers tested. The width and duration of tails of breakthrough curves in these conduit flow systems vary with the bedrock aquifers. The Galena Group has Full Widths at Half Maximums (FWHMs) of a few hours and tails that are down to background in a few days. The Prairie du Chien Group also has FWHMs of hours but has tails that continue for weeks. The St. Lawrence and Lone Rock Formations have FWHMs of months to years.

 

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