DRIFTLESS - With excitement swirling in the air around the opening of trout fishing, connections between groundwater and surface water in the Driftless are a timely topic.
The Driftless Region is blessed with some of the finest coldwater trout streams on the planet. This fuels what has been estimated as a $1.6 billion economic impact.
As such, trout fishing is a major economic driver in a region that is otherwise somewhat lacking in economic opportunities. The health and productivity of the region’s coldwater trout fisheries is a considerable asset and a benefit held in public trust for all citizens.
Kenneth W. Potter, a Department of Civil & Environmental Engineering, at UW-Madison, released a paper in February of 2019 entitled ‘Hydrology of the Driftless Area.’ In that paper, Potter explained the connection between groundwater and the quality of the region’s trout fishing resource.
“Driftless Area streams generally provide ideal habitat for a coldwater fishery. The headwater portions of these streams are relatively long and include relatively steep reaches. Perennial flow occurs throughout the extent of these streams, including the headwater portions with very small drainage areas. This perennial “baseflow” results from groundwater inflows that enter the stream from numerous discreet springs as well as from diffuse flow through channel bottoms. Because groundwater temperatures about equal the mean annual air temperature, groundwater inflows from springs and the channel bed keep segments of the streams relatively cool in the summer and prevent them from freezing in the winter. Groundwater inflows through the channel bottom also provide ideal habitat for fish spawning, and refuges for coldwater fish species during extended hot periods.”
In addition to the Southwest Wisconsin Groundwater and Geology Study (SWIGG), which is close to entering its final phase, there are several other research initiatives in southwest Wisconsin that are looking at water quality. These projects will shed additional light on how water moves through the system, and then back out into surface waters as well.
Four scientists with the Wisconsin Geological and Natural History Survey (WGNHS) are looking at a variety of factors that will shed light on what the soils of Grant, Iowa and Lafayette counties look like, whether the Rountree Formation of clay is protective of the groundwater aquifers, and how quickly water moves from the surface during rain or snowmelt events.
Those five scientists are Dr. Eric Carson, Dr. Maureen Muldoon, Dr. Eric Stewart, and Geologist Grace Graham of WGNHS.
Surficial mapsDr. Eric Carson with WGNHS is the point-person on developing surficial geological maps for counties in the Driftless Area of Wisconsin. In 2019, his team completed mapping of Crawford, Vernon, and Richland counties. His team will have Grant County maps complete by summer 2020; Iowa County by summer 2021; and Lafayette County by summer 2022 or 2023.
Carson is also working with Dr. Muldoon on a research project to determine the extent to which a layer of red clay found in the top layer of soil in southwest Wisconsin, the Rountree Formation, may be protective of groundwater.The highest bedrock formations across much of southwest Wisconsin are carbonate rocks of the Sinnipee and Prairie du Chien Groups. As those rocks chemically weather over geologic time, they produce a dense red residual clay known as the Rountree Formation.
Core samples have already been taken along Military Ridge in Grant County to determine the presence and thickness of the Rountree Formation in the area. In addition, several pits will be dug to allow researchers to understand the extent of large pores or earthworm holes in the clay, which could facilitate movement of water through the layer.The results of this investigation will merge with water quality data from the Southwest Wisconsin Groundwater and Geology (SWIGG) study to better understand the interaction between human land use, underlying geology, and groundwater contamination susceptibility in southwest Wisconsin.
Dr. Muldoon is also leading a project that has been funded by the Wisconsin DNR to create a good conceptual model of the hydrogeology of southwest Wisconsin. One of the things her work will demonstrate is how recharge (movement of water from the surface into groundwater aquifers) affects water quality at time scales ranging from hours to months.
The objectives listed in her project proposal are:
1. Develop depth-to-bedrock and water-table maps for Grant County.
2. Explore aquifer recharge dynamics and seasonal variations of water quality, specifically nitrate.
3. Provide additional characterization of the Rountree Formation at a site-specific scale.
According to Dr. Muldoon, this research will adopt two major thrusts:
1. Partnering with Research Manager Dennis Busch and Farm Director Chuck Steinert of UW-Platteville Pioneer Farm to conduct research using their existing groundwater monitoring network, consisting of 11 wells with 48 monitoring points at varying depth within the bedrock. A pair of instruments will be inserted into three wells that is programmed to record water levels, fluid temperature, and specific conductance every 30 minutes. The other wells will have devices that measure water levels and temperature. The wells will also be sampled quarterly for nitrate levels and compared with results from nearby springs.
2. Continuous monitoring of spring water will provide important information about what the water exiting the aquifers is like. In one spring, close to Pioneer Farm, the researchers will place a nitrate sensor. Continuous monitoring is the only way to understand the extent to which contaminants at the surface travel into groundwater in a fractured karst geology. In addition, to collecting data from springs located at different depths within the bedrock profile, Grace Graham will use instruments which measure temperature and conductivity at another seven springs in the area, with periodic testing for nitrate as well.
Detailed mapsIn addition, Dr. Stewart will develop bedrock maps for northern Grant county, and he and Muldoon will collaborate on depth to bedrock and water table maps as well. Such maps already exist for the rest of Grant County and Iowa County. With the help of a GIS specialist and cartographer, they will produce layered maps of northern Grant County.