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Understanding underground waterways INDIANA UNIVERSITY CENTER FOR RURAL ENGAGEMENT AND INDIANA GEOLOGICAL AND WATER SURVEY

Characterizing springs of the Indiana Uplands

There are more than 600 groundwater springs in the Indiana Uplands region, but for most of them, little is actually known about the status of their water quality and quantity. The springs are a valuable resource to the region with little surface water, but no large-scale characterization of the springs has ever taken place, and for some, no data has been collected in over 100 years. In 2019, the Indiana University Center for Rural Engagement (CRE) and Indiana Geological Water Survey (IGWS) partnered to send a team of geologists to locate 100 of the most important perennial groundwater springs throughout the Uplands and collect samples of the water for testing.

The team

The team was led by IGWS scientist Tracy Branam, who specializes in groundwater chemistry among other topics. He was assisted by other IGWS researchers Don Tripp and Sam Frushour, and IGWS assistant director of research Lee Florea, as well as Chin Zhu and Lei Gong of the Department of Earth and Atmospheric Sciences (EAS).

The project's field and lab work was conducted by four graduate students: Stephanie LeGare and Lindsey Rasnake of the O'Neill School of Public and Environmental Affairs, and Sarah Burgess (now a staff research geologist at IGWS) and Caleb Fifer of EAS.

The springs

Because of the value they provide for drinking water, power generation, and agriculture, groundwater springs have historically been the site of economic growth in the state, and mineralized springs were even the driver of a spa culture in the early 1900s that drew people from across the country to the region. Modern population growth in south-west central Indiana has been sparse in part due to the limited water supply to the area. This makes understanding the existing water supply majorly important to future growth.

During the dry season of 2019 and 2020, Branam's team worked with existing geographical data to locate 100 springs. This was a collaborative effort with the communities they visited, as the springs were spread across a variety of properties. Permission was necessary before they could visit any mill on private property, and they had to coordinate with several organizations including the Naval Surface Warfare Center Crane in Martin County, the French Lick Resort in Orange County, and the Friends of Beck's Mill nonprofit in Washington County, as well as 46 individual property owners throughout the region.

"From this diverse group of spring ownership and usage it would be impossible to accurately estimate the total number of people impacted by the project, given that it includes tourists, businesses, and private users."

- Tracy Branam

The field work

Field work for the study was conducted by the student researchers in teams of two. They visited springs over two years during the dry season of August to October. Once the teams had located the springs, they would collect filtered samples of the water in bottles to bring back to the labs, use a probe to collect field chemistry, measure the flow rate, take photos of the spring, and record the GPS coordinates of the spring.

Some of the spring sites required the teams to hike long distances through unmaintained, natural areas while carrying the sampling equipment. However, the samples they brought back would be tested in labs to provide key insights into the spring's health.

The lab work

Each springwater sample was tested for nutrients, coliform bacteria, alkalinity, major ions and trace metals, dissolved organic carbon, sulfur and carbon isotopes, and oxygen and hydrogen stable isotopes.

It was a major effort, but the IGWS team had the assistance of a number of labs including O'Neill professor Todd Royer, IUPUI associate professor Broxton Bird, Purdue associate professor Sara McMillan, the Indiana State Department of Health, the University of Kentucky, and the University of Minnesota.

The results

The ultimate goal of the project is to make the collected data available in an interactive, online map. Collected data was shared in detailed reports to the owners of sampled springs and they were informed of what other data was available so that they could pass that information on to other stakeholders in their respective counties.

The data were also used to generate more than 75 maps that have been and will be used during presentations on the study's findings. Rasnake and LeGare presented their research at the Indiana Science Communication Day in March 2020 at the Indiana Statehouse. They also gave a virtual presentation on the topic during the UNESCO Karst 2020 event held by Western Kentucky University in August 2020.

Another presentation was given at the fourth annual Water Day event in Owen County in September 2021 and a presentation is planned at the Indiana Academy of Sciences annual conference in 2022.

"Water [is] becoming an increasingly important resource throughout the world, and while Indiana has an abundance of this resource, the wise stewardship and maintenance of this resource requires a large amount of information on the various forms of this commodity."

- Tracy Branam

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The Mitchell Plateau Karst Observatory Program

The observatory program is a separate but closely-linked IGWS research project that looks to better understand the aquifers of the Mitchell Plateau through the collection of existing data, installation of monitoring systems, and the development of collaborative relationships. The program is led by Lee Florea but with much of the same motivation as Branam's study and many of the same team members including Branam, LeGare, Rasnake, Burgess, and the addition of EAS graduate student Matt Terrell.

The plateau

The Mitchell Plateau, a karst landscape, begins in the south at the Ohio River in Harrison County and cuts a jagged, north-eastern line across the state just past McCormick's Creek State Park in Owen County. A "karst" landscape is one where limestone is close to the surface and millennia of rainwater has worn away at the rock creating the systems of valleys, caves, springs, and sinkholes that create so much of the geological character of southern Indiana.

These holes and hills create a system of surface streams draining to groundwater springs that is delicate and easily disturbed by erosion, construction, and pollution. Understanding the flow of these underground springs is vital to understanding floods, landscape change, and geological mapping.

"The sinkhole-dimpled forests, fields, and farms, extensive cave systems, and deep windows into the groundwater system have fostered curiosity, encouraged exploration, and served as the focus of scientific undertakings since the mid-1800s."

- Lee Florea

The formation of the caves

The main concern of the Plateau project was a longitudinal study of the groundwater chemistry at four sites in two basins to determine the chemical processes of the karst cave formation, or speleogenesis. A cave's formation is traditionally described in one of two ways: epigene or hypogene. On a basic level, epigene caves are those that are formed by groundwater sinking into the earth and dissolving the rock while hypogene caves are the result of rainwater mixing with deep-seated brines beneath the earth, creating a chemical reaction that eats away at the rock to form air pockets that become caves.

Both of these processes involve chemical interactions between carbonic and sulfuric acids. Epigenic caves are the result of carbonic acid dissolution of the limestone, while hypogenic caves are resulted from sulfuric acid dissolution. The Plateau's karst landscape is said to be epigenic.

In early 2019, the Plateau project installed geochemical monitors at three sites in the Lost River karst basin—Flood Creek, Wesley Chapel Gulf, and Orangeville Rise—and one in the Blue Spring karst basin in the Bluespring Caverns. These monitors collected chemical data that showed the presence of sulfuric acid, a hypogene fluid, in the Bluespring Caverns, and a noted lack of the same in the Lost River basin.

The conclusion drawn from this data was that the karst basins of the Mitchell Plateau are not singularly epigene nor hypogene, but a combination of the two that changes through space and time working together to form the cave systems of southern Indiana. The collected data, observations, hypotheses, and conclusions were the basis of Sarah Burgess' master's thesis.

The installation of the monitors also provided opportunities to investigate other aspects of karst basins. For example, the Lost River karst basin has over 40% agricultural land use, where the Blue Spring karst basin's land use is low-density residential, pasture, and woodland. This provides an opportunity to compare the collected data from each and investigate the impact of agriculture on the organic carbon cycling of karst basins.

The tools

Because of karst systems' interconnected nature and the fact that most of the system is contained beneath the earth, it can often be hard to tell for sure how one cave or spring might link to another. An important piece of knowledge to have when working with groundwater basins is an understanding of its boundaries and flows. A common and reliable method of working out the boundaries or flow path of a basin or spring is dye tracing in which an amount of non-toxic and biodegradable fluorescent dye is deposited into a stream and samples are taken at points downstream to check for the dye.

While dye traces are a regular research activity, there was no single place to share the collected data for wider scientific use in Indiana. The Mitchell Plateau project worked to create a centralized, online database for members of the public, government scientists, and those in private and corporate settings to upload and share the results of dye traces they've conducted.

These dye traces reveal valuable data about how bodies of water are connected which can help to better understand the effects of heavy rainfall and potential for flooding, and prevent the contamination of springwater from above-ground sources like agriculture, road salts, or construction.

Karst flooding from heavy rainfall is a documented phenomenon, yet karst formations are rarely, if ever, taken into consideration by planning and regulation agencies. This means that towns like Orleans, Indiana, have more than 100 years of karst flooding history but are left off the National Flood Insurance Program's flood hazard maps. The Mitchell Plateau Karst Observatory's monitoring, tracing, and continuously evolving scientific study, can bring better understanding, responsiveness, and, for towns like Orleans, advocacy.

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