Managing Water Availability through Banking

Banking... in the water context, we'd think of shoreline presevation.  In the money context, we thing of repositories for funds and places to for loans.  In the water availability context, we are using the latter definition - we are banking groundwater through managed aquifer recharge.   Putting away water is a little more complicated that putting away money.  This post provides information on research now underway in Minnesota to assess feasiblity of this practice.

Managed Aquifer Recharge is defined by the American GeoSciences Institute thus: 
What is managed aquifer recharge? Aquifers are underground rock formations or sedimentary deposits porous enough to hold water. Most aquifers are naturally recharged by rainfall or other surface water that infiltrates into the ground. However, in regions where groundwater use is greater than natural recharge rates, aquifers will be depleted over time. Managed aquifer recharge (MAR), also known as water banking, consists of water management methods that recharge an aquifer using either surface or underground recharge techniques. The stored water is available for use in dry years when surface water supplies may be low.

Minnesota, the land of 10,000 lakes and the headwaters of three major river systems (Mississippi, Red River/Hudson Bay and Great Lakes/St. Laurence Seaway), is also rich in groundwater resources.  But human use has depleted these resources in many parts of the state, impacting surface water resources as well as other well water users.  

There is also a temporal problem with water availaibilty.  In the spring time there's way too much water in many places, but late in the summer things are much dryer and water supply can be problematic.  Water banking through Managed Aquifer Recharge may be an option to solve this dilema.

In the Minnesota research project,  a team led by the University of Minnesota's Water Resources Center has brought together experts across science, engineering, economics, and policy disciplines, along with outside experts and stakeholders to evaluate the need for managed aquifer recharge.   

According to a post in The Freshwater Society's Facets of Freshwater: "The study team will draw on successful examples of recharge that are already being done in the upper Midwest. These will be translated to the specific geologic, economic, and engineering conditions present in four study areas in Minnesota. They will evaluate water sources like treated surface water or wastewater for their potential to recharge groundwater. Energy use and infrastructure costs are also part of the equation and the least easily understood."

The four project areas are: 

Project staff include: 

• Carrie Jennings, Research and Policy Director, Freshwater Society and Adjunct Assistant Professor, Department of Earth Sciences 
• John Bilotta, Senior Research and Extension Coordinator, WRC and Extension Educator, MN Sea Grant
• Lucia Levers, Research Associate, WRC
• Brian Bohman, Research Fellow, Freshwater Society and WRC
• Tony Runkel and a Hydrologist, Minn. Geological Survey: Aquifer and aquitard characterization
• Bill Arnold, Faculty, CEGE, U of M: Engineering analysis
• Peter Kang, Faculty, Earth Sciences: Aquifer storage and recovery through wells
• And three postdocs and research specialists

1) Fargo-Moorhead relies on a small buried glacial aquifer that isn’t easily recharged and doesn’t have a lot of capacity. It may limit development of the region. Moorhead also has an annual flooding problem and we will ask whether recharge can siphon off some of the flood waters.

2) The Straight River Groundwater Management area near Park Rapids. This sandy area is intensively irrigated cropland and seasonal lows in the water table aquifer have the potential to have a thermal impact on a coldwater stream. The city of Park Rapids has also had problems with nitrate in shallow groundwater. We’ll study whether water is available at the right time of year to offset drawdown and if it can dilute nitrate contamination and keep the stream cool.

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3) Southern Washington County has a similar problem of aquifer depletion impacting a coldwater stream but in this case is a bedrock aquifer. Located in a growing metropolitan area, the current use may not be sustainable. The migration of 3M legacy contaminants (PFOS, PFOA) into parts of the aquifer used for a municipal supply well is a long-term problem in search of a solution. Recharging aquifers with clean water may provide relief for both of these future scenarios.

4) Greater Rochester is planning for a doubling of population due to expansion of the medical campus.  Our question: Will their bedrock aquifer be adequate and remain free of contamination or will groundwater quantity and quality limit their ability to expand?

The project is now ongoing, and will give a report to the 2021 Legislature.  We will follow this work in the LWV UMRR blog and report peridically on prgress.  

It is important to note that even if Managed Aquifer Recharge turns out to be a promising practice, there concerns and regulatory hurdles to be surmounted if it is to go into use in Minnesota.   So the research here is just one step toward a major change in water management in Minnesota.  

Some resources for more information:  

University of Minnesota Water Resources Center:
​https://www.wrc.umn.edu/banking-groundwater-managed-aquifer-recharge

Freshwater Society Facets of Freshwater: 
https://freshwater.org/2019/09/24/recharge/

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