Analysis shows groundwater use is sustainable, but does affect lake
A scientific analysis recently completed by the Minnesota Department of Natural Resources (DNR) shows that groundwater use in the White Bear Lake area meets the state sustainability standard. The analysis also shows that groundwater use in the area has contributed to lower water levels in White Bear Lake and that multi-year bans on residential irrigation will have a minimal effect on lake levels.
A high-level summary is available at www.mndnr.gov/gwmp/wbl. The DNR also published the findings of the analysis in today's edition of the White Bear Press.
We’re committed to working with local communities to make sure that the waters in and around White Bear Lake continue to provide their many benefits to the people who live and do business there, now and into the future,” said Barb Naramore, DNR assistant commissioner. “This analysis provides a valuable tool for those efforts.”
The DNR conducted this analysis in response to an August 2017 Ramsey County District Court ruling, which directed the DNR to determine whether existing water appropriation permits within 5 miles of White Bear Lake meet the state’s sustainability standard, both individually and cumulatively. That ruling also required the DNR to impose a variety of conditions on existing water permits in the area, including requirement that communities ban residential irrigation when White Bear Lake is below 923.5 feet in elevation.
As part of ongoing efforts to manage water resources in the north and east metro area, the DNR has worked with a consultant to develop a state-of-the-science groundwater flow model. This new tool allows modelers to assess the impacts of various pumping scenarios on lake and aquifer levels over time and distinguish among the relative impacts of groundwater use in different areas. Previous models could not make these kinds of assessments.
Using this new model, the DNR evaluated whether permitted pumping within a 5-mile radius of White Bear Lake is sustainable as defined in state law. The analysis confirmed that the state standard would be met even if all currently permitted groundwater users were to pump the maximum amount allowed for multiple years in a row.
The state sustainability standard requires:
- Groundwater use does not jeopardize future groundwater supplies.
- Groundwater use does not harm the White Bear Lake ecosystem.
- Groundwater use does not degrade the water quality of White Bear Lake.
- Groundwater use does not lower water levels beyond the reach of public water supplies or private domestic wells.
The DNR used the groundwater model to look at impacts based on four different scenarios: no groundwater use, existing groundwater use, existing groundwater use with a temporary residential irrigation ban, and maximum groundwater use with all permitted users pumping as much as allowed for multiple years in a row.
Water levels in White Bear Lake fluctuate naturally. Such fluctuations benefit lake health by promoting the growth of vegetation that provides aquatic habitat and stabilizes shorelines. The model shows that pumping groundwater increases these fluctuations, particularly on the lower end of the lake's water level range, making the lows lower.
While current groundwater use does not violate the sustainability standard, lower water levels, particularly those below 922.0 feet, do disrupt or diminish some recreational uses of the lake. In order to support these recreational uses, the DNR established a protective elevation of 922.0 feet in 2016. With the new model, the DNR is now able to work with the permit holders having the greatest influence on White Bear Lake, to identify potential changes to water use that can help support recreational uses of the lake.
Over the next few months, the DNR will meet with area cities, businesses and residents to discuss the analysis and its implications. The agency is working with these local interests to implement a groundwater management plan that ensures continued sustainability. A copy of the technical analysis and other information is available at www.mndnr.gov/gwmp/wbl.