SUMMARY
The State Fiscal Year 2014-2015 Clean Water Fund appropriation identified the northeast metro as an area where potential solutions are needed to address emerging water supply issues. For example, water levels in White Bear Lake and other lakes in the northeast Twin Cities metropolitan area have generally decreased since 2003. Low levels limit access and recreational use of the lakes.
A cooperative study was conducted by the U.S. Geological Survey (USGS), the Metropolitan Council, and the Minnesota Department of Health (MDH) to assess groundwater and surface-water interactions in lakes in the northeast Twin Cities Metropolitan Area (TCMA), including White Bear Lake.
An important product of the study was a creation of a groundwater-flow model focused on the northeast TCMA. The groundwater flow model will be available for future use to assess the effects of groundwater withdrawals on lake levels as well as to describe other groundwater and surface-water interactions.
The study work generally includes (1) statistical analysis of existing hydrologic information about lakes and surrounding groundwater systems, (2) stable isotope and age-dating analysis of groundwater, (3) lake-water outflow measurements at several locations in deep parts of White Bear Lake, (4) targeted groundwater-level monitoring, and (5) development of a groundwater flow model.
This effort builds on work published by the USGS in 2013 (http://pubs.usgs.gov/sir/2013/5044/), which indicated that some water from White Bear Lake was flowing to the underlying Prairie du Chien-Jordan aquifer and reaching wells that were open to the aquifer downgradient from the lake. That work also highlighted how little is known about the groundwater and surface-water interactions at many of the other northeast TCMA lakes that have low water levels and an unquantified amount of lake water flowing to underlying aquifers.
The objective of the current study was to fill the knowledge gap by characterizing groundwater and surface-water interactions in northeast TCMA lakes, including White Bear Lake. The work is supported by a combination of Minnesota’s Clean Water Fund appropriations and USGS Cooperative Matching Funds.
An understanding of interactions between groundwater and surface water in the watersheds of closed basin lakes – such as those in the northeast metro – is critical in assessing lake level responses to climate changes and anthropogenic impacts. State and city water managers and planners need this knowledge to assess how groundwater withdrawals may impact water levels in aquifers and connected lakes and to accurately assess source water protection for their water supplies.
RECENT OUTREACH/ENGAGEMENT ACTIVITES
DELIVERABLES
OUTCOMES
- Groundwater and surface water interaction in and around White Bear Lake and surrounding lakes is characterized
- Guidance provided to address groundwater and surface water interaction issues
- Land use and watershed planners will gain information to better manage activities that may impact aquifers, assisting with the protection of critical water supplies