Groundwater Model for the North and East Metro Groundwater Management Area
The DNR contracted with a nationally recognized expert in groundwater modeling, S.S. Papadopulos and Associates, Inc., to develop a new groundwater model for the North and East Metro Groundwater Management Area.
Key Information about the New Model
- The new model builds off the efforts of the Metropolitan Council and the U.S. Geological Survey over the past several years. We took the U.S. Geological Survey's steady state model and built a transient model that provides the more precise analytical tool needed to manage groundwater use in the North and East metro.
- The need for a transient model was identified in the 2015 North and East Groundwater Management Area Plan.
- The new model will help us better understand how pumping affects aquifers and lake levels within the North and East Groundwater Management Area, including White Bear Lake.
- We will be able to quantify the individual and cumulative effect that pumping wells have on lake levels.
- We can use the model to determine what effects "no pumping" or "reduced pumping" would have on lake levels.
- Combining model results with information about the ecological and recreational impacts of changes in lake levels will allow us, for the first time, to determine with reasonable certainty whether changes to established groundwater appropriations are warranted.
- With this new tool, the DNR will be able to work more effectively with local communities, businesses and residents to make carefully targeted, well-informed modifications to water use if needed to ensure sustainable use of groundwater.
Initial Results from Model Test Analysis
During the development and initial testing of the new model, we have already learned a number of important things about groundwater pumping and lake levels in White Bear Lake:
- The initial test analysis indicates that pumping from some wells has a larger effect than pumping from others.
- The three main factors in well effects are distance from the lake, pumping volume, and which aquifers are pumped.
- All of the wells that have the greatest effect on White Bear Lake were installed in the 1960s to mid-1980s, before the effects of pumping were well-understood or subject to current statutory provisions.
- Overall water use in the area has been trending lower for the past decade or so, and recent water use from the wells with the greatest effect is similar to volumes used in the 1970s and 1980s.
- The initial analysis also indicates that the aggregate effect of all permitted pumping within about five miles of White Bear Lake can be around a half foot in some years.
- During extended periods of lower than normal precipitation and when the lake is below its outlet (e.g. 2003 to 2013), the model indicates that all permitted pumping within five miles of White Bear Lake can have a cumulative effect, over many years of as much as four to five feet of lake levels.
- The new model also shows that the effects of pumping on White Bear Lake are more pronounced during years of lower net precipitation and when the lake is below its outlet.
- Minnesota law does not have a zero impact standard - i.e., groundwater appropriations that affect surface waters are not prohibited. In the case of White Bear Lake, the DNR has documented impacts to recreation during low water levels, but we have not found any evidence of ecological harm on White Bear Lake due to recent low water levels. Nor do we have any evidence that current groundwater use is creating an unsustainable drawdown on aquifer levels.
- The model demonstrates that the August 30, 2017 Ramsey County District Court order's restrictions on residential water use will be largely ineffective in changing water levels in White Bear Lake. Specifically, initial results show that the court's residential irrigation ban will only increase water levels by about one inch a year. These calculations were based on the Metropolitan Council's estimates of the volume of water used for residential irrigation.
As we have suggested during development of the North and East Metro Groundwater Management Area plan groundwater resources in the area may become oversubscribed in the future. Now is the time for the DNR to work with communities to make science-based plans to ensure a sustainable water future.
The new groundwater model will be an important tool in these efforts. We will use it to evaluate various options and inform appropriate courses of action. For the first time, we will be able to predict with reasonable certainty the effect of any groundwater appropriation changes to lake levels and the underlying aquifers. This knowledge is essential as we work collaboratively to ensure communities have sufficient water to meet their needs while also protecting our surface and groundwater resources.