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Study examines impact of growth on water supply in Ramsey

The Metropolitan Council recently completed a case study of the impacts of projected growth on a community’s local water supply.

Using a new groundwater model developed in 2007, the Council’s study looked at water-related issues in the city of Ramsey, located on the western border of Anoka County just north of the Mississippi River. Ramsey was chosen, in part, because it is in an area that could face water supply issues related to growth in the decades ahead.

The study results are encouraging, both for their local and regional implications. The city learned that the aquifer it relies on appears to be sufficient to supply projected demands, although ongoing monitoring will be critical to assess the impact of withdrawals on surface water features.

“The project is revealing a lot of valuable information about the dynamic relationship between growth and water supply in the area, and about the stress that too much growth might put on surface waters, like lakes, creeks and swamps, especially if groundwater levels were to drop too far or too fast,” explained Chris Elvrum, manager of water supply planning for the Council.

Project managers also are learning how to refine the groundwater model for use in other parts of the region in the future.

“Taking a good, hard look at groundwater supplies in the Twin Cities is very timely, given the region’s continuing growth and the potential challenges of climate change,” Elvrum said. “There have been a few cases in the recent past where local concerns have led to limitations on water withdrawals.

“However, as a region, our water supply is generally in very good shape,” he said. “And while the future is uncertain, there are steps we can take now to avoid those local impacts and ensure that our water needs will be met.”

The Council conducted the study as part of the development of a regional Water Supply Master Plan, which the Council will complete later this year.

New groundwater model plays key role  

The Council began the analysis in Ramsey with water demand forecasts developed as part of the regional water supply planning effort. Water demand forecasts are based on past use, forecasted population growth, projected land-use patterns and other factors related to growth.

Then it plugged the forecasts into the new groundwater model. Last year, working with Barr Engineering and regional stakeholders, the Council directed the development of the model – called Metro Model II – to evaluate the impacts of growth on surface waters and water supply in areas where water supply may be limited, such as Anoka County. As the name implies, this is a second generation groundwater model, which updates one first developed by the Minnesota Pollution Control Agency in the late 1990s.

In Ramsey, the model helped answer such questions as:

• What is the likely maximum potential of proposed new wells?
• How will projected demand impact groundwater levels?
• How will pumping affect surface water features, like lakes, streams and wetlands?
• What is the cumulative impact of withdrawals from multiple communities based on their projected demands?

 

Elvrum said that results of the analysis show that while the aquifer appears to be sufficient to supply projected demands, ongoing monitoring in Ramsey will be critical to assess the impact of withdrawals on surface water features.

The study results are being used by the Minnesota Department of Natural Resources (DNR) and the City to develop a monitoring plan.

“The results of the modeling and monitoring will provide greater certainty to communities as they plan ahead to assure water supply, and it will allow the DNR to make water withdrawal permitting decisions based on sound technical analysis,” Elvrum said.

“Most importantly, because water supply issues will be evaluated using the same forecasts in the same timeframe as other aspects of regional planning, water supply plans will be integrated within the City’s overall growth plan,” he said.

Water transcends geographic boundaries

Because of the need to take a longer-range view of water supply in the region, the 2006 Minnesota Legislature directed the Council to develop a first-ever regional water supply master plan.

The master plan will lay out a process for continuing to assess the seven-county region’s water supply, and a long-term strategy for managing the resource. It also will clearly lay out local, regional and state agency roles and responsibilities.

This is not the first time the Council or communities in the region have been concerned about water supply. The Southwest Metro Groundwater Work Group has been meeting since 1997 to address many of the same concerns expressed in the north metro: the impact of withdrawals on surface water features, the recharge of aquifers, water demands due to growth, sharing water across municipal lines, and the impact of possible future droughts.

Last year, Scott County began a county-wide water supply planning effort for townships within that county. And the Council is in the process of looking at other areas around the metro, including in Dakota County, where significant growth in the Lakeville and Farmington area is going to require large withdrawals from the aquifers serving that area.