Metropolitan Council Regional Groundwater Flow Modeling Twin Cities Metropolitan Area Water Supply: March 11, 2008 Lanya Ross Senior Environmental Scientist

Outline Model Purpose Model Inputs Model Calibration Example of Model Use Next Steps

Goal To ensure safe, secure, reliable, cost-effective and equitable water supplies for current and future generations.

Model Purpose What is a good estimate of the capacity of a wellfield? What will drawdown be from a proposed well? What will future regional groundwater levels be? How will future pumping affect ecological features? How might development patterns affect recharge? How do we sustainably manage our water supplies?

Metro Model 2.0 TAC 2006 – Preliminary Analysis 2007 – Model Development and Quarterly TAC Meetings 2008 – Beta Testing Calibrated Models and Scenario Running For more information: Supply/metrogroundwatermodel.htm

Model Layers: 1.Quaternary 2.St. Peter 3.Prairie du Chien 4.Jordan 5.St. Lawrence 6.Franconia 7.Ironton-Galesville 8.Eau Claire 9.Mt. Simon

Aquifer Property Zones: Quaternary

Boundaries: 1.No-Flow 2.Constant Head 3.River

Targets: 1.Head: 14,536 2.Flux: 35

Targets in Layer 9: Mt. Simon

Model Head Calibration

Layer 1 Residual Mean: m

Example of Model Use What are the impacts of projected 2050 municipal demand? Assume traditional sources used in the future Assume communities with no municipal supply do not develop a municipal supply Assume that future wells pump at the average rate reported for metro area wells in that aquifer

Results – Projected Demand

Next Steps Regional scenarios —Climate Change —Land Use Local questions —Impacts of Alternative Supplies Continue to address uncertainty

Additional Figures

Aquifer Property Zones: Prairie du Chien

Layer 3 Residual Mean: m

Head Calibration: Prairie du Chien

Head Calibration: Quaternary

Head Calibration: Mt. Simon