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Draft North & East Metro Groundwater Management Area Plan 2-17 Lakes and Wetlands The GWMA is rich in lakes and wetlands.The specific characteristics of each feature are highly variable (depth, acreage,watershed, etc.).All of these surface water features are subject to natural variations such as precipitation and weather. Surface water features with connections to groundwater may be subject to changes due to natural variations or pumping. In 2010 the Metropolitan Council applied a screening method to categorize the potential vulnerability of surface waters to pumping from bedrock or buried Quaternary aquifers'. Lakes and wetlands were categorized into four broad groups based on the difference between surface water and shallow groundwater levels and underlying geology. • The two categories of lakes and wetlands expected to be most influenced by regional aquifers are in the discharge and flow-through groups. Discharge features primarily receive groundwater inflow with limited groundwater outflow. Flow-through features both receive groundwater inflow and discharge groundwater outflow.These features are likely to be affected by changing groundwater levels (natural or human induced) in areas where they are not protected by underlying, low permeability aquitards. F Indeterminate or recharge water bodies mostly loose water to the regional groundwater system. These features are typically less responsive to pumping from bedrock or deep aquifers, but changes in aquifer heads(pressure) may diffuse to these water bodies in areas where they are not underlain by sufficiently low permeability aquitards. • Disconnected water bodies, are very weakly connected to the regional groundwater system and are not considered vulnerable to pumping impacts. e Discharge,flow-through, and indeterminate or recharge type water bodies were considered to be potentially connected to the shallow groundwater system.Those water bodies that were considered also connected to deeper aquifers were rated as potentially vulnerable. This initial screening could be modified or refined with site-specific data and/or updated regional models. Lakes and wetlands that were rated as potentially vulnerable are distributed throughout the GWMA(Figure 2-9). There are some larger zones of water bodies rated as not vulnerable, such as the southern part of Woodbury and adjacent areas, most of Grant, and the southwestern half of Blaine. While potentially vulnerable lakes and wetlands in general could be affected by regional groundwater- level decline, water levels in smaller basins could also be vulnerable to localized drawdown due to their small area and storage volume. The method used in the Metropolitan Council 2010 study was a conservative approach. Some features were rated as vulnerable based on a possible connection to the regional aquifer system but may not be highly sensitive to pumping from bedrock or deeper buried Quaternary aquifers.The analysis did not consider other factors that can influence the sensitivity of lakes and wetlands to drawdowns in the major aquifers. 'Barr Engineering,2010. Evaluation of groundwater and surface-water interaction—guidance for resources assessment: prepared for Metropolitan Council. P44