GROUNDWATER & DRINKING WATER
GROUNDWATER & DRINKING WATER
Groundwater supply and quality
Groundwater is the primary source of water for rural residents, farms, livestock facilities, and communities throughout the watershed. Fresh water supplies allow us to maintain our current standard of living. Groundwater is important not only for overall water supply but also for maintaining rare wetland and spring features on the landscape.
Public Water Systems - Drinking Water Supply Management Areas (DWSMA)
Drinking Water Supply Management Areas (DWSMA) in the Le Sueur River watershed establish a protection area through an extensive evaluation that determines the contribution area of a public water supply well, aquifer vulnerability and provide an opportunity to prioritize specific geographic areas for drinking water protection purposes. DWSMA boundaries that extend beyond city jurisdictional limits or are established in Wellhead Protection (WHP) Action Plans for nonmunicipal public water supplies, like mobile home parks, can be a special focus for local partners prioritizing drinking water protection activities.
Aquifer vulnerability determines the level of management required to protect a drinking water supply and provides an opportunity to target implementation practices in accordance with the level of risk different land uses pose.
Private Wells
Many residents of Le Sueur River Watershed rely on a private well for the water they drink. However, no public entity is responsible for water testing or management of a private well after drilling is completed. Local governments are best equipped to assist private landowners through land use management and ordinance development, which can have the greatest impact on protecting private wells.
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Surface water based drinking water systems are highly susceptible to potential contamination. Recognizing those surface water bodies that are sources of drinking water in the watershed is very important.
Arsenic
Many areas throughout the watershed are prone to high groundwater arsenic values. Prioritize areas were public and private drinking water wells are impacted by arsenic. On January 22, 2001, EPA adopted a new standard for arsenic in drinking water of 0.01 mg/l or 10 parts per billion (ppb), replacing the old standard of 50 ppb. Water systems had to meet the new standard by January 23, 2006. As of August 2008, well contractors in Minnesota test each newly drilled well for arsenic and share the results with the well owner and MDH.
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Nitrates & Downstream Impacts
Approximately 70% of Mankato's drinking water is supplied by two shallow Ranney wells that draw water from the Minnesota and Blue Earth Rivers. Source water to these wells is considered to be groundwater under the direct influence of surface water, filtered through the riverbed sediments with a very short time-of-travel. The Le Sueur River feeds into the Blue Earth River just southwest of Mankato and may influence the city well associated with it. Nitrate concentrations in Mankato Ranney Wells has reached levels of concern. Portions of the spill management area (SPA) and the emergency response area (ERA) for the city of Mankato are within the Le Sueur River Watershed. Local partners may consider focusing nitrogen BMPs in the Le Sueur Watershed due to the mutual benefits of protecting drinking water supplies.
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STRATEGIES TO PROTECT GROUNDWATER
Drinking Water Supply Management Areas (DWSMA)
Drinking Water Supply Management Areas (DWSMA) in the Le Sueur River 1W1P DWSMA boundaries establish a protection area through an extensive evaluation that determines the contribution area of a public water supply well, aquifer vulnerability and provide an opportunity to prioritize specific geographic areas for drinking water protection purposes. DWSMA boundaries that extend beyond city jurisdictional limits or are established in Wellhead Protection (WHP) Action Plans for nonmunicipal public water supplies, like mobile home parks, can be a special focus for local partners prioritizing drinking water protection activities.
Aquifer vulnerability determines the level of management required to protect a drinking water supply and provides an opportunity to target implementation practices in accordance with the level of risk different land uses pose. Promote groundwater conservation using the water supply plans in the cities of New Richland, Waseca, and Eagle Lake and expand educational programs.
Private Wells
Many residents of Le Sueur River Watershed rely on a private well for the water they drink. However, no public entity is responsible for water testing or management of a private well after drilling is completed. Local governments are best equipped to assist private landowners through land use management and ordinance development, which can have the greatest impact on protecting private wells. Other suggested activities to protect private wells include: hosting well testing or screening clinics, providing water testing kits, working with landowners to better manage nutrient loss, promoting household hazardous waste collection, managing storm water runoff, managing septic systems, and providing best practices information to private well owners.
Noncommunity Public Water Systems
Noncommunity public water systems provide drinking water to people at their places of work or play (schools, offices, campgrounds, etc.). Land use and management activities (maintaining/upgrading SSTS, well sealing, etc.) should consider effects on these public water systems. Le Sueur watershed has six of these systems, currently of unknown vulnerability. Many of these systems have aging wells that will eventually need to be replaced. Find information regarding noncommunity public water systems in the watershed in reports titled Source Water Assessments (SWA) at: https://www.health.state.mn.us/communities/environment/water/swp/swa.html
Source Water Assessments
Source Water Assessments provide a concise description of the water source used by a public water system and discuss how susceptible that source may be to contamination. Prioritize areas were public and private drinking water wells are impacted by arsenic. On January 22, 2001, EPA adopted a new standard for arsenic in drinking water of 0.01 mg/l or 10 parts per billion (ppb), replacing the old standard of 50 ppb. Water systems had to meet the new standard by January 23, 2006. As of August 2008, well contractors in Minnesota test each newly drilled well for arsenic and share the results with the well owner and MDH. Many areas throughout the watershed are prone to high groundwater arsenic values. Prioritize these protection areas by working with landowners on expanding arsenic testing to understand long-term concentrations, work with well contractors and MDH staff on well construction methods that are shown to reduce arsenic in new wells, improved education and outreach, and if possible, resources for water treatment if needed. Support the implementation of comprehensive source water protection plans for the public water supply system using surface water in the watershed.
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Sealing Abandoned Wells
Unused, unsealed wells can provide a conduit for contaminants from the land surface to reach the sources of drinking water. This activity is particularly important for abandoned wells that penetrate a confining layer above a source aquifer. Sealing wells is a central practice in protecting groundwater quality, however when resource dollars are limited it is important to evaluate private well density to identify the populations most at risk from a contaminated aquifer.
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Ongoing Research
Ground water observation wells. Consider working with DNR to install additional ground water observation wells on public lands.to monitor aquifers used as the primary water source for agricultural industries, rural residents, and the communities <insert link to OBWELL Networks>
Springs - Map springs in the watershed with assistance DNR Hydrogeology staff. Protect known springs from impacts associated with development. Protect groundwater upwelling and spring resources to protect the unique habitats and supply surface water resources during dry periods. Focus on the many springs located near the Le Sueur River in northern Blue Earth County are discharging groundwater from unconsolidated glacial materials and shallow bedrock aquifers.
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Learn More
Minnesota Department of Health - Groundwater
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