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Minnesota Department of Health (MDH) Source Water Protection initially developed county-scale nitrate risk maps in 2007 for nine southeastern Minnesota counties to assist with state and local water quality planning efforts and support a nitrate occurrence study (Southeast Minnesota Water Resources Board, 2009). The mapping effort has now expanded to include 30 counties. The nitrate risk ranking map is at an approximate scale of 1:100,000 and identifies areas where the water table aquifer is classified as having relatively high, moderate, or low sensitivity to contaminant sources originating at the ground surface, including nitrate. Such maps are useful for wellhead protection and other water planning efforts. |
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Minnesota Department of Health (MDH) Source Water Protection initially developed county-scale nitrate risk maps in 2007 for nine southeastern Minnesota counties to assist with state and local water quality planning efforts and support a nitrate occurrence study (Southeast Minnesota Water Resources Board, 2009). The mapping effort has now expanded to include 30 counties. The nitrate risk ranking map is at an approximate scale of 1:100,000 and identifies areas where the water table aquifer is classified as having relatively high, moderate, or low sensitivity to contaminant sources originating at the ground surface, including nitrate. Such maps are useful for wellhead protection and other water planning efforts. |
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Base data from National Agricultural Statistics Service, various county soil atlases, Minnesota Geological Survey's County Well Index, and MDH Environmental Health Division, Drinking Water Protection Section, Source Water Protection Unit. Final datasets prepared by MDH Source Water Protection Unit. |
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<DIV STYLE="text-align:Left;"><DIV><DIV><P STYLE="text-align:Justify;margin:0 0 7 0;"><SPAN><SPAN>Nitrate-nitrogen (nitrate) risk ranking maps have been constructed for the water table aquifer beneath eleven southeastern Minnesota counties, the seven-county Twin City Metropolitan Area, and twelve additional counties throughout central and south-central Minnesota. Additional counties will be mapped as base data becomes available. Nitrate loading to the subsurface is estimated by reclassification of land use data (ranging from 1 point for relatively low to 5 points for relatively high estimated nitrate loading). Hydrogeologic sensitivity for the water table aquifer is ranked from low (1 point) to very high (4 points) based upon the permeability of geologic materials (surficial geology, soil parent material type and bedrock type), land slope, and the relationship between depth to water and depth to bedrock. Adding the estimated nitrate loading raster to the hydrogeologic sensitivity raster simulates nitrate release to the water table, and produces the nitrate risk map for the water aquifer. The final point score can fall within nitrate risk ranges classed on the final map as low (up to 4 points), moderate (5 to 6 points), or high (7 to 9 points). The results are checked by comparison to available nitrate chemical data collected from wells within the county being mapped.</SPAN></SPAN></P><P STYLE="margin:0 0 7 0;"><SPAN /></P></DIV></DIV></DIV> |
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<DIV STYLE="text-align:Left;"><DIV><DIV><P STYLE="text-align:Justify;margin:0 0 7 0;"><SPAN><SPAN>The maps are designed to be used at a scale of approximately </SPAN></SPAN><SPAN STYLE="font-weight:bold;"><SPAN>1:100,000 </SPAN></SPAN><SPAN>(county-scale). Map accuracy at larger scales (more detail or smaller area) cannot be verified due to the scale limitations on the base data used to generate the maps.</SPAN></P><P><SPAN /></P></DIV></DIV></DIV> |
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Nitrate Risk to the Water Table Aquifer |
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["Nitrate Risk Mapping","Nitrate Probability Mapping","Nitrate Probability"] |
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en-US |
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150000000 |
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