State-Wide Nitrate Data

About the Drinking Water Data

Tables on this page:

Table 1 below shows the number of Community Water Systems by annual mean nitrate concentration category. A total of 959 systems were active as of April 2010. As nitrate sampling is required frequently, systems with no monitoring data were probably not yet active. In Minnesota, total nitrate-nitrite as nitrogen (N) is reported and compared to the nitrate Maximum Contaminant Level (MCL) of 10 milligrams per liter of water (mg/L) (as N). The number of systems in actual violation of the >10 mg/L MCL standard is not equivalent to the number of systems listed in the table with concentrations ≥10 mg/L, mainly because the MCL is based on the average of an original sample result and a confirmation sample rather than a system-wide calendar year average.

Annual mean nitrate concentrations in Minnesota Community Water Systems (CWS), 1999-2009

Year Cumulative Number of Community Water Systems Sampled, 1999-2009 Number of Community Water Systems by Concentration Category (mg/L)
<3 3 to <5 5 to <10 10+
1999 817 (85%) 795 16 6 0
2000 846 (88%) 784 12 50 0
2001 862 (90%) 797 17 48 0
2002 872 (91%) 812 40 20 0
2003 882 (92%) 814 18 50 0
2004 905 (94%) 840 22 43 0
2005 918 (96%) 849 22 47 0
2006 929 (97%) 860 24 44 1
2007 938 (98%) 865 54 19 0
2008 946 (99%) 880 45 21 0
2009 953 (99%) 882 47 24 0

*mg/L means miligrams per liter of water.


Table 2 below shows the number of Community Water Systems by annual maximum concentration category during years 1999-2009. A community water system may have a number of different wells or "entry points" to the distribution system with differing levels of nitrate. In this case, the maximum value reflects the entry point with the highest concentration, prior to any blending of water. The level of nitrate in blended water that ultimately reaches the consumer's tap may be lower.

Annual maximum nitrate concentrations in Minnesota Community Water Systems (CWS), 1999-2009

Year Cumulative Number of Community Water Systems Sampled, 1999-2009 Number of Community Water Systems by Concentration Category (mg/L)
<3 3 to <5 5 to <10 10+
1999 817 (85%) 780 26 11 0
2000 846 (88%) 774 14 57 1
2001 862 (90%) 780 27 55 0
2002 872 (91%) 797 18 57 0
2003 882 (92%) 800 23 56 3
2004 905 (94%) 825 27 51 2
2005 918 (96%) 836 27 55 0
2006 929 (97%) 843 30 55 1
2007 938 (98%) 847 34 55 2
2008 946 (99%) 858 30 56 2
2009 953 (99%) 859 35 56 3

*mg/L means miligrams per liter of water.


Table 3 below shows the number of people served by community water systems within each nitrate mean concentration category. A total of 4,234,479 people were estimated to be served by community water systems in Minnesota as of April 2010. Nitrate monitoring data are available for over 99% of these people. Although no people were exposed to annual mean nitrate concentrations at or above 10 mg/L in 2009, 3% of the population was exposed to average levels of nitrate at or above 3 mg/L. Although concentrations below the MCL appear to protect infants from methemoglobinemia, it is not clear if this level is protective of other potential health effects that may be associated with nitrate exposure. Elevated nitrate concentrations may also indicate that the water source is vulnerable to other types of contamination; and in this way, nitrate serves as an indicator chemical. Note that the estimates of number of people served by each system are rough calculations periodically updated by water purveyors. Estimates are not available for years past.

Number of people served by Community Water Systems by mean nitrate concentration, Minnesota 2009

Year Number (%) of People Served with Available Monitoring Data Number of People Served by Community Water Systems by Concentration Category (mg/L)
<3 3 to <5 5 to <10 10+
2009 4,229,097 (99.9%) 4,103,064 (97%) 50,216 (1%) 75,817 (2%) 0 (0%)

*mg/L means miligrams per liter of water.