Nitrate

Nitrate · mg/L at every place the city samples, upstream to downstream. The Big Sioux sites share one chart because they share one water; Skunk Creek gets its own, because the state assigns it different uses and different numbers.

The city labels the field “Nitrate (NO3)”; the state's standards are written as nitrate-N. Which scale these numbers are on is unconfirmed with the city, so no reference line is drawn.

From the city's SWQ Samples table, as of October 12, 2026. 7 published Nitrate values fall outside what the instrument could have read; they are listed on the site pages and left off these charts. Dashed lines are published thresholds with the rule cited, drawn for the season the rule names. No sample here is scored against them.