River levels in South Dakota.

Every gauge is ranked against its own record for this calendar day. A river that normally runs 40 cubic feet per second in August is "much below normal" at 12; one that normally runs 40,000 is not. That is why a single national colour scale works at all — the comparison is always local, and always seasonal. Gauges with fewer than ten years of record for the date are shown unclassified rather than assumed normal.

This is a daily mean read against a daily percentile, refreshed twice a day. It cannot represent a fast-rising river. For flood forecasts and warnings in South Dakota, use NOAA's National Water Prediction Service and your local National Weather Service office; for life-safety information, follow your local emergency management agency.

Every reporting USGS stream gauge in the country, coloured by how today’s flow ranks against that gauge’s own record for this calendar day.

Open the streamflow map →

Watershed Explorer

Click any point in the country and read what six federal datasets say about it — flow, drought, fire, flood forecast, satellite cyanobacteria screening and Clean Water Act impairment — each one labelled with what it is actually a fact about.

Wildfire & Smoke Map — South Dakota

Official NIFC fire perimeters and incident points under NOAA’s HRRR-Smoke near-surface forecast, filterable by size, state, and containment.

Open the national wildfire and smoke map →

U.S. Drought Map — South Dakota

The U.S. Drought Monitor — the country’s official weekly drought assessment — drawn across five severity categories from D0 to D4.

Open the national U.S. drought map →

Flood Outlook Map — South Dakota

NOAA’s river forecast centres call the next few days at every forecast gauge in the country, on the National Weather Service’s own flood categories — action, minor, moderate and major.

Open the national flood outlook map →

Impaired Waters Map — South Dakota

Every subwatershed in the country against the states’ own Clean Water Act assessments — what is impaired, what is still on the 303(d) list, what is causing it, and how much of the country nobody has assessed at all.

Open the national impaired waters map →

Cyanobacteria Bloom Map — South Dakota

NASA and EPA’s satellites read a pigment index over roughly 2,300 U.S. lakes large enough to resolve at 300 m. A pre-screening indicator, not a health assessment, and never a substitute for your state’s advisory.

Open the national cyanobacteria bloom map →

Critical Habitat & Protected Waters Map — South Dakota

Every river and stream the federal government has designated as ESA critical habitat, the listed species each unit is designated for, and who manages the protected land around it.

Open the national critical habitat map →