Rivermatics

USGS Streamgage 06306300

Tongue River at State Line near Decker, MT

Tongue River at State Line near Decker, MT is USGS streamgage 06306300 in Montana, monitoring river discharge in hydrologic subbasin 10090101. It sits on the Tongue River, alongside 5 other gauges Rivermatics tracks on the same river. It drains a watershed of about 1,453 square miles. Discharge records at this site go back to 1960. Typical flow runs near 353.1 cfs in July and 303.6 cfs in April, with the higher of the two arriving in July. Rivermatics issues a daily machine-learned flow outlook for this gauge, reaching 14 days ahead, alongside daily high and low water-temperature forecasts.

View live conditions & forecast →

Gauge details

State
Montana
Drainage area
1,453 sq mi
Gauge elevation
3,439 ft
Subbasin (HUC-8)
10090101
Coordinates
45.00914, -106.83594
USGS site number
06306300
Records begin
1960-07-08 (66 years)
Rivermatics forecast
14-day flow outlook + water temperature

14-day flow forecast

Based on observations through for Tongue River at State Line near Decker, MT. Each day carries a median estimate and the band the model expects the flow to fall within — not a single number to plan against. Forecasts are re-issued daily; see the live screen for the current outlook.

Forecast daily mean discharge in cubic feet per second, by date
Date Low p10 Expected p50 High p90 Range
35.8 39.9 45.4
33.4 39.8 50.6
31.7 39.4 52.8
31 39.5 55.6
31.2 41.4 62.7
30.6 41.5 64.9
32 44.4 71.9
35.2 52.8 92.8
35.7 54.8 98.8
34.9 54.8 103
33.5 55.1 118
32.4 55.3 126
32.1 56.3 132
30.8 56 136

All values in cubic feet per second (cfs). Estimates only — do not use them for navigation or for any safety, rescue, or emergency decision.

Typical flow by month

Long-term daily discharge percentiles from the USGS record (up to 66 years of data), averaged within each month. These describe the historical normal range — they are not a forecast and not today's reading.

Historical monthly discharge percentiles in cubic feet per second
Month Low p10 Typical p50 High p90 Range
January 102.5 160 248.5
February 110 187 341.1
March 143.8 241.3 496.3
April 180.2 303.6 602.7
May 412.1 985.2 2,143.2
June 389.5 1,475.4 3,184.7
July 101.1 353.1 956.2
August 61.4 141.2 313.8
September 94.5 180.9 355.5
October 153.2 237.4 346.7
November 143.1 207 292.4
December 106.8 166.7 242.6

All values in cubic feet per second (cfs).

Common questions

When does Tongue River at State Line near Decker, MT normally run highest?
June, on the long-term record. The median daily flow that month is about 1,475.4 cfs, against 141.2 cfs in August, the lowest month. These are historical normals for the date, not a forecast and not today's reading.
What is a normal flow for Tongue River at State Line near Decker, MT?
It depends on the month. In January, half of days historically fall near 160 cfs, with the middle 80% of days between 102.5 and 248.5 cfs. The month-by-month table on this page gives the full range.
How long has Tongue River at State Line near Decker, MT been measured?
Discharge records at USGS site 06306300 begin in 1960, about 66 years, covering roughly 9,196 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.
Is there a flow forecast for Tongue River at State Line near Decker, MT?
Yes. Rivermatics trains a machine-learned model — a temporal-fusion transformer — on this basin's observed flows, weather, and snowpack, and issues a daily flow outlook reaching 14 days ahead: a median estimate inside a confidence band, not a single number to bet on. A companion model forecasts each day's water-temperature high and low. Every forecast is scored against days the model never trained on, and that track record is published on the live gauge screen. Open live conditions to see the current outlook.
Where is Tongue River at State Line near Decker, MT?
The gauge sits at 45.00914, -106.83594, in Montana, in hydrologic subbasin 10090101, at an elevation of about 3,439 feet, draining roughly 1,453 square miles.
Can I use Tongue River at State Line near Decker, MT data for flood or safety decisions?
No. Rivermatics provides estimates, not guarantees, and the readings and forecasts here may be delayed, inaccurate, or wrong. Do not use them for navigation or for any safety, rescue, or emergency decision. Check the National Weather Service and USGS directly, and use your own judgment.

Upstream and downstream on the Tongue River

Every gauge Rivermatics tracks on this river, ordered by drainage area — upstream first. See the Tongue River in full.

Other gauges in this subbasin