Rivermatics

USGS Streamgage 06099500

Marias River near Shelby, MT

Marias River near Shelby, MT is USGS streamgage 06099500 in Montana, monitoring river discharge in hydrologic subbasin 10030203. It sits on the Marias River, alongside 3 other gauges Rivermatics tracks on the same river. It drains a watershed of about 2,716 square miles. Discharge records at this site go back to 1902. Typical flow runs near 747.5 cfs in July and 896.9 cfs in April, with the higher of the two arriving in April. Rivermatics issues a daily machine-learned flow outlook for this gauge, reaching 14 days ahead.

View live conditions & forecast →

Gauge details

State
Montana
Drainage area
2,716 sq mi
Gauge elevation
3,102 ft
Subbasin (HUC-8)
10030203
Coordinates
48.4272, -111.88984
USGS site number
06099500
Records begin
1902-04-01 (124 years)
Rivermatics forecast
14-day flow outlook

14-day flow forecast

Based on observations through for Marias River near Shelby, 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
654 757 904
619 865 1,409
649 1,025 1,840
600 911 1,539
553 802 1,272
511 715 1,088
472 651 968
420 575 842
379 514 740
342 465 667
315 428 608
301 408 569
291 391 536
276 367 498

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 124 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 117.7 215.3 419.3
February 125.3 243.5 548.4
March 194.9 393.2 1,112.3
April 387.9 896.9 2,000
May 1,127 2,306.5 4,647.7
June 920.6 2,289 5,483
July 248.5 747.5 2,045.8
August 120.6 296.8 698.5
September 111 256.5 570.1
October 157 305.5 684.6
November 171.9 312.3 654.9
December 138 248.4 518.7

All values in cubic feet per second (cfs).

Common questions

When does Marias River near Shelby, MT normally run highest?
May, on the long-term record. The median daily flow that month is about 2,306.5 cfs, against 215.3 cfs in January, the lowest month. These are historical normals for the date, not a forecast and not today's reading.
What is a normal flow for Marias River near Shelby, MT?
It depends on the month. In January, half of days historically fall near 215.3 cfs, with the middle 80% of days between 117.7 and 419.3 cfs. The month-by-month table on this page gives the full range.
How long has Marias River near Shelby, MT been measured?
Discharge records at USGS site 06099500 begin in 1902, about 124 years, covering roughly 9,197 days of published daily values. The long record is what makes the monthly percentiles on this page meaningful.
Is there a flow forecast for Marias River near Shelby, 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. 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 Marias River near Shelby, MT?
The gauge sits at 48.4272, -111.88984, in Montana, in hydrologic subbasin 10030203, at an elevation of about 3,102 feet, draining roughly 2,716 square miles.
Can I use Marias River near Shelby, 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 Marias River

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

Other gauges in this subbasin