Rivermatics

4 USGS Streamgages · Mississippi River system

Marias River flows and levels

Marias River is gauged at 4 USGS streamgages in Montana, each tracked by Rivermatics. The mainstem runs about 269 miles (432 km) from headwaters to outlet. It drains into the Mississippi River system. Drainage area at the gauges ranges from 2,716 square miles at Marias River near Shelby, MT up to 7,027 at Marias River near Loma, MT. The gauged reach falls about 529 feet, from 3,102 feet down to 2,574. Rivermatics issues a daily machine-learned 14-day flow outlook at 3 of them.

Gauges on this river, upstream to downstream

Ordered by drainage area, which is how far down the river each gauge sits. April and July figures are long-term median daily flows for that month from the USGS record — historical normals, not a forecast and not today's reading.

USGS streamgages on this river, ordered upstream to downstream
Gauge State Drainage sq mi Elevation ft April p50 cfs July p50 cfs Forecast
Marias River near Shelby, MT MT 2,716 3,102 896.9 747.5 14-day
Marias River near Chester, MT MT 4,944 2,823 524.2 792.7 14-day
Marias River at Highway 223 bridge near Chester, MT MT 5,947 2,755 — — —
Marias River near Loma, MT MT 7,027 2,574 551.9 695.7 14-day + temp

Typical flow by month at Marias River near Loma, MT

The furthest-downstream gauge on this river, so the fullest flow it carries here. Long-term daily discharge percentiles from the USGS record (up to 67 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 102.3 294.5 551.8
February 131 333.4 969.9
March 132.2 391.9 1,485.8
April 304.6 551.9 1,387.7
May 411.4 798.1 2,103.5
June 413.4 1,003.1 3,079.7
July 328.3 695.7 2,136.1
August 289.3 619.6 2,041.3
September 351 569.1 1,554
October 298.5 514.9 1,218.1
November 116.2 538.4 1,465
December 92.3 397.5 848.3

All values in cubic feet per second (cfs).

Common questions

When does the Marias River run highest?
June, on the long-term record at Marias River near Loma, MT — the furthest-downstream gauge Rivermatics tracks on this river. Median daily flow there is about 1,003.1 cfs that month, against 294.5 cfs in January, the lowest. Upstream gauges peak on their own schedule; the table on this page gives April and July for each.
How many gauges are on the Marias River?
Rivermatics tracks 4 USGS streamgages on the Marias River, across Montana. Each has its own page with the site's full flow record and monthly normals. The river may carry other gauges that publish neither daily values nor discharge statistics; those are not tracked here.
Is there a flow forecast for the Marias River?
Yes, at 3 of the 4 gauges. Rivermatics trains a machine-learned model — a temporal-fusion transformer — on each basin's observed flows, weather and snowpack, and issues a daily 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 each gauge's live screen.
What river system is the Marias River part of?
The Marias River drains into the Mississippi River system — it is a tributary somewhere in that chain, following the flowpath down to its terminal river. Rivermatics builds this from the USGS/geoconnex reference-mainstem network rather than from names.
Can I use Marias River 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.

Other rivers in the Mississippi River system

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