Rivermatics

6 USGS Streamgages · Columbia River system

Cowlitz River flows and levels

Cowlitz River is gauged at 6 USGS streamgages in Washington, each tracked by Rivermatics. The mainstem runs about 143 miles (230 km) from headwaters to outlet. It drains into the Columbia River system. Drainage area at the gauges ranges from 287 square miles at Cowlitz River at Packwood, WA up to 2,238 at Cowlitz River at Castle Rock, WA. Rivermatics issues a daily machine-learned 14-day flow outlook at 5 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
Cowlitz River at Packwood, WA WA 287 — 1,472.7 1,391 14-day
Cowlitz River at Randle, WA WA 541 — 2,960.3 1,720 14-day
Cowlitz River near Kosmos, WA WA 1,040 — 5,122.7 3,034.8 14-day
Cowlitz River below Mayfield Dam, WA WA 1,400 — 5,790 3,693.2 14-day
Cowlitz River at Toledo, WA WA 1,461 — 5,295.7 3,402.9 —
Cowlitz River at Castle Rock, WA WA 2,238 — 9,161.7 4,527.7 14-day

Typical flow by month at Cowlitz River at Castle Rock, WA

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 99 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 5,960 12,451.6 25,461.3
February 5,781.4 11,027.6 22,631
March 5,784.8 9,609.4 17,800
April 5,990 9,161.7 15,996.7
May 5,111.6 9,642.6 16,032.3
June 4,218.3 8,376.3 15,233.3
July 2,778.7 4,527.7 9,069.7
August 2,098.7 2,999.4 4,651.6
September 1,692.3 2,877 4,809
October 1,776.1 4,304.2 8,113.5
November 3,400.3 8,998.7 20,400
December 5,619.7 12,561.3 26,174.2

All values in cubic feet per second (cfs).

Common questions

When does the Cowlitz River run highest?
December, on the long-term record at Cowlitz River at Castle Rock, WA — the furthest-downstream gauge Rivermatics tracks on this river. Median daily flow there is about 12,561.3 cfs that month, against 2,877 cfs in September, 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 Cowlitz River?
Rivermatics tracks 6 USGS streamgages on the Cowlitz River, across Washington. 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 Cowlitz River?
Yes, at 5 of the 6 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 Cowlitz River part of?
The Cowlitz River drains into the Columbia 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 Cowlitz 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 Columbia River system

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