Cowlitz River

Total streamflow across the Cowlitz River was last observed at 18,770 cfs, and is expected to yield approximately 37,230 acre-ft of water today; about 79% of normal. Average streamflow for this time of year is 23,829 cfs, with recent peaks last observed on 2025-12-19 when daily discharge volume was observed at 108,900 cfs.

Maximum discharge along the river is currently at the Cowlitz River At Castle Rock reporting a streamflow rate of 8,470 cfs. This is also the highest stage along the Cowlitz River, with a gauge stage of 35.17 ft at this location. This river is monitored from 4 different streamgauging stations along the Cowlitz River, the highest being situated at an altitude of 1,053 ft, the Cowlitz River At Packwood.

Historically, the river was used for fishing and transportation by indigenous peoples. Today, it is a major source of hydroelectric power, with several major dams and reservoirs along its course, including Mayfield Dam and Riffe Lake. These dams have greatly affected the river's hydrology and the surrounding agricultural land by controlling flooding and providing irrigation. The Cowlitz River is also a popular recreational destination, with opportunities for fishing, boating, and hiking in the surrounding forests and mountains. The river is home to several species of salmon and steelhead, and efforts are being made to restore and protect their populations.