| Cowlitz River | |
|---|---|
 The Cowlitz River atKelso, Washington | |
 Map of the Cowlitz River watershed | |
  Mouth of the Cowlitz River in Washington | |
| Etymology | from theSalish,tawallitch, perhaps meaning "capturing the medicine spirit"[2] |
| Location | |
| Country | United States |
| State | Washington |
| Region | Lewis County,Cowlitz County |
| Cities | Packwood,Randle,Mossyrock,Toledo,Castle Rock,Longview,Kelso |
| Physical characteristics | |
| Source | |
| • location | Packwood |
| • coordinates | 46°39′16″N121°37′13″W / 46.65444°N 121.62028°W /46.65444; -121.62028[1] |
| • elevation | 1,190 ft (360 m)[3] |
| Mouth | Columbia River |
• location | Longview |
• coordinates | 46°5′52″N122°54′40″W / 46.09778°N 122.91111°W /46.09778; -122.91111[1] |
• elevation | 3 ft (0.91 m)[1] |
| Length | 105 mi (169 km) |
| Basin size | 2,586 sq mi (6,700 km2) |
| Discharge | |
| • location | Castle Rock[4] |
| • average | 9,122 cu ft/s (258.3 m3/s)[4] |
| • minimum | 998 cu ft/s (28.3 m3/s) |
| • maximum | 139,000 cu ft/s (3,900 m3/s) |
| Basin features | |
| Tributaries | |
| • left | Cispus River, Toutle River |
| • right | Tilton River |
TheCowlitz River is ariver in the state ofWashington in theUnited States, atributary of theColumbia River. Its tributaries drain a large region including the slopes ofMount Rainier,Mount Adams, andMount St. Helens.
The Cowlitz has a 2,586-square-mile (6,698 km2)drainage basin,[5][6] located between theCascade Range in easternLewis County, Washington and the cities ofKelso andLongview. The river is roughly 105 miles (169 km) long, not counting tributaries.
Major tributaries of the Cowlitz River include theCispus River and theToutle River, which was overtaken by volcanic mudflows (lahars) during theMay 1980 eruption ofMount St. Helens.
When thesmelt spawn in the Cowlitz River, thegulls go into a feeding frenzy that lasts for weeks. Kelso, Washington is known as the "Smelt Capital of the World".[7]
The Cowlitz River has three majorhydroelectric dams, with several small-scalehydropower and sediment retention structures within the Cowlitz Basin.
TheCowlitz Falls Project is a 70megawatthydroelectric dam built in the early 1990s and completed in 1994. The dam is 140 feet (43 m) high and 700 feet (210 m) wide. The Cowlitz Falls Project produces on average 260GWh annually forLewis County PUD. Its reservoir,Lake Scanewa, is located at the confluence of the Cowlitz and Cispus Rivers downstream ofRandle.
Mossyrock Dam began generating power forTacoma City Light in 1968. It rises 605 feet (184 m) from bedrock and created the 23-mile (37 km) longRiffe Lake (previously Davisson Reservoir). It is the highest dam in the Pacific Northwest.[8] The dam is named for the nearby city ofMossyrock, and the lake for the town of Riffe, which, along with Kosmos, was destroyed by the flooding of the Cowlitz River valley above the dam.
TheMayfield Dam is 850 feet (260 m) long and 185 feet (56 m) high. An 860-foot (260 m) tunnel connects the reservoir to the powerhouse. The dam began producing electricity in 1963.Mayfield Lake offers many recreational opportunities: there are several county and state parks and the lake is below the Mossyrock Dam. The modulated inflow from the Mossyrock Dam allows Mayfield Lake to maintain a water level that rarely fluctuates more than a few feet. It is located several miles downstream of Mossyrock.
Packwood Lake was dammed in 1964 by the Washington Public Power Supply System (now called Energy Northwest). The dam holds back the lake (previously held back by an ancient landslide), redirecting streamflow to a 27megawatt hydroelectric generator in the Cowlitz River valley floor 2,000 feet (600 m) below just outside the town ofPackwood. When designing and building the dam, care was taken so as not to affect the abundant wildlife of the lake and surrounding area: the dam raised the water level by only a few feet.
A serious side effect of theMount St. Helens1980 eruption has been the annual downstream movement of an average of 3 million tons of sediment through theNorth Fork Toutle River. The rate is 10 times pre-eruption levels. TheToutle River Sediment Retention Structure was constructed to trap this sediment before it was carried farther downstream, where it could clog the river channel, exacerbate floods along the lower Toutle and Cowlitz Rivers, and fill theColumbia River shipping channel, which still requires periodic dredging. An overflow channel has been added to divertlahars around the dam. As of 2025[update], the efficiency of the retention dam in capturing ash sediment has fallen from 80% to 20%. Downstream communities, such as Castle Rock,Longview, and Toutle, have seen increasing contamination in their water supply and difficulties in maintaining water infrastructure due to the subsequent increase of downstream sediment.[9]
Numerous road and rail bridges span the Cowlitz.
Just upstream from its mouth at the Columbia river, a railroad bridge connecting the Port of Longview to theBNSF rail line crosses the Cowlitz, with a road bridge for SR 432 (Tennant Way) beside.
Further upstream are the Allen St. and Cowlitz Way bridges, connecting West Kelso with the rest ofKelso. Just north of Kelso, a railroad bridge provides crossing for theColumbia & Cowlitz Railroad.
Connecting SR 411 to Interstate-5 is the Lexington bridge, a two-lane bridge between the large unincorporated community ofLexington to Exit 42 on the east side of the bank.
AtCastle Rock, the A St. bridge provides access from downtown to the school and residential areas across the river. A few miles north, after the Toutle River split, the BNSF line crosses the river.
Across theLewis/Cowlitz County line, between the towns ofVader andToledo, Washington,I-5 crosses the river. At Toledo, SR-505 crosses the river as well.
WhereHighway 12 crosses Mayfield Lake, just west of Mossyrock, causeways were built out to the middle of the lake, where a short bridge section connects the two sides. A small bridge provides a crossing for SR 122 at the head of Mayfield Lake. Just east of Mossyrock, the Cowlitz River Bridge on Highway 12 was the largest concrete arch bridge in North America until 1971 at 550 feet (170 m).
At the head of Riffe Lake, the 27 Road provides access to the forestland south of the Cowlitz fromMorton andGlenoma to the north.
AtRandle, SR 131 crosses the Cowlitz to provide access to the Cispus basin and the northern areas of theMount St. Helens National Volcanic Monument.
Between Randle and Packwood, Highway 12 crosses the Cowlitz at the Cora bridge.
At Packwood, Skate Creek Road spans the river, providing access to theGifford Pinchot National Forest andTatoosh Wilderness, as well as connecting the downtown and residential areas of Packwood.
Upstream from Packwood, the Cowlitz splits into the Muddy and Clear Forks, with several Forest Service and Park Service roads crossing each.
When the Cowlitz Salmon Hatchery began operation in 1968, it was the largest of its kind in the world. Currently, it produces nearly 13 million fish each year. Adjacent is the barrier dam, which diverts spawning and upriver migrating fish to a separating station where fish are sorted by species. Some of the fish are used by the hatchery while others are transported upstream to continue migration.
TheBonneville Power Administration, in cooperation with the Lewis County PUD, state and federal agencies and Tacoma Power, constructed a downstream anadromous fish collection facility as part of the Cowlitz Falls Project. The fish facility, along with the Cowlitz River Salmon Hatchery's diversion dam below Mayfield Lake, has permitted the reintroduction of salmon and steelhead in the upper Cowlitz River basin for the first time since the construction of the Mossyrock and Mayfield dams in the 1960s.
The Cowliz River's two hatcheries provide an exceptional sportfishing opportunity for recreational anglers in Washington and Oregon. The river consistently ranks as one of the states top ten steelhead and salmon producers.
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