The Wenaha River is a tributary of the Grande Ronde River, about long, in Wallowa County, northeastern Oregon. The river begins at the confluence of its north and south forks in the Blue Mountains and flows east through the Wenaha–Tucannon Wilderness to meet the larger river at the small settlement of Troy.
The Wenaha and its tributaries form an extensive network of steep canyons sliced into volcanic rock layers of the Columbia River basalts, which covered the region during massive eruptions millions of years ago. A designated Wild and Scenic River for its entire length, the Wenaha basin is one of only a few Oregon watersheds with no dams or diversions. The river basin is mostly roadless, and is considered one of the most intact big game habitats in Oregon. Elk hunting, hiking, horseback riding, and salmon and trout fishing are popular recreational activities along the river.
Once used by four Native American tribes for hunting, fishing and trade, the Wenaha River basin was surrendered by the Nez Perce to the US government in the 1860s. The few settlers that subsequently came to this rugged, inaccessible region used it primarily for livestock grazing, causing severe damage to the local grasslands and soils. Most of the Wenaha River basin has been managed by the U.S. Forest Service since 1905 as part of the Wenaha, now the Umatilla National Forest, and as a wilderness area since 1978.
Course The main stem of the Wenaha River begins at an elevation of in western Wallowa County, at the confluence of its north and south forks at Wenaha Forks. The long North Fork Wenaha River originates near Ski Bluewood to the east of Deadman Peak in Columbia County, Washington, at an elevation of , and flows south into Oregon. The long South Fork Wenaha River begins in the southwest corner of Wallowa County, at an elevation of , and flows northeast to the confluence.
From the forks, the Wenaha River flows east, cutting a deep canyon through rugged plateau country on the eastern flank of the northern Blue Mountains. Atop the steep basalt canyon walls – locally known as "breaks" – sit rolling forested uplands, including Grouse Flat and Moore Flat to the north of the river and Hoodoo and Eden Ridges south of it. It leaves the national forest and empties into the Grande Ronde River at the town of Troy, at an elevation of . The Grande Ronde is a tributary of the Snake River, in turn the largest tributary of the Columbia River.
Tributaries enter the river in the following order headed downstream: Beaver Creek, Slick Ear Creek, and Rock Creek, all from the left; Big Hole Canyon from the right; Butte Creek, left; Swamp Creek, right; Weller Creek, left; Cross Canyon, right; Fairview Creek, left; Burnt Canyon, right; Crooked Creek, left. The largest tributaries are Butte Creek, which originates in Columbia County near the headwaters of the North Fork, and Crooked Creek, which drains parts of Columbia, Garfield and Asotin counties in Washington. Both form extensive canyon systems of their own, and flow south to join the Wenaha River shortly after entering Oregon.
Watershed The Wenaha River watershed comprises , of which are in Oregon. After the Wallowa River, it is the second largest tributary of the Grande Ronde by volume of discharge. In terms of land area, the Wenaha sub-basin is just over 7 percent of the entire Grande Ronde watershed. The highest point in the watershed is Oregon Butte, at above sea level. It is bordered by the watersheds of the Walla Walla River to the west, the Touchet and Tucannon Rivers to the north, and smaller tributaries of the Grande Ronde to the south and east.
The area experiences cold, snowy winters between November and April with snowpack building as much as deep at higher elevations. Summers are very hot and dry, especially along the river bottoms. Annual precipitation ranges from in the lower southeastern part of the basin, to along the highest elevations to the west.Stine, Peter & Hessburg, Paul & Spies, Thomas & Kramer, Marc & Fettig, Christopher & Hansen, Andrew & Lehmkuhl, John & O'Hara, Kevin & Polivka, Carlos & Singleton, Peter & Charnley, Susan & Merschel, Andrew & White, Rachel. (2014). The Ecology and Management of Moist Mixed-Conifer Forests in Eastern Oregon and Washington; a Synthesis of the Relevant Biophysical Science and Implications for Future Land Management. PNW-GTR-xxx. There is no stream gaging station on the Wenaha, but Palmer's Field Guide to Oregon Rivers (2014) estimates the average discharge of the river at . Seasonal variations range from over during spring snowmelt to about in late summer and fall.
Ecology and environment
The Wenaha River basin is characterized by coniferous forest, with ponderosa pine at lower elevations and lodgepole pine mixed with western larch, fir and spruce above about . Subalpine fir is common at high elevations. The basin provides habitat for numerous animal species include Rocky Mountain elk, white-tailed deer, moose, black bear, gray wolf, coyote, cougar, bobcat, snowshoe hare, and bighorn sheep. Bird species include blue grouse, ruffed grouse, chukar, valley quail, mountain quail, Lewis's woodpecker, bald eagle, golden eagle, and peregrine falcon.
The basin is largely undisturbed by roads and development, and thus provides excellent wildlife habitat. The area supports one of the highest densities of elk population in the continental United States. Explorers' and pioneers' accounts starting in the 1860s noted that the elk population was rich to the south of the Wenaha River and across most of what is now the Wallowa-Whitman National Forest. There was no mention of elk inhabiting areas north of the river. Unrestricted hunting caused the population of elk and other big game to plummet until about 1900–1905. In 1913 elk from Montana were stocked in areas north of the river. By the 1930s, a combination of stocking, hunting restrictions, and natural migration of elk populations from south of the river greatly increased the northern elk population.
Wolves were nearly extirpated in the Blue Mountains in the 20th century due to hunting, but have since been repopulating the region. The Wenaha wolf pack was first confirmed in 2008 and has produced young in almost every year since then. As of 2022 it had grown to eight adults. The Wenaha pack's range extends over a large area of Wallowa County, primarily south of the Wenaha River. The Grouse Flats wolf pack, which had about nine adults in 2022, has been observed primarily on the north side of the Wenaha River with most of its range in Washington. The Grouse Flats pack has been implicated in a number of livestock killings and the Washington Department of Fish and Wildlife authorized lethal removal of some wolves in 2019.
The Wenaha River is considered a Type IV channel under the Rosgen Stream Classification, characterized by a shallow rocky bed interspersed with deep pools. Although the river flows through a rugged, mountainous region, its gradient is relatively low at 1.1 percent, and is bordered by floodplains with dense riparian hardwood forests along its valley floor. These characteristics contrast with the nearby Grande Ronde and Snake Rivers, which have steeper gradients and less floodplain area.Baxter, Colden V. "Fish movement and assemblage dynamics in a Pacific Northwest riverscape." Oregon State University, January 23, 2002. There are no dams or channel modifications on the Wenaha River and its tributaries; although there are a few water rights within the basin used for domestic and livestock water supply, they account for a tiny portion of the river's flow. The river is considered a critical habitat for spring chinook salmon, steelhead trout and bull trout (formerly considered the same as Dolly Varden trout). The Forest Service reported in 2000 that "the Wenaha River system may be one of the best bull trout populations remaining in Oregon." Other fish species include rainbow trout, redband trout, and mountain whitefish.
As late as the 1960s, the Wenaha River saw an average of 22,000 anadromous fish returns (salmon and steelhead) each year. The primary spawning grounds are along the main stem and South Fork, with more sparse habitat in the North Fork and Butte Creek. Although habitat along the river has remained largely undisturbed, the construction of dams on the lower Snake River greatly reduced the number of migratory fish reaching the Wenaha. From 1979 to 1984, an average of less than 100 chinook salmon returned to the river each year. Populations have remained low and unstable since then; the average chinook salmon return for the period 1995–2005 was 376 fish, not counting those of hatchery stock. Coho salmon and fall Chinook, which used to come up to the Wenaha before the dams were built, are no longer found in the river.
Geology
The surface geology of the Wenaha River basin is defined by massive basalt lava flows making up the Columbia River Basalt Group, whose rocks now cover much of the Columbia Plateau region of the Pacific Northwest. The oldest of these basalt flows are the Grande Ronde basalt, which erupted about 17–15.5 million years ago and reach a thickness of more than in parts of the Wenaha-Tucannon Wilderness. Above this is the Wanapum basalt, which erupted some 15.5–13.7 million years ago and reaches a thickness of . The youngest are the Saddle Mountains basalt, which erupted about 13.7–10 million years ago. The basalt layers are interbedded with sedimentary rocks representing deposits from periods of lesser volcanic activity, and pumice deposits and magmatic dikes indicate the sites of past eruptions. In the northern areas of the present day wilderness area some pre-eruption terrain, primarily metamorphic rock of late Paleozoic to early Mesozoic age, remains exposed.
Prior to the Blue Mountains uplift starting about 15 million years ago, the area around the Wenaha and lower Grande Ronde rivers probably drained west towards the Columbia River. As the mountains rose, a structural basin or depression (the "Troy basin") formed along the east side of the mountains. When the Saddle Mountains basalt erupted it spread northwest from the Troy basin over the Blue Mountains towards present-day Walla Walla and from there over vast areas of southern Washington. These flows blocked westward drainage from the Troy basin, and in their aftermath a landscape of lakes and peat bogs formed in the area, later to be buried by fluvial sandstones and siltstones. Fossil peat bogs eventually turned into lignite deposits in the Troy basin. Between 10–6 million years ago, drainage established a new eastern outlet towards the Snake River. The modern Wenaha and Grande Ronde channels began to take shape and cut down into the basalt layers, eventually forming a massive system of canyons. The Wenaha River channel developed along the axis of the Grouse Flat syncline, a geologic fold that formed with the Blue Mountains uplift.
History
The Wenaha River was used by the Nez Perce, Walla Walla, Cayuse and Umatilla peoples for thousands of years. Most of the lower mainstem of the river was Nez Perce territory. The name of the river comes from the Wenak band of Nez Perce, with the "ha" suffix indicating the land governed by the Wenak. The upper reaches of the river, including its north and south forks, were used seasonally by the Walla Walla and Cayuse for hunting and fishing, although they sometimes ranged further east, as far as the Minam River. Trails crisscrossed the Blue Mountains providing routes for seasonal migrations and trade. One such trail came south from the upper Tucannon River, following ridge tops south past Oregon Butte and Weller Butte, then down to the Wenaha River near its confluence with Butte Creek. From there it continued east along the Wenaha River to its confluence with the Grande Ronde, where people had forded the larger river since "time immemorial". Tucker (1940) describes the significance of a site along the trail: