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107-522: 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

214-499: A stream . It equals the product of average flow velocity (with dimension of length per time, in m/h or ft/h) and the cross-sectional area (in m or ft ). It includes any suspended solids (e.g. sediment), dissolved chemicals like CaCO 3 (aq), or biologic material (e.g. diatoms ) in addition to the water itself. Terms may vary between disciplines. For example, a fluvial hydrologist studying natural river systems may define discharge as streamflow , whereas an engineer operating

321-582: 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

428-558: A tussock moth infestation caused severe tree mortality. The project generated controversy due to its potential impact on water quality, and that it would provide little to no economic benefit. The Endangered American Wilderness Act of 1978 created the Wenaha-Tucannon Wilderness, with the effect of prohibiting further grazing, logging, mining, and road building along almost the entirety of the Wenaha River. The Wenaha River

535-473: A 10–15 million-year period, lava flow after lava flow poured out of multiple dikes which trace along an old fault line running from south-eastern Oregon through to western British Columbia. The many layers of lava eventually reached a thickness of more than 1.8 km (5,900 ft). As the molten rock came to the surface, the Earth's crust gradually sank into the space left by the rising lava. This subsidence of

642-580: 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

749-643: A maximum Pomona flow emplacement duration of several months based on the time required for rivers to be reestablished in their canyons following a basalt flow interruption. Three major tools are used to date the CRBG flows: Stratigraphy, radiometric dating, and magnetostratigraphy. These techniques have been key to correlating data from disparate basalt exposures and boring samples over five states. Major eruptive pulses of flood basalt lavas are laid down stratigraphically . The layers can be distinguished by physical characteristics and chemical composition. Each distinct layer

856-432: A reservoir system may equate it with outflow , contrasted with inflow . A discharge is a measure of the quantity of any fluid flow over unit time. The quantity may be either volume or mass. Thus the water discharge of a tap (faucet) can be measured with a measuring jug and a stopwatch. Here the discharge might be 1 litre per 15 seconds, equivalent to 67 ml/second or 4 litres/minute. This is an average measure. For measuring

963-529: A slow recession . Because the peak flow also corresponds to the maximum water level reached during the event, it is of interest in flood studies. Analysis of the relationship between precipitation intensity and duration and the response of the stream discharge are aided by the concept of the unit hydrograph , which represents the response of stream discharge over time to the application of a hypothetical "unit" amount and duration of rainfall (e.g., half an inch over one hour). The amount of precipitation correlates to

1070-465: A stratum was deposited. This is possible because, as magnetic minerals precipitate in the melt (crystallize), they align themselves with Earth's current magnetic field. The Steens Basalt captured a highly detailed record of the Earth's magnetic reversal that occurred roughly 15 million years ago. Over a 10,000-year period, more than 130 flows solidified – roughly one flow every 75 years. As each flow cooled below about 500 °C (932 °F), it captured

1177-675: Is 17.67±0.32 Ma with younger lava flows ranging to 15.50±0.40 Ma. Although the Imnaha Basalt overlies Lower Steens Basalt, it has been suggested that it is interfingered with Upper Steens Basalt. The next oldest of the flows, from 17 million to 15.6 million years ago, make up the Grande Ronde Basalt. Units (flow zones) within the Grande Ronde Basalt include the Meyer Ridge and the Sentinel Bluffs units. Geologists estimate that

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1284-602: 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

1391-792: Is believed the Yellowstone Hotspot created features like Smith Rock in Central Oregon and perhaps another flood basalt event known as Siletzia which underlies much of the Pacific Northwest coast with exposures in the Oregon Coast Range . There is additional confirmation that Yellowstone is associated with a deep hot spot. Using tomographic images based on seismic waves, relatively narrow, deeply seated, active convective plumes have been detected under Yellowstone and several other hot spots. These plumes are much more focused than

1498-624: Is characterized by coniferous forest, with ponderosa pine at lower elevations and lodgepole pine mixed with western larch , fir and spruce above about 4,500 feet (1,400 m). 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

1605-407: Is largely forested, logging was never a major industry there due to the difficulty of access. Settlers used some timber for building, but for the most part trees were cleared on the plateaus to provide more grazing land. Bright (1913) reported: Those settlers living near the breaks of the Wenaha River and Crooked Fork haul the logs to the edge and shove them over the breaks. Timber is the worst enemy

1712-518: 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

1819-997: Is made up of the Umatilla Member flows, the Wilbur Creek Member flows, the Asotin Member flows (13 million years ago), the Weissenfels Ridge Member flows, the Esquatzel Member flows, the Elephant Mountain Member flows (10.5 million years ago), the Bujford Member flows, the Ice Harbor Member flows (8.5 million years ago) and the Lower Monumental Member flows (6 million years ago). Camp & Ross (2004) observed that

1926-449: Is the Wanapum basalt, which erupted some 15.5–13.7 million years ago and reaches a thickness of 400 to 500 feet (120 to 150 m). 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

2033-596: 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 6,401 feet (1,951 m) 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

2140-416: Is the sum of processes within the hydrologic cycle that increase the water levels of bodies of water. Most precipitation occurs directly over bodies of water such as the oceans, or on land as surface runoff . A portion of runoff enters streams and rivers, and another portion soaks into the ground as groundwater seepage . The rest soaks into the ground as infiltration, some of which infiltrates deep into

2247-429: Is typically assigned a name usually based on area (valley, mountain, or region) where that formation is exposed and available for study. Stratigraphy provides a relative ordering (ordinal ranking) of the CRBG layers. Absolute dates, subject to a statistical uncertainty, are determined through radiometric dating using isotope ratios such as Ar/ Ar dating, which can be used to identify the date of solidifying basalt. In

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2354-404: Is typically expressed in units of cubic meters per second (m³/s) or cubic feet per second (cfs). The catchment of a river above a certain location is determined by the surface area of all land which drains toward the river from above that point. The river's discharge at that location depends on the rainfall on the catchment or drainage area and the inflow or outflow of groundwater to or from

2461-554: Is used both for day hikes from Troy and for multi-day backpacking or horse trips. The trail provides access to fishing, camping and scenic spots along the Wenaha River. It is also known for extreme summer heat and rattlesnakes. Numerous side trails descend into the canyons and connect with the main Wenaha River trail. Trails from the north, which link to trailheads on the Washington side, are typically blocked by snow until late spring. In total, some 200 miles (320 km) of trails crisscross

2568-532: The Chilcotin Group in south-central British Columbia , Canada . The Latah Formation sediments of Washington and Idaho are interbedded with a number of the Columbia River Basalt Group flows, and outcrop across the region. Absolute dates, subject to a statistical uncertainty, are determined through radiometric dating using isotope ratios such as Ar/ Ar dating, which can be used to identify

2675-527: The Rhine river in Europe is 2,200 cubic metres per second (78,000 cu ft/s) or 190,000,000 cubic metres (150,000 acre⋅ft) per day. Because of the difficulties of measurement, a stream gauge is often used at a fixed location on the stream or river. A hydrograph is a graph showing the rate of flow (discharge) versus time past a specific point in a river, channel, or conduit carrying flow. The rate of flow

2782-549: The Tualatin Mountains on the west side of Portland. Individual flows included large quantities of basalt. The McCoy Canyon flow of the Sentinel Bluffs Member released 4,278 km (1,026 cu mi) of basalt in layers of 10 to 60 m (33 to 197 ft) in thickness. The Umtanum flow has been estimated at 2,750 km (660 cu mi) in layers 50 m (160 ft) deep. The Pruitt Draw flow of

2889-678: The Yellowstone hotspot 's initial flood-basalt event occurred near Steens Mountain when the Imnaha and Steens eruptions began. As the North American Plate moved several centimeters per year westward, the eruptions progressed through the Snake River Plain across Idaho and into Wyoming . Consistent with the hot spot hypothesis, the lava flows are progressively younger as one proceeds east along this path. Previous to this eruptive period, it

2996-436: The 1880s and 1890s, white settlers began moving in to the tablelands above the confluence of the Wenaha and Grande Ronde rivers. Among the names given to these areas were "Eden" and "Paradise" because of the lush mountain meadows and mild summer temperatures. A plateau to the south of the river is still named Eden Ridge. Settlers continued to arrive until about 1905, when most of the suitable land had been claimed. During this time

3103-465: 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

3210-425: 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

3317-492: The 500 km (310 mi)-long Ginkgo flow of the Frenchman Springs Member, determining that it had been formed in roughly a week, based on the measured melting temperature along the flow from the origin to the most distant point of the flow, combined with hydraulics considerations. The Ginkgo basalt was examined over its 500 km (310 mi) flow path from a Ginkgo flow feeder dike near Kahlotus, Washington to

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3424-403: The CRBG deposits Ar, which is produced by K decay, only accumulates after the melt solidifies. Magnetostratigraphy is also used to determine age. This technique uses the pattern of magnetic polarity zones of CRBG layers by comparison to the magnetic polarity timescale. The samples are analyzed to determine their characteristic remanent magnetization from the Earth's magnetic field at the time

3531-428: The Columbia River Basalt Group (CRBG), similar to other large igneous provinces , was also marked by atmospheric loading through the mass exsolution and emission of volatiles, via the process of volcanic degassing. Comparative analysis of volatile concentrations in source feeder dikes to associated extruded flow units have been quantitatively measured to determine the magnitude of degassing exhibited in CRBG eruptions. Of

3638-448: The Ginkgo flow occurred in less than a week. The cooling/hydraulics analyses are supported by an independent indicator; if longer periods were required, external water from temporarily dammed rivers would intrude, resulting in both more dramatic cooling rates and increased volumes of pillow lava . Ho's analysis is consistent with the analysis by Reidel, Tolan, & Beeson (1994), who proposed

3745-538: The Grande Ronde Basalt comprises about 85 percent of the total flow volume. It is characterized by a number of dikes called the Chief Joseph Dike Swarm near Joseph , Enterprise , Troy and Walla Walla through which the lava upwelling occurred (estimates range to up to 20,000 such dikes). Many of the dikes were fissures 5 to 10 m (16 to 33 ft) wide and up to 10 miles (16 km) in length, allowing for huge quantities of magma upwelling. Much of

3852-566: The Grande Ronde basalts, but can be identified by different chemical characteristics. It flowed west to the Pacific, and can be found in the Columbia Gorge, along the upper Clackamas River, the hills south of Oregon City . and as far west as Yaquina Head near Newport, Oregon – a distance of 750 km (470 mi). The Saddle Mountains Basalt, seen prominently at the Saddle Mountains ,

3959-422: The Grande Ronde to the south and east. The area experiences cold, snowy winters between November and April with snowpack building as much as 5 feet (1.5 m) deep at higher elevations. Summers are very hot and dry, especially along the river bottoms. Annual precipitation ranges from 14 to 32 inches (360 to 810 mm) in the lower southeastern part of the basin, to 52 to 70 inches (1,300 to 1,800 mm) along

4066-657: The Grizzly Bear Complex fire burned almost 83,000 acres (34,000 ha), including a large area in the Wenaha watershed. Previous wildfire suppression had left the area overstocked and "extremely vulnerable to catastrophic wildfire." Following the fire, the Washington Department of Fish and Wildlife began forest thinning and remediation efforts in the Grouse Flats area. The Forest Service worked to stabilize damaged trails and facilitated salvage logging of timber from

4173-597: The Oregon High Lava Plains is a complementary system of propagating rhyolite eruptions, with the same point of origin. The two phenomena occurred concurrently, with the High Lava Plains propagating westward since ~10 Ma, while the Snake River Plains propagated eastward. Discharge (hydrology) In hydrology , discharge is the volumetric flow rate (volume per time, in units of m /h or ft /h) of

4280-537: The Oregon Plateau in sections up to 1 km (3,300 ft) thick. It contains the earliest identified eruption of the CRBG large igneous province. The type locality for the Steens basalt, which covers a large portion of the Oregon Plateau, is an approximately 1,000 m (3,300 ft) face of Steens Mountain showing multiple layers of basalt. The oldest of the flows considered part of the Columbia River Basalt Group,

4387-521: The Roza flow. Sulfuric acid , a by-product of emitted sulfur dioxide and atmospheric interactions, has been calculated to be 1.7Gt annually for the Roza flow and 17Gt in total. Analysis of glass inclusions within phenocrysts of the basaltic deposits have yielded emission volumes on the magnitude of 310 Mt of hydrochloric acid , and 1.78 Gt of hydrofluoric acid , additionally. Major hotspots have often been tracked back to flood-basalt events. In this case

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4494-602: The Steens Basalt flow are considered to be atypical of other dike swarm trends associated with the CRBG. These swarms, characterized by a maintained trend of N20°E, trace the northward continuation of the Nevada shear zone and have been attributed to magmatic rise through this zone on a regional scale. Virtually coeval with the oldest of the flows, the Imnaha basalt flows welled up across northeastern Oregon. There were 26 major flows over

4601-524: The Steens and Picture Gorge basalt formations. During the middle to late Miocene epoch , the Columbia River flood basalts engulfed about 163,700 km (63,200 sq mi) of the Pacific Northwest , forming a large igneous province with an estimated volume of 174,300 km (41,800 cu mi). Eruptions were most vigorous 17–14 million years ago, when over 99 percent of

4708-448: The Steens basalt, includes flows geographically separated but roughly concurrent with the Imnaha flows. Older Imnaha basalt north of Steens Mountain overlies the chemically distinct lowermost flows of Steens basalt; hence some flows of the Imnaha are stratigraphically younger than the lowermost Steens basalt. One geomagnetic field reversal occurred during the Steens Basalt eruptions at approximately 16.7 Ma, as dated using Ar/ Ar ages and

4815-783: The Teepee Butte Member released about 2,350 km (560 cu mi) with layers of basalt up to 100 m (330 ft) thick. The Wanapum Basalt is made up of the Eckler Mountain Member (15.6 million years ago), the Frenchman Springs Member (15.5 million years ago), the Roza Member (14.9 million years ago) and the Priest Rapids Member (14.5 million years ago). They originated from vents between Pendleton, Oregon and Hanford, Washington . The Frenchman Springs Member flowed along similar paths as

4922-469: The Wenaha Forest Reserve into law. J.M. Schmitz, the first forest supervisor, found that "the main reason for the overgrazing of the interior was that each spring long before the range was fit to graze there would be a race to get the sheep over the divide and located on the best camps." A meeting was held to divide the range between cattle and sheep grazing, during which the stockmen agreed to divide

5029-546: 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 4,000 feet (1,200 m) in parts of the Wenaha-Tucannon Wilderness. Above this

5136-486: 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: "At the junction of the Butte Creek and Wenaha River is Grizzly Bear Rock and the totem pole on Sentinel Rock. Numerous legends attach themselves to

5243-409: The Wenaha River was also known to pioneers as the "Little Salmon River", though this name eventually faded from use due to confusion with the nearby Salmon River . Access to this area was initially difficult and all supplies were moved by pack horses over steep mountain trails. The trail from Flora, Oregon , which crossed the Grande Ronde about a mile (1.6 km) below the Wenaha confluence, was widened in

5350-648: The Wenaha to the Grande Ronde, where they traded horses with the natives. No name was recorded for what they simply called a "small river". The flow of settlers into northeast Oregon increased with improvements to the Oregon Trail, although the rugged area around the Wenaha River would remain mostly ignored for decades to come. In 1855 the Nez Perce, under pressure from the influx of white settlers, surrendered 7.5 million acres (30,000 km) in exchange for monetary compensation and infrastructure development. The Wenaha River basin

5457-526: The Wenaha-Tucannon Wilderness. The Wenaha is one of only two northeast Oregon rivers, the other being the Imnaha River , where the Oregon Department of Fish and Wildlife allows fishing for bull trout (catch and release only). The river is also open for hatchery steelhead between September 1 and April 30. There is also good fishing for rainbow trout and mountain whitefish. Most fishing is concentrated near

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5564-424: The Wenaha. From 1979–1984, 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. The surface geology of

5671-615: The Wenaha–Grande Ronde confluence, and in 1903 it was moved a few miles up the Wenaha River. After a new station on the Wallowa River proved more productive, the Wenaha station was shut down. In 1912, the Forest Service built a cabin at Dry Gulch (about 3 miles (4.8 km) from the Wenaha's mouth) and a telephone line along the Wenaha River to connect with Troy. In 1920 the line was extended over Weller Butte to Oregon Butte, making

5778-580: The area into grazing allotments but no decision was made to reduce the number of animals. In 1907 the Wenaha Forest Reserve became the Wenaha National Forest , and in 1920 it was merged into the Umatilla National Forest, forming what are now the Pomeroy and Walla Walla Ranger Districts. The Oregon Department of Fish and Wildlife built an experimental fish egg collection station in 1901 near

5885-489: 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

5992-399: The area, stream modifications such as dams and irrigation diversions, as well as evaporation and evapotranspiration from the area's land and plant surfaces. In storm hydrology, an important consideration is the stream's discharge hydrograph, a record of how the discharge varies over time after a precipitation event. The stream rises to a peak flow after each precipitation event, then falls in

6099-583: The axis of the Grouse Flat syncline , a geologic fold that formed with the Blue Mountains uplift. 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

6206-587: The basalt was released. Less extensive eruptions continued 14–6 million years ago. Erosion resulting from the Missoula Floods has extensively exposed these lava flows, laying bare many layers of the basalt flows at Wallula Gap , the lower Palouse River , the Columbia River Gorge and throughout the Channeled Scablands . The Columbia River Basalt Group is thought to be a potential link to

6313-470: The burned area. The destroyed Crooked Creek bridge along the Wenaha River Trail was removed, but would not be rebuilt until the summer of 2023. With access limited to those on foot or horseback, the Wenaha River country remains lightly used and provides numerous backcountry recreation opportunities. The most popular recreational activity in the Wenaha basin has traditionally been elk hunting. In Oregon,

6420-485: The corresponding discharge from the rating curve. If a continuous level-recording device is located at a rated cross-section, the stream's discharge may be continuously determined. Larger flows (higher discharges) can transport more sediment and larger particles downstream than smaller flows due to their greater force. Larger flows can also erode stream banks and damage public infrastructure. G. H. Dury and M. J. Bradshaw are two geographers who devised models showing

6527-534: The crust produced a large, slightly depressed lava plain now known as the Columbia Basin or Columbia River Plateau . The northwesterly advancing lava forced the ancient Columbia River into its present course. The lava, as it flowed over the area, first filled the stream valleys, forming dams that in turn caused impoundments or lakes. In these ancient lake beds are found fossil leaf impressions, petrified wood , fossil insects, and bones of vertebrate animals. In

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6634-689: The date of solidifying basalt. In the CRBG deposits Ar, which is produced by K decay, only accumulates after the melt solidifies. Other flood basalts include the Deccan Traps (late Cretaceous period ), that cover an area of 500,000 km (190,000 sq mi) in west-central India ; the Emeishan Traps ( Permian ), which cover more than 250,000 square kilometers in southwestern China ; and Siberian Traps (late Permian ) that cover 2 million km (800,000 sq mi) in Russia . Some time during

6741-418: The discharge of a river is based on a simplified form of the continuity equation . The equation implies that for any incompressible fluid, such as liquid water, the discharge (Q) is equal to the product of the stream's cross-sectional area (A) and its mean velocity ( u ¯ {\displaystyle {\bar {u}}} ), and is written as: where For example, the average discharge of

6848-633: The discharge of a river we need a different method and the most common is the 'area-velocity' method. The area is the cross sectional area across a river and the average velocity across that section needs to be measured for a unit time, commonly a minute. Measurement of cross sectional area and average velocity, although simple in concept, are frequently non-trivial to determine. The units that are typically used to express discharge in streams or rivers include m /s (cubic meters per second), ft /s (cubic feet per second or cfs) and/or acre-feet per day. A commonly applied methodology for measuring, and estimating,

6955-410: The early 1900s to allow wagons, though crossing the river and pulling wagons up the steep slopes remained a challenge. In 1902 the first store was established in Troy, and in 1912 a flour mill was built on the Wenaha River, followed by a post office, hotel, school and other buildings. In the 1940s a road was completed along the Grande Ronde to Troy. The first cattle drive to Grouse Flats was attempted in

7062-488: The east of Deadman Peak in Columbia County, Washington , at an elevation of 5,885 feet (1,794 m), and flows south into Oregon. The 12.2-mile (19.6 km) long South Fork Wenaha River begins in the southwest corner of Wallowa County, at an elevation of 5,723 feet (1,744 m), and flows northeast to the confluence. From the forks, the Wenaha River flows east, cutting a deep canyon through rugged plateau country on

7169-464: 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 1,601 feet (488 m). The Grande Ronde

7276-434: The emission of sulphur for the Roza flow is calculated to be on the order of 12Gt (12,000 million tonnes) at a rate of 1.2Gt (1,200 million tonnes) annually, in the form of sulphur dioxide (SO2). However, other research through petrologic analysis has yielded SO2 mass degassing values at 0.12% - 0.28% of the total erupted mass of the magma, translating to lower emission estimates in the range of 9.2Gt of sulfur dioxide for

7383-510: The evil spirit slipped through the picket lines to cause endless distress. Friendly gods eventually conquered the evil spirit while in bear form and converted it into basalt rock. There the big, bad bear stands today, a perpetual symbol of what happens to evil spirits masquerading as bears." The first known Europeans to travel in this region were the expedition led by US Army officer Benjamin Bonneville in 1834. Leaving Idaho territory, they crossed

7490-520: The exposed 2,000-foot (610 m) walls of Joseph Canyon along Oregon Route 3 . The Grande Ronde basalt flows flooded down the ancestral Columbia River channel to the west of the Cascade Mountains . It can be found exposed along the Clackamas River and at Silver Falls State Park where the falls plunge over multiple layers of the Grande Ronde basalt. Evidence of eight flows can be found in

7597-443: The final bill. Of the total length of the river, 18.7 miles (30.1 km) from Wenaha Forks to the Umatilla National Forest boundary are designated as Wild, and 2.7 miles (4.3 km) in the Wenaha State Wildlife Area downstream of the forest boundary are designated as Scenic. A final 0.15 miles (0.24 km) between the Wenaha State Wildlife Area and the confluence with the Grande Ronde River are designated as Recreational. In 2015,

7704-401: The first telephone connection from Troy to Dayton and Pomeroy. In 1938 the lines along the Wenaha River were taken out, in favor of an alignment further north at higher elevation. Many of the present day hiking trails along the Wenaha River and its tributaries were also built during this time, along with nearby fire lookout towers , corrals, and other forest infrastructure. Although the Wenaha

7811-667: The flow terminus in the Pacific Ocean at Yaquina Head , Oregon . The basalt had an upper melting temperature of 1 095 ± 5 °C and a lower temperature to 1 085 ± 5 °C; this indicates that the maximum temperature drop along the Ginkgo flow was 20 °C. The lava must have spread quickly to achieve this uniformity. Analyses indicate that the flow must remain laminar , as turbulent flow would cool more quickly. This could be accomplished by sheet flow, which can travel at velocities of 1 to 8 metres per second (2.2 to 17.9 mph) without turbulence and minimal cooling, suggesting that

7918-410: The geomagnetic polarity timescale. Steens Mountain and related sections of Oregon Plateau flood basalts at Catlow Peak and Poker Jim Ridge 70 to 90 km (43 to 56 mi) to the southeast and west of Steens Mountain, provide the most detailed magnetic field reversal data (reversed-to-normal polarity transition) yet reported in volcanic rocks. The observed trend in feeder dike swarms associated with

8025-408: 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. The Wenaha River watershed comprises 296 square miles (770 km), of which 137 square miles (350 km) are in Oregon. After the Wallowa River , it

8132-417: The highest elevations to the west. 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 390 cu ft/s (11 m/s). Seasonal variations range from over 2,000 cu ft/s (57 m/s) during spring snowmelt to about 100 cu ft/s (2.8 m/s) in late summer and fall. The Wenaha River basin

8239-411: The journey. In September 1843, Whitman led an expedition from nearby Fort Nez Percés and crossed the Blue Mountains to the southeast. On September 13, after traveling over 20 miles (32 km) across a dry, rugged landscape, they reached the upper Wenaha, likely becoming the first Europeans to see the river. They camped near the river's confluence with Butte Creek and the following day they traveled down

8346-640: The lava flowed north into Washington as well as down the Columbia River channel to the Pacific Ocean ; the tremendous flows created the Columbia River Plateau . The weight of this flow (and the emptying of the underlying magma chamber) caused central Washington to sink, creating the broad Columbia Basin in Washington. The type locality for the formation is the canyon of the Grande Ronde River . Grande Ronde basalt flows and dikes can also be seen in

8453-424: The level of the stream is described by a rating curve . Average velocities and the cross-sectional area of the stream are measured for a given stream level. The velocity and the area give the discharge for that level. After measurements are made for several different levels, a rating table or rating curve may be developed. Once rated, the discharge in the stream may be determined by measuring the level, and determining

8560-552: 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. The main stem of the Wenaha River begins at an elevation of 2,809 feet (856 m) in western Wallowa County, at the confluence of its north and south forks at Wenaha Forks. The 13.8-mile (22.2 km) long North Fork Wenaha River originates near Ski Bluewood to

8667-499: The magnetic field's orientation-normal, reversed, or in one of several intermediate positions. Most of the flows froze with a single magnetic orientation. However, several of the flows, which freeze from both the upper and lower surfaces, progressively toward the center, captured substantial variations in magnetic field direction as they froze. The observed change in direction was reported as 50⁰ over 15 days. The Steens Basalt flows covered about 50,000 km (19,000 sq mi) of

8774-667: The mid-Miocene. The flows can be divided into four major categories: The Steens Basalt, Grande Ronde Basalt, the Wanapum Basalt, and the Saddle Mountains Basalt. The various lava flows have been dated by radiometric dating—particularly through measurement of the ratios of isotopes of potassium to argon . The Columbia River flood basalt province comprises more than 300 individual basalt lava flows that have an average volume of 500 to 600 cubic kilometres (120 to 140 cu mi). The transition to flood volcanism in

8881-574: The middle Miocene, 17 to 15 Ma, the Columbia Plateau and the Oregon Basin and Range of the Pacific Northwest were flooded with lava flows. Both flows are similar in composition and age, and have been attributed to a common source, the Yellowstone hotspot . The ultimate cause of the volcanism is still up for debate, but the most widely accepted idea is that the mantle plume or upwelling (similar to that associated with present-day Hawaii) initiated

8988-439: The more than 300 individual flows associated with the CRBG, the Roza flow contains some of the most chemically well preserved basalts for volatile analysis. Contained within the Wanapum formation, Roza is one of the most extensive members of the CRBG with an area of 40,300 square kilometres and a volume of 1,300 cubic kilometres. With magmatic volatile values assumed at 1 - 1.5 percent by weight concentration for source feeder dikes,

9095-522: 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

9202-455: The mouth of the river; more secluded reaches upstream require a considerable hike to access. Columbia River Basalt Group The Columbia River Basalt Group (CRBG) is the youngest, smallest and one of the best-preserved continental flood basalt provinces on Earth, covering over 210,000 km (81,000 sq mi) mainly eastern Oregon and Washington , western Idaho , and part of northern Nevada . The basalt group includes

9309-553: 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 removel 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

9416-475: The people have in this region, and clearing the ground is their most difficult problem and requires many years under the process which they are employing. It is most unfortunate that this timber must be so ruthlessly destroyed, particularly as it is the best body of timber within the Wenaha Forest, which, if taken in connection with surrounding timber, might at some future time offer an attractive logging unit when

9523-502: The period, one roughly every 15,000 years. Although estimates are that this amounts to about 10% of the total flows, they have been buried under more recent flows, and are visible in few locations. They can be seen along the lower benches of the Imnaha River and Snake River in Wallowa county. The Imnaha lavas have been dated using the K–Ar technique, and show a broad range of dates. The oldest

9630-455: The plume at 650 and 400 km (400 and 250 mi), which may correspond to phase changes or may reflect still-to-be-understood viscosity effects. Additional data collection and further modeling will be required to achieve a consensus on the actual mechanism. The Columbia River Basalt Group flows exhibit essentially uniform chemical properties through the bulk of individual flows, suggesting rapid placement. Ho and Cashman (1997) characterized

9737-409: The region is made more easily accessible than it is at the present time. In the 1960s the U.S. Army Corps of Engineers studied the lower Snake River basin and proposed numerous hydroelectric dams. One such study in 1963 proposed building the "Wenaha Dam" on the Grande Ronde River. It would have flooded an area including the town of Troy and about 5 miles (8.0 km) of the lower Wenaha River. The dam

9844-568: The relationship between discharge and other variables in a river. The Bradshaw model described how pebble size and other variables change from source to mouth; while Dury considered the relationships between discharge and variables such as stream slope and friction. These follow from the ideas presented by Leopold, Wolman and Miller in Fluvial Processes in Geomorphology . and on land use affecting river discharge and bedload supply. Inflow

9951-462: The reservation boundaries by 90 percent. All the lands in Washington and Oregon, including the Wenaha basin, were removed from the reservation boundaries. Many Nez Perce leaders refused to sign the 1863 agreement, leading to the 1877 Nez Perce War . Several bands of Nez Perce, most famously Chief Joseph's party, were driven out of their homeland in a series of battles. They were only allowed to return to their much diminished reservation in 1885. In

10058-435: 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. There are no dams or channel modifications on the Wenaha River and its tributaries; although there are

10165-617: The river is managed by the Oregon Department of Fish and Wildlife as the Wenaha Unit, with open season in the fall. Other big game species include deer, bear and cougars. The Wenaha Wildlife Area near Troy is open to upland bird hunting for grouse, chukar, wild turkey and waterfowl. The Wenaha River Trail follows the main stem and south fork for 31 miles (50 km), starting at Troy and heading west to Timothy Springs trailhead, more than 3,000 feet (910 m) higher in elevation. The trail

10272-528: 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

10379-412: 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

10486-402: The rock which possess an amazing likeness to a huge bear. Legend says Indians annually set up a village at that point while providing winter food. An evil spirit also lived there and would assume the form of a grizzly bear and then cause death and misery to the tribe. To frustrate such action, chiefs posted a sentinel to stand guard against the evil spirit, but one such sentinel slept one night and

10593-560: The rugged country west of Hells Canyon and followed Joseph Canyon down to the Grande Ronde River, and on towards the Snake. They did not explore further up the Grande Ronde, and never saw the Wenaha. In 1836 Marcus Whitman and his family came west along the Oregon Trail and established a mission near what is now Walla Walla, Washington . This was the first passage of the trail made by a white family and proved that women and children could make

10700-407: 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,

10807-433: The spring of 1887 and met numerous challenges, including deep snow and thunderstorms, on the way from Pomeroy, Washington . Following this, cattle were run in increasing numbers here and in other surrounding high country of the Blue Mountains. Thousands of sheep were also brought into the area, and by the early 1900s overgrazing had a devastating effect on the mountain meadows. In May 1905, President Theodore Roosevelt signed

10914-453: The upwelling observed with large-scale plate-tectonics circulation. The hot spot hypothesis is not universally accepted as it has not resolved several questions. The Yellowstone hot spot volcanism track shows a large apparent bow in the hot-spot track that does not correspond to changes in plate motion if the northern CRBG floods are considered. Further, the Yellowstone images show necking of

11021-420: The volume of water (depending on the area of the catchment) that subsequently flows out of the river. Using the unit hydrograph method, actual historical rainfalls can be modeled mathematically to confirm characteristics of historical floods, and hypothetical "design storms" can be created for comparison to observed stream responses. The relationship between the discharge in the stream at a given cross-section and

11128-619: The widespread and voluminous basaltic volcanism about 17 million years ago. As hot mantle plume materials rise and reach lower pressures, the hot materials melt and interact with the materials in the upper mantle , creating magma . Once that magma breaches the surface, it flows as lava and then solidifies into basalt. Prior to 17.5 million years ago, the Western Cascade stratovolcanoes erupted with periodic regularity for over 20 million years, even as they do today. An abrupt transition to shield volcanic flooding took place in

11235-529: Was first recommended to be added to the National Wild and Scenic Rivers system in 1970, but it would not be until 1988 when the Oregon Omnibus Wild and Scenic Rivers Act designated the Wenaha River a Wild and Scenic River. along with the nearby Grande Ronde and North Fork John Day Rivers . The North and South Forks of the Wenaha were also considered for Wild and Scenic designation, but were not included in

11342-422: Was included within the original 1855 reservation, with the western boundary of the reservation at the divide between the Wenaha and Walla Walla river basins. "The Wenaha River or Little Salmon was one of Old Chief Joseph ’s favorite hunting and fishing grounds... it is not likely that he would have consented to give them up". The US government failed to honor the terms of the 1855 treaty, and in 1863 forcibly reduced

11449-468: Was never built due to opposition from the U.S. Fish and Wildlife Service and state fish and game agencies for "irreparable damages to fisheries resources". Around 1965, the Forest Service canceled all sheep grazing allotments in what would eventually become the Wenaha-Tucannon Wilderness. In the mid-1970s, the Forest Service proposed salvage logging 30,000 acres (12,000 ha) above the South Fork after

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