Geology topics

Research about Douglas County, Oregon

Source-linked reports with geographic coverage including Douglas County, Oregon.

7 recordsLinked to original sources

USGS2016

Effects of stream-adjacent logging in fishless headwaters on downstream coastal cutthroat trout

To investigate effects of headwater logging on downstream coastal cutthroat trout ( Oncorhynchus clarkii clarkii ) populations, we monitored stream habitat and biotic indicators including biomass, abundance, growth, movement, and survival over 8 years using a paired-watershed approach. Reference and logged catchments were located on private industrial forestland on ∼60-year harvest rotation. Five clearcuts (14% of the logged catchment area) were adjacent to fishless portions of the headwater streams, and contemporary regulations did not require riparian forest buffers in the treatment catchment. Logging did not have significant negative effects on downstream coastal cutthroat trout populations for the duration of the sample period. Indeed, the only statistically significant response of fish populations following logging in fishless headwaters was an increase in late-summer biomass (g·m −2 ) of age-1+ coastal cutthroat trout in tributaries. Ultimately, the ability to make broad generalizations concerning effects of timber harvest is difficult because response to disturbance (anthropogenically influenced or not) in aquatic systems is complex and context-dependent, but our findings provide one example of environmentally compatible commercial logging in a regenerated forest setting.

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USGS2014

Breeding site selection by coho salmon (Oncorhynchus kisutch) in relation to large wood additions and factors that influence reproductive success

The fitness of female Pacific salmon ( Oncorhynchus spp.) with respect to breeding behavior can be partitioned into at least four fitness components: survival to reproduction, competition for breeding sites, success of egg incubation, and suitability of the local environment near breeding sites for early rearing of juveniles. We evaluated the relative influences of habitat features linked to these fitness components with respect to selection of breeding sites by coho salmon ( Oncorhynchus kisutch ). We also evaluated associations between breeding site selection and additions of large wood, as the latter were introduced into the study system as a means of restoring habitat conditions to benefit coho salmon. We used a model selection approach to organize specific habitat features into groupings reflecting fitness components and influences of large wood. Results of this work suggest that female coho salmon likely select breeding sites based on a wide range of habitat features linked to all four hypothesized fitness components. More specifically, model parameter estimates indicated that breeding site selection was most strongly influenced by proximity to pool-tail crests and deeper water (mean and maximum depths). Linkages between large wood and breeding site selection were less clear. Overall, our findings suggest that breeding site selection by coho salmon is influenced by a suite of fitness components in addition to the egg incubation environment, which has been the emphasis of much work in the past.

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USGS2000

Ecology and conservation of a rare, old-growth-associated canopy lichen in a silvicultural landscape

Nephroma occultum Wetm. is a rare, epiphytic lichen associated with old-growth forests of northwestern North America. We describe its distribution, abundance, and habitat within the managed landscape of a southwestern Oregon watershed. Because this species is found mainly in the canopy, we used direct canopy access (tree climbing) in combination with ground (litter) searches for our surveys. We recommend this dual approach when confident determination of presence or absence of a canopy species is needed. Our surveys confirm that N. occultum is a rare old-growth associate within the area of this study, the southernmost extension of its known range. It was both rare across the landscape and uncommon in our primary study site, a 500 yr old stand. It was most often found growing close to the trunk on branches of large Pseudotsuga menziesii , but its distribution was sporadic even within an old-growth stand. The scarcity of very old stands, in combination with the limited ability of this species to disperse within and between stands, has likely contributed to its rarity within the watershed. Management for N. occultum should focus on populations and habitat needs rather than on individuals. Our calculations show that cutting with retention of individual trees surrounded by small buffers could result in the eventual loss of N. occultum from the study area.

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USGS1984

Water-resources of western Douglas County, Oregon

In western Douglas County, Quaternary coastal dune sands and marine terrace deposits may have the best potential for ground-water development. Yields of 200 gallons per minute have been reported from wells completed in Quaternary fluvial deposits along the lower Umpqua River. The entire area is underlain by Tertiary marine sediments that yield quantities of water barely adequate for domestic use. On the basis of wells sampled and the constituents analyzed, ground-water quality was generally good, but the recommended criteria level of 300 micrograms per liter for iron was exceeded in about one-third of the samples. Average annual runoff from eight streams in western Douglas County was estimated to range from 2.4 cubic feet per second per square mile for Elk Creek to 6.8 cubic feet per second per square mile for Scholfield Creek. The estimated 7-day , 20-year low flow ranges from 0.01 cubic foot per second per square mile for Weatherly Creek to 3.6 cubic feet per second per square mile for the Smith River. The dissolved-solids of the Umpqua River is small and stable, with little seasonal and yearly variation. Likewise, the eight small streams in the project area have small dissolved-solids but have noticeably higher nitrite plus nitrate nitrogen concentrations than those of the Umpqua River. All the lakes in the project area have dissolved-solids concentrations of less than 100 milligrams per liter and, except for Loon Lake, have limited phosphorus available for algal production. Tahkenitch and Elbow Lakes are considered to be the most active in terms of biological productivity.

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USGS1979

Lakes of Oregon, Volume 6: Douglas County

An inventory of lakes and reservoirs in Oregon is useful in evaluating the surface-water supply of the State and in providing answers to questions about Oregon's lakes. Much of the information on lakes and reservoirs previously collected by Federal and State agencies has never been published. Those data were compiled and used as a basis for collecting additional information. This report provides information for use by city, county, and State planning groups in planning interpretative studies. The information also will be useful to sportsmen, tourists, and others interested in preserving the recreational value of Oregon's lakes. Because of the large number of lakes and reservoirs in Oregon, a single report covering the State would be bulky. Therefore, lake information is being issued in several volumes on a county or multicounty basis. Volume 1, released in 1973 covered Clatsop, Columbia, and Tillamook Counties; volume 2 (1974) included Benton, Lincoln, and Polk Counties; volume 3 (1975) included Hood River, Multnomah, Washington, and Yamhill Counties; volume 4 (1976) included Clackamas County; and volume 5 (1977) included Marion County. Douglas County was selected for volume 6. (See figure 1.) In addition to office compilation of existing data, each lake was visited. Most visits were made in summer or early fall when lakes were most accessible and when water temperature and biological activity were near maximum.

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USGS1977

Availability and quality of ground water in the Winston area, Douglas County, Oregon

A map of the Winston area, Douglas County, Oreg., shows areal geology and locations and chemical diagrams of wells with water analyses. Another map of the area has diagrams showing the depth to water, pumping level, total depth, and yields of selected wells. Reported yields of wells range from less than 1 to as much as 70 gallons per minute; the average is less than 10. A table listing chemical analyses of water shows that, although most ground water is of adequate quality for domestic use, some wells yield water with dissolved constituents in excess of recommended limits. (Woodard-USGS)

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USGS1975

Availability and quality of ground water in the Sutherlin area, Douglas County, Oregon

The purpose of this map report is to present information in a form that will enable water users, potential water users, and planners to estimate the likelihood of obtaining ground water in adequate quantity and of suitable quality at desired locations. The Sutherlin area is in Douglas County in southwestern Oregon and includes about 280 square miles (720 km 2 ) entirely within the Umpqua River drainage basin.

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