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At least 721 records · Page 40Linked to original sources
USGS2012

Discharge rates of fluid and heat by thermal springs of the Cascade Range, Washington, Oregon, and northern California

Fluid and heat discharge rates of thermal springs of the Cascade Range have been determined using the chloride inventory method. Discharge rates of thermal spring groups range from 1 to 120 L s −1 . Most of the fluid (50%) and heat (61%) are discharged from two hot spring groups in northern Oregon. Total discharge from thermal springs in the Cascade Range of California, Oregon, and Washington is about 340 Ls −1 , which corresponds to about 8.2×10 4 kJ s −1 of heat. This does not include hot springs developed on the flanks of Mount St. Helens after the 1980 eruption. The Cascade Range consists of geologically and technically distinct segments; rates of convective heat discharge by the thermal springs in these segments correlate with volcanic rock extrusion rates for the last 2 m. y. In Oregon and Washington, many streams without known thermal or mineral springs in their drainage basins also were sampled for chloride and sodium to detect chemical anomalies that might be associated with previously unknown thermal or mineral waters. Only three chloride anomalies not associated with known thermal or mineral springs were identified in the streams of the Cascade Range.

Journal of Geophysical Research↗
USGS2010

Distribution and condition of larval and juvenile Lost River and shortnose suckers in the Williamson River Delta restoration project and Upper Klamath Lake, Oregon

Federally endangered Lost River sucker ( Deltistes luxatus ) and shortnose sucker ( Chasmistes brevirostris ) were once abundant throughout their range but populations have declined. They were extirpated from several lakes in the 1920s and may no longer reproduce in others. Poor recruitment to the adult spawning populations is one of several reasons cited for the decline and lack of recovery of these species and may be the consequence of high mortality during juvenile life stages. High larval and juvenile sucker mortality may be exacerbated by an insufficient quantity of suitable or high quality rearing habitat. In addition, larval suckers may be swept downstream from suitable rearing areas in Upper Klamath Lake into Keno Reservoir, which is seasonally anoxic. The Nature Conservancy flooded about 3,600 acres (1,456 hectares) to the north of the Williamson River mouth (Tulana Unit) in October 2007 and about 1,400 acres (567 hectares) to the south and east of the Williamson River mouth (Goose Bay Unit) a year later to retain larval suckers in Upper Klamath Lake, create nursery habitat, and improve water quality. The U.S. Geological Survey joined a long-term research and monitoring program in collaboration with The Nature Conservancy, the Bureau of Reclamation, and Oregon State University in 2008 to assess the effects of the Williamson River Delta restoration on the early life-history stages of Lost River and shortnose suckers. The primary objectives of the research were to describe habitat colonization and use by larval and juvenile suckers and non-sucker fishes and to evaluate the effects of the restored habitat on the health and condition of juvenile suckers. This report summarizes data collected in 2009 by the U.S. Geological Survey as a part of this monitoring effort. The Williamson River Delta appeared to provide suitable rearing habitat for endangered larval Lost River and shortnose suckers in 2008 and 2009. Larval suckers captured in this delta typically were larger than those captured in the adjacent lake habitat in 2008, but the opposite was true for larval shortnose suckers in 2009. Mean sample density was greater for both species in the Williamson River Delta than adjacent lake habitats in both years. Larval suckers captured in the restoration area, however, had less food in their guts compared to those captured in Upper Klamath or Agency Lakes. Differential distribution among sucker species within the Williamson River Delta and between the delta and adjacent lakes indicated that shortnose suckers likely benefited more from the restored Williamson River Delta than Lost River or Klamath largescale suckers ( Catostomus snyderi ). Catch rates in shallow-water habitats with vegetation within the delta were higher for shortnose and Klamath largescale suckers than for larval Lost River suckers in 2008 and 2009.However, catch rates at the mouth of the Williamson River in 2008 and in Upper Klamath Lake in 2009 were higher for larval Lost River suckers than for larvae identified as either shortnose or Klamath largescale suckers. Shortnose suckers also comprised the greatest portion of age-0 suckers captured in the Williamson River Delta in 2008 and 2009. The relative abundance of age-1 shortnose suckers was high in our catches compared to age-1 Lost River suckers in 2009 in the delta and adjacent lakes, which may or may not indicate shortnose suckers experienced better survival than Lost River suckers in 2008. Age-0 and age-1 suckers were similarly distributed throughout the Williamson River Delta in 2008 and 2009. Age-0 suckers used shallow vegetated and unvegetated habitats primarily in mid- to late July in both years. A comparison of catch rates between our study and a concurrent study in Upper Klamath Lake indicated that Goose Bay was the most used habitat in 2009 and the Tulana Unit was the one of the least used habitats in 2008 and 2009 by age-0 suckers. Catch rates for age-1 suckers, however, indicated that bo

Oregon↗
USGS1997

Summary of information on aquatic biota and their habitats in the Willamette Basin, Oregon, through 1995

Available information on aquatic biota of the Willamette Basin was reviewed and summarized to describe current and historical conditions as part of the U.S. Geological Survey's National Water-Quality Assessment Program. Biological parameters emphasized include the status, distribution, and trends of aquatic biota, particularly algae, macroinvertebrates, and fish; the condition of aquatic and riparian habitat in which these biota reside; and the response of these biota to natural and human-associated impacts, including the level, type, and effect of contaminants. Considerable data are available on aquatic biota in the Willamette Basin, although the information is highly uneven relative to taxa and spatial scope. Extensive information exists for high-profile taxa, such as salmonid fishes, but less information is available for macroinvertebrates, and relatively little data exist for algae. Additionally, some areas such as the H.J. Andrews Experimental Forest and the main stem Willamette River have been extensively studied, whereas data are limited for many other areas. The basin supports a diverse aquatic macroinvertebrate fauna. Available data indicate a relatively high diversity of taxa and a high richness of Ephemeroptera, Plecoptera, Trichoptera (EPT) taxa in the upper reaches of the basin. In the lower main stem reaches, macroinvertebrate assemblages are dominated by pollution tolerant organisms and those adapted to low dissolved oxygen levels. Most of the limited data on algae are from sampling in the main stem Willamette River. Diatoms and blue-green algae are the dominant algal forms. Approximately 61 fish species occur in the basin, although nearly half are introduced. Species richness and distribution are highly correlated with elevation, stream gradient, and water temperature. High elevation, cold water, mountain streams are characterized by a few species of salmonids, sculpins, suckers, and whitefish. Low elevation, main stem reaches of major rivers and streams are dominated by warm water species, such as bass, catfish, and several species in the pan fish group. The only species of fish listed as threatened or endangered is the Oregon chub (Oregonichthys crameri). The effect of an expanding human presence in the Willamette Basin has substantially altered aquatic and riparian habitats, and the biota that use or reside in these habitats. Construction of dams, channelization and bank stabilization of rivers, species introductions, supplementations of fisheries through aquaculture, timber harvesting, agricultural activities, and urbanization have contributed to changes in aquatic habitats and biota from historical conditions. Aquatic toxicological investigations in the basin have focused primarily on fish. These studies have addressed chlorinated pesticides, polychlorinated biphenyls (PCBs), dioxins and furans, polycyclic aromatic hydrocarbons (PAHs), and trace elements in aquatic tissue, as well as fish health assessments, skeletal abnormalities, and aquatic toxicological responses. Several pesticides exceeded U.S. Environmental Protection Agency and State water-quality criteria for the protection of aquatic life. Elevated PCB, dioxin, and furan concentrations were associated with point sources, such as pulp and paper mills. Elevated concentrations of mercury in aquatic tissue were associated with several reservoirs. Fish health assessments and skeletal abnormality studies detected high levels of abnormalities in fish from the main stem Willamette River. Few investigations have examined aquatic toxicological responses, such as enzyme induction assays, growth assays, and biomarker studies.

Oregon↗
USGS2012

Distribution and condition of larval and juvenile Lost River and shortnose suckers in the Williamson River Delta restoration project and Upper Klamath Lake, Oregon

Federally endangered Lost River sucker (Deltistes luxatus) and shortnose sucker (Chasmistes brevirostris) were once abundant throughout their range but populations have declined. They were extirpated from several lakes in the 1920s and may no longer reproduce in other lakes. Poor recruitment to the adult spawning populations is one of several reasons cited for the decline and lack of recovery of these species and may be the consequence of high mortality during juvenile life stages. High larval and juvenile sucker mortality may be exacerbated by an insufficient quantity of suitable or high-quality rearing habitat. In addition, larval suckers may be swept downstream from suitable rearing areas in Upper Klamath Lake into Keno Reservoir, where they are assumed lost to Upper Klamath Lake populations. The Nature Conservancy flooded about 3,600 acres (1,456 hectares) to the north of the Williamson River mouth (Tulana) in October 2007, and about 1,400 acres (567 hectares) to the south and east of the Williamson River mouth (Goose Bay Farms) in October 2008, in order to retain larval suckers in Upper Klamath Lake, create nursery habitat, and improve water quality. The U.S. Geological Survey joined a long-term research and monitoring program in collaboration with The Nature Conservancy, the Bureau of Reclamation, and Oregon State University in 2008 to assess the effects of the Williamson River Delta restoration on the early life-history stages of Lost River and shortnose suckers. The primary objectives of the research were to describe habitat colonization and use by larval and juvenile suckers and non-sucker fishes and to evaluate the effects of the restored habitat on the health and condition of juvenile suckers. This report summarizes data collected in 2010 by the U.S. Geological Survey as a part of this monitoring effort and follows two annual reports on data collected in 2008 and 2009. Restoration modifications made to the Williamson River Delta appeared to provide additional suitable rearing habitat for endangered Lost River and shortnose suckers from 2008 to 2010 based on sucker catches. Mean larval sample density was greater for both species in the Williamson River Delta than adjacent lake habitats in all 3 years. In addition to larval suckers, at least three age classes of juvenile suckers were captured in the delta. The shallow Goose Bay Farms and Tulana Emergent were among the most used habitats by age-0 suckers in 2009. Both of these environments became inaccessible due to low water in 2010, however, and were not sampled after July 19, 2010. In contrast, age-1 sucker catches shifted from the shallow water (about 0.5-1.5 m deep) on the eastern side of the Williamson River Delta in May, to deeper water environments (greater than 2 m) by the end of June or early July in all 3 years. Differential distribution among sucker species within the Williamson River Delta and between the delta and adjacent lakes indicated that shortnose suckers likely benefited more from the restored Williamson River Delta than Lost River or Klamath largescale suckers (Catostomus snyderi) . Catch rates in shallow-water habitats within the delta were higher for shortnose and Klamath largescale sucker larvae than for larval Lost River suckers in 2008, 2009, and 2010. Shortnose suckers also comprised the greatest portion of age-0 suckers captured in the Williamson River Delta in all 3 years of the study. The relative abundance of age-1 shortnose suckers was high in our catches compared to age-1 Lost River suckers in 2009 and 2010. The restored delta also created habitat for several piscivorous fishes, but only two appeared to pose a meaningful threat of predation to suckers - fathead minnows (Pimephales promelas) and yellow perch (Perca flavescens) . Fathead minnows that prey on larval but not juvenile suckers dominated catches in all sampling areas. Yellow perch also were abundant throughout the study area, but based on their gape size and co-occurrence with suckers, most were only capable of preying on larvae. Low May lake-surface elevation, below average snow pack, and anticipated irrigation demands indicated late summer water levels in Upper Klamath Lake would be unusually low in 2010. In response to concerns by the Fish and Wildlife Service and The Nature Conservancy that low-water conditions might strand fish on the delta, low water seine surveys were implemented. Eleven fishes, including both endangered suckers, were captured in seine surveys, including both species of suckers, which continued to use shallow water less than 0.4 m deep through September 21. Lake elevation declined to 1,261.54 m (4,138.9 feet) in mid-September 2010, but did not appear to strand fish or cause large-scale fish mortality.

Oregon↗
USGS2000

Water quality modeling in the systems impact assessment model for the Klamath River basin - Keno, Oregon to Seiad Valley, California

This report describes the water quality model developed for the Klamath River System Impact Assessment Model (SIAM). The Klamath River SIAM is a decision support system developed by the authors and other US Geological Survey (USGS), Midcontinent Ecological Science Center staff to study the effects of basin-wide water management decisions on anadromous fish in the Klamath River. The Army Corps of Engineersa?? HEC5Q water quality modeling software was used to simulate water temperature, dissolved oxygen and conductivity in 100 miles of the Klamath River Basin in Oregon and California. The water quality model simulated three reservoirs and the mainstem Klamath River influenced by the Shasta and Scott River tributaries. Model development, calibration and two validation exercises are described as well as the integration of the water quality model into the SIAM decision support system software. Within SIAM, data are exchanged between the water quantity model (MODSIM), the water quality model (HEC5Q), the salmon population model (SALMOD) and methods for evaluating ecosystem health. The overall predictive ability of the water quality model is described in the context of calibration and validation error statistics. Applications of SIAM and the water quality model are described.

California, Oregon↗
USGS1978

Mineral resources of the Charles Sheldon wilderness study area, Humboldt and Washoe Counties, Nevada, and Lake and Harney Counties, Oregon

A mineral survey of the Charles Sheldon wilderness study area, located in Humboldt and Washoe Counties, Nevada, and Lake and Harney Counties, Oregon was conducted in 1974 and 1975 (fig. 1A, 1B, 1C). The mineral resource potential was evaluated by geological, geochemical, and geophysical studies by the U.S. Geological Survey, and by the examination of mines, prospects, and other mineralized localities by the U.S. Bureau of Mines. The investigation identified several areas of significant mineral potential within the study area which includes the Charles Sheldon Antelope Range and the Sheldon National Antelope Refuge (fig. 1B). The Virgin Valley area contains reserves of precious opal, small quantities of decorative building stone, and low-grade uranium resources. The investigation indicates that there are several areas of potential for the discovery at depth of mercury and for base and complex precious metal sulfide deposits within the study area. Reservoir temperatures, estimated from the analysis of thermal springs, suggest that the area has low-to-moderate potential for geothermal resources. The potential for oil, gas, or coal is very low.

Nevada, Oregon↗
USGS2007

Escherichia coli and Suspended Sediment in Berger Ditch at Maumee Bay State Park, Oregon, Ohio, 2006

Berger Ditch discharges to the marina at Maumee Bay State Park (MBSP), just east of the MBSP bathing beach. Recent studies by U.S. Geological Survey (USGS) and University of Toledo researchers have identified the ditch as a source of Escherichia coli (E. coli), an indicator bacterium that is used to assess recreational water quality. An automatic sampler was installed at a USGS streamgage on Berger Ditch. Samples were collected as a function of streamflow, including negative flow conditions. Instantaneous discharges of E. coli and suspended sediment from Berger Ditch were calculated. When samples were collected, streamflow ranged from -21 to 227 cubic feet per second (ft3/s) and over the entire time period, streamflow ranged from -23 to 243 ft3/s. Discharges of E. coli ranged from 2.5 ? 108 to greater than 2.6 ? 1010 colony-forming units per second (cfu/s), and suspended-sediment discharges ranged from 0.01 to 2.2 kilograms per second (kg/s). One sample was collected during negative flow conditions, and discharges of E. coli and suspended sediment in this sample were -4.3 ? 108 cfu/s and -0.015 kg/s, respectively.

Open-File Report↗
USGS2012

Evaluation of long-term water-level declines in basalt aquifers near Mosier, Oregon

The Mosier area lies along the Columbia River in northwestern Wasco County between the cities of Hood River and The Dalles, Oregon. Major water uses in the area are irrigation, municipal supply for the city of Mosier, and domestic supply for rural residents. The primary source of water is groundwater from the Columbia River Basalt Group (CRBG) aquifers that underlie the area. Concerns regarding this supply of water arose in the mid-1970s, when groundwater levels in the orchard tract area began to steadily decline. In the 1980s, the Oregon Water Resources Department (OWRD) conducted a study of the aquifer system, which resulted in delineation of an administrative area where parts of the Pomona and Priest Rapids aquifers were withdrawn from further appropriations for any use other than domestic supply. Despite this action, water levels continued to drop at approximately the same, nearly constant annual rate of about 4 feet per year, resulting in a current total decline of between 150 and 200 feet in many wells with continued downward trends. In 2005, the Mosier Watershed Council and the Wasco Soil and Water Conservation District began a cooperative investigation of the groundwater system with the U.S. Geological Survey. The objectives of the study were to advance the scientific understanding of the hydrology of the basin, to assess the sustainability of the water supply, to evaluate the causes of persistent groundwater-level declines, and to evaluate potential management strategies. An additional U.S. Geological Survey objective was to advance the understanding of CRBG aquifers, which are the primary source of water across a large part of Oregon, Washington, and Idaho. In many areas, significant groundwater level declines have resulted as these aquifers were heavily developed for agricultural, municipal, and domestic water supplies. Three major factors were identified as possible contributors to the water-level declines in the study area: (1) pumping at rates that are not sustainable, (2) well construction practices that have resulted in leakage from aquifers into springs and streams, and (3) reduction in aquifer recharge resulting from long-term climate variations. Historical well construction practices, specifically open, unlined, uncased boreholes that result in cross-connecting (or commingling) multiple aquifers, allow water to flow between these aquifers. Water flowing along the path of least resistance, through commingled boreholes, allows the drainage of aquifers that previously stored water more efficiently. The study area is in the eastern foothills of the Cascade Range in north central Oregon in a transitional zone between the High Cascades to the west and the Columbia Plateau to the east. The 78-square mile (mi 2 ) area is defined by the drainages of three streams - Mosier Creek (51.8 mi 2 ), Rock Creek (13.9 mi 2 ), and Rowena Creek (6.9 mi 2 ) - plus a small area that drains directly to the Columbia River.The three major components of the study are: (1) a 2-year intensive data collection period to augment previous streamflow and groundwater-level measurements, (2) precipitation-runoff modeling of the watersheds to determine the amount of recharge to the aquifer system, and (3) groundwater-flow modeling and analysis to evaluate the cause of groundwater-level declines and to evaluate possible water resource management strategies. Data collection included the following: 1. Water-level measurements were made in 37 wells. Bi-monthly or quarterly measurements were made in 30 wells, and continuous water-level monitoring instruments were installed in 7 wells. The measurements principally were made to capture the seasonal patterns in the groundwater system, and to augment the available long-term record. 2. Groundwater pumping was measured, reported, or estimated from irrigation, municipal and domestic wells. Flowmeters were installed on 74 percent of all high-capacity irrigation wells in the study area. 3. Borehole geophysical data were collected from a known commingling well. These data measured geologic properties and vertical flow through the well. 4. Streamflow measurements were made in Rock, Rowena, and Mosier Creeks. A long-term recording stream-gaging station was reestablished on Mosier Creek to provide a continuous record of streamflow. Streamflow measurements also were made along the creeks periodically to evaluate seasonal patterns of exchange between streams and the groundwater system. Major findings from the study include: 1. Annual average precipitation ranges from 20 to 54 inches across the study area with an average value of about 30 inches. Based on rainfall-runoff modeling, about one-third of this water infiltrates into the aquifer system. 2. Currently, about 3 percent of the water infiltrated into the groundwater system is extracted for municipal, agricultural, and rural residential use. The remainder of the water flows through the aquifer system, discharging into local streams and the Columbia River. About 80 percent of recent pumping supports crop production. The city of Mosier public supply wells account for about 10 percent of total pumping, with the remaining 10 percent being pumped from the private wells of rural residents. 3. Groundwater-flow simulation results indicate that leakage through commingling wells is a significant and likely the dominant cause of water level declines. Leakage patterns can be complex, but most of the leaked water likely flows out the CRBG aquifer system through very permeable sediments into Mosier Creek and its tributary streams in the OWRD administrative area. Model-derived estimates attribute 80-90 percent of the declines to commingling, with pumping accounting for the remaining 10-20 percent. Although decadal trends in precipitation have occurred, associated changes in aquifer recharge are likely not a significant contributor to the current water level declines. 4. As many as 150 wells might be commingling. To evaluate whether or not the local combination of geology and well construction have resulted in aquifer commingling at a particular well, the well needs to be tested by measuring intraborehole flow. During geophysical testing of one known commingling well, the flow rate through the well between aquifers ranged between 70 and 135 gallons per minute (11-22 percent of total annual pumping in the study area). Historically, when aquifer water levels were 150-200 feet higher, this flow rate would have been correspondingly higher. 5. Because aquifer commingling through well boreholes is likely the dominant cause of aquifer declines, flow simulations were conducted to evaluate the benefit of repairing wells in specified locations and the benefit of recharging aquifers using diverted flow from study area creeks. As part of this analysis, maps were generated that show which areas are more vulnerable to commingling. These maps indicate that the value of repairing wells in the area generally coincident with the OWRD administrative area is higher than in areas farther upstream in the watershed. Simulation results also indicate that artificial recharge of the aquifers using diverted creek water will not significantly improve water levels in the aquifer system unless at least some commingling wells are repaired first. Repairs would entail construction of wells in a manner that prevents commingling of multiple aquifers. The value of artificially recharging the aquifers improves as more wells are repaired because the aquifer system more efficiently stores water.

Oregon↗
USGS1985

Preliminary study of the water-temperature regime of the North Santiam River downstream from Detroit and Big Cliff dams, Oregon

A riverine-temperature model and associated data-collection system were developed to help the Corps of engineers determine cost benefits of selective-withdrawal structures for future use with dams on the Willamette River System. A U.S. Geological Survey Lagrangian reference frame, digital computer model was used to simulate stream temperatures on the North Santiam River downstream of the multipurpose Detroit dam and a reregulating dam (Big Cliff), from river mile 45.6 to 2.9. In simulation, only available air-temperature and windspeed information from a nearby National Weather Service station at Salem, Oregon were used. This preliminary investigation found that the model predicted mean daily temperatures to within 0.4 C standard deviation. Analysis of projected selective-withdrawal scenarios showed that the model has the sensitivity to indicate water-temperature changes 42.7 miles downstream on the North Santiam River. (USGS)

Water-Resources Investigations Report↗
USGS1980

A summary report of the regional geology, environmental geology, OCS resource appraisal, petroleum potential, and operational considerations in the area of proposed lease sale 73, offshore California

This report reviews geological, geophysical and technological data pertinent to proposed Lease Sale 73. Under consideration is the entire continental margin of California that is bounded on the west by the 2500 meter isobath. This area encompasses the whole of the southern California Borderland, the continental shelves of central and northern California, and the upper part of the continental slope from Mexico on the south to Oregon on the north. The area includes both leased and unleased tracts and lies adjacent to highly productive coastal basins of central and northern California . Because the geology of the south and north parts of this large area differ, they are considered separately in this report.

California↗
USGS2017

Overview for geologic field-trip guides to volcanoes of the Cascades Arc in northern California

The California Cascades field trip is a loop beginning and ending in Portland, Oregon. The route of day 1 goes eastward across the Cascades just south of Mount Hood, travels south along the east side of the Cascades for an overview of the central Oregon volcanoes (including Three Sisters and Newberry Volcano), and ends at Klamath Falls, Oregon. Day 2 and much of day 3 focus on Medicine Lake Volcano. The latter part of day 3 consists of a drive south across the Pit River into the Hat Creek Valley and then clockwise around Lassen Volcanic Center to the town of Chester, California. Day 4 goes from south to north across Lassen Volcanic Center, ending at Burney, California. Day 5 and the first part of day 6 follow a clockwise route around Mount Shasta. The trip returns to Portland on the latter part of day 6, west of the Cascades through the Klamath Mountains and the Willamette Valley. Each of the three sections of this guidebook addresses one of the major volcanic regions: Lassen Volcanic Center (a volcanic field that spans the volcanic arc), Mount Shasta (a fore-arc stratocone), and Medicine Lake Volcano (a rear-arc, shield-shaped edifice). Each section of the guide provides (1) an overview of the extensive field and laboratory studies, (2) an introduction to the literature, and (3) directions to the most important and accessible field localities. The field-trip sections contain far more stops than can possibly be visited in the actual 6-day 2017 IAVCEI excursion from Portland. We have included extra stops in order to provide a field-trip guide that will have lasting utility for those who may have more time or may want to emphasize one particular volcanic area.

California↗
USGS2009

Derivation of Nationally Consistent Indices Representing Urban Intensity Within and Across Nine Metropolitan Areas of the Conterminous United States

Two nationally consistent multimetric indices of urban intensity were developed to support studies of the effects of urbanization on streams in nine metropolitan areas of the conterminous United States: Atlanta, Georgia; Birmingham, Alabama; Boston, Massachusetts; Dallas-Fort Worth, Texas; Denver, Colorado; Milwaukee-Green Bay, Wisconsin; Portland, Oregon; Raleigh, North Carolina; and Salt Lake City, Utah. These studies were conducted as a part of the U.S. Geological Survey's National Water-Quality Assessment Program. These urban intensity indices were used to define gradients of urbanization and to interpret biological, physical, and chemical changes along these gradients. Ninety census, land-cover, and infrastructure variables obtained from nationally available databases were evaluated. Only variables that exhibited a strong and consistent linear relation with 2000 population density were considered for use in the indices. Housing-unit density (HUDEN), percentage of basin area in developed land (P_NLCD1_2), and road density (ROADDEN) were selected as the best representatives of census, land-cover, and infrastructure variables. The metropolitan area national urban intensity index (MA-NUII) was scaled to represent urban intensity within each metropolitan area and ranged from 0 (little or no urban) to 100 (maximum urban) for sites within each metropolitan area. The national urban intensity index (NUII) was scaled to represent urban intensity across all nine metropolitan areas and ranged from 0 to 100 for all sites. The rates at which HUDEN, P_NLCD1_2, and ROADDEN changed with changes in population density varied among metropolitan areas. Therefore, these variables were adjusted to obtain a more uniform rate of response across metropolitan areas in the derivation of the NUII. The NUII indicated that maximum levels of urban intensity occurred in the West and Midwest rather than in the East primarily because small inner-city streams in eastern metropolitan areas are buried and converted to storm drains or sewers and because of higher density development in the Western and Central United States. The national indices (MA-NUII, NUII) were compared to indices that were derived independently for each metropolitan area (MA-UII) based on variables that were of local interest. The MA-UIIs, which were based on 5 to 40 variables, tended to overestimate urban intensity relative to the national indices particularly when the MA-UII was composed of large numbers of variables that were not linearly related to population density as in Denver, Dallas-Fort Worth, and Milwaukee-Green Bay.

Scientific Investigations Report↗