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K. Campbell

Publications and source records attributed to K. Campbell.

At least 19 recordsLinked to original sources
USGS2021

Spectral damping scaling factors for horizontal components of ground motions from subduction earthquakes using NGA-Subduction data

This article develops global models of damping scaling factors (DSFs) for subduction zone earthquakes that are functions of the damping ratio, spectral period, earthquake magnitude, and distance. The Next Generation Attenuation for subduction earthquakes (NGA-Sub) project has developed the largest uniformly processed database of recorded ground motions to date from seven subduction regions: Alaska, Cascadia, Central America and Mexico, South America, Japan, Taiwan, and New Zealand. NGA-Sub used this database to develop new ground motion models (GMMs) at a reference 5% damping ratio. We worked with the NGA-Sub project team to develop an extended database that includes pseudo-spectral accelerations (PSA) for 11 damping ratios between 0.5% and 30%. We use this database to develop parametric models of DSF for both interface and intraslab subduction earthquakes that can be used to adjust any subduction GMM from a reference 5% damping ratio to other damping ratios. The DSF is strongly influenced by the response spectral shape and the duration of motion; therefore, in addition to the damping ratio, the median DSF model uses spectral period, magnitude, and distance as surrogate predictor variables to capture the effects of the spectral shape and the duration of motion. We also develop parametric models for the standard deviation of DSF. The models presented in this article are for the RotD50 horizontal component of PSA and are compared with the models for shallow crustal earthquakes in active tectonic regions. Some noticeable differences arise from the considerably longer duration of interface records for very large magnitude events and the enriched high-frequency content of intraslab records, compared with shallow crustal earthquakes. Regional differences are discussed by comparing the proposed global models with the data from each subduction region along with recommendations on the applicability of the models.

Earthquake Spectra↗
USGS2011

Effects of climate change and land use on water resources in the Upper Colorado River Basin

The health of the Colorado River watershed is critical to the socioeconomic and ecosystem well-being of the Southwestern United States. Water in springs, streams, and rivers supports a range of aquatic and riparian ecosystems that contain many endangered species. Terrestrial habitats support a wide array of plants and wildlife. In addition, this region is enjoyed by millions of people annually for its recreational and esthetic opportunities. The Colorado River provides water for about 25 million people and is used to irrigate 2.5 million acres of farmland. However, competition for this water is expected to increase as human populations dependent on this water are projected to increase to 38 million by 2020. Climate change is expected to further exacerbate water issues in this region. Drought in the Southwest during 2000-04, caused by both reduced precipitation and a series of the hottest years on record, resulted in streamflows lower than during the 1930s Dust Bowl or the 1950s. Increased temperatures alone are a major factor in reducing surface-water flows in this region. For instance, precipitation received during the winter of 2005 was at the 100-year average. However, low soil moisture and high January-July temperatures resulted in flows that were only 75 percent of average. Climate models predict future warmer temperatures and reduced precipitation in the Upper Colorado River Basin (UCRB), which would reduce water available to humans and ecosystems.

Arizona, Colorado, New Mexico, Utah, Wyoming↗
USGS2009

Assessment of lake sensitivity to acidic deposition in national parks of the Rocky Mountains

The sensitivity of high-elevation lakes to acidic deposition was evaluated in five national parks of the Rocky Mountains based on statistical relations between lake acid-neutralizing capacity concentrations and basin characteristics. Acid-neutralizing capacity (ANC) of 151 lakes sampled during synoptic surveys and basin-characteristic information derived from geographic information system (GIS) data sets were used to calibrate the statistical models. The explanatory basin variables that were considered included topographic parameters, bedrock type, and vegetation type. A logistic regression model was developed, and modeling results were cross-validated through lake sampling during fall 2004 at 58 lakes. The model was applied to lake basins greater than 1 ha in area in Glacier National Park ( n = 244 lakes), Grand Teton National Park ( n = 106 lakes), Great Sand Dunes National Park and Preserve ( n = 11 lakes), Rocky Mountain National Park ( n = 114 lakes), and Yellowstone National Park ( n = 294 lakes). Lakes that had a high probability of having an ANC concentration <100 μeq/L, and therefore sensitive to acidic deposition, are located in basins with elevations >3000 m, with <30% of the catchment having northeast aspect and with >80% of the catchment bedrock having low buffering capacity. The modeling results indicate that the most sensitive lakes are located in Rocky Mountain National Park and Grand Teton National Park. This technique for evaluating the lake sensitivity to acidic deposition is useful for designing long-term monitoring plans and is potentially transferable to other remote mountain areas of the United States and the world.

Colorado;Idaho;Montana;Wyoming↗
USGS2008

Evaluating regional patterns in nitrate sources to watersheds in national parks of the Rocky Mountains using nitrate isotopes

In the Rocky Mountains, there is uncertainty about the source areas and emission types that contribute to nitrate (NO 3 ) deposition, which can adversely affect sensitive aquatic habitats of high-elevation watersheds. Regional patterns in NO 3 deposition sources were evaluated using NO 3 isotopes in five National Parks, including 37 lakes and 7 precipitation sites. Results indicate that lake NO 3 ranged from detection limit to 38 μeq/L, δ 18 O (NO 3 ) ranged from −5.7 to +21.3‰, and δ 15 N (NO 3 ) ranged from −6.6 to +4.6‰. δ 18 O (NO 3 ) in precipitation ranged from +71 to +78‰. δ 15 N (NO 3 ) in precipitation and lakes overlap; however, δ 15 N (NO 3 ) in precipitation is more depleted than δ 15 N (NO 3 ) in lakes, ranging from −5.5 to −2.0‰. δ 15 N (NO 3 ) values are significantly related ( p < 0.05) to wet deposition of inorganic N, sulfate, and acidity, suggesting that spatial variability of δ 15 N (NO 3 ) over the Rocky Mountains may be related to source areas of these solutes. Regional patterns show that NO 3 and δ 15 N (NO 3 ) are more enriched in lakes and precipitation from the southern Rockies and at higher elevations compared to the northern Rockies. The correspondence of high NO 3 and enriched δ 15 N (NO 3 ) in precipitation with high NO 3 and enriched δ 15 N (NO 3 ) in lakes, suggests that deposition of inorganic N in wetfall may affect the amount of NO 3 in lakes through a combination of direct and indirect processes such as enhanced nitrification.

Environmental Science & Technology↗
USGS2008

Comparisons of the NGA ground-motion relations

The data sets, model parameterizations, and results from the five NGA models for shallow crustal earthquakes in active tectonic regions are compared. A key difference in the data sets is the inclusion or exclusion of aftershocks. A comparison of the median spectral values for strike-slip earthquakes shows that they are within a factor of 1.5 for magnitudes between 6.0 and 7.0 for distances less than 100 km. The differences increase to a factor of 2 for M5 and M8 earthquakes, for buried ruptures, and for distances greater than 100 km. For soil sites, the differences in the modeling of soil/sediment depth effects increase the range in the median long-period spectral values for M7 strike-slip earthquakes to a factor of 3. The five models have similar standard deviations for M6.5-M7.5 earthquakes for rock sites and for soil sites at distances greater than 50 km. Differences in the standard deviations of up to 0.2 natural log units for moderate magnitudes at all distances and for large magnitudes at short distances result from the treatment of the magnitude dependence and the effects of nonlinear site response on the standard deviation. ?? 2008, Earthquake Engineering Research Institute.

Earthquake Spectra↗
USGS2008

Trends in snowpack chemistry and comparison to National Atmospheric Deposition Program results for the Rocky Mountains, US, 1993-2004

Seasonal snowpack chemistry data from the Rocky Mountain region of the US was examined to identify long-term trends in concentration and chemical deposition in snow and in snow-water equivalent. For the period 1993-2004, comparisons of trends were made between 54 Rocky Mountain Snowpack sites and 16 National Atmospheric Deposition Program wetfall sites located nearby in the region. The region was divided into three subregions: Northern, Central, and Southern. A non-parametric correlation method known as the Regional Kendall Test was used. This technique collectively computed the slope, direction, and probability of trend for several sites at once in each of the Northern, Central, and Southern Rockies subregions. Seasonal Kendall tests were used to evaluate trends at individual sites. Significant trends occurred during the period in wetfall and snowpack concentrations and deposition, and in precipitation. For the comparison, trends in concentrations of ammonium, nitrate, and sulfate for the two networks were in fair agreement. In several cases, increases in ammonium and nitrate concentrations, and decreases in sulfate concentrations for both wetfall and snowpack were consistent in the three subregions. However, deposition patterns between wetfall and snowpack more often were opposite, particularly for ammonium and nitrate. Decreases in ammonium and nitrate deposition in wetfall in the central and southern rockies subregions mostly were moderately significant (p<0.11) in constrast to highly significant increases in snowpack (p<0.02). These opposite trends likely are explained by different rates of declining precipitation during the recent drought (1999-2004) and increasing concentration. Furthermore, dry deposition was an important factor in total deposition of nitrogen in the region. Sulfate deposition decreased with moderate to high significance in all three subregions in both wetfall and snowpack. Precipitation trends consistently were downward and significant for wetfall, snowpack, and snow-telemetry data for the central and southern rockies subregions (p<0.03), while no trends were noted for the Northern Rockies subregion.

Atmospheric Environment↗
USGS2008

Comparison of total mercury and methylmercury cycling at five sites using the small watershed approach

The small watershed approach is well-suited but underutilized in mercury research. We applied the small watershed approach to investigate total mercury (THg) and methylmercury (MeHg) dynamics in streamwater at the five diverse forested headwater catchments of the US Geological Survey Water, Energy, and Biogeochemical Budgets (WEBB) program. At all sites, baseflow THg was generally less than 1 ng L −1 and MeHg was less than 0.2 ng L −1 . THg and MeHg concentrations increased with streamflow, so export was primarily episodic. At three sites, THg and MeHg concentration and export were dominated by the particulate fraction in association with POC at high flows, with maximum THg (MeHg) concentrations of 94 (2.56) ng L −1 at Sleepers River, Vermont; 112 (0.75) ng L −1 at Rio Icacos, Puerto Rico; and 55 (0.80) ng L −1 at Panola Mt., Georgia. Filtered (<0.7 μm) THg increased more modestly with flow in association with the hydrophobic acid fraction (HPOA) of DOC, with maximum filtered THg concentrations near 5 ng L −1 at both Sleepers and Icacos. At Andrews Creek, Colorado, THg export was also episodic but was dominated by filtered THg, as POC concentrations were low. MeHg typically tracked THg so that each site had a fairly constant MeHg/THg ratio, which ranged from near zero at Andrews to 15% at the low-relief, groundwater-dominated Allequash Creek, Wisconsin. Allequash was the only site with filtered MeHg consistently above detection, and the filtered fraction dominated both THg and MeHg. Relative to inputs in wet deposition, watershed retention of THg (minus any subsequent volatilization) was 96.6% at Allequash, 60% at Sleepers, and 83% at Andrews. Icacos had a net export of THg, possibly due to historic gold mining or frequent disturbance from landslides. Quantification and interpretation of Hg dynamics was facilitated by the small watershed approach with emphasis on event sampling.

Environmental Pollution↗
USGS2008

Experimental and field observations of breach dynamics accompanying erosion of Marmot Cofferdam, Sandy River, Oregon

A key issue faced in dam removal is the rate and timing of remobilization and discharge of stored reservoir sediments following the removal. Different removal strategies can result in different trajectories of upstream sediment transport and knickpoint migration. We examine this issue of for the Marmot Dam removal in Sandy River, Oregon, USA using both physical experiments and field studies accompanying removal of the dam in October 2007. The physical experiment was designed to provide insights on how and if the position of a cofferdam notch will affect how reservoir sediments are remobilized, with the goal of minimizing the volume of sediment stranded in terraces. Data and observations indicate that at lower failure discharges, notch position impacts the location of cofferdam failure as well as the location of the first major knickpoint and its trajectory. In particular, notch positions that force the river to migrate laterally in order to adjust to natural valley orientation and morphology were most effective in removing larger volumes of sediment and reducing terrace heights. Actual cofferdam notching to maximize erosion produced extremely rapid and significant erosion of reservoir sediments. Comparison of model results with field observations suggests that the physical experiments provided solid predictions of rates of erosion and overall knickpoint trajectory.

Conference Paper↗
USGS2007

Nitrogen saturation in the Rocky Mountains: Linking emissions, deposition, and ecosystem effects using stable isotopes of nitrogen compounds

Elevated levels of atmospheric N deposition are affecting terrestrial and aquatic ecosystems at high elevations in Rocky Mountain National Park and adjacent areas of the Front Range of Colorado. Federal and state agencies are now working together to develop cost-effective means for reducing atmospheric N deposition. A discussion on N saturation covers the need for better understanding of N emission source areas and source types that contribute to N deposition in the Rocky Mountains Front Range of Colorado; reductions in NO emissions that resulted from Clean Air Act Amendments, which caused NO3 deposition to decrease between 1984 and 2003; factors contributing to N deposition, e.g., rapid population growth and energy development; origins of NO3, e.g., as NO emissions from fossil fuel combustion, including stationary sources (e.g. emission from coal combustion in electric generating units), and mobile sources (vehicle emissions); disperse stationary sources from energy resource development, e.g., natural gas production; and the importance of incorporating local source characterization and finer spatial and temporal sampling into future studies, which could provide additional insight into N deposition source attribution. This is an abstract of a paper presented at the 100th Annual Conference and Exhibition of the Air and Waste Management Association (Pittsburgh, PA 6/26-29/2007).

Conference Paper↗
USGS2006

Atmospheric deposition of current-use and historic-use pesticides in snow at National Parks in the Western United States

The United States (U.S.) National Park Service has initiated research on the atmospheric deposition and fate of semi-volatile organic compounds in its alpine, sub-Arctic, and Arctic ecosystems in the Western U.S. Results for the analysis of pesticides in seasonal snowpack samples collected in spring 2003 from seven national parks are presented herein. From a target analyte list of 47 pesticides and degradation products, the most frequently detected current-use pesticides were dacthal, chlorpyrifos, endosulfan, and ??- hexachlorocyclohexane, whereas the most frequently detected historic-use pesticides were dieldrin, ??-hexachlorocyclohexane, chlordane, and hexachlorobenzene. Correlation analysis with latitude, temperature, elevation, particulate matter, and two indicators of regional pesticide use reveal that regional current and historic agricultural practices are largely responsible for the distribution of pesticides in the national parks in this study. Pesticide deposition in the Alaskan parks is attributed to long-range transport because there are no significant regional pesticide sources. The percentage of total pesticide concentration due to regional transport (%RT) was calculated for the other parks. %RT was highest at parks with higher regional cropland intensity and for pesticides with lower vapor pressures and shorter half-lives in air. ?? 2006 American Chemical Society.

Environmental Science & Technology↗
USGS2005

Spatial and temporal variability in the amount and source of dissolved organic carbon: Implications for ultraviolet exposure in amphibian habitats

The amount, chemical composition, and source of dissolved organic carbon (DOC), together with in situ ultraviolet (UV-B) attenuation, were measured at 1&ndash;2 week intervals throughout the summers of 1999, 2000, and 2001 at four sites in Rocky Mountain National Park (Colorado). Eight additional sites, four in Sequoia and Kings Canyon National Park/John Muir Wilderness (California) and four in Glacier National Park (Montana), were sampled during the summer of 2000. Attenuation of UV-B was significantly related to DOC concentrations over the three years in Rocky Mountain ( R 2 &thinsp;=&thinsp;0.39, F&thinsp; =&thinsp;25.71, P < 0.0001) and across all parks in 2000 ( R 2 &thinsp; =&thinsp;0.44, F &thinsp;=&thinsp;38.25, P < 0.0001). The relatively low R 2 values, however, reflect significant temporal and spatial variability in the specific attenuation per unit DOC. Fluorescence analysis of the fulvic acid DOC fraction (roughly 600&ndash;2,000 Daltons) indicated that the source of DOC significantly affected the attenuation of UV-B. Sites in Sequoia&ndash;Kings Canyon were characterized by DOC derived primarily from algal sources and showed much deeper UV-B penetration, whereas sites in Glacier and Rocky Mountain contained a mix of algal and terrestrial DOC-dominated sites, with more terrestrially dominated sites characterized by greater UV-B attenuation per unit DOC. In general, site characteristics that promoted the accumulation of terrestrially derived DOC showed greater attenuation of UV-B per unit DOC; however, catchment vegetation and soil characteristics, precipitation, and local hydrology interacted to make it difficult to predict potential exposure from DOC concentrations.

California, Colorado, Montana↗
USGS2003

Hatching success in salamanders and chorus frogs at two sites in Colorado, USA: Effects of acidic deposition and climate

The snowpack in the vicinity of the Mount Zirkel Wilderness Area is among the most acidic in the western United States. We analyzed water chemistry and examined hatching success in tiger salamanders and chorus frogs at ponds there and at nearby Rabbit Ears Pass (Dumont) to determine whether acid deposition affects amphibians or their breeding habitats at these potentially sensitive locations. We found a wide range of acid neutralizing capacity among ponds within sites; the minimum pH recorded during the experiment was 5.4 at one of 12 ponds with all others at pH ??? 5.7. At Dumont, hatching success for chorus frogs was greater in ponds with low acid neutralizing capacity; however, lowest pHs were >5.8. At current levels of acid deposition, weather and pond characteristics are likely more important than acidity in influencing hatching success in amphibian larvae at these sites.

Colorado↗
USGS2001

Major-ion chemistry of the Rocky Mountain snowpack, USA

During 1993-97, samples of the full depth of the Rocky Mountain snowpack were collected at 52 sites from northern New Mexico to Montana and analyzed for major-ion concentrations. Concentrations of acidity, sulfate, nitrate, and calcium increased from north to south along the mountain range. In the northern part of the study area, acidity was most correlated (negatively) with calcium. Acidity was strongly correlated (positively) with nitrate and sulfate in the southern part and for the entire network. Acidity in the south exceeded the maximum acidity measured in snowpack of the Sierra Nevada and Cascade Mountains. Principal component analysis indicates three solute associations we characterize as: (1) acid (acidity, sulfate, and nitrate), (2) soil (calcium, magnesium, and potassium), and (3) salt (sodium, chloride, and ammonium). Concentrations of acid solutes in the snowpack are similar to concentrations in nearby wetfall collectors, whereas, concentrations of soil solutes are much higher in the snowpack than in wetfall. Thus, dryfall of acid solutes during the snow season is negligible, as is gypsum from soils. Snowpack sampling offers a cost-effective complement to sampling of wetfall in areas where wetfall is difficult to sample and where the snowpack accumulates throughout the winter. Copyright ?? 2001 .

Atmospheric Environment↗
USGS1999

A method for nitrate collection for δ 15 N and δ 18 O analysis from waters with low nitrate concentrations

Recently, methods have been developed to analyze NO3- for &delta;15N and &delta;18O, improving our ability to identify NO3- sources and transformations. However, none of the existing methods are suited for waters with low NO3- concentrations (0.7-10 &micro;M). We describe an improved method for collecting and recovering NO3- on exchange columns. To overcome the lengthy collection loading times imposed by the large sample volumes (7-70 L), the sample was prefiltered (0.45 &micro;m) with a large surface area filter. Switching to AG2X anion resin and using a coarser mesh size (100-200) than previous methods also enhanced sample flow. Placement of a cation column in front of the anion column minimized clogging of the anion column by dissolved organic carbon (DOC) accumulation. This also served to minimize transfer of unwanted oxygen atoms from DOC to the 18O portion of the NO3- sample, thereby contaminating the sample and shifting &delta;18O. The cat-AG2X method is suited for on-site sample collection, making it possible to collect and recover NO3- from low ionic strength waters with modest DOC concentrations (80-800 &micro;M), relieves the investigator of transporting large volumes of water back to the laboratory, and offers a means of sampling rain, snow, snowmelt, and stream samples from access-limited sites.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1997

Nitrogen fluxes in a high elevation Colorado Rocky Mountain basin

Measured, calculated and simulated values were combined to develop an annual nitrogen budget for Loch Vale Watershed (LVWS) in the Colorado Front Range. Nine-year average wet nitrogen deposition values were 1·6 ( s =0·36) kg NO 3 -N ha −1 , and 1·0 ( s =0·3) kg NH 4 -N ha −1 . Assuming dry nitrogen deposition to be half that of measured wet deposition, this high elevation watershed receives 3·9 kg N ha −1 . Although deposition values fluctuated with precipitation, measured stream nitrogen outputs were less variable. Of the total N input to the watershed (3·9 kg N ha −1 wet plus dry deposition), 49% of the total N input was immobilized. Stream losses were 2·0 kg N ha −1 (1125 kg measured dissolved inorganic N in 1992, 1–2 kg calculated dissolved organic N, plus an average of 203 kg algal N from the entire 660 ha watershed). Tundra and aquatic algae were the largest reservoirs for incoming N, at approximately 18% and 15% of the total 2574 kg N deposition, respectively. Rocky areas and forest stored the remaining 11% and 5%, respectively. Fully 80% of N losses from the watershed came from the 68% of LVWS that is alpine. © 1997 John Wiley & Sons, Ltd.

Hydrological Processes↗
USGS1997

Assessment of climate change and freshwater ecosystems of the Rocky Mountains, USA and Canada

The Rocky Mountains in the USA and Canada encompass the interior cordillera of western North America, from the southern Yukon to northern New Mexico. Annual weather patterns are cold in winter and mild in summer. Precipitation has high seasonal and interannual variation and may differ by an order of magnitude between geographically close locales, depending on slope, aspect and local climatic and orographic conditions. The region's hydrology is characterized by the accumulation of winter snow, spring snowmelt and autumnal baseflows. During the 2–3-month ‘spring runoff’ period, rivers frequently discharge > 70% of their annual water budget and have instantaneous discharges 10–100 times mean low flow.

Hydrological Processes↗