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Research about Colorado

Source-linked reports with geographic coverage including Colorado.

At least 919 records · Page 51Linked to original sources
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.

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USGS2003

Flood flows, leaf breakdown, and plant-available nitrogen on a dryland river floodplain

We tested the hypothesis that decomposition in flood-inundated patches of riparian tree leaf litter results in higher plant-available nitrogen in underlying, nutrient-poor alluvium. We used leafpacks ( n = 56) containing cottonwood ( Populus deltoides ssp. wislizenii ) leaf litter to mimic natural accumulations of leaves in an experiment conducted on the Yampa River floodplain in semi-arid northwestern Colorado, USA. One-half of the leafpacks were set on the sandy alluvial surface, and one-half were buried 5 cm below the surface. The presence of NO 3 − and NH 4 + presumed to result from a leafpack's submergence during the predictable spring flood pulse was assessed using an ion-exchange resin bag (IER) placed beneath each leafpack and at control locations. Leafpacks and IERs were collected one week after flood peak (71 days total exposure) at half the stations; the remainder were collected three weeks later (93 days exposure). A multi-peaked spring flood with above-average maximum discharge inundated leafpacks for total time periods ranging from 133 to 577 hours. Litter lost from 43 to 68 percent of its initial organic matter (OM) content. Organic matter loss increased with total time inundated and total time of exposure on the floodplain. Burial retarded OM loss if the total time inundated was relatively long, and substrate texture (sand vs. silt) affected OM loss in a complex manner through interactions with total time inundated and total time of exposure. No pulse of N attributable to leaf breakdown was detected in the IERs, and leafpack litter showed no net change in the mass of nitrogen present. Patterns of leafpack and IER nitrogen levels suggested that litter removed N from floodwater and thereby reduced N availability in underlying sediment. Immobilization of floodwater-N by litter and N mineralization outside the flood period may be important components of N flux in semi-arid and arid floodplain environments.

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USGS2003

Responses of Englemann spruce forests to nitrogen fertilization in the Colorado Rocky Mountains

Two old-growth coniferous forests in Colorado with differing initial soil conditions responded differently to four years of low-level fertilization with ammonium nitrate. The site (Fraser) with an average initial organic horizon soil C:N ratio of 36 and nitrogen (N) pool of 605 kg/ha showed no significant increase in net N mineralization rates. At the Fraser site, foliar and organic horizon soil percentage N increased significantly. In contrast, N mineralization rates and inorganic soil N increased significantly at the site (Loch Vale) with greater soil N (C:N of 24, N pool of 991 kg/ha), while foliar N and soil percentage N in the organic layer did not change. We predict continued fertilization at Fraser will narrow the soil C:N ratio to a point where increases in biogeochemical N cycling and fluxes will be detected. Additional N inputs to the site with already low soil C:N ratios will enhance N mineralization rates and leaching losses. The coniferous forests at Fraser and Loch Vale are similar in species composition, stand age, substrate, aspect, and climate. The differences in soil conditions strong enough to cause contrasting responses to fertilization could be due to differences in atmospheric N deposition. Regardless of the reason, the size of the organic soil N pool and C:N ratio of mature coniferous forests in Colorado controls the responsiveness of N pools and fluxes to fertilization, and even low levels of fertilization are sufficient to initiate measurable biogeochemical changes.

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USGS2003

Effects of river flow regime on cottonwood leaf litter dynamics in semi-arid northwestern Colorado

We compared production and breakdown of Fremont cottonwood ( Populus deltoides wislizenii ) leaf litter at matched floodplain sites on the regulated Green River and unregulated Yampa River in semi-arid northwestern Colorado. Litter production under trees was similar at sites in 1999 (250 g/m 2 , oven-dry) but lower in 2000 (215 and 130 g/m 2 ), a drought year that also featured an outbreak of defoliating beetles at the Yampa River site. Our production values were similar to the few others reported for riparian forests within semi-arid or arid areas. Leaf litter in portions of the floodplain not inundated during the spring flood lost organic matter at the same rate as leaves placed in upland sites in 1998 and 2000: 35 to 50% of organic matter during an approximately 160-day spring and summer period. Inundated litter lost 55 to 90% of its organic matter during the same period. Organic matter loss from inundated leaves increased with duration of inundation and with deposition of fine sediment. Pooled across locations, leafpack data suggested that nitrogen concentration (mg N/kg organic matter) increased until about 65% of the initial organic matter was lost. This increase likely reflected the buildup of microbial decomposer populations. The role of insects and other macroinvertebrates in litter breakdown apparently was minor at both sites. Large spatial and temporal variation in litter dynamics in aridland floodplain settings is ensured by microtopographic variation in the alluvial surface coupled with year-to-year variation associated with most natural flood regimes. Factors reducing flood flow frequency or magnitude will reduce overall breakdown rates on the floodplain towards those found in drier upland environments.

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USGS2003

Tectonic evolution of the Proterozoic Colorado Province, Southern Rocky Mountains: A summary and appraisal

The Colorado province is a major component of a >1000-km-wide belt of Paleoproterozoic ocean-arc rocks that occupies the southwestern United States. Known as the Transcontinental Proterozoic provinces, this belt of largely juvenile rocks was added to the southern margin of the North American craton during the interval 1.8-1.70 Ga by convergent tectonism along the Cheyenne belt. A growing body of data suggests that these rocks were deposited, at least locally, on older rocks of earliest Proterozoic and Archean ages, probably correlative with the Trans-Hudson and Penokean orogens. The volcano-plutonic and associated sedimentary rocks of the Colorado province record two major, regional orogenies: (1) an older, protracted thermotectonic episode (1.78-1.70 Ga), named the Colorado orogeny, which involved mainly amphibolite-facies metamorphism during piecemeal assembly of various ocean-arc terranes; and (2) a younger, Mesoproterozoic intra-continental orogeny, named the Berthoud orogeny, which involved associated regional heating and A-type plutonism chiefly during the interval 1.45-1.40 Ga. The term "Colorado orogeny" is proposed for the regional Paleoproterozoic dynamothermal deformation. To distinguish differences in the geodynamics and ages of deformation and facilitate comparisons from place to place, type localities are proposed for separate phases or events of the Colorado orogeny. The central Front Range is suggested as a type area for the Berthoud orogeny, because the character and orientation of structures there are readily distinguished from those of the older Colorado orogeny.

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USGS2003

Data summary and loading sources for selected water-quality characteristics of streams in blowdown areas, North Fork Elk River Watershed, Colorado, March 1999-August 2000

On October 25, 1997, in and around the Routt National Forest and the Mount Zirkel Wilderness Area, a winter snowstorm occurred in conjunction with heavy winds that resulted in the destruction of thousands of acres of old-growth tree stands. The U.S. Geological Survey, in cooperation with the U.S. Forest Service, collected water-quality data at five sites in the North Fork Elk River watershed where most of the blowdown occurred. In this report, these data are used to characterize water quality in areas affected by the blowdown compared to that of relatively undisturbed areas. No difference was detected between loads of the selected constituents from the five water-quality sampling sites.

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USGS2003

Ferricrete, manganocrete, and bog iron occurrences with selected sedge bogs and active iron bogs and springs in the upper Animas River watershed, San Juan County, Colorado

During 1996 to 2000, the Bureau of Land Management, National Park Service, Environmental Protection Agency, United States Department of Agriculture (USDA) Forest Service, and the U.S. Geological Survey (USGS) developed a coordinated strategy to (1) study the environmental effects of historical mining on Federal lands, and (2) remediate contaminated sites that have the greatest impact on water quality and ecosystem health. This dataset provides information that contributes to these overall objectives and is part of the USGS Abandoned Mine Lands Initiative. Data presented here represent ferricrete occurrences and selected iron bogs and springs in the upper Animas River watershed in San Juan County near Silverton, Colorado. Ferricretes (stratified iron and manganese oxyhydroxide-cemented sedimentary deposits) are one indicator of the geochemical baseline conditions as well as the effect that weathering of mineralized rocks had on water quality in the Animas River watershed prior to mining. Logs and wood fragments preserved in several ferricretes in the upper Animas River watershed, collected primarily along streams, yield radiocarbon ages of modern to 9,580 years B.P. (P.L. Verplanck, D.B. Yager, and S.E. Church, work in progress). The presence of ferricrete deposits along the current stream courses indicates that climate and physiography of the Animas River watershed have been relatively constant throughout the Holocene and that weathering processes have been ongoing for thousands of years prior to historical mining activities. Thus, by knowing where ferricrete is preserved in the watershed today, land-management agencies have an indication of (1) where metal precipitation from weathering of altered rocks has occurred in the past, and (2) where this process is ongoing and may confound remediation efforts. These data are included as two coverages-a ferricrete coverage and a bogs and springs coverage. The coverages are included in ArcInfo shapefile and ArcInfo interchange file format.

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USGS2003

Specification aggregate quarry expansion - A case study demonstrating sustainable management of natural aggregate resources

Many countries, provinces, territories, or states in the European Union, Australia, Canada, the United States, and elsewhere have begun implementing sustainability programs, but most of those programs stop short of sustainable management of aggregate resources. Sustainable practices do not always have to be conducted under the title of sustainability. This case study describes how Lafarge, a large multinational construction materials supplier, implemented the principles of sustainability even though there was an absence of existing local government policies or procedures addressing sustainable resource management. Jefferson County, Colorado, USA, is one of three counties in the six-county Denver, Colorado, region that has potentially available sources of crushed stone. Crushed stone comprises 30 percent of the aggregate produced in the area and plays a major role in regional aggregate resource needs. Jefferson County is home to four of the five crushed stone operations in the Denver region. Lafarge operates one of those four quarries. Lafarge recently proposed to expand its reserves by exchanging company-owned land for existing dedicated open space land adjacent to their quarry but owned by Jefferson County. A similar proposal submitted about 10 years earlier had been denied. Contrary to the earlier proposal, which was predicated on public relations, the new proposal was predicated on public trust. Although not explicitly managed under the moniker of sustainability, Lafarge used basic management principles that embody the tenets of sustainability. To achieve the goals of sustainable aggregate management where no governmental policies existed, Lafarge not only assumed their role of being a responsible corporate and environmental member of the community, but also assumed the role of facilitator to encourage and enable other stakeholders to responsibly resolve legitimate concerns regarding the Lafarge quarry proposal. Lafarge successfully presented an enlightened proposal where the county will gain 745 acres of new open space land in exchange for 60 acres of current open space land adjacent to the quarry. The process involved collaborative efforts by all stakeholders and resulted in an outcome that balances the needs of society, the environment, and business.

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USGS2003

A spatial database of bedding attitudes to accompany Geologic Map of Boulder-Fort Collins-Greeley area, Colorado

This digital map shows bedding attitude data displayed over the geographic extent of rock stratigraphic units (formations) as compiled by Colton in 1976 (U.S.Geological Survey Map I-855-G) under the Front Range Urban Corridor Geology Program. Colton used his own mapping and published geologic maps having varied map unit schemes to compile one map with a uniform classification of geologic units. The resulting published color paper map was intended for planning for use of land in the Front Range Urban Corridor. In 1997-1999, under the USGS Front Range Infrastructure Resources Project, Colton's map was digitized to provide data at 1:100,000 scale to address urban growth issues(see cross-reference). In general, the west part of the map shows a variety of Precambrian igneous and metamorphic rocks, major faults and brecciated zones along an eastern strip (5-20 km wide) of the Front Range. The eastern and central part of the map (Colorado Piedmont) depicts a mantle of Quaternary unconsolidated deposits and interspersed Cretaceous or Tertiary-Cretaceous sedimentary rock outcrops. The Quaternary mantle is comprised of eolian deposits (quartz sand and silt), alluvium (gravel, sand, and silt of variable composition), colluvium, and few landslides. At the mountain front, north-trending, dipping Paleozoic and Mesozoic sandstone and shale formations (and sparse limestone) form hogbacks, intervening valleys, and in range-front folds, anticlines, and fault blocks. Localized dikes and sills of Tertiary rhyodacite and basalt intrude rocks near the range front, mostly in the Boulder area.

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USGS2003

Investigation of water quality in the Great Sand Dunes National Monument and Preserve, Saguache County, Colorado, February 1999 through September 2000: Qualifying for outstanding waters designation

Great Sand Dunes National Monument and Preserve is located on the eastern side of the San Luis Valley in south-central Colorado. The monument covers 60.4 square miles in Saguache and Alamosa Counties and lies at the base of the Sangre de Cristo Mountains, where a unique combination of climate, topography, and hydrology has created and maintained the Nation?s tallest inland sand dunes. The Sangre de Cristo Mountains, which rise to more than 14,000 feet to the north and east of the dunes, are the source of several streams that flow around the dunes and eventually recharge the aquifer beneath the valley. Sand Creek and Medano Creeks are the largest of the streams in the monument that originate in the Sangre de Cristo Mountains; several ephemeral streams flow into Sand Creek and Medano Creek. Maintaining the high surface-water quality in the Great Sand Dunes National Monument and Preserve is identified as a critical issue by the National Park Service. Additionally, the National Park Service has indicated a desire to pursue an Outstanding Waters Designation, which offers the highest level of water-quality protection available under the Clean Water Act and Colorado regulations. This designation is designed to prevent any degradation from existing conditions (Chatman and others, 1997). Assessment is needed to evaluate whether the water quality of the streams in the monument meets the requirements for an Outstanding Waters Designation. Historically, prospecting and mining activities have occurred in the watersheds of Sand and Medano Creeks; currently, however, there is no mining activity in those watersheds. In addition, the camping and recreation that occur upstream from the monument on national preserve lands and water activities that occur in Medano Creek during the summer are a potential source of human-waste contamination. Figure 1. Location of study area, sampling sites, and indication of sites that meet or exceed instream standards. The U.S. Geological Survey (USGS), in cooperation with the National Park Service, investigated the water quality at 15 sites (fig. 1) from February 1999 through September 2000 to identify baseline water-quality conditions and to determine if the water met standards to qualify for the Outstanding Waters Designation. This report describes current water-quality conditions in streams in the monument and compares the water-quality data to Colorado instream standards to assist the State of Colorado Water Quality Control Commission in the determination of qualification for Outstanding Waters Designation.

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USGS2003

Limnology of Blue Mesa, Morrow Point, and Crystal Reservoirs, Curecanti National Recreation area, during 1999, and a 25-year retrospective of nutrient conditions in Blue Mesa Reservoir, Colorado

The U.S. Geological Survey and the National Park Service conducted a water-quality investigation in Curecanti National Recreation Area in Colorado from April through December 1999. Current (as of 1999) limnological characteristics, including nutrients, phytoplankton, chlorophyll-a, trophic status, and the water quality of stream inflows and reservoir outflows, of Blue Mesa, Morrow Point, and Crystal Reservoirs were assessed, and a 25-year retrospective of nutrient conditions in Blue Mesa Reservoir was conducted. The three reservoirs are in a series on the Gunnison River, with an upstream to downstream order of Blue Mesa, Morrow Point, and Crystal Reservoirs. Physical properties and water-quality samples were collected four times during 1999 from reservoir, inflow, and outflow sites in and around the recreation area. Samples were analyzed for nutrients, phytoplankton and chlorophyll-a (reservoir sites only), and suspended sediment (stream inflows only). Nutrient concentrations in the reservoirs were low; median total nitrogen and phosphorus concentrations were less than 0.4 and 0.06 milligram per liter, respectively. During water-column stratification, samples collected at depth had higher nutrient concentrations than photic-zone samples. Phytoplankton community and density were affected by water temperature, nutrients, and water residence time. Diatoms were the dominant phytoplankton throughout the year in Morrow Point and Crystal Reservoirs and during spring and early winter in Blue Mesa Reservoir. Blue-green algae were dominant in Blue Mesa Reservoir during summer and fall. Phytoplankton density was highest in Blue Mesa Reservoir and lowest in Crystal Reservoir. Longer residence times and warmer temperatures in Blue Mesa Reservoir were favorable for phytoplankton growth and development. Shorter residence times and cooler temperatures in the downstream reservoirs probably limited phytoplankton growth and development. Median chlorophyll-a concentrations were higher in Blue Mesa Reservoir than Morrow Point or Crystal Reservoirs. Blue Mesa Reservoir was mesotrophic in upstream areas and oligotrophic downstream. Both Morrow Point and Crystal Reservoirs were oligotrophic. Trophic-state index values were determined for total phosphorus, chlorophyll-a, and Secchi depth for each reservoir by the Carlson method; all values ranged between 29 and 55. Only the upstream areas in Blue Mesa Reservoir had total phosphorus and chlorophyll-a indices above 50, reflecting mesotrophic conditions. Nutrient inflows to Blue Mesa Reservoir, which were derived primarily from the Gunnison River, varied on a seasonal basis, whereas nutrient inflows to Morrow Point and Crystal Reservoirs, which were derived primarily from deep water releases from the respective upstream reservoir, were steady throughout the sampling period. Total phosphorus concentrations were elevated in many stream inflows. A comparison of current (as of 1999) and historical nutrient, chlorophyll-a, and trophic conditions in Blue Mesa Reservoir and its tributaries indicated that the trophic status in Blue Mesa Reservoir has not changed over the last 25 years, and more recent nutrient enrichment has not occurred.

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USGS2003

Using water-quality profiles to characterize seasonal water quality and loading in the upper Animas River Basin, southwestern Colorado

One of the important types of information needed to characterize water quality in streams affected by historical mining is the seasonal pattern of toxic trace-metal concentrations and loads. Seasonal patterns in water quality are estimated in this report using a technique called water-quality profiling. Water-quality profiling allows land managers and scientists to assess priority areas to be targeted for characterization and(or) remediation by quantifying the timing and magnitude of contaminant occurrence. Streamflow and water-quality data collected at 15 sites in the upper Animas River Basin during water years 1991-99 were used to develop water-quality profiles. Data collected at each sampling site were used to develop ordinary least-squares regression models for streamflow and constituent concentrations. Streamflow was estimated by correlating instantaneous streamflow measured at ungaged sites with continuous streamflow records from streamflow-gaging stations in the subbasin. Water-quality regression models were developed to estimate hardness and dissolved cadmium, copper, and zinc concentrations based on streamflow and seasonal terms. Results from the regression models were used to calculate water-quality profiles for streamflow, constituent concentrations, and loads. Quantification of cadmium, copper, and zinc loads in a stream segment in Mineral Creek (sites M27 to M34) was presented as an example application of water-quality profiling. The application used a method of mass accounting to quantify the portion of metal loading in the segment derived from uncharacterized sources during different seasonal periods. During May, uncharacterized sources contributed nearly 95 percent of the cadmium load, 0 percent of the copper load (or uncharacterized sources also are attenuated), and about 85 percent of the zinc load at M34. During September, uncharacterized sources contributed about 86 percent of the cadmium load, 0 percent of the copper load (or uncharacterized sources also are attenuated), and about 52 percent of the zinc load at M34. Characterized sources accounted for more of the loading gains estimated in the example reach during September, possibly indicating the presence of diffuse inputs during snowmelt runoff. The results indicate that metal sources in the upper Animas River Basin may change substantially with season, regardless of the source.

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USGS2003

Ground-water-quality assessment of shallow aquifers in the Front Range Urban Corridor, Colorado, 1954-98

Historical (1954­98) water-quality data for major ions, trace elements, major plant nutrients, and organic constituents collected in 3,870 sampling events at 2,138 shallow wells represent ground-water quality in shallow aquifers that underlie the Front Range Urban Corridor in Colorado. Nonparametric summary statistics and maps of concentrations across the study area indicate that ground water in the study area included fresh to saline water. Sulfate concentrations were elevated in the north and northeast parts of the study area, possibly due to Pierre Shale and Laramie Formation shale outcrops in those areas. Apart from isolated areas of known contamination, chloride concentrations were generally less than 100 milligrams per liter across the study area. Wells with elevated nitrate concentrations usually were located near rivers and streams downgradient from metropolitan areas. Elevated nitrate concentrations in wells that were not along the South Platte River were possibly from individual sewage disposal system usage or from fertilizer application to land. Spatial distribution for organic compounds for which more than 40 percent of the data were above the detection limit (atrazine, methyl-tert-butylether, and prometon) is not widespread across the study area, but this may reflect limitations of data availability. Summary statistics calculated or estimated by decade are influenced by the temporal variability of data across the study area. The median values of specific conductance, chloride, and nitrate from the 1970’s are less than values from the 1980’s and 1990’s, which, because most samples from the l970’s were collected in the western part of the study area, indicates that water quality in the western part of the study area is generally different than the rest of the study area. Chloride may be introduced to ground water from runoff of road deicers or chlorinated organics in transportation/transitional areas, where the median concentration is the greatest (85.0 milligrams per liter). Nitrate median concentrations are several times greater where the land is cultivated or used for agricultural business, which may reflect use of nitrogen fertilizers and the presence of animal feeding operations. Most inorganic and organic constituents exceeded drinking-water standards in only a small percentage of samples. Exceptions to this include sulfate; nitrate; trace elements aluminum, cadmium, iron, and manganese; and organic compounds 1,1-dichloroethylene, tetrachloroethylene, trichloroethylene, benzene, and dichloromethane.

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