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Person

Rachel G Gidley

Hydrologist
Email: rgidley@usgs.gov
Office Phone: 970-628-7172
ORCID: 0000-0002-9840-8252
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The U.S. Geological Survey is investigating sources of fecal bacteria in streams in the Grand Valley of western Colorado by using quantitative polymerase chain reaction microbial source tracking (MST) markers. The CowM2 MST marker was not detected in water-quality samples collected in 2022, which raised questions about the use of the marker for investigations in western Colorado. The presence or absence of bacteria associated with MST markers can be affected by geographic location, animal health, and diet. Known-source cattle fecal samples were collected in the Grand Valley to determine the presence or absence of the CowM2 marker in the feces of local cattle. A total of five samples were collected, representing...
This U.S. Geological Survey (USGS) data release provides benthic algae data collected from the upper White River Basin, Colorado, during August 2020 and July 2021. All data are reported as raw calculated values and are not rounded to USGS significant figures. The dataset includes samples collected at 20 USGS water-quality sites. Benthic algae were identified to the lowest possible taxonomic level, and abundance (density) and biovolume are reported.
Categories: Data
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The U.S. Geological Survey (USGS), in cooperation with the Grand Valley Drainage District and the Colorado Water Conservation Board, conducted a loading analysis for selected constituents and tributaries to the Colorado River in the Grand Valley, western Colorado, using data from 1991 to 2018, to characterize concentrations, stream loading, and load reductions for Escherichia coli, total recoverable iron, and dissolved selenium for stream segments on the State of Colorado 303(d) list of impaired waters. Escherichia coli, total recoverable iron, and dissolved selenium concentrations and streamflow data were compiled from the Water Quality Portal (WQP). The data were submitted to the WQP by the USGS, Colorado Department...
Channel Characteristics, benthic algae, and water quality model data for selected sites in the upper White River Basin, Colorado, 2018-21
This U.S. Geological Survey (USGS) data release provides benthic algae and stream channel characteristics data collected from 20 water-quality sites in the Upper White River Basin, Colorado., during 2018-2021. Also included are input and output data from streamflow and water-quality regression models used to characterize streamflow and water-quality conditions at 3 sites in the Upper White River Basin, Colorado. The data were collected by the USGS. All data are reported as raw calculated values and are not rounded to USGS significant figures. Phytoplankton were identified to the lowest possible taxonomic level, and abundance (density) and biovolume are reported.
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Mitigating the effects of salinity (total dissolved solids) and selenium on water quality in the lower Gunnison River Basin (LGRB) of western Colorado is a major concern for land managers. In cooperation with the Bureau of Reclamation, the U.S. Geological Survey completed a study to develop multiple linear regression models to estimate salinity and selenium loads. The objective of the study was to refine existing models by improving the regressions and using additional geospatial and water-quality data. This data release presents the basin characteristics and loads used to calibrate the models. Also provided are salinity and selenium yield rasters determined by empirical Bayesian kriging of loads estimated by the...
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