<br />
<br />ammonia plus organic nitrogen, nitrite plus nitrate,
<br />phosphorus, and orthophosphorus were collected by
<br />the equal-width-increment method (Horowitz and
<br />others, 1994) to ensure sample representativeness,
<br />Samples were analyzed by the USGS National Water-
<br />Quality Laboratory in Denver, Colorado, using
<br />methods described by Fishman and Friedman (1989),
<br />Water-quality data resulting from synoptic sampling
<br />are presented in table 3 in the "Supplemental Informa-
<br />tion" section at the back of this report, These data are
<br />discussed in a section titled "Synoptic Sampling" in
<br />the "Summer 1999" section and in the "Winter 2000
<br />Synoptic Sampling" section,
<br />Diurnal measurements of temperature, specific
<br />conductance, measured pH, and dissolved oxygen
<br />concentrations were measured from the bank of five
<br />sites on the Yampa River during August 23-26,1999,
<br />This period was chosen to represent streamflow condi-
<br />tions that existed during summer synoptic sampling,
<br />The Yampa River sites (fig, I) measured diur-
<br />nally were:
<br />1, Above Elk River, 402936106565000, site 3,
<br />2, Below Craig, 09247600, site 6,
<br />3, Near Maybell, 09251000, site 8,
<br />4, At Deerlodge Park, 09260050, site II, and
<br />5, At mouth (Echo Park), 403136108585900, site 12.
<br />Results of diurnal measurements are presented
<br />graphically and discussed in the subsection titled
<br />"Diurnal Measurements" in the section titled
<br />"Summer 1999:'
<br />Reconnaissance measurements of temperature,
<br />specific conductance, pH, and dissolved oxygen
<br />concentration were measured during August 30-
<br />September 3, 1999, along the Yampa River between
<br />Deerlodge Park and the mouth of the river (Echo
<br />Park), Results of these measurements are discussed in
<br />the subsection titled "Reconnaissance Measurements
<br />in Dinosaur National Monument" in the section titled
<br />"Summer 1999," except for dissolved oxygen
<br />measurements, which were discarded because of
<br />equipment malfunction,
<br />
<br />Acknowledgments
<br />
<br />Gratitude is extended to the people who made
<br />possible the successful completion of this study and
<br />report. Dan Beyer (Colorado State University) noticed
<br />the apparent historical increase in measured pH at
<br />Yampa River near Maybell and approached the
<br />
<br />,
<br />, ':
<br />
<br />National Park Service with his concerns, Roy Irwin
<br />(National Park Service, Fort Collins, Colorado) and
<br />Steve Petersburg (National Park Service, Dinosaur
<br />National Monument) were itlstrumental in initiating
<br />and conceiving the scope of the study and providing
<br />access and logistical support in the National Monu-
<br />ment. Michael McHale (National Park Service, Dino-
<br />saur National Monument) took time away from his
<br />pressing duties during the flood-prone summer of
<br />1999 to make water-quality measurements at the
<br />mouth of the Yampa River. Timothy Modde, Mark
<br />Fuller, and David Beers (U,S, Fish and Wildlife
<br />Service, Vernal, Utah) graciously allowed the author to
<br />join them on a fish-study float trip through Yampa
<br />Canyon in Dinosaur National Monument to make
<br />reconnaissance water-quality measurements for this
<br />study, Paul von Guerard (USGS, Grand Junction,
<br />Colorado) worked hard to promote, develop, and
<br />review the progress of this study and offered valuable
<br />technical insights, John Turk (USGS, Lakewood,
<br />Colorado) was instrumental in establishing the scope
<br />and approach of the study and authoring the study
<br />proposal. Robert Boulger, Joseph Sullivan, Jeffrey
<br />Foster, Patricia Solberg, and Kenneth Butcher (USGS,
<br />Grand Junction, Colorado), along with Richard Neam,
<br />Dennis Smits (USGS, Lakewood, Colorado), and
<br />Joseph Dungan (USGS, Meeker, Colorado), collected
<br />water-quality and hydrologic data for this study,
<br />
<br />INTERPRETATION OF DATA COLLECTED
<br />FOR THIS STUDY
<br />
<br />Data from collection of synoptic samples during
<br />August 16-19, 1999, and March 13-16, 2000, and
<br />from diurnal measurements during August 23-26,
<br />1999, provide a framework to interpret water-quality
<br />data historically collected at the Yampa River near
<br />Maybell, including pH. In addition, reconnaissance
<br />field measurements taken on the Yampa River between
<br />Deerlodge Park and the mouth of the river (Echo Park)
<br />during August 30 through September 3, 1999, give an
<br />estimate of the maximum pH expected on the Yampa
<br />River in Dinosaur National Monument during low
<br />flow and warm weather,
<br />
<br />6 Evaluation of Trends in pH in the Vamps River, Northwestern Colorado, 1950-2000
<br />
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