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<br />Biota <br /> <br />Historic biological data of the following types are available at the two <br />NASQAN sites: (1) total phytoplankton; and (2) periphyton biomass (dry and ash <br />weight). Similar biological data-collection programs are being conducted as <br />part of cooperative programs with the U.S. Environmental Protection Agency and <br />the U.S. Bureau of Land Management (table 2). <br /> <br />From the stream-reconnaissance study (August-September 1975), biological <br />data were collected for periphyton and benthic invertebrates. Benthic invert- <br />ebrates were determined from triplicate Surber (1 ft2 or 0.1 m2) samples at <br />most sites. Three periphyton strips were used at each site during the recon- <br />naissance survey, and were retrieved within 4 to 6 weeks following the survey. <br />The described biological data for the reconnaissance survey during August- <br />September 1975 wi 11 be repeated during low-flow conditions 1 year later for <br />the 26 specified monitoring sites designated by numbering code "M" in table 2. <br /> <br />Biological data collected during the reconnaissance will be incorporated <br />with historic data to assess ambient conditions on an areal basis. <br /> <br />Waste-Assimilative-Capacity Analysis <br /> <br />(Work task I-E) <br /> <br />In consultation with the Colorado Department of Health, Routt County, and <br />the U.S. Environmental Protection Agency, the U.S. Geological Survey has con- <br />ducted an intensive data-collection and modelIng study for the malnstem Yampa <br />River reach between Steamboat Springs and Hayden. This reach of the river is <br />about 38 miles (61 km) in length. Fifteen channel cross sections within this <br />reach have been delineated and are designated by codes YM-Q through YM-14 in <br />table 3. At each cross section, field measurements were made of dissolved <br />oxygen, temperature, specific conductance, and pH. In addition, samples were <br />co 11 ected for 1 aboratory determl nat I on of 5-day b i ochemi cal oxygen demand <br />(BODs), 20-day bIochemical oxygen demand (BOD20), selected nitrogen species <br />(nitrite plus nitrate, Kje1dahl-N, and ammonia) and total phosphorus. Samples <br />were also collected at ,each site for determination of fecal and total col iform <br />bacteria. <br /> <br />Supplemental biological information has been collected at the mainstem <br />sampling sites in collaboration with U.S. Environmental Protection Agency per- <br />sonnel. Artificial substrate samplers for benthic inverte~rates were placed <br />during the week of August 18-22, 1975, and periphyton strips were placed dur- <br />ing the first week in September 1975. It is envisioned that the biological <br />information will complement the physical and chemical data collected during <br />late September 1975" and wi 11 aid In the interpretation of the model ing re- <br />sults. In addition to the mainstem stations, intermittent measurements were <br />made prior to and after the intensive sampling at 17 inflow tributary streams <br />(code YT, table 3) in the study reach. Also, effluents from point discharges <br />in the reach (code YE, table 3) were sampled either by Routt County or by <br />Co I orado Department of Hea 1 th personne 1. The eff1 uent d i scha rge samp 1 es were <br />collected from major sewage facilities in the Steamboat Springs and Hayden <br />areas. Additional physical data on channel-sectlon profiles, effective width <br /> <br />14 <br />