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standard criteria were used in the final survey. The Excel-macro eliminated all non-RTK
<br />hits as indicated by the GGA string. This eliminates false spikes in the sonar data
<br />sometimes caused by fish or woody debris. Spikes were identified by making a running
<br />average of the six nearest sonar pings (three prior and three after). An individual depth
<br />reading was marked as "bad" if the difference in between the moving average and the
<br />individual ping was greater than 15 cm. If an RTK GPS reading had a "bad" sonar ping
<br />recorded directly before or after it, that GPS reading was ignored. For those RTK GPS
<br />signals with "good" sonar recordings before and after them, the depth for that GPS
<br />position was determined through a linear interpolation of the sonar data based on the time
<br />tags. Topographic data were also visually examined by creating Triangular Irregular
<br />Networks (TIN).
<br />HYDRAULIC SIMULATION
<br />In the first two years of the project, hydraulic simulation and 2-D flow modeling
<br />was contracted with the Earth Resources Department of Colorado State University
<br />(CSU). Greg Stewart, a CSU graduate student, collected and input the data to the
<br />RMA2-hydraulic model. He performed the analysis during the time period June 1998 to
<br />June 2000. Stewart (2000) gives details on hydraulic methods, problems and innovations
<br />used for making flow simulations at 15-Mile Reach (Corn Lake) and the Duffy Tunnel
<br />site.
<br />Stewart performed most of the installation and operation of technical equipment
<br />and data handing for the 2-D modeling. Following his departure, no 2-D modeling was
<br />performed until a new contractor was found. In 2002, a new contract was finalized with
<br />Utah State University. Dr. Craig Addley, contract administrator for 2-D modeling at
<br />Utah State University (USU), supervised modeling for the.remaining four sites and some
<br />new modeling on Corn Lake. The USU lab used a 2-dimensional, quasi-3-dimensional
<br />model developed by Jonathan Nelson of the USGS. The technical description of this
<br />model and underlying equations can be found in Nelson (1996), Thompson et al. (1998),
<br />Nelson et al. (1995), McLean et al. (1999), Topping et al. (2000).
<br />The 2-D model flow simulations for the Yampa River were meant to cover the
<br />range of flow typical in the base flow period, which typically varies between 125 and 200
<br />cfs. Flows simulations at Sevens and Lily Park were produced at 40, 60, 80, 100, 125,
<br />150, 200, 250, 300, 400; 500 and 600 cfs by USU. The Duffy site modeled by Stewart
<br />was at flows of 60, 80, 100, 125, 150, 200, 250, 300, 400, 500 and 600 cfs. On the
<br />Colorado River base flow was typically much higher than on the Yampa and did not
<br />commonly fall below 600 cfs. Stewart ran flow simulations at Corn Lake at 600, 700,
<br />800, 900, 1000, 1200, 1400, 1600, and 1800 cfs. The same flows were modeled for the
<br />Clifton site by USU, with additional simulation at flows of 200; 250, 300, 350,-400, 450,
<br />500 and 2000 cfs. Some follow-up modeling was done on the Colorado River so that
<br />both sites were modeled down to 100 cfs. Flows on the Dolores River ranged from a
<br />low at 10 cfs and a high of 500 cfs.
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