9568

• UCREFRP Catalog Number: 9568
• Author: Resource Consultants Inc.
• Title: Sediment Transport Studies of the Little Snake, Yampa, and Green River Systems.
• USFW Year: 1991.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

Mathers Hole Reach

The National Park Service (NPS) (O'Brien, 1984) dermed rating curves for the Mathers Hole reach
based on data collected in 1982 and 1983. The rating curves were prepared for total sediment load, as well
as various components of the total load. A continuation of that analysis for the Nature Conservancy dermed
the bias correction (based on the Ferguson procedure) for the total suspended load rating curve (O'Brien,
1987).

Review of the NPS data notebooks provided the raw data necessary to derive the bias
correction factors for the other rating curves. Only the 1983 data set was utilized since the 1982 data
set was limited and did not include a breakdown of sand load and wash load. Rating curves without
bias correction and developed from all flow data reproduced the mean value fairly well; application
of the bias correction resulted in significant overprediction (Table 5.3). In both of these cases the
suspended sediment load began overpredicting the total load at about 16,000 cfs. Rating curves
based on 2000 cfs data and greater resulted in underprediction without bias correction and
over prediction with bias correction (Table 5.3). Figure 5.3 illustrates the fit of the various rating
curves against the raw data, and the rating coefficients which are recommended for use in the
computation of effective discharge are summarized in Table 5.1.

An important factor in interpreting the Mathers Hole results is recognition of the variability of
rating curves developed from a supply limited reach. Statistical analysis of seasonal data (rising versus
recessional limbs) and yearly data (1982 versus 1983) by O'Brien (1984) "...demonstrates the variability of
the concentration and sediment load on a seasonal and annual basis. Since the sediment load in the river is
supply limited, large differences should be expected from year to year" (page 37). Therefore, the rating
curves developed from only one or two years of data may not be indicative of long term sediment transport
conditions. In fact, the 1983 year was a year of high water and sediment runoff (see page 1, Appendix B).

Table 5.3 Results of bias correction analysis for Mathers Hole.
Raw Original Conected
Data No Obs. Mean of R"2 Correction Mean of
Os Mean n a b Preel. Val. Coef. C a b Corr. Val
TOTAL LOAD
For Q > 2000 '83 32944 34 3.21198E-Ol 1.25671 30080 0.605 1.1779 3.79061E..ol 1.25671 35432
All Flows, '83 26716 43 7.440S4E-02 1.42000 25384 0.762 1.3831 1.02913E-Ol 1.42000 35109
SUSPENDED LOAD
For Q > 2000 '83 32903 34 3.22923E-Ol 1.25619 30041 0.604 1.1788 3.80676E-Ol 1.25619 35414
All Flows, '83 26716 43 7.4S891E-02 1.41960 25352 0.162 1.3839 1.03227E-Ol 1.41960 3508S
SAND LOAD
For Q > 2000 '83 14037 34 1.25673E-04 2.00963 13609 0.741 1.2512 1.57244E-04 2.00963 17028
All Flows, '83 11932 40 5.08949&09 3.12594 19478 0.909 1.5728 8.00463&09 3.12594 30634
WASH LOAD
For Q > 2000 '83 18781 34 2.94267E+OO 0.9S083 16273 0.411 1.2284 3.61468E+OO 0.9S083 19989
All Flows, '83 16040 40 4.700S5E-02 1.40760 15293 0.796 1.2643 5.94288E-02 1.40760 19335

Jensen Gage

Rating curve information for the Jensen gage on the Green River was available from the USGS.
Table 5.1 summarizes the rating curve coefficients.

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