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<br />00847 <br /> <br />4.1.1. Watcr parametcrs <br /> <br />Water parameters monitored within this program consist of main-stem and tributary Ilow <br />rate, scdimentload. turbidity, temperature, and grain-size distribution of suspended scdiment. <br />Thc first four of these parameters are measured mainly with stream gages. whose data are <br />transmitted by telemetry to the Flagstaff Field Center. The gaging, stations are located at river <br />miles O. -3. -6, -9. -II. and -16; downstream within the Paria River, Shinumo Creck, Tapeats <br />Creek. Spenser Creek, Havasu Creek, Kanab Creek, Bright Angel Creek. Little Colorado River, <br />and Diamond Creek; and within Ihe main channel above the Littlc Colorado River conllucnce. <br />near Phantom Ranch, above National Canyon. and above Diamond Creek. In the recent past. <br />grain-size distributions were only mcasured from collected water samples. The remote-sensing <br />PEP suggested that in-stream optical devices be explored for measuring turbidity (Berlin et aI., <br />t 998), but turbidity was already recorded by the gaging slat ions. However, grain-size distribution <br />within the suspended sediment, which is not obtained by the conventional water-gaging stations, <br />is now being continuously monitored using L1SST (Laser In-Situ Scattering and <br />Transmissometry) submersible instruments thaI measure particle concentration, particle size <br />spectra, pressure, and temperature. These instruments are portable and are easily relocated. <br />Spatial water temperature is measured with strings of thermistors that are deployed by boat crews. <br />Our previous discussion on mapping warm back.water areas showed that airborne TIR data can <br />provide rapid, wide-area water temperature maps for the CRE, but the cost of these spatial data <br />are high relative to the point-specific data provided by the in sillt dctectors. especially high- <br />frequency data collections. Use of remote-sensing data for mapping the water temperature will <br />obviously be determined by the specific requirements of the program within any given year. <br /> <br />Although strcam instrumental ion is the most accuratc method for obtaining sediment <br />load, and turbidity, thc instruments provide only point-specific data and relatively few points <br />within the CRE. Airborne image data, calibrated by these in silll instrurments, have the potential <br />for producing regional water-parameter maps for improved understanding of the spatial relations <br />between sediment transport and deposition within the CRE. Multispectral, visible-wavelength <br />image data have been used to estimate turbidity and total suspended sediment load using ground <br />calibration data to relate spectral response to absolute water values (e.g.. Whitlock et aI., 1978; <br />Goodin et a!.. 1993; Jcrome et a!., t 996; Sathyendranath et a!., 1997; Fraser, 1998a, 1998b; <br />Pozdoyakov et a!., 1998; Tassan, 1998). Some of the better correlations between turbidity or total <br />suspended sediment and spectral response have been obtained in the 0.695-0.720 micrometer <br />wavelength region (Goodin et aI., 1993; Tassan, 1998; Fraser, 1998a). but this wavelength region <br />does not provide the greatest water pcnetration. <br /> <br />Chavez et al. (2002a,b) correlated radiance-ratio mcasurements of the main stem at <br />selected CRE locations with total suspended sediment concentrations (TSSC; mgll) and silt/clay <br />ratios that were obtained from nearby water-gage stations. They found good correspondence <br />(correlation coefficienl of 0.95; Figure 21) for these two data sets, but not for sand concentration <br />(correlation coefficienl of 0.60; Figure 21). The observed rclations were used to map TSSC <br />concentrations and silt-day ratios for segments of the CRE that were imaged with C1R sensors in <br />September of 2000 (Figure 22). <br /> <br />Spectral response due to total suspended load or turbidity is affected by mineral <br />composition and quantity and dissolved organic maller, all of which affect thc backscatter and <br />absorption coefficients of water. Thus, the rclations developed by Chavez need to be established <br />at various locations within the CRE for corridor-wide application. Chavez believes that just three <br />locations within the CRE are necessary in order to capture the variations produced by diffcrent <br /> <br />\9 <br />