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<br />At 10,day inlervals for 90 days each year. food base is determined within pool. cobble, <br />rime. shoreline. and nearshore environments. The food base surveys are performed at river miles <br />,15,5.0,60,64, 138, and 205. For Ihc pools, food base is examined allive locations along each <br />of three transecls; each transect is aboul 30 m aparl. The five sampling locations along the <br />transects include the thalweg. <28 m'/s, base flow. lower varial. and upper varial zones. Cobb/e- <br />rime sample collections occur within the deepest accessible zone. as well as the lower and upper <br />varial zones. Population data are collecled for five biotic classes. Associaled dala are also <br />collected. such as water temperature, dissolved oxygen, pH, specilic conductance, substratum <br />type. microhabilat conditions, total P and N, Secchi depth, water velocity, depth. site, and time of <br />day. Shoreline habitats are sampled to detennine (I) invertebrates in emergent vegetation, (2) <br />fine sedimem volume, and (3) tychoplankton. Nearshore habitats are surveyed to obtain (I) <br />temperature profiles wilh reading every 5 cm within shoreline vegetalion and 0.5 m from the <br />shoreline and (2) surface (:S 0.5 m depth) drift samples of coarse- (500 micron mesh) and fine- <br />particulale (0.5 micron mesh) organic matter. <br /> <br />Although the remote-sensing PEP (Berlin et al.. 1998) recommended that airborne <br />multispectral image data be explored for mapping Ihese parameters, most chemical constituems in <br />water and other properties related to chemistry (pH) cannot be detected with airborne sensors. <br />Even though certain elements and compounds do absorb in the visible through TIR wavelength <br />region, their concentrations in water need to exceed I wt % for Iheir delection. When aqueous <br />chemical concentrations reach such high levels, such as in estuaries and lakes. it has been shown <br />that their concentrations can be mapped (Chavez et aI., 1997), but such techniques cannot provide <br />depth-conccntration profiles, which are obtained during GCMRC ill situ monitoring. In addition, <br />an airborne rem ole-sensing approach for aquatic food base parameters would be limited 10 Ihe <br />ckarer~ shallower water areas, wuuld provide only certain parameters (Alberotanza et al.. 1999) <br />such as algae, vegetation flotsum, plankton, organic matlcr, surfacc drift, total dissolvcd solids <br />(specific conductance), and could nol deteclthe biotic species that are monitored by GCMRC. <br />Even though multispeclral sensors exist thai provide wavelength dala appropriate for moniloring <br />some of the food base parameters. oblaining such data through commercial vendors at the high <br />frequency currently obtained by ill situ monitoring would cost so much thai remole-sensing <br />would not be a viable option for present foodbase monitoring. Pat Chavez tested this <br />multispectral sensor by acquiring 7.5-cm image data within Glen Canyon to detennine the ability <br />of the data to map fish food base and nesting habitats. The results oflhis study will be available <br />during the summer 01'2003. If useful results are obtained, a similar sensor could be purchased by <br />GCMRC ($15,000) and flown at relatively low cost to provide daJa for various monitoring <br />requirements. However, orthoreclified image data would be mosh:seful, which requires <br />expensive Global Positioning System (GPS) and IMU instrumentation. Image data could be <br />rectified using an existing com rolled image base, but this georectification process is time <br />consuming and would cosl more than Ihe data collection. <br /> <br />Remote sensing can provide wide-area monitoring for two other aquatic parameters: <br />water surface temperature and substrate type. Mapping water surface temperature is discussed in <br />the following section on warm backwalers: substrate mapping is discussed in a section within the <br />physical resource program in which channel substrate is a primary collection parameter. <br /> <br />3.1.3, Warm Backwaters <br /> <br />One of the objectives of the CRE moniloring is the preservation of the native Humpback <br />Chub. whose population has diminished due to the cold, low-flow waler releases since <br />construction of the Glen Canyon Dam. Chub prefer warm (18-22 oc), turbid. and sheltered water <br /> <br />12 <br />