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<br />. <br /> <br />tl <br />':1 <br /> <br />~ <br /> <br />Downstream Thermal Monitoring <br /> <br />" <br />x <br /> <br />.: <br /> <br />The purpose of this monitoring component is to describe downstream thennal conditions <br />in the Colorado River and its tributaries and evaluate warming patterns that vary with <br />geomorphic reach and release patterns from Glen Canyon Dam. Thennal conditions are <br />of significant importance to fish, aquatic invertebrates, aquatic vegetation, and other <br />components of the ecosystem. Evaluation of warming patterns is needed to describe <br />baseline levels, the potential for instream warming of dam releases, and provide a basis <br />on which to evaluate the operation of a temperature control device on Glen Canyon Dam. <br /> <br />Thennal monitoring is perfonned at several sites on the Colorado River in Grand Canyon <br />and at major tributary mouths. Submersible monitors are placed unobtrusively at ten <br />main-channel locations on the Colorado River spaced approximately 50 km apart, and ten <br />tributary sites in Grand Canyon (Table 2), Instruments are downloaded and serviced on a <br />quarterly basis, in oonjunction with other scheduled research trips, <br /> <br />Monitoring of parameters other than temperature, takes place at USGS gaging stations in <br />Grand Canyon, GCMRC directly supports data collection efforts at the Colorado River at <br />Lees Ferry, Colorado River above the Little Colorado River and at the Colorado River <br />near Grand Canyon gages as part of the Integrated Water Quality Program, These gages <br />collect temperature, specific conductance and turbidity data. The Lees Ferry Gage and <br />Diamond Creek Gage are also national water quality monitoring sites (NASQAN). These <br />sites collect periodic dissolved organic camon, dissolved oxygen, bacteria counts, <br />nitrogen, and phosphorous data. While these latter efforts are not supported by the <br />IWQP, these data are available to downstream researchers. Sampling for these latter <br />constituents occurs six times per year, rather then on a continuous basis. <br /> <br />., <br />r <br />.~ <br /> <br />:~ <br /> <br />Methods <br /> <br />0'. <br /> <br />Measurements are currently being made with Onset Stowaway XTI32 -{)5+370 C <br />temperature sensors housed in submersible cases with an external thermistor lead <br />attached to the case, This submersible case is then deployed inside a short length of <br />3 1/2" steel pipe and connected withplastic-coated galvanized cable to a stable object <br />near the river's shore. Deployments are made so the unit is fully submerged during the <br />range of expected flows but not resting on the riverbed where it can become buried in <br />sediment. Monitors are downloaded on a quarterly basis. <br /> <br />1"'. <br />L1: <br />f'. <br />) <br /> <br />" <br /> <br />" <br /> <br />''<1 <br /> <br />..;,.~ <br /> <br />10/25/00 <br /> <br />DRAFT <br /> <br />7 <br />