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<br />APPENDIX C <br /> <br />GCMRC Lake Powell Water Quality Monitoring Program <br /> <br />The current Lake Powell Water Quality Monitoring Program is linked closely with other water <br />quality monitoring programs below Glen Canyon Dam, which address other downstream <br />management objectives. The Lake Powell program consists of monthly surveys of the forebay <br />above Glen Canyon Dam and quarterly surveys ofthe entire reservoir. The objective of the <br />program is to characterize the chemical and physical parameters of the water in Lake Powell to <br />determine the effects of Glen Canyon Dam operations and separate these effects from other <br />natural processes affecting reservoir water quality. This program is linked to a long-term record <br />of similar measurements collected by the Bureau of Reclamation and Glen Canyon Environmental <br />Studies since 1965, which describes the entire history of Lake Powell since its impoundment by <br />Glen Canyon Dam. <br /> <br />Pending formal approval by the Adaptive Management Work Group, this program represents an <br />ongoing water quality monitoring effort by GCMRC that would remain in place throughout the <br />five-year period of this work plan. <br /> <br />Monitoring activities are designed to meet the stated information needs of Management <br />Objective I for Lake Powell Water Quality: <br /> <br />MO 1: Lake Powell Water Oualitv Prevent impacts that adversely affect the water quality <br />(physical, chemical, biological) of Lake Powell due to dam operations and ensure that fully <br />informed AMWG decisions are possible both now and in the future. <br /> <br />Field activities include collecting a profile of measurements throughout the water column at each <br />station for temperature, specific conductance (an indirect measure of salinity), pH, dissolved <br />oxygen, turbidity, and oxidation-reduction potential. This profile describes the degree of <br />stratification, or mixing, and the range of temperature, salinity, and dissolved oxygen <br />concentrations at a particular station. This information is used to describe the behavior and fate of <br />inflow currents, advective and convective mixing processes, and the effect of Glen Canyon Dam <br />withdrawal currents under different operational scenarios. It is also used to characterize the <br />overall quality of the reservoir as well as that of the major strata within the reservoir. For <br />example, monitoring of dissolved oxygen levels in the deepest stratum of the reservoir, or <br />hypolimnion, can be used to predict when significant levels of hydrogen sulfide could occur. <br /> <br />In addition to the profile of physical and chemical characteristics, several samples may be <br />collected at a station for further chemical analysis. Analysis of major cation and anion <br />concentration is performed to quantify the individual components of salinity and to identify the <br />origin of a parcel of water to further understand reservoir hydrodynamics. Analysis of nutrient <br />compounds of phosphorus and nitrogen is also performed to determine the level of primary <br />productivity that the reservoir can support and describe nutrient levels in reservoir releases or <br />zones of potential release. <br /> <br />Quarterly lake-wide surveys include the major tributary arms of the Colorado, San Juan, and <br />Escalante Rivers. Occasional sampling is done in mid-Navajo Canyon because of its potential <br />for frequent hypolimnetic hypoxia Other work on Lake Powell side channels and embayments <br />has not been part of past programs but could be included in future work. An assessment of the <br />potential effects of dam operations to the water quality of side channels and embayments should <br />be conducted before establishing a long-term monitoring program for side channels and <br />embayments. A study by the USGS for this work has been proposed by the GCNRA with external <br />funding. <br />