Integrated Quality of Water Program Upstream Component
Lake Powell Owing to prolonged drought conditions in the Colorado River Basin, Lake Powell has been drawn down to its lowest surface elevation since 1973. At an elevation of 3603.73 feet above mean sea level the reservoir was at about 50% of its total capacity. Also associated with the reservoir drawdown was an increased release temperatures through the summer of 2003 as the warmer surface layers of the reservoir were brought closer to the penstock withdrawal elevation. Release temperatures reached 12 deg C in September 2003, the warmest temperatures observed for that time of year since 1973. Dissolved oxygen levels were at very low levels throughout the reservoir in September 2003 owing to resuspension of deltaic sediments. These conditions were reported at the October 2003 Colorado Ecosystem Science Symposium in Tucson, Arizona.
The GCMRC long-term monitoring program for Lake Powell continues, with monthly forebay and quarterly reservoir surveys. These surveys consist of the collection of a profile of physical and chemical parameters through the water column, sampling at discrete depths for major ion and nutrient concentrations, and biological sampling for chlorophyll, phytoplankton, and zooplankton at selected stations in the reservoir forebay, main channel, and major tributary arms of the reservoir. Continuous water quality monitors are in place for thermal monitoring in the reservoir forebay and for a broader suite of parameters in the reservoir tailwater. Sampling is conducted from the GCMRC 32 foot Uniflite limnology vessel, with assistance from the National Park Service and Bureau of Reclamation Upper Colorado Regional Office.
The database (WQDB) for Lake Powell and Grand Canyon water quality is nearing completion and being integrated with GCMRC’s Oracle database management system. These data comprise all Bureau of Reclamation (BOR), GCES, and GCMRC water quality monitoring information collected since 1965, representing the entire water quality history of Lake Powell. The consolidation and management of these data has made it possible to evaluate the information collected from this long-term effort and make changes to achieve a more efficient program. Revisions in major ion and nutrient sampling, plankton sampling, and inflow monitoring are expected during FY 2004.
These data are available for input to the CEQUAL-W2 reservoir model in cooperation with the USBR. Initial model development and calibration is being provided by Amy Cutler of the BOR. Eventually there is the prospect that simulation modeling may replace some of the extensive field sampling effort on the reservoir. An annual report of 2003 monitoring results is in development.
GCMRC receives funding for the Lake Powell Water Quality Monitoring Program from Bureau of Reclamation Operation and Maintenance funds, based on an agreement with the Technical Work Group. Adaptive Management Program funds are not used directly for Lake Powell monitoring. The Bureau provides additional support for model development and technical field assistance. In 2003, Reclamation agreed to provide laboratory analytical services through a service agreement, eliminating the need for GCMRC to contract directly for these services and reducing its direct funding to GCMRC. GCMRC has further reduced salary requirements for Lake Powell as the downstream water quality program has developed.