The State of Natural and Cultural Resources in the Colorado River Ecosystem:
JUNE 30, 1999 DRAFT REPORT
Grand Canyon Monitoring and Research Center
Flagstaff, AZ 86001
Updated: 30 June 1999
Table of Contents
- Executive Summary
- Introduction and Administration
- Physical Resources and Processes: Climate, Hydrology, Sediment
- Water Quality: Lake Powell and the Colorado River Downstream
- Aquatic Biological Resources: Foodbase, Habitat, Native Fish, Non-native Fish
- Terrestrial Biological Resources: Vegetation, Habitat, Wildlife
- Endangered Species and Species of Concern
- Cultural Resources: Archeological Sites; TCP's; Ethonobiology; Havasupai, Hopi, Hualapai, Navajo, Southern Paiute and Zuni Tribes
- Socio-economic Resources: River Running, Angling, Hydropower Production
- Acknowledgements
- Bibliography
- Top of Page
Water Quality
Glen Canyon Dam, constructed and operated by the Bureau of Reclamation, impounds the Colorado River to form Lake Powell, a 32.3 km3 (26.2 MAF) reservoir with a surface area of 65,069 ha (160,784 ac) extending 290 km (180 miles) up the Colorado River at its full pool elevation of 1128 m (3700 ft) above mean sea level. Shoreline length has been estimated at 3,057 km (1900 mi.). The drainage area above Lake Powell is 279,000 km2 (108,000 mi2) (Stanford and Ward, 1991). Lake Powell is located on the border of Utah and Arizona within Glen Canyon National Recreation Area . Lake Powell began filling in 1963 and reached a full pool elevation in June of 1980.
Fig. WQ1.1: Lake Powell geographic setting and major tributaries. Graph courtesy of Bill Vernieu, GCMRC Lake Powell Program. Updated 1 June, 1999.
Fig. WQ1.2: Filling history of Lake Powell (upper graph), and inflow and outflow history (lower graph), 1965 to 1998. Graph courtesy of S. Hueftle, GCMRC Lake Powell Program. Updated 1 June, 1999.
Fig. WQ1.3: Map of Lake Powell Reservoir and Glen Canyon Dam tailwaters sampling stations. Graph courtesy of S. Hueftle, GCMRC Lake Powell Program. Updated 1 June, 1999.
Fig. WQ1.4: Temperature, conductivity (a reflection of salinity levels), and dissolved oxygen in the Forebay of Glen Canyon Dam, from December 1964 to August 1998. Penstock and river outlet works elevations are indicated at 1057 m and 1028 m. Water Years 1964-1998. Graph courtesy of S. Hueftle, GCMRC Lake Powell Program. Updated 1 June, 1999.
Fig. WQ1.5: Productivity and transparency in Lake Powell is related to the turbidity of inflow. The upper graph shows chlorophyll a concentration and Secchi depth (m) over distance from Glen Canyon Dam in Water Years 1991-1999. Graph courtesy of S. Hueftle, GCMRC Lake Powell Program. Updated 1 June 8, 1999.
Fig. WQ1.6: Temperature (oC), specific conductance (uS/cm), turbidity (NTU), dissolved oxygen (mg/L), pH, DO saturation (%) and water density (kg/m3) in the main channel of Lake Powell. Sample depths represented by *. Penstock elevation is 1057 m, river outlet elevation is 1028 m, and reservoir surface elevation is 1125.6 m (3693') above sea level. Graph courtesy of S. Hueftle, GCMRC Lake Powell Program. Updated 1 June 8, 1999.
Continuous Tailwater Monitoring
The objective of the tailwater monitoring program is to characterize the quality of water released from Glen Canyon Dam and measure changes occurring in the tailwater below Glen Canyon Dam. These characteristics are the result of long-term climatological and hydrological processes in the Colorado River basin, advective and convective mixing processes within Lake Powell, and the operation of Glen Canyon Dam. The water quality of Glen Canyon Dam releases forms a baseline from which changes occur downstream and directly affect the aquatic ecosystem. A ten-year period of record exists for these data.
Continuous monitoring of tailwater quality is performed below Glen Canyon Dam and at Lees Ferry. Monitors are maintained inside Glen Canyon Dam, in the tailwater immediately below the dam, and at Lees Ferry, 25 km (15.5 mi.) downstream of the dam. Measurements of temperature, specific conductance, dissolved oxygen, and pH are currently made at 20-minute intervals and logged within the monitor. Monitors are downloaded, serviced, and recalibrated on a monthly basis. On a monthly basis, chemical sampling for nutrients and major ions, and biological sampling for chlorophyll, phytoplankton, and zooplankton is performed inside Glen Canyon Dam and at Lees Ferry.
Grand Canyon Thermal Monitoring
The purpose of this monitoring is to describe thermal conditions in the Colorado River and its tributaries and evaluate warming patterns that vary with geomorphic reach and release patterns from Glen Canyon Dam. Thermal conditions are of significant importance to fish, aquatic invertebrates, aquatic vegetation, and other components of the ecosystem. Evaluation of warming patterns is needed to describe baseline levels and the potential for instream warming of dam releases.
Thermal monitoring is performed at several sites on the Colorado River in Grand Canyon and at major tributary mouths (Error! Reference source not found.). Submersible monitors are placed unobtrusively at 8 main-channel locations on the Colorado River spaced approximately 50 km apart, and 9 tributary sites in Grand Canyon. An isolated group of warm springs near Fence Fault (RM 30) that have been identified as potential spawning areas is also monitored. Instruments are downloaded and serviced on a quarterly basis, in conjunction with other scheduled research trips. Monitoring of parameters other than temperature, such as dissolved oxygen, specific conductance, and turbidity is not currently performed.
Table 1. Grand Canyon thermal monitoring locations
Mainstem Monitoring Sites |
|---|
Colorado R. above Little Colorado R. |
Colorado R. near Grand Canyon |
Colorado R. at RM 127 |
Colorado R. above National Canyon |
Colorado R. at RM194 |
Colorado R. above Diamond Ck. |
Colorado R. at RM230 |
Colorado R. above Spencer Canyon |
Tributary Monitoring Sites |
|---|
Paria R. above Lees Ferry |
Nankoweap Creek |
Little Colorado R. above Mouth |
Bright Angel Creek |
Shinumo Creek |
Tapeats Creek |
Kanab Creek |
Havasu Creek |
Spencer Creek |
Monitored Parameters
Common physical and chemical parameters of water quality are routinely collected during the measurement of a reservoir profile, continuously in the tailwater below Glen Canyon Dam, and in conjunction with the collection of all chemical samples. These measurements are taken using a multi-probe instrument, such as a Hydrolab Surveyor3/H20 or Hydrolab Recorder. These measurements include temperature (degrees C), specific conductance (m S), pH, dissolved oxygen (mg/L), and turbidity (NTU).
Chemical samples for major ion analysis are collected to characterize the overall chemical makeup of the water being sampled. Laboratory analysis includes specific conductance, pH, total dissolved solids and total suspended solids, which describe the physical aspects of the water. Chemical concentrations are also determined for the major cations and anions (sodium, calcium, magnesium, potassium, sulfate, chloride, carbonate, and bicarbonate). Alkalinity determinations are also performed in the field concurrently with the collection of a chemical sample.
Samples are also collected to determine the concentration of nutrient compounds (total phosphorus, soluble reactive phosphorus, dissolved ammonia nitrogen, total Kjeldahl nitrogen, and dissolved nitrate-nitrite nitrogen). These nutrient compounds support primary productivity in the reservoir and downstream aquatic ecosystem. Phosphorus levels in the reservoir and tailwater are low; most concentrations are below detectable limits by currently used analytical procedures. Further exploration of techniques to achieve lower detection levels is being pursued, depending on the need for this resolution (Error! Reference source not found.).
Biological
The objective of the biological program is to characterize, both in the lake and within the tailwaters, long-term, seasonal, and spatial trends in abundance, community structure, and primary and secondary productivity. This is a long-term program focusing on broader trends. Quantification of shorter-term effects must be addressed by separate research programs. Specific goals of the program include the following:
Quantify primary productivity in the reservoir and tailwaters. We can determine trophic status with long-term, seasonal and reach trends in chlorophyll and phytoplankton. Using statistical correlation, limiting and determinative factors of the food-base (physical, chemical, biotic) can be determined.
Use biological indicators to evaluate water quality trends. Zooplankton and especially phytoplankton have been used to indicate trophic status, presence of pollutants and other chemical concentrations relevant to plankton growth. Lake Powell can both benefit from previous research (Hutchinson 1967) as well as be instrumental in developing an index for arid reservoirs.
Quantify secondary productivity of the reservoir and tailwaters. Zooplankton are integral both as predators upon themselves and algae and as prey for fisheries, particularly during the periodic crash of reservoir forage fish. The ability to track fisheries lies in part on tracking zooplankton dynamics, both spatially and temporarily.
Frequency and Timing of Sampling
Currently, lake wide surveys are conducted on a quarterly basis to correspond to significant seasonal processes occurring in the reservoir. These surveys are timed to coincide with the timing of these processes, rather than being based on strict calendar intervals.