Pre-And Post-Operational Effects of a Temperature Control Device On
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Pre-and Post-Operational Effects of a Temperature Control Device on Physical, Chemical, and Biological Attributes of Shasta Lake, California: Phase 1, Spring 1995 through Fall 1997 Open File Report 98-251 U.S. Department of the Interior U.S. Geological Survey Prepared in Cooperation with uses the U.S. Bureau of Reclamation science for a changing world U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY Pre- and Post-Operational Effects of a Temperature Control Device on Physical, Chemical, and Biological Attributes of Shasta Lake, California: Phase 1, Spring 1995 through Fall 1997 by iDavine M. Lieberman, U.S. Geological Survey ^Michael J. Horn, U.S. Bureau of Reclamation Open-File Report 98-251 Prepared in cooperation with the U.S. Bureau of Reclamation This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards (or with the North American Stratigraphic Code). Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. !p.O. Box 25007 (D-8220), Denver, Colorado 80225 2P.O. Box 25007 (D-8220), Denver, Colorado 80225 Abstract: A temperature control device (TCD) was installed on Shasta Dam, California which began to operate in spring 1997 for the purpose of cooling downstream river temperatures to aid recovery of chinook salmon in the Sacramento River. This study began in spring 1995 to investigate pre- and post-TCD effects on the limnology of Shasta reservoir. The maximum pool of cold water observed was a function of runoff, as bypass operations resulted in an almost complete yearly depletion of the cold water pool. Maximal surface temperatures and the strongest thermocline occurred during the month of August. Winter mixing was confined to the upper 50 m of the water column. Metalimnetic and hypolimnetic oxygen minima occur yearly in summer. Degree of oxygen depletion was related to distance from river inflow, while rate of movement of hypolimnetic minima downstream was dependent on deep level withdrawals from the dam. Preliminary observations show the TCD affected metalimnetic temperature gradients, movement of riverine inflows through the reservoir, and strength of DO minima. Secchi transparency was highest in the main lake and the Sacramento Arm and, lowest in the McCloud and Pit Arm, and was indicative of differences in productivity between the arms. Patterns of nutrient cycling within the reservoir differed between epilimnetic and hypolimnetic waters. Hypolimnetic nutrient maxima were related to high flow events, while epilimnetic waters responded more to in reservoir events, such as stratification and changes in productivity. During spring and summer months, TCD releases of surface to mid-level water caused the hypolimnion to act as a nutrient sink. Composite chl a concentrations (0 to 5 m) ranged from BDL to 30 ug/L. Mean composite chl a concentrations for the period 1995 to 1997 were: main lake (2 ug/L), Sacramento River Arm (2 ug/L), McCloud River Arm (2.7 ug/L), Pit River Arm (5.2 ug/L), and the Pit-McCloud confluence (3 ug/L). Diatoms, Melosira islandica and Melosira varians dominated the algal population. Greatest algal biovolume occurred in the Pit River Arm. Biovolume increased significantly from 1995 to 1997. Seasonal algal peaks occured in spring, and again on early fall coinciding with development and breakdown of thermal stratification. Greatest mean zooplankton biomass occurred in the Sacramento River Arm and was lowest in the McCloud River Arm. Cladocerans were the dominant zooplankton at the main lake station and Sacramento River Arm. Cladoceran and copepod biomass was equally distributed at other stations. In Shasta and Keswick tailwaters, <25 um POM composed the greatest proportion of total POM contributing 90% to the total. Total POM averaged 0.8 g/m3 and 0.9 g/m3 in Shasta and Keswick tailwaters, respectively. In 1997, there was a significant increase in zooplankton biomass in the drift that was attributed to TCD operations. Copepods, cladocerans, and even rotifers increased. Cladocerans composed less and copepods made up more of the total zooplankton biomass. Releases of surface water during the most productive time of year resulted in entrainment of zooplankton and a significant downstream increase in biomass. As with zooplankton biomass, phytoplankton biovolume increased significantly (by a factor of 10) in 1997 over 1995 and 1996. Table of Contents: Page List of Figures: ........................................................... iii List of Tables: ............................................................ vii I. Introduction: ........................................................... 1 II. Methods and Materials: ................................................... 2 1. Reservoir Sampling: .................................................. 2 2. River Sampling: ..................................................... 3 HI. RESULTS AND DISCUSSION ............................................ 4 1. Physical Limnology: .................................................. 4 A. General Trends: ............................................... 4 B. Interflows: ................................................... 7 2. Secchi Transparency: ................................................. 8 3. Nutrient Dynamics: .................................................. 9 4. Primary and Secondary Productivity: .................................... 12 A. Chlorophyll: ................................................. 12 B. Phytoplankton: ............................................... 13 C. Zooplankton: ................................................ 15 5. River Studies: Downstream Drift In Shasta and Keswick Tailwaters Below Shasta Lake: ........................................................ 17 A. Temperatures: ............................................... 17 B. Particulate Organic Matter (POM): ............................... 18 C. Zooplankton: ................................................ 20 D. Phytoplankton and Chlorophyll: .................................. 22 IV. Post TCD Results: 22 V. Management Implications: ............................................... 24 VII. Acknowledgments: ..................................................... 25 VI. Literature Cited: 25 List of Figures: Page Figure 1. Seasonal patterns of inflow (cfs), discharge (cfs) and reservoir elevation (Feet above msl) for Shasta Lake, CA, 1995-1997 ..................................... 34 Figure 2. Map of limnological sampling stations in Shasta Lake. Main lake (S6), Sacramento River Arm (S7, S15), McCloud River Arm (S8 and S14), Pit River Arm (S9, S12, S13), Squaw Creek Arm (SI 1), and Pit-McCloud Confluence (S10). River stations are located in Shasta tailwaters (SO) and Keswick tailwaters (Kl). ......................... 35 Figure 3 a-e. Time series isopleths of dissolved oxygen (mg/L), temperature (°C) and specific conductance (yuS/cm) for Shasta Lake sampling stations, a. S6; b. S7; c. S8; d. S9; e. S10 .................................................................. 36 Figure 4 a-e. Time series isopleths of Relative Thermal Resistance to Mixing (RTRM) coefficients for Shasta Lake sampling stations a. S6; b. S10; c. S9; d. S8; e. S7. .............. 41 Figure 5 a-t. Monthly isopleth description of temperature (°C ), dissolved oxygen (percent saturation), pH, and specific conductance (/^S/cm) for the Pit River arm for 1996 and 1997. a. February 1996; b. March 1996; c. April 1996; d. May 1996; e. June 1996; f. July 1996; g. August 1996; h. September 1996; i. October 1996; j. January 1997; k. February 1997; 1. March 1997; m. April 1997; n. May 1997; o. June 1997; p. July 1997; q. August 1997; r. September 1997; s. October 1997; t. November 1997. ............ 44 Figure 6 a-t. Monthly isopleth description of temperature (°C ), dissolved oxygen (percent saturation), pH, and specific conductance (yuS/cm) for the Sacramento River arm for 1996 and 1997. a. February 1996; b. March 1996; c. April 1996; d. May 1996; e. June 1996; f. July 1996; g. August 1996; h. September 1996; i. October 1996; j. January 1997; k. February 1997; 1. March 1997; m. April 1997; n. May 1997; o. June 1997; p. July 1997; q. August 1997; r. September 1997; s. October 1997; t. November 1997. ............ 64 Figure 7. Comparison of chl a concentrations (ug/L) from surface to 30m between the main lake (S6), Sacramento River Arm (S7), McCloud River Arm (S8), Pit River Arm (S9), and the Pit-McCloud Confluence (S10) from August 1995 thru October 1997. ............. 84 Figure 8. Seasonal cycle of inflow temperatures for the Sacramento river at Delta, station (DLT), and for the Pit river at station (PMN). ..................................... 85 Figure 9. Isopleth description of 1997 flood inflow patterns using turbidity as an indicator for October 1996, January 1997, February 1997, March 1997. ...................... 86 Figure 10 a-b. Secchi depth transparencies (m) for Shasta Lake from May 1995 thru November 1997. a. main lake (S6) and forebay (SI6); b. Sacramento River Arm (S7) and upper Sacramento River Arm (SI5). ........................................... 87 in Figure 11 a-b. Secchi depth transparencies (m) for Shasta Lake from May 1995 thru November 1997. a. McCloud River Arm (S8) and upper McCloud River Arm (S14); b. Pit River Arm (S9), upper Pit (S12), upper upper Pit (S13), and Squaw Creek (SI 1). ......... 88 Figure 12. Seasonal patterns of epilimnetic and hypolimnetic nitrate-nitrogen for Shasta Lake sampling stations from 1995-1997. .......................................