Effects of Unregulated Tributaries on a Regulated Mainstem
Total Page：16
File Type：pdf, Size：1020Kb
Effects of unregulated tributaries on a regulated mainstem Ecogeomorphology 2009, UC Davis, CA Nicholas Buckmaster, Adam Clause, Tyler Hatch, Heather Jackson, Anna Stephenson Table of Contents: List of Figures……………………………………………………..3 Introduction……………………………………………………....4 Tuolumne River System………………………………………....5 Physical Template………………………………………….……9 Climate…………………………………………….……...9 Geomorphology………………………………………….10 Hydrograph……………………………………………....13 Water Quality…………………………………………….16 Biological Systems ……………………………………………...19 Riparian Vegetation……………………………………...20 In-stream Production..………………………………...…23 Consumers………………………………………………..24 Benthic Macroinvertebrates……………………....24 Amphibians……………………………………….30 Fishes……………………………………………...32 Conclusion………………………………………………………..43 Literature Cited……………………………………………………44 2 List of Figures FIGURE 1. General Conceptual Model FIGURE 2. Generalized geologic map of the Tuolumne watershed FIGURE 3. Tuolumne River Water and Power Infrastructure (Null et al. 2009) FIGURE 4. Map of the Tuolumne Watershed FIGURE 5a. Detailed conceptual models of individual tributary interactions FIGURE 5b. Detailed conceptual model of mainstem interactions FIGURE 6. Graph of average daily discharge in the Tuolumne, Clavey and North Fork. FIGURE 7. Temperature of Mainstem and Tributaries taken every ½ hr FIGURE 8. An example of a ‘recruitment box.’ FIGURE 9. Riparian diversity of all species identified FIGURE 10. Invertebrate functional feeding group percentages FIGURE 11. Relative abundances of macroinvertebrates in the middle Tuolumne FIGURE 12 Family-level richness of macroinvertebrates in the middle Tuolumne system FIGURE 13. Percent Ephemeroptera, Plecoptera and Trichoptera in the middle Tuolumne FIGURE 14. Invertebrate drift at Indian Bar. FIGURE 15: Fish species present in the mainstem of the Tuolumne river FIGURE 16. Spawning (blocks) and optimal temperatures (lines) for the fish common to the Tuolumne FIGURE 17. Clavey River average Monthly Temperatures and Flows FIGURE 18. 2008-2009 Hydrograph and Thermograph of the Mainstem (At Lumsden) FIGURE 19 North Fork of the Tuolumne Hydrograph FIGURE 20 Survey Locations on Clavey FIGURE 21. Clavey River fish surveys above and below the falls FIGURE 22. Survey locations on the North Fork FIGURE 23. North Fork dive data above and below the falls List of Tables TABLE 1 Water quality parameters from June 2009 TABLE 2 Dominant plant communities of the middle reaches of the Tuolumne River watershed 3 Introduction River ecosystems are complex, with the physical template defining the biological interactions that occur (Vannote et al. 1980). On a broad scale these biological interactions have been described as a continuum, varying in tandem with physical changes along the length of a river system (Vannote et al. 1980). In the Sierra Nevada of California, anthropogenic forces such as dams and species introductions also strongly shape these systems. Dams can severely modify a river ecosystem, shifting the patterns of physical and biological continuums up or down river of a natural state (Ward and Stanford 1995). Unregulated tributaries can provide important heterogeneity to these regulated rivers, and may ameliorate the influence of upstream impoundments on a mainstem (Ward and Stanford 1995, Stevens et al. 1997, Takao et al. 2008). In an effort to explicitly examine how these physical, biological, and anthropogenic forces interact to shape the ecology and geomorphology of river systems, we developed a conceptual model of the Tuolumne River and two of its major unregulated tributaries. Specifically, we looked at the potential influences of the North Fork Tuolumne River and the Clavey River on the middle reaches of the mainstem of the Tuolumne River (Figure 1). FIGURE 1: Generalized conceptual model of the impact of tributaries on the middle reaches of the Tuolumne River. 4 The Tuolumne River System The Tuolumne River is located on the West slope of the central Sierra Nevada, with headwaters in the famous Yosemite National Park. The Sierras consist of many different rock types, but granite dominates at higher elevations, overlain in areas by tertiary volcanics. In the foothill metamorphic belt, accreted terrains and low grade metamorphics become predominant (Figure 2). Veins of quartz and gold associated with the famous motherload brought miners to foothill reaches in the mid to late 1800s. Mining activity drove the construction of early diversion dams in the Tuolumne foothills in the 1850s. Later, hydraulic mining activities generated a vast amount of gravel in tailing piles, which were often washed into the river. FIGURE 2: Generalized geologic map of the Tuolumne watershed (Mount et al. 2009) As the population of California increased, so did the demand for pure drinking water and electrical power. Eleanor Dam was constructed in 1918, followed by O’Shaughnessy Dam, finished in 1924 to create the hotly debated Hetch Hetchy Reservoir. In 1938 the San Francisco Power and Utility Commission (SFPUC) raised O’Shaughnessy Dam to 430ft, increasing the reservoir capacity to 360,360 acre feet. And finally, in 1955 SFPUC finished Cherry Dam to 5 create a third major impoundment in the central Sierras to supply the San Francisco Bay area with power and water. In conjunction with these three dams, the SFPUC infrastructure also includes six bay area reservoirs, three powerhouses and an array of tunnels and aqueducts. The Turlock and Modesto Irrigation Districts also own and operate aspects of the greater Tuolumne “plumbing system,” including the La Grange and New Don Pedro Dams, to generate power and provide water for people and crops in the fertile central valley of California (Figure 3) (Null et al 2009). Cherry Creek Tuolumne Eleanor Creek River O'SHAUGHNESSY ELEANOR DAM DAM CHERRY DAM Kirkwood Powerhouse Cherry Power Lower Cherry Tunnel Canyon Tunnel Aqueduct Mountain Tunnel Holm Lower Cherry Tuolumne Powerhouse Diversion Dam River Early Intake Cherry Creek Tuolumne Mountain Tunnel River NEW DON PEDRO Priest Reservoir RESERVOIR & POWERHOUSE Foothill Tunnel Moccasin La Grange Dam Reservoir & Powerhouse Modesto Turlock Canal Canal San Joaquin Pipelines 1,2,3 Ag. & Urban Ag. & Urban Demand Demand San Joaquin River LEGEND l s e g n n i n r u p Other Bay T S s Area Cities l Reservoir s a t a s LOCAL p y y r SAN FRANCISCO Powerhouse B C RESERVOIRS River Pipeline Non-storage Reservoir SFPUC Demand Regions Treatment Plant FIGURE 3: Tuolumne River Water and Power Infrastructure (Null et al. 2009) 6 The Tuolumne River is joined by several tributaries below O’Shaughnessy Dam, including Cherry Creek (also regulated by SFPUC), the South and Middle Forks, Clavey River, and the North Fork (Figure 4). The impacts of the latter two tributaries are the focus of the conceptual model described here. Cherry Creek Clavey North River Fork Tuolumne Mainstem Middle & South Forks FIGURE 4: Map of the Tuolumne Watershed, with major subwatersheds shown; red lines represent major dams in the system. The generalized conceptual, shown above in Figure 1, illustrates the basic physical and biological factors as well as their interactions, both within the regulated mainstem and the unregulated tributaries. The large arrows in the center of the model highlight the most important ecogeomorphic subsidies from these unregulated systems that impact the regulated mainstem. Because each of these stream systems have slightly different physical and biological factors, Figure 5 shows more detailed models of the interactions within each tributary system and the mainstem. By creating these higher resolution models, we were able to more clearly demonstrate the differences between the impacts of each tributary. While each detailed model includes the same generalized factors and influences, the pattern and magnitude of those interactions varies across the systems. It is also important to note that this model is in no way a complete representation of the riverine system – it has been refined to emphasize the factors deemed most important with respect to the effects of unregulated tributaries on the regulated mainstem. 7 FIGURE 5a: Detailed conceptual models of individual tributary interactions 8 FIGURE 5b: Detailed conceptual model of mainstem interactions Physical Template The primary physical drivers in this system include climate, geomorphology of the region, hydrograph of each river, and water quality parameters throughout the system. These four physical factors form a template on which the biotic interactions take place. They interact with one another, and can also be influenced by biotic feedback loops. Each one of these factors, their interactions with other physical drivers, and their role in the ecosystem as a whole are discussed here in more detail. Climate The west slope of the central Sierra Nevada experiences a Mediterranean climate, with cool wet winters and hot dry summers. Because this mountain range is relatively tall and located near the edge of the continental plate, water that evaporates from the ocean moves inland until it reaches the Sierras where the air is forced up and drops its moisture. The higher reaches of the watershed receive this precipitation as snow, while the lower reaches receive it as winter rains. Variability in precipitation type and resulting flow events causes many of the differences that we see in the hydrographs and temperatures of Sierra streams. Air temperature is also a 9 driving force determining the water temperature of these aquatic systems. As the river drops