Difference between revisions of "TCD Learning Page"
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Two different modifications are being suggested as direct piping of cold water to the intake. One proposed solution came from a 2020 technology search by yet2 sponsored by the Bureau of Reclamation focused on new technologies to control water temperature of reservoir release flows. This proposed solution would be a floating pumping platform that could be placed into the forebay to pump water at a fixed or variable water depth directly to the intake of the penstock (Makai Ocean Engineering; Figure 1). Difference variations for this model could range from several pumping stations suppling cold water to the penstocks or only a selective few of penstocks. A second proposed solution would be Trunnion cold water withdrawal. The idea behind this system is that a pipe is hinged and sealed at the intake to bring in cold water (Sherman 2000; Figure 2). For both suggestions, the theory is that enough cold water could be mixed in the penstock to reduce temperatures discharging from the dam. | Two different modifications are being suggested as direct piping of cold water to the intake. One proposed solution came from a 2020 technology search by yet2 sponsored by the Bureau of Reclamation focused on new technologies to control water temperature of reservoir release flows. This proposed solution would be a floating pumping platform that could be placed into the forebay to pump water at a fixed or variable water depth directly to the intake of the penstock (Makai Ocean Engineering; Figure 1). Difference variations for this model could range from several pumping stations suppling cold water to the penstocks or only a selective few of penstocks. A second proposed solution would be Trunnion cold water withdrawal. The idea behind this system is that a pipe is hinged and sealed at the intake to bring in cold water (Sherman 2000; Figure 2). For both suggestions, the theory is that enough cold water could be mixed in the penstock to reduce temperatures discharging from the dam. | ||
| + | [[Image:Trunnion.jpg|thumb|center|400px|Depiction of a trunnion attached to the face of Glen Canyon Dam]] | ||
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=='''Bypass'''== | =='''Bypass'''== | ||
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The SEIS estimated an average hydropower impact from the Cool Mix alternative of $61.73 million (226.29 GWh) over a 45-month period or $15.43 million (56.57 GWh) per year (tables 3-12 and 3-17 in Bureau of Reclamation, 2024). Bypassed water does not produce hydropower and replacement costs are estimated to be ~$1 to $2 million per week (WAPA 2024, personal communication). Observed costs are tracking estimates presented in the SEIS. | The SEIS estimated an average hydropower impact from the Cool Mix alternative of $61.73 million (226.29 GWh) over a 45-month period or $15.43 million (56.57 GWh) per year (tables 3-12 and 3-17 in Bureau of Reclamation, 2024). Bypassed water does not produce hydropower and replacement costs are estimated to be ~$1 to $2 million per week (WAPA 2024, personal communication). Observed costs are tracking estimates presented in the SEIS. | ||
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| + | [[File:SEISbypass.jpg|400px]] | ||
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Revision as of 15:43, 22 October 2025
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Temperature ControlBefore Glen Canyon Dam was constructed, the natural flow cycle of the Colorado River included a seasonal warming trend in the late summer as the water temperature would increase from the near freezing winter temperature to approximately 85 degrees. Once the dam was constructed, the temperature of the water released downstream became relatively steady at between 45-50 degrees as water was drawn year round from the deep, fixed level penstock intakes (used for power production). Near the dam, these cold releases are tolerated by the trout fishery, but as this water moves downstream, it only warms to about 60 degrees which is not warm enough to allow endangered, native, warm water fish, such as the humpback chub, to reproduce in the mainstem of the Colorado River. The U.S. Fish and Wildlife Service (FWS) issued a biological opinion in 1994, that recommended that temperature control modifications to the existing intake structures at the dam, be investigated by the Bureau of Reclamation (Reclamation). Temperature control modifications would allow for water to be drawn from different depths of the reservoir. Instead of only drawing water from the existing intake openings which are fairly deep and cold, the temperature control modifications would allow for water to be drawn from closer to the reservoir surface, which is much warmer. The goal would be to determine the right temperature combination of the cold and warmer water withdrawals to benefit the native endangered fish, while avoiding the possibility of encouraging competitors (non-native, warm-water fish) into the system. [1] |
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