Tuesday, November 8, 2011
Stakeholder meeting materials
Thanks to all who attended our recent stakeholder meeting in Moccasin.
Meeting materials from the November 4, 2011 stakeholder meeting are now
available for viewing and download here. Our next meeting is tentatively scheduled for April 13, 2012.
Friday, October 28, 2011
Natural resources symposium
The Sacramento-Shasta Chapter of the Wildlife Society will be hosting their Natural Resources Symposium on November 2, 2011. The symposium will feature talks on climate change, birds and mammals, mitigation and restoration, vernal pools, and regulated flow effects.
The regulated flow effects session will feature topics relevant to our work on the Tuolumne, including an overview of UTREP, a talk by UTREP collaborator Sarah Kupferberg on regulated flows and frogs, and a presentation by UC Davis scientist Sarah Yarnell on suitable snowmelt recession rates below dams.
Registration info can be found on the Sacramento-Shasta Chapter's website.
View or download the agenda here.
The regulated flow effects session will feature topics relevant to our work on the Tuolumne, including an overview of UTREP, a talk by UTREP collaborator Sarah Kupferberg on regulated flows and frogs, and a presentation by UC Davis scientist Sarah Yarnell on suitable snowmelt recession rates below dams.
Registration info can be found on the Sacramento-Shasta Chapter's website.
View or download the agenda here.
Friday, October 21, 2011
Fall stakeholder meeting
The next meeting of the Upper Tuolumne River Stakeholder Group is set
for November 4, 2011 from 11am - 3pm at the Moccasin Administration Building
(map). View or download the agenda here.
Water Year 2011 turned out to be the second wettest year on record for the Upper Tuolumne, providing ample spill volumes for testing flow thresholds and snowmelt management techniques at O'Shaughnessy Dam. At the stakeholder meeting, Yosemite National Park will update the group on Tuolumne Wild & Scenic planning and Looking Downstream, we'll hear about new SFPUC collaborations to improve snowmelt forecasting, get updated on O'Shaughnessy Dam flow recommendations, and learn about efforts by UC Davis researchers to study the "lower" Upper Tuolumne River.
If you plan to attend the Stakeholder Group meeting, please email Bill Sears at wsears@sfwater.org.
Water Year 2011 turned out to be the second wettest year on record for the Upper Tuolumne, providing ample spill volumes for testing flow thresholds and snowmelt management techniques at O'Shaughnessy Dam. At the stakeholder meeting, Yosemite National Park will update the group on Tuolumne Wild & Scenic planning and Looking Downstream, we'll hear about new SFPUC collaborations to improve snowmelt forecasting, get updated on O'Shaughnessy Dam flow recommendations, and learn about efforts by UC Davis researchers to study the "lower" Upper Tuolumne River.
If you plan to attend the Stakeholder Group meeting, please email Bill Sears at wsears@sfwater.org.
Tuesday, September 27, 2011
2011 Yosemite Hydroclimate Meeting
View or download the agenda here.
Thursday, August 11, 2011
River flows and rafting update
The latest update from Adam Mazurkiewicz at Hetch Hetchy Water and Power...
We are seeing continued recession of flows all across the Sierra. What a runoff year! I think the last few weeks have offered a great flow range for boating on the mainstem, but a late start for the Cherry Creek Run. That is just the hand Mother Nature has dealt us. As I mentioned in last week’s update, starting 8/10 expect typical releases into Cherry Creek. So for the remainder of the season we will be on the “normal” boating schedule, with HHWP release totaling ~1100 cfs for 4 hours and arriving at Lumsden (Meral’s Pool) around 9am (see Dreamflows for full schedule). Given it has been such a wet and cool year the additional accretions may make the usual flows slightly higher.
In GENERAL following the “rafting hours" there may be continued elevated flows, ~750-850 cfs from the HHWP project. Flows in the night and early morning (from HHWP) may be in the 550-650 cfs. I know there are camps that “dry” out following the boating release, so take this into consideration. The timing will vary depending on where you are along the river. On Sundays, flows will be in the lower range in the “off-rafting” hours. These flows may vary, but I wanted to share the “general” schedule with folks, so no one is surprised.
I do want to remind folks that August 17th and 30th are scheduled maintenance days and HHWP is utilizing the time. There have been inquiries regarding the releases following Labor Day. There will not be boating flows possible after Labor Day due to maintenance work.
If there are any changes/updates/issues I will send out a notice. Enjoy the last few weeks of the boating year!
We are seeing continued recession of flows all across the Sierra. What a runoff year! I think the last few weeks have offered a great flow range for boating on the mainstem, but a late start for the Cherry Creek Run. That is just the hand Mother Nature has dealt us. As I mentioned in last week’s update, starting 8/10 expect typical releases into Cherry Creek. So for the remainder of the season we will be on the “normal” boating schedule, with HHWP release totaling ~1100 cfs for 4 hours and arriving at Lumsden (Meral’s Pool) around 9am (see Dreamflows for full schedule). Given it has been such a wet and cool year the additional accretions may make the usual flows slightly higher.
In GENERAL following the “rafting hours" there may be continued elevated flows, ~750-850 cfs from the HHWP project. Flows in the night and early morning (from HHWP) may be in the 550-650 cfs. I know there are camps that “dry” out following the boating release, so take this into consideration. The timing will vary depending on where you are along the river. On Sundays, flows will be in the lower range in the “off-rafting” hours. These flows may vary, but I wanted to share the “general” schedule with folks, so no one is surprised.
I do want to remind folks that August 17th and 30th are scheduled maintenance days and HHWP is utilizing the time. There have been inquiries regarding the releases following Labor Day. There will not be boating flows possible after Labor Day due to maintenance work.
If there are any changes/updates/issues I will send out a notice. Enjoy the last few weeks of the boating year!
Tuesday, August 2, 2011
Upper Tuolumne River flow update
Here's the latest update for Upper Tuolumne River flow conditions and Hetch Hetchy Project releases from Adam Mazurkiewicz, hydrologist for Hetch Hetchy Water and Power (HHWP).
Recently, thunderstorms have brought flows up quickly on the mainstem of the Tuolumne as measured by the Tuolumne at Grand Canyon gage. These thunderstorms have been over the Tuolumne and Merced watersheds, while Cherry and Eleanor have remained storm free. The additional precipitation and stunning longevity of the snowpack have caused some changes in the forecast and operations.
Starting August 1st, there will be additional water below Kirkwood Powerhouse (KPH), while releases below Holm Powerhouse (HPH) will be reduced to ~400-500 cfs throughout the day. Expect 700 cfs additional water below KPH. Given the spill occurring at Hetch Hetchy the flow at Lumsden on August 1st will be 2400 - 2600 cfs.
Tuesday August 2nd: Flows will be similar to Monday and the 2400-2600 cfs range should hold, but may fall to the lower end as spill from Hetch Hetchy may recede.
Wednesday August 3rd: Flows will be dependent on the inflow recession to Hetch Hetchy and any thunderstorms which may occur. Snowmelt should continue to be receding, but there will be flows for boating in a range of 2100 – 2600 cfs.
Thursday August 4th: Flows to allow for Cherry Creek run boating are right near the threshold given the uncertainty of spill at Hetch Hetchy. This estimate cannot be guaranteed but is based on the best current forecast and operation information so please check current flow conditions using the USGS gage stations or the Dreamflows estimate (these notices are also posted on the Dreamflows website). There will be boating flows at Lumsden between 2000 and 2500 cfs.
For the Cherry Creek run specifically, flows at the confluence are a total of what is below Hetch Hetchy, Eleanor and Cherry, HPH and additional water from KPH. Cherry and Eleanor are at minimum seasonal release (15 and 20 cfs) and are scheduled to remain at those rates unless thunderstorms generate significant inflows. Both these reservoirs are near their capacities. KPH is scheduled to contribute ~700 cfs. Spill from Hetch Hetchy will continue to follow natural recession as part of a UTREP flow experiment. It is expected spills from Hetch Hetchy will be between 800 and 1000 cfs on Thursday (total = approx. 1550-1750 cfs). Release from HPH between the hours of 0100 and 0900 hrs will be ~150 cfs, at 0900 to 1200 hrs releases will go up to ~250 cfs, at 1200 hrs releases will go up to 350 cfs. That brings the early day flow estimate to be between 1800 and 2000 cfs (which includes an estimate of accretions) going up to 1900 to 2100 cfs at 0900 hrs. Spill at Hetch Hetchy will control the variation from that estimate.
These estimates are subject to change due to mountain thunderstorms or unscheduled shutdowns. If you're out on the river, check gages for latest flow information.
Recently, thunderstorms have brought flows up quickly on the mainstem of the Tuolumne as measured by the Tuolumne at Grand Canyon gage. These thunderstorms have been over the Tuolumne and Merced watersheds, while Cherry and Eleanor have remained storm free. The additional precipitation and stunning longevity of the snowpack have caused some changes in the forecast and operations.
Starting August 1st, there will be additional water below Kirkwood Powerhouse (KPH), while releases below Holm Powerhouse (HPH) will be reduced to ~400-500 cfs throughout the day. Expect 700 cfs additional water below KPH. Given the spill occurring at Hetch Hetchy the flow at Lumsden on August 1st will be 2400 - 2600 cfs.
Tuesday August 2nd: Flows will be similar to Monday and the 2400-2600 cfs range should hold, but may fall to the lower end as spill from Hetch Hetchy may recede.
Wednesday August 3rd: Flows will be dependent on the inflow recession to Hetch Hetchy and any thunderstorms which may occur. Snowmelt should continue to be receding, but there will be flows for boating in a range of 2100 – 2600 cfs.
Thursday August 4th: Flows to allow for Cherry Creek run boating are right near the threshold given the uncertainty of spill at Hetch Hetchy. This estimate cannot be guaranteed but is based on the best current forecast and operation information so please check current flow conditions using the USGS gage stations or the Dreamflows estimate (these notices are also posted on the Dreamflows website). There will be boating flows at Lumsden between 2000 and 2500 cfs.
For the Cherry Creek run specifically, flows at the confluence are a total of what is below Hetch Hetchy, Eleanor and Cherry, HPH and additional water from KPH. Cherry and Eleanor are at minimum seasonal release (15 and 20 cfs) and are scheduled to remain at those rates unless thunderstorms generate significant inflows. Both these reservoirs are near their capacities. KPH is scheduled to contribute ~700 cfs. Spill from Hetch Hetchy will continue to follow natural recession as part of a UTREP flow experiment. It is expected spills from Hetch Hetchy will be between 800 and 1000 cfs on Thursday (total = approx. 1550-1750 cfs). Release from HPH between the hours of 0100 and 0900 hrs will be ~150 cfs, at 0900 to 1200 hrs releases will go up to ~250 cfs, at 1200 hrs releases will go up to 350 cfs. That brings the early day flow estimate to be between 1800 and 2000 cfs (which includes an estimate of accretions) going up to 1900 to 2100 cfs at 0900 hrs. Spill at Hetch Hetchy will control the variation from that estimate.
These estimates are subject to change due to mountain thunderstorms or unscheduled shutdowns. If you're out on the river, check gages for latest flow information.
Monday, July 18, 2011
Whitewater boating and climate change
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| Scott Ligare photo. |
Thursday, July 7, 2011
Songbird monitoring in Poopenaut Valley
Sarah Stock, wildlife biologist with the Resources Management and Science Division of Yosemite National Park, discusses recent songbird monitoring conducted as part of Yosemite's Looking Downstream Project.
In order to gain a more complete understanding of the ecology downstream of O'Shaughnessy Dam, we have been studying bird populations in Poopenaut Valley since 2007. Having characterized the breeding bird community and detected about 100 species in total, this year (2011) we are vigilantly observing the timing of when migratory birds arrive, set up and defend their territories, and initiate nesting. In Poopenaut Valley, nest searching provides a more in-depth look at how the changing water level affects breeding birds in terms of their reproductive success and the timing of nest building, egg hatching, and fledging.
Since bird surveys began this year on April 27, we have detected over 80 bird species in the Poopenaut Valley study area. In addition to the regular, resident species that are present year-round, we have observed many north-bound spring migrants. Pulses of Warbling Vireos and Black-headed Grosbeaks, two of our Riparian Focal Species, were noticeable amongst the flocks of migrating Bullock’s Orioles, Yellow-rumped Warblers, Chipping Sparrows, and Red-winged Blackbirds. By the first week of May, the first pair of Yellow Warblers, another Focal Species, had set up territory. Although the nesting season seems to be somewhat delayed this year because of colder temperatures, late May nest searching yielded nests of American Robin, Bullock’s Oriole, Cassin’s Vireo, House Wren, and Yellow Warbler. Further, several pairs of Song Sparrows have been exhibiting nesting behavior, though we have not confirmed any of their nests.
In some regards the delayed nesting season is good; once the spring snowmelt begins and high flow releases from O’Shaughnessy Dam start to flood the riparian vegetation, any active nests along the Tuolumne River would likewise flood. If birds nest after the beginning of the planned high flow releases, they will only be able to place their nests in locations where they will be less likely to flood. Environmental flow recommendations being developed under UTREP for O’Shaughnessy Dam will likely include measures that should prevent nesting in low lying riparian areas that may be subsequently flooded by spring snowmelt releases.
An interesting aspect of early season breeding surveys is the possibility for finding unusual species that are still migrating toward breeding grounds farther north. This year, we have added seven new species to the total number of species detected: American Coot, American Crow, Common Yellowthroat, Gray Flycatcher (six individuals), Virginia Rail, Wood Duck, and Yellow-headed Blackbird. All of these species are considered rare in Yosemite National Park, which suggests that Poopenaut Valley is an important stopover for birds during spring migration.
In order to gain a more complete understanding of the ecology downstream of O'Shaughnessy Dam, we have been studying bird populations in Poopenaut Valley since 2007. Having characterized the breeding bird community and detected about 100 species in total, this year (2011) we are vigilantly observing the timing of when migratory birds arrive, set up and defend their territories, and initiate nesting. In Poopenaut Valley, nest searching provides a more in-depth look at how the changing water level affects breeding birds in terms of their reproductive success and the timing of nest building, egg hatching, and fledging.
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| NPS biological technician, Matt Brady, conducts a bird survey on the north side of the Tuolumne River in Poopenaut Valley (Sarah Stock photo). |
In some regards the delayed nesting season is good; once the spring snowmelt begins and high flow releases from O’Shaughnessy Dam start to flood the riparian vegetation, any active nests along the Tuolumne River would likewise flood. If birds nest after the beginning of the planned high flow releases, they will only be able to place their nests in locations where they will be less likely to flood. Environmental flow recommendations being developed under UTREP for O’Shaughnessy Dam will likely include measures that should prevent nesting in low lying riparian areas that may be subsequently flooded by spring snowmelt releases.
An interesting aspect of early season breeding surveys is the possibility for finding unusual species that are still migrating toward breeding grounds farther north. This year, we have added seven new species to the total number of species detected: American Coot, American Crow, Common Yellowthroat, Gray Flycatcher (six individuals), Virginia Rail, Wood Duck, and Yellow-headed Blackbird. All of these species are considered rare in Yosemite National Park, which suggests that Poopenaut Valley is an important stopover for birds during spring migration.
Tuesday, July 5, 2011
Wapama Falls bridge
Two backpackers died crossing the Wapama Falls bridge on June 29 during late season high flows on Falls Creek, which feeds Wapama Falls and empties into Hetch Hetchy Reservoir. Falls Creek reached its highest flow of the snowmelt season on the 29th due to a late Alaskan cold front bringing heavy rain to the high country and accelerating snowmelt.
Wapama Falls bridge spans a steep and dynamic portion of Wapama Falls with massive boulders and swift flows, even during low flow periods. Please use caution and common sense when crossing swift water. Read more at LAist.
Wapama Falls bridge spans a steep and dynamic portion of Wapama Falls with massive boulders and swift flows, even during low flow periods. Please use caution and common sense when crossing swift water. Read more at LAist.
Monday, June 13, 2011
NPS bat research in Poopenaut Valley
Sarah Stock, wildlife biologist with the Resources Management and Science Division of Yosemite National Park, discusses recent bat monitoring conducted as part of Yosemite's Looking Downstream Project.
There are about 1,240 bat species worldwide, 24 of which are native to California. In Yosemite National Park, 17 bat species are known to occur and five are special status species that have experienced statewide declines. While population declines in California are mostly caused by habitat degradation outside of the park, this serves to highlight the importance of parkland as a refuge for bat species and means that bats may be more sensitive to management activities within the park.
The Poopenaut Valley is a unique area downstream of O’Shaughnessy Dam on the Tuolumne River in Yosemite National Park. With its open wet meadows, riparian vegetation, and seasonal pond, the valley provides important habitat for bats. Bats are essential in maintaining ecosystem health by controlling insect populations through nighttime foraging. Most bat species forage either over water or within the adjacent riparian zone, where plant and insect productivity is higher than in drier upslope areas.
National Park Service (NPS) biologists are incorporating the study of bats into ongoing UTREP and Looking Downstream Project efforts in the Poopenaut Valley. The seasonal pond occupying the north side of the valley supports numerous aquatic and terrestrial species. When the pond fills in winter and spring due to snowmelt and runoff from winter rains, an entire food web develops. As the pond fills and the temperature increases, aquatic vegetation begins to grow, and aquatic and terrestrial insect populations begin to develop, which in turn provide food for garter snakes, Pacific chorus frogs, and bats.
Using advanced acoustic monitoring techniques, park biologists are working to understand how bats use the Poopenaut Valley pond and other habitats in the valley. The monitoring effort uses a system of specialized acoustic detectors to match bat echolocation calls to known recordings. In this work, NPS biologists are looking at how bats use the valley during the year and are measuring the amount of bat foraging that takes place in relation to the amount of water present in the seasonal pond.
Data from a pilot study in 2010 and preliminary surveys through mid-May of 2011 indicate that 12 different bat species occur in Poopenaut Valley, including four California Species of Special Concern (Townsend’s big-eared bat, pallid bat, spotted bat, and western mastiff bat). The other eight bat species detected include hoary bat, silver-haired bat, western pipistrelle, Mexican free-tailed bat, California myotis, Yuma myotis, long-eared myotis, and fringed myotis.
This research will be integrated into other work in the Poopenaut Valley to characterize the food web response (including bats) to varying water levels. Since filling of the pond each year is related to flows released from O’Shaughnessy Dam to the Tuolumne River, this research will aid in developing a better understanding of how water releases affect bat populations and the ecology of the seasonal pond, providing guidance to the NPS and SFPUC in making informed flow management decisions.
There are about 1,240 bat species worldwide, 24 of which are native to California. In Yosemite National Park, 17 bat species are known to occur and five are special status species that have experienced statewide declines. While population declines in California are mostly caused by habitat degradation outside of the park, this serves to highlight the importance of parkland as a refuge for bat species and means that bats may be more sensitive to management activities within the park.
The Poopenaut Valley is a unique area downstream of O’Shaughnessy Dam on the Tuolumne River in Yosemite National Park. With its open wet meadows, riparian vegetation, and seasonal pond, the valley provides important habitat for bats. Bats are essential in maintaining ecosystem health by controlling insect populations through nighttime foraging. Most bat species forage either over water or within the adjacent riparian zone, where plant and insect productivity is higher than in drier upslope areas.
National Park Service (NPS) biologists are incorporating the study of bats into ongoing UTREP and Looking Downstream Project efforts in the Poopenaut Valley. The seasonal pond occupying the north side of the valley supports numerous aquatic and terrestrial species. When the pond fills in winter and spring due to snowmelt and runoff from winter rains, an entire food web develops. As the pond fills and the temperature increases, aquatic vegetation begins to grow, and aquatic and terrestrial insect populations begin to develop, which in turn provide food for garter snakes, Pacific chorus frogs, and bats.
Using advanced acoustic monitoring techniques, park biologists are working to understand how bats use the Poopenaut Valley pond and other habitats in the valley. The monitoring effort uses a system of specialized acoustic detectors to match bat echolocation calls to known recordings. In this work, NPS biologists are looking at how bats use the valley during the year and are measuring the amount of bat foraging that takes place in relation to the amount of water present in the seasonal pond.
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| Bat detection equipment installed near the Poopenaut Valley pond. Photo: Sarah Stock. |
This research will be integrated into other work in the Poopenaut Valley to characterize the food web response (including bats) to varying water levels. Since filling of the pond each year is related to flows released from O’Shaughnessy Dam to the Tuolumne River, this research will aid in developing a better understanding of how water releases affect bat populations and the ecology of the seasonal pond, providing guidance to the NPS and SFPUC in making informed flow management decisions.
Thursday, June 2, 2011
A new species in Yosemite: Scott's Oriole
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| An adult Scott's Oriole. Photo: Brian Small. |
Check out a recording of Scott's Oriole below:
Tuesday, May 24, 2011
Update 2: O'Shaughnessy Dam releases
Cool weather continues to preserve the snowpack and moderate inflows to Hetch Hetchy Reservoir, which has been allowed to rise above 300,000 acre-feet to prepare for UTREP high flow releases this week. Releases began yesterday (May 23rd) as part of a slightly modified schedule.
In order to confirm Poopenaut Valley wetland inundation flow thresholds, bench releases were made today at 3,300 cfs and 3,700 cfs. These will be followed by releases at 4,800 cfs (May 25 @ 08:00) and 5,700 cfs (May 25 @ 15:00). The peak release of 8,500 cfs will begin on May 26 @ 08:00 and begin to ramp down on May 28 @ 08:00. Following the peak, releases will be ramped down to 5,700 cfs to support Poopenaut Valley inundation. These releases are being monitored by equipment in Poopenaut Valley and by NPS staff as part of Yosemite National Park's Looking Downstream Project.
Releases are currently 3,700 cfs from O’Shaughnessy Dam, 700 cfs from Kirkwood powerhouse, 1,900 cfs from Cherry Creek, 900 from the Middle and South Fork Tuolumne, and about 200 cfs of accretion flow. Dreamflows is a few hours behind recent changes (due to travel time) and is at 6,400 cfs and on its way to 7,400 cfs. See realtime flow links at right for current flow information.
Flow estimates (plus or minus 500 cfs) for Lumsden are:
May 25: 7,400 cfs in the morning, rising through the day to 9,400 cfs around 6 pm
May 26: 9,400 cfs in the morning, rising to 12,200 cfs around 1 pm
May 27: 12,200 cfs all day
May 28: 12,200 cfs in the morning, decreasing to 10,100 cfs around 3 pm.
May 29: 10,100 cfs in the morning, decreasing to 9,400 cfs around 3 pm
Releases from O'Shaughnessy Dam will hold constant from May 30 through at least June 3, and the approximately 9,400 cfs at Lumsden will rise or fall based on the tributary contributions and snowmelt. If warmer weather follows the cold Memorial Day weekend, the ~9,400 cfs will continue to June 8.
In order to confirm Poopenaut Valley wetland inundation flow thresholds, bench releases were made today at 3,300 cfs and 3,700 cfs. These will be followed by releases at 4,800 cfs (May 25 @ 08:00) and 5,700 cfs (May 25 @ 15:00). The peak release of 8,500 cfs will begin on May 26 @ 08:00 and begin to ramp down on May 28 @ 08:00. Following the peak, releases will be ramped down to 5,700 cfs to support Poopenaut Valley inundation. These releases are being monitored by equipment in Poopenaut Valley and by NPS staff as part of Yosemite National Park's Looking Downstream Project.
Releases are currently 3,700 cfs from O’Shaughnessy Dam, 700 cfs from Kirkwood powerhouse, 1,900 cfs from Cherry Creek, 900 from the Middle and South Fork Tuolumne, and about 200 cfs of accretion flow. Dreamflows is a few hours behind recent changes (due to travel time) and is at 6,400 cfs and on its way to 7,400 cfs. See realtime flow links at right for current flow information.
Flow estimates (plus or minus 500 cfs) for Lumsden are:
May 25: 7,400 cfs in the morning, rising through the day to 9,400 cfs around 6 pm
May 26: 9,400 cfs in the morning, rising to 12,200 cfs around 1 pm
May 27: 12,200 cfs all day
May 28: 12,200 cfs in the morning, decreasing to 10,100 cfs around 3 pm.
May 29: 10,100 cfs in the morning, decreasing to 9,400 cfs around 3 pm
Releases from O'Shaughnessy Dam will hold constant from May 30 through at least June 3, and the approximately 9,400 cfs at Lumsden will rise or fall based on the tributary contributions and snowmelt. If warmer weather follows the cold Memorial Day weekend, the ~9,400 cfs will continue to June 8.
Tuesday, May 10, 2011
Update: O'Shaughnessy Dam high flow releases
Due to cool temperatures and some highly variable weather, inflows to Hetch Hetchy Reservoir have dropped significantly. In the last 4 days at 8,500 ft in the Tuolumne watershed, conditions have gone from 65F daytime highs at 8,500 feet to 3” of new snow at 8,500 ft. Cool conditions are expected to persist through May 17th. The low inflows mean that Hetch Hetchy operators will not have adequate levels of water storage in the reservoir to implement the "test drive" of ecological high flow releases as planned next week. Instead, the planned high flow test drive will be delayed by a week; Hetch Hetchy operators plan to begin ramping on Sunday, May 22.
Here's the current plan for the releases at O'Shaughnessy Dam (OSD) and resulting flows at Lumsden:
Here's the current plan for the releases at O'Shaughnessy Dam (OSD) and resulting flows at Lumsden:
- May 12 - 22: OSD release of 1,400 cfs. Lumsden flows will be approximately 5200 when combined with Cherry, Kirkwood powerhouse, and Middle and South Forks flows;
- May 23 -24: OSD release of 3,300 cfs. Lumsden flow will be approximately 7100 cfs;
- May 25: OSD release of 4,800 cfs. 8,800 cfs at Lumsden;
- May 26: OSD release of 5,700 cfs. 9700 cfs at Lumsden;
- May 27 – 29: OSD release of 8,500 cfs. 12,500 cfs at Lumsden;
Wednesday, May 4, 2011
High flow releases from O'Shaughnessy Dam
This has been a very wet winter with recent snow survey results indicating the snowpack in the Upper Tuolumne watershed at 184% of average May 1st snow conditions. Currently, the snow line is near 5600 feet and has melted on south and west slopes up to approximately 6400 ft; above 6400 feet the snow coverage is 100%. Warm temperatures over the last week have been melting this low elevation snow and generating streamflows in the watershed. Over all, SFPUC hydrologists believe over 500,000 acre-feet of excess runoff ("spill") is likely to occur over the next 2-3 months at O'Shaughnessy Dam.
As discussed at the April 8 stakeholder meeting, draft UTREP flow recommendations for O'Shaughnessy Dam include high flow releases during the snowmelt season to meet sediment transport and Poopenaut Valley wetland inundation objectives. This year, the SFPUC and NPS will take those recommendations for a "test drive" to help identify any potential operational issues. Beginning May 15th, operators at O'Shaughnessy Dam will begin high flow releases, starting with test wetland inundation "benches" at 3300, 3700, 4800, and 5700 cfs.
These releases will be monitored by equipment in the Poopenaut Valley and NPS staff will take photos to confirm inundation of wetland surfaces. A peak release for sediment transport of 8500 cfs is targeted for May 19th and 20th, followed by a 5700 cfs bench or a continued 8500 cfs release if it is necessary to control Hetch Hetchy reservoir elevations. Although variable weather conditions could require changes to this plan, the "test drive" will provide us with a valuable opportunity to evaluate the operational procedures needed to implement a new set of flow recommendations at O'Shaughnessy Dam.
As discussed at the April 8 stakeholder meeting, draft UTREP flow recommendations for O'Shaughnessy Dam include high flow releases during the snowmelt season to meet sediment transport and Poopenaut Valley wetland inundation objectives. This year, the SFPUC and NPS will take those recommendations for a "test drive" to help identify any potential operational issues. Beginning May 15th, operators at O'Shaughnessy Dam will begin high flow releases, starting with test wetland inundation "benches" at 3300, 3700, 4800, and 5700 cfs.
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| High flow release from O'Shaughnessy Dam in 2009. (W. Sears photo) |
These releases will be monitored by equipment in the Poopenaut Valley and NPS staff will take photos to confirm inundation of wetland surfaces. A peak release for sediment transport of 8500 cfs is targeted for May 19th and 20th, followed by a 5700 cfs bench or a continued 8500 cfs release if it is necessary to control Hetch Hetchy reservoir elevations. Although variable weather conditions could require changes to this plan, the "test drive" will provide us with a valuable opportunity to evaluate the operational procedures needed to implement a new set of flow recommendations at O'Shaughnessy Dam.
Wednesday, April 27, 2011
River bugs: benthic macroinvertebrates
When trying to understand river health, aquatic biologists often look not at fish, but rather fish food: benthic macroinvertebrates (or BMI). BMI are effective integrators of physical, chemical, and biological processes and are valued as indicators of river ecosystem health due to various BMI species occupying primary, secondary, tertiary, and higher-level consumer levels in riverine food webs. They are, in turn, a critical food resource for a variety of vertebrates, including fish.
Over the last three years, Jeff Holmquist and Jutta Schmidt-Gengenbach of the University of California White Mountain Research Station have been studying BMI in the river reach downstream of O'Shaughnessy Dam as part of the Looking Downstream Project and UTREP. The goal is to develop an understanding of BMI species diversity and abundance in the Tuolumne, and characterize how BMI assemblages change with flow. Current and future work will focus on food web dynamics and long term changes in BMI assemblages resulting from implementation of ecosystem-based environmental flow recommendations for O'Shaughnessy Dam.
Jeff and Jutta recently completed the first survey in their fourth year of sampling with assistance from dam operators at Hetch Hetchy Water and Power who were able to reduce releases from O'Shaughnessy Dam to allow access to the river channel.
Top left: Larva of predaceous diving beetle from pond habitats. The larvae of some species can reach almost two inches in length. Adults are smaller, but are also aquatic predators. (Holmquist photo)
Top right: Drift net in place below O'Shaughnessy Dam in the Tuolumne River. The net catches insects that enter the water column. BMI floating downstream (known as "Drift") are a natural phenomenon and an important source of food for fishes. In addition to BMI, surprisingly large numbers of terrestrial insects are found in drift samples. A one-hour sample can include close to 1,000 insects and 125 species. (Holmquist photo)
Bottom right: A backswimmer, found in pond habitats. These insects swim on their backs and have one pair of legs specialized as oars. Backswimmers have a stinging beak that is used in prey capture. The beak is visible in the photo and runs along 3/4 of the length of the body. (Holmquist photo)
Bottom left: Tossing a throw trap in the Poopenaut pond, 3 miles downstream of O'Shaughnessy Dam. The trap encloses a known volume of water column and associated substrate, and animals are removed with a bar seine. The device is effective at catching fauna that might avoid other collecting devices. The pond has a high level of diversity and abundance, sometimes over 1,000 insects per square meter. (Schmidt-Gengenbach photo)
Over the last three years, Jeff Holmquist and Jutta Schmidt-Gengenbach of the University of California White Mountain Research Station have been studying BMI in the river reach downstream of O'Shaughnessy Dam as part of the Looking Downstream Project and UTREP. The goal is to develop an understanding of BMI species diversity and abundance in the Tuolumne, and characterize how BMI assemblages change with flow. Current and future work will focus on food web dynamics and long term changes in BMI assemblages resulting from implementation of ecosystem-based environmental flow recommendations for O'Shaughnessy Dam.
Jeff and Jutta recently completed the first survey in their fourth year of sampling with assistance from dam operators at Hetch Hetchy Water and Power who were able to reduce releases from O'Shaughnessy Dam to allow access to the river channel.
Top left: Larva of predaceous diving beetle from pond habitats. The larvae of some species can reach almost two inches in length. Adults are smaller, but are also aquatic predators. (Holmquist photo)
Top right: Drift net in place below O'Shaughnessy Dam in the Tuolumne River. The net catches insects that enter the water column. BMI floating downstream (known as "Drift") are a natural phenomenon and an important source of food for fishes. In addition to BMI, surprisingly large numbers of terrestrial insects are found in drift samples. A one-hour sample can include close to 1,000 insects and 125 species. (Holmquist photo)
Bottom right: A backswimmer, found in pond habitats. These insects swim on their backs and have one pair of legs specialized as oars. Backswimmers have a stinging beak that is used in prey capture. The beak is visible in the photo and runs along 3/4 of the length of the body. (Holmquist photo)
Bottom left: Tossing a throw trap in the Poopenaut pond, 3 miles downstream of O'Shaughnessy Dam. The trap encloses a known volume of water column and associated substrate, and animals are removed with a bar seine. The device is effective at catching fauna that might avoid other collecting devices. The pond has a high level of diversity and abundance, sometimes over 1,000 insects per square meter. (Schmidt-Gengenbach photo)
Photo: above the Tuolumne
Taken while flying West over Yosemite. The area around Yosemite National Park is a major corridor for East-West flights, posing a challenge for Yosemite National Park staff attempting to manage soundscapes in wilderness areas of the Park. Visible are three of the higher elevation reservoirs of the Hetch Hetchy Project, including (left to right) Cherry Reservoir, Lake Eleanor, and Hetch Hetchy Reservoir. The dark abyss just right of center is the Tuolumne River Gorge. The Early Intake area is just off the bottom left corner. Click on the photo for a larger version. (W. Sears photo)
Sunday, April 17, 2011
Wapama Falls bridge repaired
NPS reports as of Friday April 15th, that the bridge at Wapama Falls has been repaired. The trail to Rancheria is now open to hikers and backpackers. Stock use should be allowed in the next few weeks.
Tuesday, April 12, 2011
Stakeholder meeting materials
Thanks to all who attended our recent stakeholder meeting in Moccasin. Meeting materials from the April 8, 2011 stakeholder meeting are now available for viewing and download here.
Friday, February 4, 2011
Wapama Falls bridge repair
On October 3-4, 2010 the Hetch Hetchy area experienced a severe electrical storm. During one 24-hour period, the Hetch Hetchy Reservoir rose approximately 25 feet and the foot bridge near Wapama Falls was destroyed due to falling rock and flood flows from Falls Creek. Yosemite National Park's current plan is to repair and open the bridges by April 2011 in time for early spring backpackers and hikers.
Sunday, January 30, 2011
Stakeholder meeting date change
Due to scheduling conflicts including the Salmonid Restoration Federation conference, the date of the next stakeholder meeting has moved from March 25 to April 8, 2011. We hope everyone can make this new date. Meeting details will be emailed to participants ahead of the meeting. Please email Bill Sears (wsears@sfwater.org) if you plan to attend.
Friday, January 14, 2011
Amphibian Population Task Force Meeting
The meeting and field trip provided a unique opportunity for scientists with the SFPUC, McBain & Trush, the NPS, and others working on developing new environmental flow recommendations for O'Shaughnessy Dam under the UTREP project to obtain critical input on methods and results that have been used to quantify the magnitude, duration, frequency, and timing of flows needed to support amphibians (particularly foothill yellow-legged frog) in the Tuolumne River downstream of O'Shaughnessy Dam.
Input gained from the meeting will be incorporated into our current studies and will be reflected in the final draft flow recommendations report due in the first half of this year.
California/Nevada Amphibian Population Task Force: www.canvamphibs.com