Monday, October 6, 2014

Request for proposals

The SFPUC is requesting consultant proposals to provide as-needed river ecosystem science support for the Upper Tuolumne River Ecosystem Program. Details can be found on the SFPUC's website.
 

Wednesday, June 18, 2014

Rim Fire vegetation tracker

The Forest Carbon research team at NASA Ames Research Center has launched the Rim Fire Tracker online map viewer to help track regenerating vegetation areas within the 2013 burned severity classes.  The maps feature changes in current (2014) Landsat 8 NDVI (normalized difference vegetation index) compared to last October's (post-burn) NDVI.  The map layers will be updated every month with a new Landsat NDVI difference product.   Subsequent image analysis of the vegetation community in regenerating areas will be added to this map viewer over time. Tools are provided to zoom to a location, identify values, and download map layers.  Subsequent image analysis of the vegetation community in regenerating areas will be added based on the methods published previously by Potter et al. (2012).

Monday, April 14, 2014

Looking Downstream 2013 update

Yosemite National Park's 2013 update report for the "Looking Downstream" project is available for download in the library.

Draft O'Shaughnessy Dam Instream Flow Management Plan

The draft O'Shaughnessy Dam Instream Flow Management Plan is available for download via links provided below.  The plan is comprised of a main document (211 pp) and 13 technical appendices (619 pp).  The main document is intended to provide a thorough description of proposed future instream flow releases for O'Shaughnessy Dam and a summary of analyses used to develop the plan.  In-depth, discipline-specific technical descriptions of analytical methods and results are provided in the appendices document for more technical readers. Implementation of the plan will require environmental review, planned for 2014/2015.

Main document (41 MB pdf)
Appendices (136 MB pdf)

Saturday, April 5, 2014

Tuolumne River whitewater access opens

Whitewater boating access for the Cherry and Lumsden runs on the Tuolumne River is open for the season.  Access is by shuttle only and free, mandatory permits are required via the Groveland Ranger Station.  For more information on white water and other recreation on the Stanislaus National Forest, see the Stanislaus National Forest recreation update.  Boaters are asked to watch for hazards associated with the Rim Fire such as landslides and fallen trees.

Friday, April 4, 2014

Wapama rockfall

Recent rockfall source area adjacent to
Wapama Falls (photo: Greg Stock, NPS)
A rockfall occurred just east of Wapama Falls on the North side of Hetch Hetchy Reservoir on March 31st, covering approximately 600 ft of the Wapama Falls trail.  The falls can still be reached from the west, but the trail is closed just east of the falls.  The National Park Service does not currently have an estimated date for reopening the closed section of trail.

Friday, March 28, 2014

Prescribed fire at Hetch Hetchy

Prescribed burn near O'Shaughnessy
Dam.  Photo courtesy of Yosemite
Fire Management.
National Park Service and US Forest Service fire crews completed a 57 acre prescribed fire near O'Shaughnessy Dam today.  The combination of recent rains, minimal snowpack, and slightly unsettled weather made for ideal prescribed fire conditions; these conditions typically don't exist in March due to snowpack and wet fuels. The fire treated vegetation and fuels around the buildings and other infrastructure near O’Shaughnessy Dam, and was designed to reduce surface and “ladder fuels” that allow ground fire to leap to the tree canopy and cause crown fires. The treated area will offer a “fuel break” for firefighters to safely protect structures at the O’Shaughnessy Dam.   The area burned with low intensity during the 2013 Rim Fire.

Thursday, March 27, 2014

Colorado River Delta re-watered by pulse flow

Seasonal high flow water releases, or pulse flows, are increasingly used to simulate natural hydrology and manage river habitats downstream of dams and diversions. Beginning March 23rd and continuing for eight weeks, about 1 percent of the Colorado River’s waters will be released into the Colorado River Delta in Mexico.  The release is part of a five-year pilot project designed to restore the delta environment and is part of an amendment to a decades old treaty between the United States and Mexico on management of Colorado River water.  Read more online.

Tuesday, January 21, 2014

Southern Sierra Fire and Hydroclimate Workshop

The first jointly scheduled Southern Sierra Fire and Yosemite Hydroclimate Workshop will be held April 22-24, 2014 in Yosemite Valley.  The workshop is focused on developing an integrated view of the physical landscape, climate effects, hydrology, and fire regimes of the Sierra Nevada.  This workshop was rescheduled from the original date back in October 2013 due to the federal government shutdown.  To register, visit the California Fire Science Consortium website.

Friday, January 17, 2014

November 2013 stakeholder meeting materials available

Presentations and other meetings materials from the November 15, 2013 Upper Tuolumne River Stakeholder Group meeting are now available here.

Tuesday, January 14, 2014

New USGS Ward's Ferry stream gage

The USGS has installed a new stream gage near Ward's Ferry Bridge, at the upstream end of Don Pedro Reservoir, to monitor Rim Fire-related water quality parameters.  The gage currently records stage, water temperature, conductance, turbidity, dissolved oxygen, and pH.  The gage is funded by Modesto and Turlock irrigation districts, and the SFPUC.


Friday, January 10, 2014

2011-2012 Yosemite "Looking Downstream" report available

Yosemite National Park's 2011-2012 update report for the "Looking Downstream" project is available for download in the library.  

Looking Downstream is a long-term interdisciplinary study designed to better understand the physical processes and ecology of the mainstem Tuolumne River between O’Shaughnessy Dam and the western boundary of Yosemite National Park, with a focus on the biologically diverse Poopenaut Valley.  The project provides critical information used to manage environmental water releases from O’Shaughnessy Dam.

Wednesday, November 27, 2013

Economic Impact of the 2013 Rim Fire on Natural Lands

To support new methods of valuing watersheds and the ecosystem services they provide, the San Francisco Public Utilities Commission funded Earth Economics to develop a preliminary assessment of the economic impact of the Rim Fire. The preliminary assessment includes loss estimates related to air quality, carbon sequestration, flood protection, erosion control, biological control, water filtration, pollination, habitat and biodiversity, property and aesthetic values, and recreational values. This initial effort provides support to federal, state, and local governments in justifying more robust, long-term investments in watersheds and forest health. The assessment is available here.

Tuesday, November 12, 2013

Glen Canyon Dam high flow releases

For over 5 years the SFPUC and NPS have collaborated on experimental flood releases from O'Shaughnessy Dam to support development of a new instream flow management plan for the upper Tuolumne River between the dam and Early Intake.  The releases have primarily been conducted to test flow thresholds for sediment transport and Poopenaut Valley wetland inundation.  Similar flood release experiments have been underway on other rivers; among the most widely reported are the releases from Glen Canyon Dam into the Grand Canyon on the Colorado River.

The Glen Canyon Dam Adaptive Management Program began in 1997 as an effort to use high flow releases to manage sediment (primarily sand) for the benefit of backwater habitats that provide key fish and wildlife habitat, reducing erosion of archaeological sites, restore and enhancing riparian vegetation, and restoring sand bar beaches for recreational boating and camping.  The releases maintain water supply obligations by releasing less water during other parts of the year, mimicking pre-dam flows and water temperatures.

This week, the Glen Canyon program is conducting a second high flow experimental release from Glen Canyon Dam under a protocol approved in 2012. The protocol calls for conducting more frequent high flow experimental releases from the dam timed to occur following sediment inputs to the Colorado River from downstream tributaries. Large amounts of sediment were deposited over the summer due to major rainstorms.  The volume of sediment available is about three times larger than the volume available during the last high flow release in the fall of 2012.

Read more on the 2013 releases from the LA Times and the US Bureau of Reclamation. Also, checkout some of the science and multimedia products the USGS is producing related to the high flow releases.

Friday, November 8, 2013

Re-scheduled fall stakeholder meeting

The re-scheduled fall stakeholder meeting will take place on Friday, November 15, 2013.  Please RSVP (wsears@sfwater.org) if you plan to attend.  View the draft agenda here.

Tuesday, October 15, 2013

Postponed: fall stakeholder meeting

Due to the continuing federal shutdown, federal stakeholders and partners will likely be unable to attend or provide updates at the scheduled stakeholder meeting on October 18th.  Given the importance of their participation to UTREP and the interests of upper Tuolumne stakeholders we are rescheduling the stakeholder meeting for November 15th, 2013, pending confirmation with federal agencies.  An update will be provided when the meeting is finalized.

Friday, September 27, 2013

Capturing pre- and post-burn imagery in "gigapixels"

UC Davis has done it again, this time with "gigapixel" imagery of the Clavey River confluence, before and after the Rim Fire.  A gigapixel image contains more than 100 times the information captured by a typical 10 megapixel digital camera.  Gigapixel imagery is a product of NASA, Google, and Carnegie Mellon University efforts to develop imaging technologies for NASA Mars rovers.  The technique has been used in Yosemite Valley to document rockfall hazards, and as UC Davis has illustrated, gigapixel imagery has potential for broad application in watershed and river management to document changing landscapes over time.

Thursday, September 26, 2013

UC Davis travels to the bottom of the Rim Fire

Several UC Davis Center for Watershed Sciences staff received permission from the Stanislaus National Forest to hike into the mainstem Tuolumne River near the Clavey River confluence to investigate the fate of river monitoring gear after the Rim Fire.  Here's what they found.

Tuesday, September 24, 2013

Fall stakeholder meeting

Quick note: the Fall 2013 meeting of the Upper Tuolumne River Stakeholder Group will take place on October 18th in Moccasin.  An agenda is currently being developed.  If you'd like to attend, RSVP to wsears@sfwater.org.

Wednesday, September 18, 2013

Southern Sierra Fire and Hydroclimate Workshop

The Southern Sierra Fire and Hydroclimate Workshop is scheduled for October 1-4, 2013 at the Yosemite Lodge in Yosemite Valley.  This event combines, for the first time, the annual Yosemite Hydroclimate workshop and the Wildland Fire Science workshop.  The workshop focuses on an integrated view of the physical landscape, climate effects, hydrology, and fire regimes of the Sierra Nevada.   Given the recent Rim Fire, which burned portions of the Stanislaus National Forest and Yosemite National Park, this and future workshops should provide a useful forum for tracking fire science efforts in the coming years.   More information and registration details can be found here.

Friday, August 30, 2013

Rim Fire timelapse

Some incredible videos are coming out of the firefighting efforts on the Rim Fire.  Although most are readily available via Twitter and other social media, we'll be sharing a few that provide some perspective on one of the largest fires in California history.  Here's one from Yosemite National Park.

Monday, August 26, 2013

Rim Fire

The Rim Fire, which began on August 17th near Jawbone Ridge, has now burned through a majority of the UTREP study area.  Firefighting efforts are ongoing; updates can be obtained from Inciweb and CalFire.  Several other resources are available online to track the Rim Fire, including ESRI's Rim Fire map and the KPCC fire tracker, and the Twitter feeds of Yosemite National Park Fire Management and CalFire.

Tuesday, April 30, 2013

The Airborne Snow Observatory Project

LiDAR data from the ASO project
NASA and Cal Tech's Jet Propulsion Laboratory are conducting a pilot project this spring, known as the Airborne Snow Observatory (ASO), to more precisely estimate the volume of water present in the snowpack within the Hetch Hetchy watershed.  The project utilizes frequent aircraft flights and specialized sensors to develop water volume estimates that are potentially more accurate than existing methods, and provide data on a weekly basis versus the existing monthly snow surveys.  The techniques developed in the pilot project may eventually help reservoir operators better manage reservoir operations and UTREP ecological releases.  Read more about the Airborne Snow Observatory Project in this Washington Post articlethis LA Times story, and this KQED radio bit.

Spring stakeholder meeting materials

The agenda and presentations from the April 19th, 2013 Upper Tuolumne River Stakeholder Group meeting are now available online.  The Fall stakeholder meeting is scheduled for October 18, 2013 in Moccasin.

Tuesday, March 19, 2013

Powered paragliding the Tuolumne River Canyon

Pine Mountain Lake resident Rex Pemberton and fellow powered paraglider David Royer take a spectacular low altitude flight down the Tuolumne River canyon.

Monday, March 18, 2013

SFPUC comments on the Draft Tuolumne River Plan

In January, Yosemite National Park released the Tuolumne Wild and Scenic River Comprehensive Management Plan and Draft Environmental Impact Statement (also known as the Tuolumne River Plan or TRP). The TRP describes management alternatives for the Tuolumne River Wild & Scenic river corridor within the park, including portions of the UTREP study downstream of O'Shaughnessy Dam.

The SFPUC has submitted comments to Yosemite National Park regarding the TRP.  SFPUC comments can be viewed or downloaded here.  The comment period closes today, March 18th.

Saturday, February 9, 2013

What is a natural hydrograph?

The pre-development or "natural" state of a river system provides important context for river ecosystem management and rehabilitation: What did the river system look like before major development?  What is the "natural" hydrologic regime?  How are species adapted to the natural hydrograph?  These are all questions that the UTREP is investigating in the upper Tuolumne, and are common to many other river ecosystem management efforts.

On January 18, 2013, the Delta Science Program and the UC Davis Center for Aquatic Biology & Aquaculture (CABA) hosted a seminar to explore how we use, and what we mean by, a natural hydrograph or unimpaired flows.  The seminar focuses on the California Bay-Delta, but is relevant to work on the upper Tuolumne and elsewhere.

Video of the seminar is available on the CABA website.

Tuesday, February 5, 2013

Lyell Glacier in the news

The San Francisco Chronicle reported on the retreat of the Lyell Glacier in Yosemite National Park, at the headwaters of the Tuolumne River.  Recent work by NPS on the rate of retreat was presented at the Fall 2012 meeting of the Upper Tuolumne River Stakeholder Group.

Friday, January 11, 2013

Tuolumne Wild & Scenic River Plan released

Yosemite National Park has released the Tuolumne Wild and Scenic River Comprehensive Management Plan and Draft Environmental Impact Statement (Tuolumne River Plan/DEIS). The plan describes management alternatives (including a preferred alternative) for the Tuolumne River Wild & Scenic river corridor within Yosemite National Park, including portions of the UTREP study area.  Studies by UTREP collaborators, including the NPS Looking Downstream Project efforts, contributed to development of the plan.  The upper Tuolumne River was designated by the U.S. Congress in 1984 under the Wild and Scenic Rivers Act. The park has also released the Merced River Plan, which addresses Wild & Scenic River management within the Merced River corridor, including Yosemite Valley.

Tuesday, December 4, 2012

Tuolumne climate change sensitivity

Earlier this year, the SFPUC completed a report on the potential changes (increase or decrease) in Tuolumne River inflows to Hetch Hetchy Reservoir with anticipated changes in climate.  The study used modeled temperature and precipitation data from a range of previously modeled climate change scenarios.  While the likelihood of any particular climate future was not assessed, and the report doesn't seek to address potential water supply impacts of climate change, the simulated 2040, 2070, and 2100 hydrologic conditions show a progressively altered snow and runoff regime in the watershed. Snow accumulation is reduced and snow melts earlier in the spring. Fall and early winter runoff increases while late spring and summer runoff decreases, and these changes become more significant at the later time periods. Total runoff is projected to decrease under the climate change scenarios evaluated, in some cases marginally and others significantly. The consequences of these potential changes for UTREP efforts is unknown at this time, but will be considered in our ongoing instream flow work.

Monday, December 3, 2012

October stakeholder meeting materials

The agenda and presentations from the October stakeholder meeting are now available.

Sunday, December 2, 2012

Clavey confluence timelapse

This past spring, UC Davis researchers installed time lapse cameras, water stage recorders, and temperature monitoring equipment in both the mainstem Tuolumne River (regulated by Hetch Hetchy Project facilities - particularly Holm Powerhouse) and the Clavey River (an unregulated tributary to the Tuolumne) near their confluence.  Video gurus at UC Davis then layered the time lapse video, stage, and temperature data of both rivers, providing a visual comparison of temperature and hydrology dynamics in the regulated and unregulated streams. This work is part of a larger UC Davis effort to learn more about how tributaries and stream confluences affect hydrology and geomorphology.  Watch the video in HD on Vimeo for best effect, and to learn more about how the video and data were compiled.

Time Lapse Hydrography - Tuolumne and Clavey Rivers 2012 with Temperatures from Center for Watershed Sciences on Vimeo.

Tuesday, May 29, 2012

Pacific Northwest Watershed Managers group tour

From April 30 to May 4, 2012, the SFPUC hosted the Pacific Northwest Watershed Managers (PNWM) group on a tour of the SFPUC water system, from the San Francisco Peninsula to Hetch Hetchy.  The group consists of watershed managers from the six largest unfiltered municipal water supply systems along the Pacific coast of North America, and was created to facilitate the exchange of information about programs, policies, and best management practices.  Materials discussed during the tour are available for viewing and download below.

Please note: we use Google Docs to host files online. Smaller files will be previewed in Google Docs, while larger files can only be downloaded.   If a file is displayed in Google Docs, but you'd rather download it, go to the "File" menu and select "Download original".  In some cases, Google can't preview the file and will say so; choose "Download" to download the file to your computer.  If you are having issues, email wsears@sfwater.org.

Tour handouts and presentations
Alameda Creek tour itinerary
Alameda Creek handouts (several SFPUC presenters)
Tuolumne River tour itinerary
Tuolumne River handouts (Bill Sears, SFPUC)
Hetch Hetchy Project operations overview (Adam Mazurkiewicz, SFPUC)
Upper Tuolumne River Ecosystem Project overview (Bill Sears, SFPUC)
Alameda Creek historical ecology overview (Robin Grossinger, Bronwen Stanford, SFEI)

Wednesday, April 25, 2012

Spring snowmelt management: a frog year?

As the spring unfolds and late rains continue to fall, it's clear this is not the dry year it could have been.  However, the rains came too late to make up for the mostly precipitation-free winter.  The good news is this provides another opportunity to test the snowmelt management strategies being developed for O'Shaughnessy Dam to benefit the Poopenaut Valley wetlands and the rest of the Tuolumne River ecosystem.  This year, operational tests will focus on managing available snowmelt spill to fill the Poopenaut Valley pond while also providing good conditions for foothill yellow-legged frogs.  Dry years provide the best opportunity to benefit the small foothill yellow-legged frog population present upstream of Early Intake.  In wetter years the upper mainstem Tuolumne features higher and more variable snowmelt flows that can last into the summer.  Wet year high flows can delay egg-laying or scour egg clutches, and are challenging for egg and tadpole development, as they likely were even under natural conditions.  Dry year snowmelt spill flows are designed to peak early and provide more stable flow conditions for egg laying and tadpole development.  Filling the Poopenaut pond will provide good conditions for benthic macroinvertebrates, chorus frogs, garter snake, bats, and other wildlife that depend on the pond ecosystem over the remainder of spring and into early summer.

Planned snowmelt management hydrograph.
Flow releases from O'Shaughnessy Dam will remain at current levels through Friday, April 27 to accomodate biological monitoring work, but will increase on Saturday to 200 cfs and possibly slightly higher thru Monday.  Flows will ramp up on Tuesday, with a peak on Wednesday (May 2) of 4100 cfs.  The peak will be timed for mid-day Wednesday to allow the highest flow to pass boaters in the Lumsden reach went they are off the water in the evening and allow for observation at O’Shaughnessy Dam and the Poopenaut Valley overlook during daylight.  The current plan is to ramp down to 250 cfs by Thursday afternoon; however flows may stay higher if needed to manage snowmelt inflows.


Monday, March 26, 2012

Poopenaut Valley groundwater study

Poopenaut Valley
UC Santa Cruz and NPS researchers recently published their work on Poopenaut Valley groundwater modeling and monitoring in the Journal of Hydrology.  The researchers monitored experimental high flow releases from O'Shaughnessy Dam to assess the relative importance of inundation versus groundwater rise in establishing and maintaining riparian wetland conditions to determine how restoration benefits might be achieved while reducing total flood discharge.  The observations helped to calibrate a numerical model that was used to test scenarios for controlled flood releases.

Modeling of the groundwater–wetland system suggests that inundation of surface soils is the most effective mechanism for developing wetland conditions, although an elevated water table helps to extend the duration of soil saturation.  Results of the study will be incorporated into flow recommendations being developed for O'Shaughnessy Dam by UTREP.

Looking Downstream 2009 & 2010 reports available

We've just uploaded NPS update reports on ecological monitoring in the Poopenaut Valley for 2009 and 2010.  In 2009 and 2010, NPS scientists continued to conduct extensive monitoring of wetland and meadow hydrology, birds, vegetation, and benthic macroinvertebrates. New work in these two reports includes groundwater modeling by UC Santa Cruz and bat surveys conducted by NPS.

Wednesday, March 21, 2012

Spring stakeholder meeting

The next meeting of the Upper Tuolumne River Stakeholder Group is set for April 13, 2012 from 11am - 2:30pm at the Moccasin Administration Building (map).  View or download the agenda here.  If you plan to attend the Stakeholder Group meeting, please email Bill Sears at wsears@sfwater.org.

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.

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.

Tuesday, September 27, 2011

2011 Yosemite Hydroclimate Meeting

The Resources Management and Science Division of Yosemite National Park will host the annual Yosemite Hydroclimate Meeting on October 6-7, 2011 at the Yosemite Lodge. The meeting is open to the public and features talks on hydrology and climate relevant to management of Yosemite.  Two talks will focus on recent high flow experiments during spring snowmelt releases downstream of O'Shaughnessy Dam as part of UTREP.

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!

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.

Monday, July 18, 2011

Whitewater boating and climate change

Scott Ligare photo.
Scott Ligare and Josh Viers of UC Davis have posted results of research into the effects of climate change on whitewater boating in the Sierra on UC Davis' California WaterBlog. Under mild warming (+2° C or 3.6°F), changes in runoff are likely to increase the average number of boatable weeks per year. However, under extreme warming (+6° C or 10.6° F) there will be a significant decrease in the average boatable weeks per year across the Sierra Nevada. These results vary depending upon location and gradient of the run. Read more on the UC Davis California WaterBlog.

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.

NPS biological technician, Matt Brady, conducts a bird survey
on the north side of the Tuolumne River in Poopenaut Valley
(Sarah Stock photo).

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.

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.

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.

Bat detection equipment installed near the
Poopenaut Valley pond.  Photo: Sarah Stock.
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.

Thursday, June 2, 2011

A new species in Yosemite: Scott's Oriole

An adult Scott's Oriole.  Photo: Brian Small.
On May 31, NPS Biological Technician Matt Brady observed a second year male Scott's Oriole (Icterus parisorum) in Poopenaut Valley. This species has not previously been reported within Yosemite National Park and thus brings the park's bird list to 261 species. It is the first sighting in the park and the second within surrounding Tuolumne County.  Scott's Oriole's are native to the southwestern United States and Mexico. NPS biologists working in the Poopenaut Valley have seen a number of unusual species for the park this spring, including Gray Flycatcher, American Coot, Common Yellowthroat, Yellow-headed Blackbird, Wood Duck, and Green-tailed Towhee.


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.

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:
  • 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;
The length of the 8,500 cfs high flow release will depend on weather and inflows.  Wetland inundation bench flows will be released after the peak, however the timing will again depend on weather.  High flows at Lumsden (>9,000 cfs) are likely to continue – assuming normal spring/warming weather – through at least June 8.  We'll provide updates here as the snowmelt season unfolds.

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.

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)

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

Last week Yosemite National Park hosted the California/Nevada Amphibian Population Task Force Meeting in Yosemite Valley. The meeting was well attended and brought together some of the foremost experts in western amphibian populations. The two days of presentations at the Yosemite Lodge provided some valuable insights into the recent declines and conservation efforts underway for imperiled amphibians. The meeting ended with a field tour of the UTREP and Looking Downstream projects by SFPUC and NPS staff including Greg Stock, Yosemite park geologist (shown above presenting to participants on O'Shaughnessy Dam).

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

Monday, November 1, 2010

Yosemite Nature Notes: Glaciers

The newest installment of Yosemite Nature Notes by Steve Bumgardner is now on YouTube. This latest episode focuses on the Maclure and Lyell glaciers, which form the headwaters of the Tuolumne River, and features Greg Stock (Park Geologist with Yosemite National Park), Pete Devine (Naturalist at the Yosemite Conservancy), and mountain guide Josh Helling.

Thursday, October 21, 2010

New species found in Yosemite National Park

A new species of pseudoscorpion has been discovered in the talus slopes of Yosemite National Park. Read more from Yosemite's Resources Management and Science Division.

Wednesday, October 13, 2010

Fall stakeholder group meeting

The next meeting of the Upper Tuolumne River Stakeholder Group is set for October 22, 2010, 11am - 3pm at the Moccasin Administration Building (map).

Rain and snow fall this year provided significant amounts of water enabling a number of field experiments to test high flow geomorphic, hydrologic, and ecological thresholds. This work, combined with the substantial work conducted by Yosemite National Park scientists in Poopenaut Valley, has generated a large amount of data that is currently being analyzed and incorporated into draft flow recommendations for O'Shaughnessy Dam.

At the stakeholder meeting, the SFPUC and Yosemite National Park will provide an update regarding new information generated by the 2010 studies, present an overview of the draft flow recommendations, and provide a revised schedule for distributing the draft UTREP study report.

If you plan to attend the Stakeholder Group meeting, please email Jen Vick at jvick@sfwater.org.

Thursday, October 7, 2010

Behind the Scenes: Yosemite Nature Notes

Steve Bumgardner posted some "behind the scenes" video of his recent trek to Lyell Glacier with Greg Stock (Yosemite National Park geologist) and crew. The Lyell and Maclure glaciers form the glacial headwaters of the Tuolumne River and will be featured in an upcoming episode of Yosemite Nature Notes.

Tuesday, October 5, 2010

Yosemite Hydroclimate Conference

Yosemite National Park will host the annual Yosemite Hydroclimate Conference on October 7-8, 2010 at Yosemite Lodge. The conference is open to the public and features a variety of speakers and topics relevant to management of the park. Download the schedule here.

Monday, October 4, 2010

Sierra Nevada yellow-legged frog research


The New York Times published a story on San Francisco State University researcher Vance Vredenburg and his work with the Sierra Nevada yellow-legged frog (Rana sierrae). Read the article in the New York Times (registration may be required).

Thursday, August 27, 2009

O'Shaughnessy Dam instream flow evaluation study plan

As part of the Upper Tuolumne River Ecosystem Project, McBain & Trush have developed a study plan that focuses on our initial objective of developing ecosystem-based instream flow recommendations for O'Shaughnessy Dam. Many aspects of the plan have been underway since the inception of the Ecosystem Project, while others are new and will be implemented through December 2010. In particular, the SFPUC and McBain & Trush have worked closely with the USFWS to develop the flow-habitat relationship studies which are currently underway and will continue into the fall, with followup work in 2010.

Upper Tuolumne River Ecosystem Project: O'Shaughnessy Dam Instream Flow Evaluation Study Plan (PDF | 1.7MB)

Sunday, June 7, 2009

UC Davis Extension course: The Tuolumne River - Ecology, Resource Management, and Whitewater

UC Davis Extension is offering a two-day educational rafting trip with field demonstrations and on-river lectures about aquatic and riparian ecology, geology, geomorphology, hydrology, controversial water resource development and the rich human history of the Tuolumne River. See the UC Davis Extension website for more information. Note: currently both classes are full, but wait listing is available.

Wednesday, May 6, 2009

Upper Tuolumne River Stakeholder Group fall meeting date and time

The next meeting of the Upper Tuolumne River Stakeholder Group is set for November 13, 2009, 11am - 3pm at the Moccasin Administration Building. Stay tuned, we'll provide an update later this year with a proposed agenda and other materials.

Tuesday, March 17, 2009

Upper Tuolumne River Stakeholder Group meeting

The SFPUC Natural Resources Division and Hetch Hetchy Water and Power Division will host the spring meeting of the Upper Tuolumne River Stakeholder Group in Moccasin on Friday, March 20. The agenda includes a morning session with updates from Yosemite National Park, the Tuolumne River Trust, and SFPUC. Following lunch, Yosemite and SFPUC scientists will discuss ongoing climate change studies being conducted to help understand the potential impacts on management of Yosemite National Park and the Upper Tuolumne watershed. Finally, the SFPUC will provide updates on work in 2009 as part of the Upper Tuolumne River Ecosystem Project.

The meeting will be held in the Moccasin Administration Building, and lunch will be provided by Hetch Hetchy Water and Power. If you plan to attend, please email Bill Sears (wsears@sfwater.org) so we can have enough lunch for all.

Tuesday, January 27, 2009

Preliminary temperature modeling data assessment report available

An initial report assessing the quality and availability of data needed for water temperature modeling has been completed by SFPUC consultant Merritt Smith Consulting. The findings of the report will be used to build a water temperature model for the Upper Tuolumne River to evaluate the historical stream temperature regime and the effects of future environmental water release recommendations from Hetch Hetchy Project facilities.

Preliminary Analysis of Available Data for Modeling Temperature in the Hetch Hetchy Reach (PDF | 0.7MB)

Monday, January 26, 2009

Sediment supply and transport report available

SFPUC consultants McBain & Trush have produced a preliminary sediment transport report for the Upper Tuolumne River between O'Shaughnessy Dam and Early Intake. The report is a first step towards characterizing the sediment transport dynamics of the upper river and developing a model that can be "gamed" to help assess the effects of future environmental flow recommendations for O'Shaughnessy Dam on sediment dynamics in the river.

Preliminary Sediment Source and Sediment Transport Capacity Evaluation: O’Shaughnessy Dam to Poopenaut Valley (PDF | 1.1MB)

Monday, November 10, 2008

Glacial retreat story on KQED's California Report

KQED reporter Sasha Khokha hiked to Yosemite's Dana Glacier in the Upper Tuolumne River watershed to discuss climate change and its effects across the Sierra Nevada Range with Hassan Basagic of Portland State University. The story includes an interview with Greg Stock, Yosemite National Park Geologist. Listen to the "shrinking glaciers" story on KQED.

Sunday, October 19, 2008

Lyell Glacier story in the Sacramento Bee

Tom Knudson writes about a recent Yosemite Association hike to the Lyell Glacier in the Upper Tuolumne River watershed and the return of 81-year-old Hal Klieforth to the glacier after first visiting it 58 years ago. Read the story and view video and maps at the Sacramento Bee.

Thursday, June 26, 2008

May 2008 O'Shaughnessy Dam experimental flood

In late May 2008, the SFPUC and Yosemite National Park conducted an experimental flood on the Upper Tuolumne River to test ideas about the role snowmelt runoff played in supporting the Poopenaut Valley ecosystem in Yosemite National Park before O'Shaughnessy Dam was built. Information gathered by project scientists monitoring the flood will help in developing ecological goals for water releases to support the unique wetlands and ponds in the Poopenaut Valley.

To help document the effects of the experimental flood on the Poopenaut Valley, the project team utilized time lapse photography. The three videos we've included here were taken on the day of peak flooding in the valley.

Valley overview


North Pond "continental divide"
video

South meadow
video