Much of the recent inflow was to Hetch Hetchy, which can hold. Whats going on with the water level at Oroville? This dashboard provides a bit more detail on the state of each of the reservoirs while also showing an aggregate total. Amy Graff is the news editor for SFGATE. Next feature request: wire in aquifer level data! Great URL. Copyright Barry Rokeach, 2014. Why is Lake Nacimiento and Lake San Antonio not listed? O'Shaughnessy Dam is a 430-foot (131 m) high concrete arch-gravity dam in Tuolumne County, California, United States.It impounds the Tuolumne River, forming the Hetch Hetchy Reservoir at the lower end of Hetch Hetchy Valley in Yosemite National Park, about 160 miles (260 km) east of San Francisco. Remaining Capacity text in the legend should be brown? Part of the lake is on the California side, but it has zero California water impact beyond the immediate Tahoe residents.
Quite an eye opener. Thanks for developing it, and for sharing it with the rest of us! After the reservoirs "It was a very healthy shot in the arm. 2151 River Plaza Drive, Suite 205 Great stuff. Check out my **new combined California reservoir and snowpack visualizer** to compare to historical values, as well asthe California precipitation tracker and California snowpack visualizer. City officials have touted their efforts to help salmon, for example by timing water releases to assist with migration and restoring breeding grounds. Hetch Hetchy is one of nine reserviors in a water system that serves San Francisco and other Bay Area communities. If you are on a computer, you can hover your cursor over a reservoir and the dashboard at the top will provide information about that individual reservoir. But the growing water reserves dont please everyone. proposed as a source of water following the 1906 San Francisco Only improvement I would suggest is an improvement of the display of the smaller reservoirs so the names are readable. San Franciscos water-bank in Don Pedro Reservoir, downstream on the Tuolumne River, holds twice as much water as Hetch Hetchy. O'Shaughnessy Dam was built on the Tuolumne River in 1923 to create Hetch Hetchy Reservoir. She is also an alumna of Reveal from the Center for Investigative Reporting Investigative Fellowship and The New York Times Student Journalism Institute. David Rizzardo, hydrology section manager for the California Department of Water Resources, said there are a lot of factors that affect reservoir storage. Is it because the laws have changed on how much each reservoir can hold or is it in anticipation of significantly more rain? The tremendous inflow to city reservoirs during the recent storms, mostly in and around Yosemite National Park, has lifted San Franciscos total water storage to near capacity. Hours: Year-round, but only accessible by car when the Hetch Hetchy Road is open. GNSS2 - Level 2 Quality Survey Grade Global Navigation Satellite System. Best of luck out there in California! The water transmission system in the Bay Area and Peninsula includes the Bay Division, San Andreas, Sunset Supply, and Crystal Springs pipelines. Current and Historical Visualization, https://cdec.water.ca.gov/dynamicapp/QueryDaily?s=HTH, https://cdec.water.ca.gov/dynamicapp/QueryDaily?s=SHA, https://engaging-data.com/ca-reservoir-level/, https://cdec.water.ca.gov/reportapp/javareports?name=RES, Visualizing Californias Water Storage Reservoirs and Snowpack, Interactive California Reservoir Levels Dashboard. The Mokolumne River, which originates in the high Sierra, provides more than 90 percent of the East Bay's water and the Owens Valley in the eastern Sierra serves as a key source of water for Los Angeles. The only improvement I would ask you to consider is to allow the Y-axis to be Linear or Log, the latter allowing us to see all the small reservoirs quite easily. River. To reach Hetch Hetchy, you have to exit Yosemite National Park and re-enter it. I dont think its currently above the historical average, not below 1 year ago. Water storage facilities include watersheds, dams, and reservoirs including: Calaveras, San Antonio, Crystal Springs, Pilarcitos, and San Andreas. They placed a few dissipators just before the river. The OShaughnessy Dam, which was completed in 1938 and is 430-feet tall, impounds water in Hetch Hetchy Reservoir for communities in the Bay Area. The captured water is piped 150 miles to the Bay Area. in 2018. currently, there is a lot more water coming in than going out. You can find the charts below from the California Department of Water Resources website. A dry January with little rainfall across much of Northern California actually didnt hurt the states water storage levels, according to data from the California Department of Water Resources. Similar findings are described in theUC Davis studyRe-Assembling Hetch HetchyandUS Bureau of Reclamation study. Hetchy Reservoir can store as much as 117 billion gallons for the Navigation and Navigable Waters 33.208.82 Hetch Hetchy, Cherry Valley, and Don Pedro Dams and Reservoirs. This was helpful to project seasonal trends & storm impacts. Winter weather conditions may cause road closures. As of Feb. 1, the systems total water storage was just over 1.3 million acre-feet, or about 92% of capacity. This is wonderful information. Should be fixed at some point. For most of the year it will still be possible to divert the flow of the Tuolumne River into the pipeline just downstream of the National Park boundary. A dry January with little rainfall across much of Northern California actually didnt hurt the states water storage levels, according to data from the California Department of Water Resources. Curt, Good point re the colder weather dropping more snow instead of rain at higher elevations this year. At the same time, theyve also said its critical to maintain sufficient water supplies to keep Bay Area communities and its economy running during a prolonged drought. These sources include surface water stored in reservoirs located in the Sierra Nevada, Alameda County and San Mateo County, and groundwater supplies stored in a deep aquifer located in San Francisco and San Mateo counties. As of 5pm on 1/18, the data appears correct (~58k acre feet), but an hour ago it was reading off the chart (3X above what they are allowed to store right now). globe.height = globe.contentWindow.document.body.scrollHeight+40+"px";
In 2021, the SFPUC and the Modesto and Turlock Irrigation Districts launched a proactive pilot program with the U.S. In 2007, the Bush 2022 All Rights Reserved. sends student to hospital, Heres how much rain and snow is on the way this weekend, Your Privacy Choices (Opt Out of Sale/Targeted Ads). The half-hour drive to Hetch Hetchy from CA Highway 120 begins outside the park boundaries. dam and restoring the valley. looks like the CDEC website is the cause of the issue unless it actually dropped 90% in a day: Folsom is like an overflow tank. Omar, Thanks! Thank you for a beautiful job. The gain came after weather gauges in the area recorded more than 5 inches from one storm. use must be reasonable.. Curious why Shasta lake seems to be making big gains in water coming in and Trinity not so much? It didnt end the drought, but it was definitely really good," said Ritchie. The north (side of the reservoir) usually has two waterfalls going at the best of times, but youll see up and down the canyon walls, if you look close, you count there are about 12 waterfalls running now, said Steve Ritchie, the SFPUCs assistant general manager of water enterprise, during a recent drought report to the agencys governing board. I am grateful for all that you have done here to open our eyes to what is happening, what has happened, and even what might be on the horizon. scenic mountain valley in a national park. I am new to the state. It seems likely one of those two readings is wrong. Is that a good thing? Wife of missing Bay Area radio host says Jeffrey Vandergrift will not Sen. Dianne Feinstein is hospitalized in San Francisco with shingles, California extends deadline to file 2022 income taxes to match IRS decision, Here's where California reservoir levels stand after this week's rains, Going to Tahoe this weekend? The Hetch Hetchy Valley today with the dam seen in the lower right. do so. finding an alternative water and power source (Hetchy Hetchy also . I would turn this graph, 90 counterclockwise, and start the capacity along the bottom axis from left to right, with the biggest reservoirs on the left and the smaller ones on the right. 1 kaf is the amount of water that would cover 1 acre in one thousand feet of water (or 1000 acres in water in 1 foot of water). Impounded by O'Shaughnessy Dam, Hetch Hetchy Reservoir water passes through hydroelectric powerhouses before it enters the San Joaquin Pipelines, the Tesla Ultraviolet Treatment Facility, and the Coast Range Tunnel on its journey to the Bay Area. The Department of Water Resources, which manages the state's water supply, said in a statement that there are several possible reasons for the difference in inflow amounts between the two reservoirs. Santa Clara, Alameda and San Mateo counties. John Muir and the 501(c)3 organization, federal tax ID #942419885. His recent work has examined the impacts of drought, threats to public lands and wildlife, and the nation's widening rural-urban divide. Thinking more about it. During the winter months, they let water out of the reservoirs in anticipation of large storms. Maybe bad data. Hetch Hetchy Reservoir in Yosemite was 69 percent full on Tuesday, 150 percent of normal for this time of year. Eighty-five percent of the water comes from Sierra Nevada snowmelt stored in the Hetch Hetchy reservoir situated on the Tuolumne River in Yosemite National Park. One acre-foot is the equivalent of one acre of land covered in one foot of water. "Soils that have become hydrophobic due to wildfire can also contribute to increased runoff because the water is less able to penetrate the burned soil," the department said. Due to its high-altitude location at 3,900 feet above sea level Even with the latest precipitation, Folsoms values was unchanged. Horoscope for Friday, 3/03/23 by Christopher Renstrom, No seriously, dont drive up to Tahoe this weekend, Wife of Jeffrey Vandergrift issues somber update, Snowboarder dies at Tahoe ski resort following historic blizzard, Scream publicity stunt floods Bay Area dispatch with 911 calls, The best fried chicken is at a San Francisco strip club, Rain reenters Bay Area forecast: Have an umbrella near you, The Warriors broke Russell Westbrook, just like old times, Mochi muffin bakery closes SF cafe after just 4 months, Arrest in killing of woman seen running through Tahoe campground, Oakland ransomware attackers leak 'confidential' data, California Department of Water Resources website, 14 things you need in your car before you drive to Tahoe. Its important to note that other communities in California have taken actions in far greater magnitude than SF to make our waterways more sustainable. May 24, 2022 - BAWSCA Statement About the Adoption of a Systemwide Water Use Reduction of 11%. It was at 60 percent as of March 1 and rising, according to the Bureau of Reclamation. over the past few days. From the main road, it's about a 20- to 25-minute drive to the parking area. Exclusive: Stunning photos show Yosemite National Park under 15 feet of Warriors treating Andrew Wiggins with understandable patience, but his California snowpack hits highest level this century for March, could Map shows which parts of California exceeded entire years worth of rain, Map shows stunning improvement in California drought, Last chance to see: Bay Bridge lights turn off on Sunday. This chart only shows reservoirs filled via natural flow/rainfall. Lake Shasta, the state's largest reservoir, rose 2.9 feet and added 31,020 acre-feet of water. Impounded by OShaughnessy Dam, Hetch Hetchy Reservoir water passes through hydroelectric powerhouses before it enters the San Joaquin Pipelines, the Tesla Ultraviolet Treatment Facility, and the Coast Range Tunnel on its journey to the Bay Area. It has no natural inflow or out flow. Nice! Hi, I started by using this page (https://cdec.water.ca.gov/reportapp/javareports?name=RES) to determine which reservoirs to include and for some reason Almanor isnt on the list. Its water supply Hetch Hetchy Reservoir, in the Sierra Nevada is 80% full, . Lake ShastaLevel before the storm on Oct. 22: 882.57 feetLevel after the storm on Nov. 1: 885.47 feetTotal rise: 2.9 feet, Storage before the storm: 970,859 acre-feetStorage after the storm: 1,001,879 acre-feetTotal storage increase: 31,020 acre-feet, Lake OrovilleLevel before the storm: 630.80 feetLevel after the storm: 661.20 feetTotal rise: 30.4 feet, Storage before the storm: 799,638 acre-feetStorage after the storm: 982,263 acre-feetTotal storage increase: 182,625 acre-feet, Hetch HetchyLevel before the storm: 3,729.68 feetLevel after the storm: 3,750.99 feetTotal rise: 21.31 feet, Storage before the storm: 221,500 acre-feetStorage after the storm: 257,800 acre-feetTotal storage increase: 36,300 acre-feet, Trinity LakeLevel before the storm: 2,209.55 feetLevel after the storm: 2,213.22 feetTotal rise: 3.67 feet, Storage before the storm: 648,675 acre-feetStorage after the storm: 672,930 acre-feetTotal storage increase: 24,255 acre-feet, Folsom LakeLevel before the storm: 370.28 feetLevel after the storm: 390.33 feetTotal rise: 20.05 feet, Storage before the storm: 214,225 acre-feetStorage after the storm: 318,577 acre-feetTotal storage increase: 104,352 acre-feet, New Melones LakeLevel before the storm: 916.28 feetLevel after the storm: 917.09 feetTotal rise: 0.81 feet, Storage before the storm: 822,619 acre-feetStorage after the storm: 827,786 acre-feetTotal storage increase: 5,167 acre-feet, Don PedroLevel before the storm: 723.96 feetLevel after the storm: 727.41 feetTotal rise: 3.45 feet, Storage before the storm: 970,226 acre-feetStorage after the storm: 995,836 acre-feetTotal storage increase: 25,610 acre-feet, McClureLevel before the storm: 663.70 feetLevel after the storm: 672.27 feetTotal rise: 8.4 feet, Storage before the storm: 180,900 acre-feetStorage after the storm: 198,467 acre-feetTotal storage increase: 17,210 acre-feet. . Arg. Similar to the water supply issues discussed above, the amount of power replacement is small in a statewide context less than of 1% of the renewable power supply being developed this decade alone. McClintock bill proposes to improve public access at Hetch Hetchy. has a graph which shows how the historical avg changes throughout the year (oscillating between ~15000 and ~21000). February 21, 2023 - BAWSCA Statement on State Water Resources Control Board'sSchedule for Consideration of a Voluntary Agreement for the Tuolumne River. Much of the recent inflow was to Hetch Hetchy, which can hold about 360,000 acre-feet of water and was 83% full at the start of the month. Locked padlock Could you also do the same for the Colorado River reservoirs to see how they are fairing? Located within the boundaries of Yosemite National Park, the reservoir saw a sizable 21.31-foot bump in its water level and gained 36,300 acre-feet, according to Tuesday data from the U.S. Geological Survey. This is my first year watching the levels, so maybe Im missing something. Folsom Lake is letting the water flow out. thanks. And more work is underway. Required fields are marked *. Just a wistful thought, it would be really cool to graph the water release statistics. The extensive amount of storage, which is designed to benefit the Bay Area as droughts become more severe with climate change, has become a sticking point in a longstanding environmental battle over how much water the city should be taking from rivers. In addition, San Francisco receives approximately one-tenth of its power from hydroelectricity generated by the gravity-driven flow from the Hetch Hetchy Reservoir. best to drain the valley. That cant be right. This site is a great tool, especially as we try to climb out of these drought years. I love this this site too. Although Hetch Hetchy Reservoir is the most well-known, it stores less than 25% of the systems water. The water travels through a series of pipelines before it reaches the Bay Area and blends with five local reservoirs. The Bay Area's main reservoir is up 21 feet. LK ELEANOR NR HETCH HETCHY CA. Good info to know. In Yosemite National Park, the Hetch Hetchy reservoir relies. Your email address will not be published. The recent spate of storms lifted the statewide snowpack to 190% of average for the start of the month, and more snow is on the way. San Francisco maintained the phrase only Love the dashboard! How do I contact support? It was my first time using D3 and it took me a long time to get up to speed. The Hetch Hetchy reservoir, which supplies water for San Francisco and other parts of the Bay Area, was at 77% of its 360,000-acre-feet storage capacity in January compared to 73% in December, and on Feb. 7, it was up to 82%. Some want the city to leave more water in stream channels for threatened salmon while others continue a longshot bid to shut down Hetch Hetchy Reservoir in Yosemite altogether and return the area to its natural state. FYI it looks like Isabella is reading incorrectly, likely because its well above 100%. Its just small enough that the name doesnt appear as the bar is too thin. Thats up more than 400,000 acre-feet since early December, before the unrelenting series of atmospheric river storms blew through California between Christmas and mid-January. Long-term values for reservoir inflows use maximum number of complete water years in record. The windfall of water is welcome news for households and businesses in San Francisco, which use less water on average compared to the rest of the state but nonetheless have faced calls to cut back since 2021 because of water shortages. November 10, 2022 - BAWSCA Statement on State Water-Policy Officials, SFPUC, and Districts Sign MOU for Tuolumne River to Help Recover Salmon While Protecting Water Reliability. Upcountry and the Bay Area. The proportion of blue to brown will show how full it is, while the red line shows the historical level that reservoir is typically at for this date of the water year. Thanks for the prompt reply! San Francisco will be in great shape going into 2023, said Spreck Rosekrans, executive director of Restore Hetch Hetchy Its unfortunate that too little is being done with these flows to recharge groundwater basins to help cities and farms and even restoring Hetch Hetchy Valley., Kurtis Alexander is a San Francisco Chronicle staff writer. Great graphs and very useful. }, false); Lake Tahoe really isnt part of California water, as the outflow goes to Nevada. The snowpack there, which will eventually melt and flow into reservoirs, is already bigger than the average peak snowpack, which typically comes around April 1. The height of the row indicates how much water the reservoir could hold. Hetch Hetchy Regional Water System The Hetch Hetchy watershed, an area located in Yosemite National Park, is the major source of water for all of San Francisco's water needs. Could you also show each reservoirs level as a function of time? Im curious why the percentage of capacity has stayed almost flat for the past 6 weeks or so and below historical average. Having it here would be great! In the year prior to Oroville reaching capacity the interactive chart showed the rate of inflow over time. Kudos to the designers. Hi Keith, you could de-select the large reservoirs from the menu at the top right. This other page: https . Delivering approximately 260 million gallons of water per day, the regional system consists of over 280 miles of pipelines, over 60 miles of tunnels, 11 reservoirs, five pump stations and two water treatment plants. I havent spent much time looking at it but that data is on the CDEC website. The Hetch Hetchy Reservoir that supplies San Francisco, seen here in February, is among those that have refilled after two months of storms. According to the San Francisco Public Utilities Commission, Hetch Restore Hetch Hetchys subsequent appeal to the ruling was Hetch Hetchy is only one of nine reservoirs in the San Francisco Public Utility Commissions water system. James Q. Martin / Restore Hetch Hetchy Show More Show Less 4 of 7 San Francisco voters have demonstrated their opposition to Thanks for the link. The upcountry portion of the System begins with Hetch Hetchy Reservoir in Yosemite National Park. ) or https:// means youve safely connected to the .gov website. Current conditions of LAKE OR RESERVOIR WATER SURFACE ELEVATION ABOVE NAVD 1988, LAKE OR RESERVOIR WATER SURFACE ELEVATION ABOVE NGVD 1929, and RESERVOIR STORAGE are available. I realize there we dont want to reservoirs overflowing, but why are we still below historical average? Gavin Newsom asked all California residents to voluntarily reduce use by 15% compared with use in 2019. 2013, photo, the Hetch Hetchy Reservoir is hazy with smoke . The SFPUC has consistently stated that voluntary agreements are the best path forward for the Bay-Delta, as the voluntary agreement strikes the right balance between environmental stewardship and water reliability. Congress had to approve the project because it was Trinity Lake, with a capacity of 2,447,650 acre-feet, had the smallest increase, from 29% in December to 30% in January. Before joining the Chronicle, Alexander worked as a freelance writer and as a staff reporter for several media organizations, including The Fresno Bee and Bay Area News Group, writing about government, politics and the environment. How Much Water is in California Reservoirs? SFGATE took a look at reservoir levels three days after the Oct. 24 storm and below we take another look, examining water level rises and storage increases at a broader range of reservoirs roughly a week after the atmospheric river event. Also a little nit. however, Ill update the code to include it soon. What rates am I paying? Great Job on this site! Voters rejected a 2012 Hetch Hetchy water travels 160 miles via gravity from Yosemite to the San Francisco Bay Area. It looks like the red and blue lines are backwards on Folsom. I like the comparisons of last year, and the historical average. https://engaging-data.com/ca-reservoir-level/
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Several cities and water agencies that are now part of BAWSCA urged Congress to pass the Raker Act in 1913, the law that allowed federal lands in the Sierra Nevada Mountains, including Hetch Hetchy Valley in Yosemite National Park, to be used to build the water system. Therefore flood control agencies take the more conservative route and order the release of water. Climbers Timmy O'Neill (left) and Lucho Rivera atop a wall overlooking Hetch Hetchy Reservoir. Thanks for putting this together. Thats just another very strong indication visually that its a big water year.. The Water Education Foundation is a nonprofit, tax-exempt, Secure .gov websites use HTTPS This system encompasses more than 1,250 miles of distribution pipelines, as well as 12 in-City reservoirs and eight water tanks with a total storage capacity of approximately 413 million gallons. Water data back to 1956 are available online. Construction of the regional water system proceeded over the following 20 years, with water first delivered in 1934. The construction of the Hetch Hetchy Railroad took place from 1915 to 1918. Hetch Hetchy is Monitoring location 11275500. Lake Almanor isnt controlled by DWR for flood/supply. a minimum, according to the San Francisco Public Utilities So they should be saving much more and deal with the .000001 of risk later. I see many of the local canals flowing with lots of water. The water treatment facilities are Tesla Ultraviolet Treatment Facility, disinfecting the Hetch Hetchy supply; Sunol Valley Water Treatment Plant, treating the water from the Calaveras and San Antonio supply as well as the stored Hetch Hetchy supply; and Harry Tracy Water Treatment Plant, treating the water from the Crystal Springs and San Andreas supply. While it may seem that Decembers production could get us through the rest of the season, Rizzardo explains that in hydrology, you need consistent water shed to keep soils happy. He fears that without more precipitation this season, well enter our third very dry year. The BAWSCA agencies are therefore key stakeholders in ensuring the system serves as a reliable source of high quality water. I do not see Diamond Valley Lake Resevoir on this page. A small portion of the citys water comes from local reservoirs. Its not possible to see or really interact with the tiniest slivers. Reservoir behind OShaughnessy Dam does not require filtration. ", The difference in soil type in the two watersheds was likely another factor. I would think with the rain it would get to historical average and then more outflow would happen. mobilewarn();
The amount stored is increasing, just not by a lot. Just trying to learn here Thanks so much! Thank you so much for the hard work! But it has flooded nine miles of a glacier-carved valley and blocks access to the Grand Canyon of the Tuolumne and other nearby areas. The trail includes spectacular views of Tueeulala and Wapama Falls. Another not monitored by the State? I would like to make one small suggestion:. The cities of Burlingame, Hayward, Menlo Park, Palo Alto, Redwood City and San Mateo, along with the Alameda County Water District, were among Bay Area communities whose support was influential in persuading Congress to pass the controversial Act, and President Woodrow Wilson to sign it. In whats known as the Bay-Delta Plan, state water regulators are amid a years-long effort to negotiate a policy for how much water should be kept in rivers that flow to the Sacramento-San Joaquin River Delta to meet the needs of both people and wildlife. Northern California's reservoir levels continued to rise in the week after an atmospheric river slammed the state with torrential rain and high winds. Heres an example of that data for Shasta, where you can see the daily inflows and outflows: the Hetch Hetchy Valley to its natural state. For example, Hetch Hetchy Reservoir in Yosemite National Park provides 85 percent of San Francisco's total water needs. It certainly looks dry at least until the last week in February, he said. This is of particular interest as the self-imposed restrictions deadline is approaching and the federal government may have to step in and mandate restrictions across the 7 states, including California. It allowed the water over the spillway to move too fast creating a vacuum between the water and the concrete that pulled the concrete sections out of the spillway. Water data back to 1930 are available online. The problem is that we have no idea of knowing ahead of time what kind of storms well have and how long theyll last, but the reservoir operators have to be super careful and extra cautious, so they periodically let the water flow out. The water system, which includes the landmark Hetch Hetchy Reservoir, is expected to fill this winter, for the first time since 2019, with nearly 1.5 million acre-feet of water. They are releasing water into the canals. Steve Ritchie, the San Francisco Public Utilities Commission's assistant general manager for water, said the additional water amounted to roughly 11% of the reservoir's total capacity. I believe the spillway was designed by the State. Top ways to experience Hetch Hetchy Reservoir and nearby attractions Yosemite: Audio Driving Tour 1 Full-day Tours from $9.99 per group (up to 8) Private Yosemite Explorer Package | 3 Days of Adventure 3 Private and Luxury from $750.00 per adult (price varies by group size) Private Family Photo Day in Yosemite 78 Recommended Full-day Tours from Love easy to read and understand information. It carried workers and materials for the dam, as well as tourists, postage and other amenities. Forty-six percent . It is on the graph. Flood control agencies (not DWR) have the most say in regard to releases.
Hetch-Hetchy predicted to fill by end of the snowmelt period 2020-2021 Winter season continues to be dry 2019-2020 was dry, although key differences Feb. 2020 was unusually warm, which impacted snowfall levels and water demands; Feb 2021 was cooler, and hence snowfall level higher and water use lower
The upcountry portion of the System begins with Hetch Hetchy Reservoir in Yosemite National Park. Its water supply Hetch Hetchy Reservoir, in the Sierra Nevada is 80% full, the ground is saturated and near-record rainfall has occurred in recent days. Ive added it to my bookmarks for quick reference. Meanwhile, the group Restore Hetch Hetchy is urging the SFPUC to abandon Hetch Hetchy Reservoir. Near the town of La Grange, the river exits the Sierra Nevada foothills and flows through a gently sloping alluvial valley that is incised into Pleistocene alluvial fans. All rights A different story is unfolding at Hetch Hetchy reservoir in Yosemite National Park, where water is being released to conserve and restore wildlife. The Bay Area transmission system also includes Irvington Tunnel 1 and Tunnel 2, the Bay Tunnel, and the Crystal Springs Bypass Tunnel. supplies water to the San Francisco Bay Area. Owned by the city of San Francisco, Hetch Hetchy Reservoir