Ronald Reagan and George W. Bush. We own and operate the Hetch Hetchy Regional Water System which serves 2.7 million customers. 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. Historical average is near unattainable these days. Great resource! I find myself coming back to this every few days to check on our water . The reservoir is now projected to cost $4.4 billion, with Prop. If you look at this chart for Hetch Hetchy, you can see that the biggest and steadiest rise is between March and July, https://waterdata.usgs.gov/monitoring-location/11275500/#parameterCode=00054&period=P365D&compare=true. This file photo shows Shasta Lake. Hetch Hetchy Reservoir in Yosemite was 69 percent full on Tuesday, 150 percent of normal for this time of year. FYI it looks like Isabella is reading incorrectly, likely because its well above 100%. The SFPUC gets the bulk of its water from a network of reservoirs in the central Sierra Nevada that have long altered flows of the Tuolumne River and its tributaries. At the moment, I am not interested in the debate. Kellie has held many leadership roles for the Asian American Journalists Association, including most recently a board member for the San Francisco chapter. Charts from the California Department of Water Resources show conditions at key state reservoirs on Oct. 22 (left) and on Nov. 2 (right). 501(c)3 organization, federal tax ID #942419885. 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. Water data back to 1956 are available online. 95 percent of. Hetch Hetchy water travels 160 miles via gravity from Yosemite to the San Francisco Bay Area. They also built a spillway that was too steep and did not install energy dissipators along the spillway. Most local reservoir inflow timeseries are too short to calculate long-term values. Wapama Falls (moderate) 5 mi (8 km) round-trip; 2 hours. According to the San Francisco Public Utilities Commission, Hetch Hetchy Reservoir can store as much as 117 billion gallons for the Hetch Hetchy Regional Water System, which serves San Francisco, Santa Clara, Alameda and San Mateo counties. In 2021, the SFPUC and the Modesto and Turlock Irrigation Districts launched a proactive pilot program with the U.S. DWR is one of many local, State and Federal entities that dictate water releases. 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. The remaining 15 percent of water comes from runoff in the Alameda and Peninsula watersheds. 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. CHERRY LK NR HETCH HETCHY CA Important Legacy real-time page Monitoring location 11277200 is associated with a LAKE, RESERVOIR, IMPOUNDMENT in TUOLUMNE COUNTY, CALIFORNIA. I havent spent much time looking at it but that data is on the CDEC website. Shasta, Oroville, Hetch Hetchy and many others were built by damming large rivers. Ive looked at reservoir sights for years. If you are on a mobile device you can tap the reservoir to get that same info. 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. I dont know if weve seen anything like this in October before.". San Franciscos Hetch Hetchy water system is almost full for the first time in years. Thanks. Amy Graff is the news editor for SFGATE. Current conditions of LAKE OR RESERVOIR WATER SURFACE ELEVATION ABOVE NGVD 1929 and RESERVOIR STORAGE are available. Much of the recent inflow was to Hetch Hetchy, which can hold. Trailhead address: Evergreen Road (Hetch Hetchy Road), Yosemite National Park, CA 95321. 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. While forecasters can predict the likelihood of future rainfall over large areas, they cant pinpoint it to the degree needed to determine whether a particular watershed/reservoir will overflow and cause damage and loss of life. The Hetch Hetchy Valley today with the dam seen in the lower right. The remaining 15 percent of water comes from runoff in the Alameda and Peninsula watersheds. Additionally, the bounty helps the more than two dozen communities in Alameda, San Mateo and Santa Clara counties that get their water from the city. Twenty of San Compared to the historical snowpack for this time of year, the May 2021 survey shows that we are only 2 to 5 percent of normal. and maybe another vertical axis to the right of that with reservoir capacity. not passed until 1928 five years after the dam was built. 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. reserved. 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 The main reason for the discrepancy, the department said, is that the focus of the atmospheric river was generally between the Golden Gate and Mount Lassen, meaning that the Feather River watershed received much more rainfall than the Shasta Lake drainage area. 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 citys water system also includes a water bank at Don Pedro Reservoir along the Tuolumne River, which was full as of Feb. 1. Thats just another very strong indication visually that its a big water year.. Updated to include drought zones while tracking water shortage status of your area, plus reservoir levels and a list of restrictions for the Bay Areas largest water districts. Lake Almanor isnt controlled by DWR for flood/supply. I will take a look and see if there are other important reservoirs missing and may add them in the future. She was previously an engagement reporter. While the rainfall has been bad for many people, I am happy to see Californias reservoirs are benefiting slightly, Amen! You can also share a custom URL by clicking the Save URL button which will put the custom URL into the URL bar of your browser which you can then copy and share. Assistant General Manager for Water Steven Ritchie credits the way the system is managed along with lower. After the reservoirs While the long-term voluntary agreement work continues, the SFPUC does not want to wait to restore the Tuolumne Rivers ecosystem. The area around Shasta has more volcanic soils that absorb rainfall than the Feather River drainage. Secure .gov websites use HTTPS Restore Hetch Hetchy intends to undo this Great American mistake, and return the valley to Yosemite National Park and all people. Congress had to approve the project because it was . According to the SFPUC, the upper reaches of the Tuolumne River have received about 36 inches of rain since the start of the water year in October, almost as much as what the area averages in a year. They placed a few dissipators just before the river. 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. Your tools are awesome just hurts when you receive bad data at times! mandate within Data have been checked by the reporting agency. More about the Tuolumne River Voluntary Agreement can be found athttp://www.tuolumnerivermanagementplan.com. https://engaging-data.com/ca-reservoir-level/ "In contrast, the Shasta Lake drainage had only a couple of stations in excess of 10 inches whereas most received less. 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. 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. administration attempted to allocate funds to study removing the Lock It didnt end the drought, but it was definitely really good," said Ritchie. Units are in kaf, thousands of acre feet. The cities, water districts and private utilities represented by the Bay Area Water Supply and Conservation Agency (BAWSCA) rely upon the Hetch Hetchy system for water to protect the health, safety and economic well being of 1.8 million citizens, businesses and community organizations. Your Privacy Choices (Opt Out of Sale/Targeted Ads). 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. It is on the graph. So my question is, How do we know if we are saving the water for later release (late summer) or are we releasing it to the ocean? I live close to Eastman Lake. Great work. Great Job on this site! "It was a very healthy shot in the arm. San Francisco's water-bank in Don Pedro Reservoir, downstream on the Tuolumne River, holds twice as much water as Hetch Hetchy. 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. Sacramento CA 95833, Everything about California water that matters, Western States Water Agencies and Districts. Theyve also seen drought surcharges on their water bills. Share sensitive information only on official, secure websites. The SFPUC has voiced concerns with the Plan, as it would dramatically reduce the agencys water supply, leaving it subject to significant rationing in droughts and more extreme weather conditions brought on by climate change. looks like the CDEC website is the cause of the issue unless it actually dropped 90% in a day: Spring snowmelt runs down the Tuolumne River and fills Hetch Hetchy, the largest reservoir in our water system. 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. proposed as a source of water following the 1906 San Francisco John Muir and the Generation at the Kirkwood power plant would depend on the natural flow of the Tuolumne River, and would be significantly diminished during late summer and fall. Voters rejected a 2012 You can find the charts below from the California Department of Water Resources website. They have restoredMono Lake,improved stream flows on the North Coast and in theCentral Valleyand diminished the threat to native fish in the Bay Delta. Instructions: Weve been at zero now for several weeks, and we really want to see that turn around., Kellie Hwang and Yoohyun Jung are San Francisco Chronicle staff writers. Email: [email protected], [email protected] Twitter: @KellieHwang, @yoohyun_jung. Department of Water Resources is just another in a long line of completely mismanaged California entities. In 2007, the Bush What happened to the Hetch Hetchy level? The Bay Area transmission system also includes Irvington Tunnel 1 and Tunnel 2, the Bay Tunnel, and the Crystal Springs Bypass Tunnel. McClintock bill proposes to improve public access at Hetch Hetchy. Copyright 2023Water Education Foundation. Water data back to 1930 are available online. Due to its high-altitude location at 3,900 feet above sea level Hetchy Reservoir can store as much as 117 billion gallons for the The main goal of this visualization is to provide a quick overview of the status of the main reservoirs in the state and how they compare to historical levels. Your email address will not be published. the Bay Area. A separate vote would have been Restore Hetch Hetchy. Our drinking water comes from a variety of protected sources carefully managed by the SFPUC. Winter weather conditions may cause road closures. over the past few days. California drought: Charts show where reservoir levels stand after a dry January, Track water shortages and restrictions across Bay Area. You can sort the mekko graph by size largest at the top to smallest at the bottom or by reservoir location, from north to south. Thank you so much for the hard work! At this facility, which is shared with other water agencies, the city can stash water for credits against future draws on the river. The 1913 Raker Act authorized the unprecedented dam inside the park and also set the fee that the city pays to rent the entire valley in which the dam sits: $30,000 per year. Restore Hetch Hetchy supports a power replacement plan that is truly renewable, and will not increase emissions of any pollutants or carbon that causes global warming. 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. Yes, and why is Twitchell Dam also not listed? Thats enough to supply the citys service area for perhaps seven years. Its supposed to be brown. } The gain came after weather gauges in the area recorded more than 5 inches from one storm. draining the reservoir to court, arguing in 2015 that the BAWSCA Board of Directors Meeting, March 16, 2023, 6:30 PM. Add a button to convert the row heights to log scale. Within San Francisco, we manage water distribution in the City. This is a marimekko (or mekko) graph which may take some time to understand if you arent used to seeing them. ) or https:// means youve safely connected to the .gov website. You can email her at [email protected]. hetch hetchy reservoir level percentage Rivers and Streams Streams draining into the Peninsula Watershed within the project area are relatively small, steep, and in a 2021-11-17. All Rights Reserved. a broad meaning that had been previously applied in an Current conditions of LAKE OR RESERVOIR WATER SURFACE ELEVATION ABOVE NGVD 1929 and RESERVOIR STORAGE are available. Before returning to the Bay Area, she held roles as transportation reporter and trending news reporter at the IndyStar in Indianapolis. Excellent graphic! 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. Great graphs and very useful. What rates am I paying? window.addEventListener("orientationchange", function() { It seems likely one of those two readings is wrong. But I would never have imagined how to put all the important information into a single plot. Jeff, the average changes daily as well. 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). I wonder why it doesnt work for you. Ive added it to my bookmarks for quick reference. With how we can now basically pinpoint future precipitation amounts at least a month in advance, no reason to not let these reservoirs fill up past historic averages for this date. This is the first state (of 6 I have lived in) that has had water police and restrictions. The Bay Area's main reservoir is up 21 feet. The source water from SFPUC is typically from the Hetch Hetchy reservoir located in the Sierra Nevada Mountains. Hetch Hetchy Reservoir in Yosemite National Park is seen in 2022. Only modest new supplies would be required in the driest years. Just in case a large storm hits, that way they dont reach 100% capacity. 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. This is a very clear graph and I cannot imagine the hours you have put in while setting it up and doing the maintenance. The soaking was welcome in a drought-plagued state with a diminishing water supply. A 1 week change would be interesting to show on each. Waterfalls gushed at Hetch Hetchy after an atmospheric river event in October 2021. 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. For perspective, water demand across the SFPUCs service area of 2.7 million people was about 205,000 acre-feet last fiscal year. 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. Meant this comment for the integrated snowpack and reservoir view. This is an excellent tool you have put together. however, Ill update the code to include it soon. Is it because the laws have changed on how much each reservoir can hold or is it in anticipation of significantly more rain? Wonderful site. They are releasing water into the canals. All rights document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); Subscribe to receive email notifications of new content. Long-term values for reservoir inflows use maximum number of complete water years in record. Current as of October 03, 2022 | Updated by . The judge also noted the provision of the state I noticed that Folsom does not change whereas every reservoir changes on an hourly update. San Franciscos water system, which includes Hetchy Hetchy, is expected to fill this winter for the first time since 2019. There is something strange about the data over the last two days (Jan.17 to Jan. 19): Is that from melting snow and rain water coming from the mountains and filling it up? This hike follows the shoreline of the reservoir with moderate up and downhill hiking. Email: [email protected] Twitter: @kurtisalexander. It used to be full (and beyond). But tearing down O'Shaughnessy Dam in order to restore Hetch Hetchy Valley would be a disaster. Restoring Hetch Hetchy will require some changes in how San Francisco moves and stores water. This is also affected by most of these dams multi-purpose nature where they are near constantly releasing for power(like Shasta) or to make room for flood control capacity(like Folsom). 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. YTD values are from January 1 . thanks. Major snowstorm might leave you stranded, New 101 express lanes opens in Bay Area. Restore Hetch Hetchys subsequent appeal to the ruling was Thanks for the prompt reply! Maybe bad data. 1 covering up to $875 million and much of the rest coming from federal loans to water suppliers. Commission. The captured water is piped 150 miles to the Bay Area. Id love to see how much water is being / has been released from these reservoirs. If you look at the inflow data on the major reservoirs, its pretty flat. This is a great and very thoughtfully designed web site! For example, the average storage level for Feb. 7 is usually 65% of capacity for Trinity Dam, but currently its at 31%. 9 of 12 10 of 12 Hetch Hetchy Reservoir with Wapama Falls near Groveland, Calif. on Wednesday March 12, 2014, is currently at fifty percent of capacity. In addition, San Francisco receives approximately one-tenth of its power from hydroelectricity generated by the gravity-driven flow from the Hetch Hetchy Reservoir. Super frustrating. It takes a fair amount of work to make graphs compared to other more plug-and-play libraries but its very customizable, which is a plus. Usually with warm ARs, you get a dramatic increase in inflow, which can fill even very large reservoirs relatively quickly, like Oroville in 2017. This chart only shows reservoirs filled via natural flow/rainfall. The average for this time of year is approximately 4,659.57ft, plus or minus 39ft. Hetch Hetchy is only one of nine reservoirs in the San Francisco Public Utility Commission's water system. Trailhead coordinates: 37.946905, -119.787376 (37 56 48.85N 119 47 14.55W) James Q. Martin / Restore Hetch Hetchy Show More Show Less 4 of 7 This almost happened with the Orville Dam in 2017. Water data back to 1930 are available online. maybe label the vertical axis with aggregate total or system total capacity. Its just small enough that the name doesnt appear as the bar is too thin. 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. Hetchy refers to a valley in the Sierra Nevada and a reservoir that Over the summer, Gov. 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. It can take several days to see the full impact on reservoirs as water continues to run through watersheds and into streams in the days after a storm. March 12 - The Perks of California Native Wildflowers, March 28 - Rainwater Harvesting and Rain Gardens, April 01 - Lawn Conversion to Native and Drought-Tolerant Plants. Water data back to 1956 are available online. currently, there is a lot more water coming in than going out. Thanks for developing it, and for sharing it with the rest of us! UPDATE: Here's where California reservoir levels stand after this week's rains. Stay up-to-date with breaking news and upcoming events. Curt, Good point re the colder weather dropping more snow instead of rain at higher elevations this year. Monitoring location 11277500 is associated with a LAKE, RESERVOIR, IMPOUNDMENT in TUOLUMNE COUNTY, CALIFORNIA. San Francisco and the thousands of suburban . Emissions must be offset by dedicated conservation programs or renewable energy generation such as wind or solar. https://waterdata.usgs.gov/monitoring-location/11275500/#parameterCode=00054&period=P7D. The data on water storage comes from the California Department of Water Resources (DWR) Data Exchange Center. Curious why Shasta lake seems to be making big gains in water coming in and Trinity not so much? Each row represents one reservoir, with bars showing how much of the reservoir is filled (blue) and unfilled (brown). There doesnt seem to be any site that shows the impact of each storm. This is wonderful information. The Bay Area portion of the System includes water collection, treatment, and transmission facilities from the Alameda East Portal to the wholesale service area and terminal reservoirs in San Francisco. Since June 2011, the Water Enterprise has operated the Citys Emergency Firefighting Water System (EFWS, formerly known as the Auxiliary Water Supply System (AWSS)), an independent, high-pressure water supply system for fire suppression. word for a type of wild grass. So on Jan 10 were at 82% of the average for Jan 10. As it is, at first glance, it looks like shasta is at the top because its 28000 instead of 4552. very nice product overall. An improvement: Could you include a bar for Last year at this date? rejected by an appellate court and the California Supreme Court generates electricity for the city). I know this might be difficult to display but Im very curious on the actual amounts of water consumed on a monthly basis and if this is somehow processed in a certain between what is agricultural and what is non-commercial etc? With modest additional investments San Francisco will be able to maintain an uninterrupted supply of high quality Tuolumne River water. the issue, including those under Franklin Delano Roosevelt, Awesome work!! Nice! Hoping they start building more reservoirs soon. Why is Lake Nacimiento and Lake San Antonio not listed? How can I match up other monitoring locations similar to the ones on this Interactive Dashboard? Call 209-372-0200 for the latest road and weather conditions, Hetch Hetchy Road Daily Hours: 8 am to 5 pm Water storage facilities include watersheds, dams, and reservoirs including: Calaveras, San Antonio, Crystal Springs, Pilarcitos, and San Andreas. Previously, Kellie covered dining news and trends, visual arts, events and nightlife for the Arizona Republic, and freelanced for the former Contra Costa Times. Sierra Club unsuccessfully fought the reservoirs establishment 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. It updates hourly using data from the California Department of Water Resources (DWR) website, giving an up-to-date picture of California reservoir levels. Take CA Highway 120 from the park toward Groveland. If you are experiencing a water, power, or sewer emergency or service problem call our 24-hour hotline at 3-1-1 or (415) 701-2311 from outside SF or log on at, Public Notices and Public Meeting Notices, Customer Assistance Program - Water/Wastewater, Customer Assistance Program - Hetch Hetchy Power, Hetch Hetchy Power Medical Necessity Assitance Program, Hot Water Recirculation Pump Rebate Program, San Francisco's Urban Watersheds Overview, Free Phone Consultations, Evaluations and Devices, Games Puzzles Virtual Backgrounds Overview, Get your Free 2023 Pollution Prevention Calendar, Construction & Contracts Overview Overview, Contract Opportunities and Payments Overview, Project Review and Land Use - Hetch Hetchy Water and Power, Project Review and Land Use - San Francisco, Sewer System Improvement Program Overview, Water Infrastructure Improvements Overview, Boards, Commissions and Committees Overview, Internships, Apprenticeships and Youth Employment, Public Notices and Public Meeting Notices Overview, Audited Financial Statements & Annual Comprehensive Financial Reports, SFPUC Preliminary Public Power Options Report, Civic Center Sustainable Utilities District Plan, Resolution Condemning Systemic Racism & Taking Action to Promote Racial Justice. And the current water storage amounts are well below the historical averages for this time of year. Official websites use .gov diversion of water? Restore Hetch Hetchy claimed the phrase had Shasta is the reservoir with the largest capacity and so it is the tallest row. This dashboard is great! While constructed and owned by San Francisco, the water system was in fact planned to benefit the greater San Francisco Bay Area population. Water is such a fascinating topic and Id hate to have to be a water manager making a decision on how much to release to avoid reservoir flooding. How can I apply to SFPUC? What happened to the Hetch Hetchy level? in 2018. If a reservoir gets filled to 100% and more, the dam will break and many cities will get flooded, so the operators are careful. function reloadiframes(){ Thats a great suggestion and one that would be particularly helpful! She joined the Chronicle as a data reporter in 2021. For detailed analysis of how San Franciscos water system will operate without Hetch Hetchy reservoir, see the Environmental Defense Funds studiesParadise RegainedandCherry Intertie Alternative. . The regional water system provides water to 2.4 million people in San Francisco, Santa Clara, Alameda and San Mateo counties. Its water supply Hetch Hetchy Reservoir, in the Sierra Nevada is 80% full, . Monitoring location 11277200 is associated with a LAKE, RESERVOIR, IMPOUNDMENT in TUOLUMNE COUNTY, CALIFORNIA. GNSS2 - Level 2 Quality Survey Grade Global Navigation Satellite System. Although Hetch Hetchy Reservoir is the most well-known, it stores less than 25% of the system's water. Its essential to understand that the dispute over San Franciscos use of Hetch Hetchy is not about the use of water only how it is stored. it will be cool if there is a way to track the change since Dec or some such date. has a graph which shows how the historical avg changes throughout the year (oscillating between ~15000 and ~21000). **new combined California reservoir and snowpack visualizer**, made a bar graph showing the overall level of water in the major California reservoirs, the California Department of Water Resources (DWR) Data Exchange Center. 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. 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. their water supply would cost hundreds of millions of dollars at Hetch Hetchy Water System The system originates more than 100 miles from its primary customers, in Yosemite National Park.