How much water is in California’s reservoirs?
Check out my new Colorado river reservoirs visualization.
I also added the ability to select specific reservoirs to display on the graph and share a custom URL which will point those selected reservoirs (click on “list” button on top right of dashboard).
If you are reading this, it’s probably the winter rainy season in California again, and time to check on the status of the water in the California reservoirs. I previously made a “bar graph” showing the overall level of water in the major California reservoirs. This dashboard provides a bit more detail on the state of each of the reservoirs while also showing an aggregate total. It updates hourly using data from the California Department of Water Resources (DWR) website, giving an up-to-date picture of California reservoir levels.
This is a marimekko (or mekko) graph which may take some time to understand if you aren’t used to seeing them. Each “row” represents one reservoir, with bars showing how much of the reservoir is filled (blue) and unfilled (brown). The height of the “row” indicates how much water the reservoir could hold. Shasta is the reservoir with the largest capacity and so it is the tallest row. 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. The blue line indicates the reservoir’s water level one year ago today. There are many very small reservoirs (relative to Shasta) so the bars will be very thin to the point where they are barely a sliver or may not even show up.
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. If you are on a mobile device you can tap the reservoir to get that same info. It’s not possible to see or really interact with the tiniest slivers. 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.
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.
If you click on the “list” button in the top right of the dashboard, it will show a list of the reservoirs (in order of size from largest to smallest) and you can check which ones you would like to display. 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. You can also use it to monitor only the reservoirs you are most interested in.
Units are in kaf, thousands of acre feet. 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). It is also the amount of water in a cube that is 352 feet per side (about the length of a football field). Shasta is very large and could hold about 3.5 cubic kilometers of water at full (but not flood) capacity.
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120 Responses to Interactive California Reservoir Levels Dashboard
FYI Hetch Hetchy’s suddenly reading at just 6.4% of capacity. Pretty sure it was near 100% yesterday.
Does anyone know how much the snowpack will affect the various water reservoir levels indicated on this fabulous website? I mean i know it will vary between reservoirs and their location to snow pack but I would love to be learn some rough percent
It’s hard to generalize, which is likely why this isn’t an easy answer to find. For example Lake Shasta looks likely to fill completely- compare the current water and snow levels to those in 2019 (the last really good snow year) and you get enough water to get it to full. But when? If we get a hot early summer and the snow melts rapidly they will likely using the spillway to keep lake levels down. If on the other hand we get a slow melt the lake could be full very late in the season and we could be very well set up. So with that as a caveat we’re likely on our way to low 90s percent full California wide around 1 July this year (is my estimate).
They’ll all be full in regards to their conservation pool, with the possible exception of New Melones, which is simultaneously over-designed and over-allocated. A very large majority will need to let go of the equivalent of all inflows from the end of April to the end of the season. This is the dilemma with California’s water storage setup. We have the equivalent of 2 years of water in the snowpack and will capture essentially none of it. As a result, same problem once more if we follow up with more than 3 drought years.
Year after year, Cogswell Dam in LA County receives by far the most rainfall. This year it’s over 62 inches. Yet it seems like the lake is so tiny that it doesn’t even register on your chart. I don’t know why the county does such a poor job of collecting the water that comes down and then it takes it from so many other places. It’s wasteful.
In this area, Los Angeles County Flood Control District manages not just Cogswell but San Gabriel, Morris, Santa Fe and Whittier Narrows dams and captures over 95% of all precipitation that falls on average over the San Gabriel watershed to recharge our groundwater basin where we get 80% of our water, the other 20% being imported from primarily the State Water Project. I am not affiliated with them in any way, I just think they’re actually doing a pretty good job. Look at our water wholesaler (Upper San Gabriel Valley Municipal Water District) website http://www.upperdistrict.org for information- it’s quite interesting.
Would love to be able to click through to an individual reservoir and see a graph of its water level over time.
Wondering why Trinity seems so relatively unresponsive to fill.
Apparently it relies more on the snowpack melting than the rain runoff to fill it.
Did a little research, and I think I have an answer. Looks like its down to the peculiarity of the winter weather that has been received in the area. First it should be said that Trinity Lake’s watershed is not very large and that Trinity Lake fills what would be alpine valleys at a relatively high elevation for a reservoir this large (~2300ft). Back to the precipitation… There is an enormous amount of water trapped in snow above ~4000 feet and it is melting very slowly. Below 4000 feet it is melting, but there is relatively little. The area above 4000 feet represents about 2/3 of the lake’s watershed. According to the U.S. Forest Service, the lake’s watershed is ~920,000 acres. The lower third of the watershed has an average of roughly 5 inches of water equivalent. This equates to ~150,000 acre-feet. The upper third averages more than 30 inches, or ~1.5 million acre-feet. Over the last week the lake has received ~67,000 acre-feet, mostly from the lower portion as the temperature above 5000 feet has barely gotten above freezing of late.
There’s construction occurring on Trinity Dam, the levels need to be low in order to perform the work. It would be at or above the historical average if the repairs weren’t necessary.
You are correct that work is taking place on the Dam penstock and that this requires low water levels. However, according to information from the Bureau of Reclamation, water releases from the dam are only up to the amount required to maintain river flows. There is no additional outflow to enable the repairs.
Can you do California ground water next?
I love your interactive chart and how it updates every hour. I check your site a couple of times a day to see the increase in water levels. I wonder if you can get data on CA groundwater levels and do simple data updates. Thanks!
at what level does the emergency spillway come into play for lake Isabella? If on March 11, 2023 42,163cfs are entering from Kern river into the lake?
42k not enough to cause big problems with a low res to start with
With the Isabella Dam Safety Modification Project construction complete, the limit of 361kaf in place since 2006 is being lifted and the full 568kaf is available.
They say that the current rainfall is “well within the capacity of Isabella Lake.”
“We estimate that reservoir volume at the conclusion of this event will be between 230,000 and 270,000 acre-feet. The overall capacity of Isabella Lake is 568,000 acre-feet. We are coordinating with our state and local partners to update our projections multiple times a day.”
They don’t think that they will need to use emergency spillways at this time, but will use current outlet works for any increase in outflow.”
Why is the Trinity chart unchanging even though the fill level continues to increase. The full level graph hasn’t visually changed for weeks.
It’s going up very slowly. Inflows aren’t very high.
Because half the inflows are being offset by outflows to generate electricity.
Plus it’s a high elevation reservoir, so should fill more later from snowpack, doesn’t fill as fast from rainfall
From what I have read, Trinity gets more of its water from snow melt than many of the others. It should go up nicely once the snow melts in the higher elevations.
In the last two days it has really started to fill up more rapidly. Rainfall and higher temperatures affecting low level snowpack I suspect.
But what explains why it is only at half of its historical average for this date in the year? I understand that it may fill up my re in the spring due to snow melt as its primary source, but that doesn’t explain why it is so low compared to where it usually has been on this date historically.
Most likely because it started the precip year at such a low level; with the drought being so severe, it’s only natural to assume it’ll take longer to return to historical norms.
That is exactly as I see it. When I was there last September I had never seen it so low. You have to go back a long way to when you could take a boat under the Stuart Fork bridge! Mind you that was before they increased the Trinity River flow for environmental reasons.
Love it, Chris — thank you!
I’d love to see a reservoir chart that is percentage historical average vs time to track the trend of gaining or losing compared to average.
Love all the water data and charts!
Like this? https://engaging-data.com/filling-california-reservoir/
Great site, and great comments!
Very impressive work indeed.
This was eye opening. Great site.
Would like to see Tahoe added. Thanks.
Lake Tahoe really isn’t part of California water, as the outflow goes to Nevada. Part of the lake is on the California side, but it has zero California water impact beyond the immediate Tahoe residents.
Nate, thanks for the insight. Good info to know.
Good info. Would liked to see which are fed mostly by snow melt – like Trinity – which is one reason it’s so low.
Great resource! Next feature request: wire in aquifer level data! It would be really interesting to visualize whether we’re able to replenish ground water this year after all the precipitation.
Arg. Meant this comment for the integrated snowpack and reservoir view.
I second that request. I’ve been meaning to search for aquifer levels. Having it here would be great!
I’m curious why the percentage of capacity has stayed almost flat for the past 6 weeks or so and below historical average. I would think with the rain it would get to historical average and then more outflow would happen. I realize there we don’t want to reservoirs overflowing, but why are we still below historical average? Is it because the laws have changed on how much each reservoir can hold or is it in anticipation of significantly more rain? This is my first year watching the levels, so maybe I’m missing something.
Thinking more about it. It could be the 180% of historical average of snowpack, which will be melting in a couple months. Maybe bad data. Lot’s of possibilities, just curious. Thanks.
For the higher elevations, more of their water comes directly from snowmelt.
If you look at this chart for Hetch Hetchy, you can see that the biggest and steadiest rise is between March and July
Curt, Good point re the colder weather dropping more snow instead of rain at higher elevations this year.
My guess would be that the recent systems have been cold and so they are predominantly dropping snow on the watershed. If you look at the inflow data on the major reservoirs, its pretty flat. The amount stored is increasing, just not by a lot. 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). Usually with warm ARs, you get a dramatic increase in inflow, which can fill even very large reservoirs relatively quickly, like Oroville in 2017.
Not sure if you’re familiar, but there’s a statewide summary that consolidates most info:
You can then look at individual reservoirs, which give varying types of data:
Storage change is roughly 2(inflow-outflow) to give an idea of inflow when the data isn’t there.
Thanks. Very helpful.
Omar, Thanks! Great URL. Hetch Hetchy is Monitoring location 11275500. How can I match up other monitoring locations similar to the ones on this Interactive Dashboard? Also, do they provide inflows and outflows for locations? Thanks.
Why is Lake Nacimiento and Lake San Antonio not listed?
Yes, and why is Twitchell Dam also not listed?
Most likely size, and its part of Hetch Hetchy from wiki: Hetch Hetchy water is stored in local facilities including Calaveras Reservoir, Crystal Springs Reservoir, and San Antonio Reservoir.
What happened to the Hetch Hetchy level? It used to be full (and beyond).
It’s currently listed on this page as 29kaf full, but the usgs.gov page below says Hetch Hetchy is at 299.7kaf full.
looks like the CDEC website is the cause of the issue unless it actually dropped 90% in a day:
Should be fixed at some point.
I do not see Diamond Valley Lake Resevoir on this page.
Diamond Valley Lake is a man-made storage reservoir for storing imported water only. It has no natural inflow or out flow. This chart only shows reservoirs filled via natural flow/rainfall.
It’s great seeing all the reservoirs in California at or near historical averages.
Could you also do the same for the Colorado River reservoirs to see how they are fairing? 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.
That’s a great suggestion and one that would be particularly helpful! Awesome work!! 🙂
It looks like the red and blue lines are backwards on Folsom. I don’t think it’s currently above the historical average, not below 1 year ago.
This is wonderful information. Thank you so much for the hard work! I am new to the state. I live in the central valley. I hear from the farmers that “we waste 80% of the water by flushing it into the ocean.” I also hear the environmentalists say, “the streams and wildlife need water, so flush it into the ocean.” It’s an interesting dilemma. At the moment, I am not interested in the debate. However, I am interested in how much we are saving. This is the first state (of 6 I have lived in) that has had water police and restrictions. I see many of the local canals flowing with lots of water. 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. They are releasing water into the canals. This website along with another shows that Eastman’s level is still rising even though we have not had rain in more than a week. Is that from melting snow and rain water coming from the mountains and filling it up? Are they releasing water to relieve the pressure in anticipation of more water? Just trying to learn here… Thanks so much!
What period does CA use for “Historical Average?” It will be very different depending on the period chosen.
I believe it is 1991 to 2020.
There is something strange about the data over the last two days (Jan.17 to Jan. 19):
The overall storage is said to have dropped by 57.4 to 56.4 (or 302 kaf). For each of the top 8 reservoirs the storage has increased by a total of 217 kaf, however).
That can’t be right…
No it is correct. During the winter months, they let water out of the reservoirs in anticipation of large storms. Just in case a large storm hits, that way they don’t reach 100% capacity. The problem is that we have no idea of knowing ahead of time what kind of storms we’ll have and how long they’ll last, but the reservoir operators have to be super careful and extra cautious, so they periodically let the water flow out. If a reservoir gets filled to 100% and more, the dam will break and many cities will get flooded, so the operators are careful. This almost happened with the Orville Dam in 2017.
They also built a spillway that was too steep and did not install energy dissipators along the spillway. They placed a few dissipators just before the river.
That’s a very poor design. 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. I believe the spillway was designed by the State. I had a class in spillway design many years ago. For the class we based all our designs on the USACE spillway design manual.
I just wanted to thank you for your hard work on this site. I love it and use it regularly.
Great work. FYI it looks like Isabella is reading incorrectly, likely because it’s well above 100%.
Isabella is filling quite slowly in order to test out the new $500 million spillway. It won’t be full until Spring snowmelt.
It’s fluctuating between ~107% and ~20% from one hour to the next (reading 107.6 atm). It seems likely one of those two readings is wrong…
The information on Isabella has been fluctuating drastically (by a factor of 10!) over the past few days. I think the problem is with the CDEC database (as the LakesOnline website also has had incorrectly high information). 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).
Your tools are awesome – just hurts when you receive bad data at times!
Great visualization Chris! I’d love to see how much water is being / has been released from these reservoirs. Have you looked into that side of the water management equation?
I haven’t spent much time looking at it but that data is on the CDEC website. I was thinking that it would be interesting to compare inflows and outflows. Here’s an example of that data for Shasta, where you can see the daily inflows and outflows:
currently, there is a lot more water coming in than going out.
Thanks for the link. Water is such a fascinating topic and I’d hate to have to be a water manager making a decision on how much to release to avoid reservoir flooding. Hoping they start building more reservoirs soon.
Really appreciate the work you did to build this graph. So many facets beautifully chartered.
Department of Water Resources is just another in a long line of completely mismanaged California entities. Absolutely zero reason to be releasing this much water from these reservoirs. 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.
Yep. Super frustrating. Historical average is near unattainable these days. So they should be saving much more and deal with the .000001 of risk later.
DWR is one of many local, State and Federal entities that dictate water releases. Flood control agencies (not DWR) have the most say in regard to releases. While forecasters can predict the likelihood of future rainfall over large areas, they can’t pinpoint it to the degree needed to determine whether a particular watershed/reservoir will overflow and cause damage and loss of life. Therefore flood control agencies take the more conservative route and order the release of water.
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. Then it has the appearance of something filling up, while still providing all the detail.
Very nice work. I find myself coming back to this every few days to check on our water 🙂
Love this. Thank you! Quite an eye opener. Our reservoirs were alarmingly low. Even with all the rain and floods, still a long way to fill them to capacity.
I notice Briones Reservoir is not on the list. Another not monitored by the State?
Wonderful site. I’ll pass it along to friends.
Thanks!! This is amazing
This dashboard is great! I like the comparisons of last year, and the historical average. Didn’t realize how bad things were there. Best of luck out there in California! Greetings from Mount Laurel New Jersey.
Great graphs and very useful. Thanks for putting this together. Only improvement I would suggest is an improvement of the display of the smaller reservoirs so the names are readable. Especially for small ones it is hard to identify them and click on them.
I have to agree with many people here what a great job making such a clear graph of what’s happening. Kudos to the designers.
While the rainfall has been bad for many people, I am happy to see Californias reservoirs are benefiting slightly
Amen! it will be cool if there is a way to track the change since Dec or some such date
All of this work is nothing short of brilliant. 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.
This is a very clear graph and I cannot imagine the hours you have put in while setting it up and doing the maintenance. Thank you for a beautiful job.
Great stuff. Lake Almanor isn’t controlled by DWR for flood/supply. So included in DWR #’S. That said, most of its outflow makes its way down Feather River (via Rock Creek Reservoir) and ultimately into Orville. So it’s volume is ‘counted’ as Orville ‘inflow’.
These graphs will always read low because they represent the percentage of the seasonal average at some point before the end of the season.
Jeff, the average changes daily as well. So on Jan 10 we’re at 82% of the average for Jan 10.
If we reach 100% after the current rains and then it stops raining for the season, then our percentage will start going down.
This other page:
has a graph which shows how the historical avg changes throughout the year (oscillating between ~15000 and ~21000).
Very thankful for this website!
maybe label the vertical axis with “aggregate total” or system total capacity. and maybe another vertical axis to the right of that with “reservoir capacity”. As it is, at first glance, it looks like shasta is at the top because its 28000 instead of 4552. very nice product overall.
I’ve looked at reservoir sights for years. This is the best one out there. Thanks for providing it for public information. I’ve added it to my bookmarks for quick reference.
A 1 week change would be interesting to show on each. Maybe just acre/ft with ^ or down arrow.
Excellent graphic! I’m curious: Lk Almanor is the 8th largest reservoir in CA. Why is it not listed?
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 isn’t on the list. I will take a look and see if there are other important reservoirs missing and may add them in the future.
Interesting. Thanks for the prompt reply!
Could the reason be that the water from Lake Alma or seems to be used for energy generation, and that there does not seem to be any agricultural or urban use?
This is a great and very thoughtfully designed web site!
Excellent work! Thank you.
A truly excellent project. I have wanted to do exactly this plot for years. But I would never have imagined how to put all the important information into a single plot. I would like to make one small suggestion:. Add a button to convert the row heights to log scale. This would allow us to see important, but noise-level reservoirs like hetch hetchy.
Hi Keith, you could de-select the large reservoirs from the menu at the top right.
Curious why Shasta lake seems to be making big gains in water coming in and Trinity not so much?
I love this this site too. Why isn’t Lake Sonoma included?
It is on the graph. It’s just small enough that the name doesn’t appear as the bar is too thin.
Thank you for the time and effort in creating the graphs. I noticed that Folsom does not change whereas every reservoir changes on an hourly update. Even with the latest precipitation, Folsom’s values was unchanged.
For some strange unknown reason, they are not allowing the lake to fill up. Folsom Lake is letting the water flow out.
Folsom is like an overflow tank. They are draining it currently so that it can serve as that overflow if needed given how much rain is coming down and expected over the next week.
Could you also show each reservoir’s level as a function of time? There doesn’t seem to be any site that shows the impact of each storm.
In the year prior to Oroville reaching capacity the interactive chart showed the rate of inflow over time. This was helpful to project seasonal trends & storm impacts. I appreciate the information you are providing.
An improvement: Could you include a bar for “Last year at this date”?
A question: the “Historical Avg*”, is it the value of year-today or natural year?
This site is a great tool, especially as we try to climb out of these drought years. Saved to my favorites now. Thanks for developing it, and for sharing it with the rest of us!
Nice! Just a wistful thought, it would be really cool to graph the water release statistics. One of the big challenges in water management is controling the release. Sometimes this is well done sometimes it is poorly done.
All the best…
I know this might be difficult to display but I’m 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? I’d only be interested in the totals from Oroville and Shasta.
I LOVE this site.
What’s going on with the water level at Oroville?
Great Job on this site! Love easy to read and understand information.
This is an excellent tool you have put together. Thanks for taking the time to do that. 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.
Also a little nit. “Remaining Capacity” text in the legend should be brown?
It’s supposed to be brown. I wonder why it doesn’t work for you.
Love the dashboard! How come the totals disagree with the cal map graphic?
thanks. the map graph doesn’t include berryessa. however, I’ll update the code to include it soon.