Interactive California Reservoir Levels Dashboard

Posted In: Environment | Water

How much water is in California’s reservoirs?

Check out my **new combined California reservoir and snowpack visualizer** to compare to historical values, as well as the California precipitation tracker and California snowpack visualizer.
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.

Data and Tools
The data on water storage comes from the California Department of Water Resources’ (DWR) Data Exchange Center. Python is used to extract the data from this page hourly and wrangle the data in to a clean format. Visualization was done in javascript and specifically the D3.js visualization library. It was my first time using D3 and it took me a long time to get up to speed. 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. It was the only tool that I could find that would allow me to make a vertical marimekko graph.

california reservoir levels dashboard


60 Responses to Interactive California Reservoir Levels Dashboard

  1. San Vuong says:

    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.

  2. Kyle Mackey says:

    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.

  3. Greg says:

    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!

  4. Randal Son says:

    What period does CA use for “Historical Average?” It will be very different depending on the period chosen.

  5. Heinz Roggenkemper says:

    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…

    • Water Jesus says:

      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.

  6. Pete says:

    Great work. FYI it looks like Isabella is reading incorrectly, likely because it’s well above 100%.

    • randy says:

      Isabella is filling quite slowly in order to test out the new $500 million spillway. It won’t be full until Spring snowmelt.

      • Pete says:

        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…

      • John says:

        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!

  7. Donna says:

    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?

    • chris says:

      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.

      • Donna says:

        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.

        • Donna says:


        • Brad says:

          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.

  8. Depewtydawg says:

    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.

  9. Very nice work. I find myself coming back to this every few days to check on our water 🙂

  10. Yassin says:

    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.

  11. Cathleen Cadffrey says:

    I notice Briones Reservoir is not on the list. Another not monitored by the State?

    Wonderful site. I’ll pass it along to friends.

  12. luc says:

    Thanks!! This is amazing

  13. Pete Doviak says:

    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.

  14. Manfred says:

    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.

  15. Mike G says:

    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

  16. D.K. says:

    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.

  17. Tom Straus says:

    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.

  18. Mark R Murray says:

    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’.

  19. Jeff L. says:

    These graphs will always read low because they represent the percentage of the seasonal average at some point before the end of the season.

    • Vince says:

      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!

  20. TED MACKECHNIE says:

    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.

  21. Laura Katz says:

    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.

  22. Andrew says:

    A 1 week change would be interesting to show on each. Maybe just acre/ft with ^ or down arrow.

  23. scott says:

    Excellent graphic! I’m curious: Lk Almanor is the 8th largest reservoir in CA. Why is it not listed?

  24. David says:

    Excellent work! Thank you.

  25. Keith Hartman says:

    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.

  26. Patrick says:

    Curious why Shasta lake seems to be making big gains in water coming in and Trinity not so much?

  27. Karen Walker says:

    I love this this site too. Why isn’t Lake Sonoma included?

  28. Puki says:

    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.

    • Michael Ober says:

      For some strange unknown reason, they are not allowing the lake to fill up. Folsom Lake is letting the water flow out.

      • Paul Roberts says:

        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.

  29. Sam says:

    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.

  30. Joe says:

    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.

  31. Elz says:

    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?

  32. Brian says:

    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!

  33. David A says:

    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…

  34. Peter Spence says:

    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.

  35. EarthwormSally says:

    I LOVE this site.

  36. Gary says:

    What’s going on with the water level at Oroville?

  37. Ron Griswold says:

    Great Job on this site! Love easy to read and understand information.

  38. John Gardner says:

    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.

  39. Darcy says:

    Also a little nit. “Remaining Capacity” text in the legend should be brown?

  40. Darcy says:

    Love the dashboard! How come the totals disagree with the cal map graphic?

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