Year-end Look at the California Water Situation

 

It's the last day of 2022, and the third year of a stunning drought in California. It's been raining pretty much across the state during December, and there are hopes of alleviating the drought a bit. Let's hope so. The map above from the California Data Exchange Center gives a pretty clear idea of the situation. Reservoirs across the state are for the most part well below normal, and in the case of the biggest (Shasta, Oroville, etc.), still ominously low. I hope to revisit this diagram in a few weeks and see some changes, but we will see.

The long-term predictions earlier this year were for a continuation of dry conditions, so the current onslaught of atmospheric river storms is somewhat of a surprise, albeit a welcome one. But of course, one has to be wary of what one wishes for. There are flood watches up all around the state as one more storm will blow through to end the year.

There is also the cautionary tale of the previous rain year. We had some record storms in October and December last year, and things were looking great, but then January and February were about as dry as can be. I recorded a mere 0.08 inches in those two months.

Still, this year has some promise. From the weather station in the Geotripper backyard 13 miles east of Modesto, we've had 7.14 inches of precipitation in December, the highest total in the 32 years that I've been keeping statistics (I've recorded more than 5 inches in six different years, but never more than 6). Even with the earlier dry months, we should round out 2022 with about 8.6 inches as we move into the critical months of January and February when most of the precipitation should happen.

Despite the rain, I felt a need to check out our local barometer of runoff conditions. The Tuolumne River cannot serve in this capacity because of the numerous reservoirs upstream that very carefully control the daily flow levels. I checked instead at Dry Creek, of which there are many in California. This particular Dry Creek has its headwaters in the lower foothills of the Sierra Nevada Mother Lode, and flows for about 40 miles before joining the Tuolumne River in Modesto. Ironically, there is almost always some water in Dry Creek, obviously from rain runoff during the winter season, but also from irrigation overflow during the dry summer months. Without any substantial flood control structures, it is a good measure of runoff conditions during storms.

The creek was running about 600 cubic feet per second when I got this picture, which is about twice the current flow of the reservoir-controlled Tuolumne River. As can be seen from the discharge graph from the USGS Water Resources site, it has already been well over 1,500 cfs a couple of times in the last week. I haven't seen this much water in the creek in a couple of years.

Of course, the local picture is not the most important statistic. Everything in California's water infrastructure depends on the snow conditions, especially in the Sierra Nevada. Although these atmospheric river storms we are experiencing derive from tropical sources and are warmer than we might want, the current snow conditions are promising. Check out the report:

Let's hope this keeps up. A lot of forests, rivers, animals and people are depending on it.

What are conditions like in your region?

Liveblogging the Deluge: 2018 Short Version

High water on the Tuolumne River, February 2018, about 15,000 cubic feet per second.

Why "short"? What deluge? Hasn't this been another dry year?

Tuolumne River on January 19, 2018, flow at about 300 cubic feet per second.

If you've been reading over the last year, you would know that I started what I thought would be a short blog series (Liveblogging the Deluge) on what looked like (and almost was) a record-breaking atmospheric storm that hit California last January. The storm hit, and then there was another. And another. Prodigious amounts of snow and rain fell in central and northern California through the end of April, putting an end to California's historically bad five-year drought, and filling the state's dry reservoirs. So much snow accumulated in the drainage of the Tuolumne River that the main reservoir, Don Pedro, was constantly at the edge of overflowing, so the outflow was maintained at near flood-level (averaging 9,000 cubic feet per second, briefly to 15,000 cfs) through July. We really had no chance to see the changes on the floodplain until September.

Tuolumne River on March 25, 2018, flow at about 4,500 cubic feet per second

And then...when the "storm door" was supposed to open in November, barely anything happened. My backyard gauge told the story: October, 0.07", November 1.15", December 0.0". January finally brought an almost normal amount, 3.44", but the next month was one of the driest Februarys ever recorded, with my gauge recording a mere 0.37". Statewide, the snowpack was a mere 20-25% of normal. At Don Pedro Reservoir, there was a lot of water in storage, but realizing that there would be almost no snowmelt, the operators kept the outflow into the lower Tuolumne River at very low levels, about 300 cubic feet per second. They left a minimum of space for emergency flood control.

Tuolumne River, January 19, 2018, flow at 300 cubic feet per second.

And then March happened. The storm door opened in a big way, and three major storms blew through the state raising havoc with floods and mudflows in numerous localities, including some of the areas affected by the horrific fires of last summer (and December, unfortunately). Locally, we received 3.36", but my little town was one of the driest spots in the state. The snow in the Sierra Nevada was measured in feet, including 7-8 feet in a few places.

Tuolumne River on March 25, flow at 4,500 cubic feet per second.

It wasn't a drought ending month, but it took the snowpack from disastrous to merely disappointing. Current levels range from 44% to 66% of normal. And now the operators at Don Pedro Reservoir can expect some runoff amounts that will be semi-normal. That means they'll need a bit more reservoir space....

I noticed the first ramping up of river flows about a week ago, when the discharge was tripled to about 1,000 cubic feet per second. I could hear the river again (the velocity of the water at 300 cfs is very low). But then when I walked the river trail yesterday, the river was raging along at 4,500 cubic feet per second. Not a flood, but a higher level than at almost any point during the entire run of the 2012-2017 drought. The islands and gravel bars that were being used by fisher-people and picnickers were once again underwater. The slough at the west end of the Parkway Trail where I walk was once again flowing. This is good on a number of counts: salmon and other fish will have a better chance of survival and getting to the sea, and the invasive weed river hyacinth will probably not gain root in the upper areas of the river. The river weed choked the slough and parts of the river channel during the drought, smothering out other vegetation, and making life difficult for fish and aquatic wildlife.

Farther afield, the outlook is reasonably good. Most of California's reservoirs are at or well-above normal (flood-damaged Lake Oroville is an exception at 75% of normal). Don Pedro came up at least 8 feet during the storms in March.

While good for the snowpack and reservoirs, the storms did a lot of damage. Roads were washed out in numerous places in the foothills of the Sierra Nevada. We almost lost a smaller reservoir on Moccasin Creek. In the end, the "Deluge" was a lot shorter than the one we got last year, but in a year as dry as this, it was good to have a little extra water "in the bank". With the uncertainties related to global warming, and the expectation of future extended droughts, every drop counts.

Liveblogging the Deluge, April Edition: Seeing Half Dome Reminded Me of Something

It's easy to get distracted by life at times. After four months of well-above average rainfall and snowfall caused by a series of atmospheric river storms, we here in California were left in a rather precarious situation where our reservoirs were too full and experiencing damage, and where our rivers were swollen with snowmelt, straining the levees and threatening to flood valley towns. Then the storms stopped for awhile. Locally, we only had one series of storms worth noting in March, and only 1.85 inches of rain fell. That's above average for the month, but it's also the lowest monthly total since November. We climbed past the 20 inch mark for only the fifth time in the 28 years that I've been measuring rain in the backyard. If not another drop fell, this would be the fourth wettest year that I've measured since 1990 (another inch is expected this weekend). But we've now had a few weeks of dry conditions, and it can be easy to forget that there is still a situation...up there.

I was reminded of this as I drove south to teach a class this evening. I noticed it was unusually clear, and I realized it was a good day to photograph Half Dome from Oakdale Waterford Highway on the floor of the Great Valley. It's one of the better vantage points for spying the iconic dome, and it was nicely framed by the snow-covered high country. There is still a massive amount of snow up there, and I realized it was time to get an update on the deluge that California has been experiencing this year after half a decade of crippling drought.

Here's how things stand. The brief respite from the constant storms has allowed the dam operators to release some of their excess water, preparing for the coming snowmelt runoff. We've been lucky so far, avoiding any extended heat waves that could have caused serious problems. They've got some breathing space in reservoirs. And they'll need that space...

...because there is still a LOT of snow left in the high country of the Sierra Nevada. The April 1st snow report shows that the mountains are at 159% of normal for this time of year. The Tuolumne River drainage has enough snow to fill Don Pedro Reservoir once over. The operators know it, and the river downstream has not been allowed to drop below flood stage since January 4. It's running at 11,400 cubic feet per second, and will probably remain close to that level through the beginning of summer. I can barely imagine how the river channel will be changed when it emerges months from now.

We are not out of the woods yet. Floods are still a possibility, especially if we get hit by a heat wave. And we still have at least one more major storm coming this weekend. Stay dry out there!

Liveblogging the Deluge: Perspectives on the Biggest Storm in a Decade, Part Five

We finally got a taste of some of the kinds of squalls that are leading to flooding across much of Northern California. Luckily it was brief, and we have not had problems in our immediate vicinity. The view in the video above is out our front door a few moments after I got home from work, driving in conditions that were much the same as what you can see here.

Radar signal of the storm in the video above, courtesy of  Ryan Hollister @phaneritic

My dear friends who live in hurricane-prone regions are welcome to snicker a bit at my sense of awe at the violence coming from the sky. I live in a dry region, and downpours like this are pretty rare. We got 1.67 inches today, and only six days have had a higher total in the 26 years I've been measuring precipitation in my back yard. That brings our four day storm total to 3.35 inches. Again, that can hardly compare to some of the high numbers coming from the coastal mountains or the Sierra Nevada, but it represents about a quarter of an entire year's rain total in an average year in my village (just over 13 inches in the years I've been measuring).

National Park Service Photo

Meanwhile, the big flood danger in Yosemite has passed as the storm surge topped out at 12.7 feet and subsided a few hours later. Yosemite is in the process of reopening the valley floor to tourism. Highway 140 on the Merced River was closed by mud and rockslides (good pictures at the link). Snow has been falling in the valley and the adjacent high country, which is a good development. We need to build the snowpack to have any hope of putting a dent in the drought.

Dry Creek at around 1,000 cfs yesterday. We'll see how it looks tomorrow at peak runoff. 7,000 cfs is expected.

The Tuolumne River continues to cause some headaches as dam operators try to tread a delicate path between high flows from Don Pedro Reservoir and high flows along Dry Creek, an unconstrained waterway that has been flowing at more than a thousand cubic feet per second for several days. The creek has my undivided attention right now, as flows are expected to crest at more than 7,000 cubic feet per second tomorrow. I hope to get out and snap some pictures.

I have had little to say about the Stanislaus River. New Melones Reservoir is huge, and the Stanislaus is a relatively small river compared to the Tuolumne. As a consequence, the water level in the reservoir has been low throughout the drought. It began this week at 27% of capacity, about 47% of normal for this time of year. The lake has risen about 20 feet this week, and now stands at 31% of capacity (54% of normal).

It's been an interesting week...

Liveblogging the Deluge: Perspectives on the Biggest Flood in a Decade, Part Three

Pictures are emerging from Yosemite Valley! See the update below.

NPS Webcam Photo from Happy Isles at upper end of Yosemite Valley

The flood on the Merced River in Yosemite Valley has crested at 12.7 feet (10,488 cubic feet per second). The highest flow was recorded at 4AM, and the waters are beginning to recede. There are more storms to come in the next few days, but they will be colder, and will start producing snow instead of rain. Although there has been some damage around the valley floor, this has to be seen as one of the best possible outcomes for Yosemite, given the power of this particular atmospheric river storm, and the level of flooding seen elsewhere in Northern California. It is still dangerous out there.

Meanwhile, on the Tuolumne River, releases have begun again from Don Pedro Reservoir, ramping up from almost nothing to 5,320 cubic feet per second. The operators are trying to modulate flows from Don Pedro with the unconstrained flows from Dry Creek to prevent flooding in the low-lying areas of Modesto downstream from the confluence of the two waterways. Flooding commences at about 9,000 cfs in that area. Inflows at Don Pedro are around 15,000 cfs right now (*see the new update below); if the dam didn't exist, the river in Modesto would be approaching 20,000 cfs.

There is a lot going on with the flooding around Northern California, and Southern California is finally getting some precipitation as well. I've been concentrating on the activity on the Merced, Tuolumne, and Stanislaus River drainage basins. Updates will follow as conditions warrant.

UPDATE (1/9/17 11:20AM): The LA Times has a pretty good roundup of flood news from around the state:  http://www.latimes.com/local/lanow/la-me-ln-sierra-storm-20170108-story.html.

UPDATE (1/9/17 11:30AM): The inflow to Don Pedro Reservoir actually reached nearly 38,000 cubic feet per second  yesterday! Water level in the dam jumped 7 feet to 796 feet, for a total of 10 feet since the storm began. The lake gained just over 100,000 acre-feet, to 1,620,000 acre-feet. The lake would overflow at 830 feet, or just over 2 million acre-feet.

UPDATE (1/9/17 12:50PM): Yosemite National Park has posted some photos of flood related effects in the Yosemite Valley area. Here are a few of them...

NPS photo

NPS Photo

NPS photo

UPDATE (1/9/17 7:30PM): At about 3PM, the Merced River receded below flood stage in Yosemite Valley. It's a relief that the flood wasn't worse, especially given greater runoff to the north where there have been some really serious problems during the day. Another storm is moving in, but it's colder and will be mostly snow, which is a very good thing.

UPDATE (1/9/17 9:00PM): As of this evening, Don Pedro Reservoir has surpassed the 800 foot elevation, gaining 5 feet to 801.84 feet, for a gain of another 50,000 acre-feet to 1,690,000 acre-feet. That's about 83% of capacity.

Liveblogging the Deluge: Perspectives on the Biggest Flood in a Decade, Part Two

Check back for updates at the end of this blog...

First off, let me emphasize that I am writing almost exclusively about the central Sierra Nevada and adjacent Great Valley, particularly the drainage of the Merced, Tuolumne, and Stanislaus Rivers. I say this because some very serious things are happening farther to the north, and flooding is occurring in a number of places. If you live in those areas, you need very much to be listening to emergency response officials, and not reading random blogs!

Screen capture of Yosemite Falls from video on NPS Facebook Page

That being said, it looks like we have good news emerging from the storm. Although the rain has been heavy at times, it did not reach the apocalyptic levels that seemed possible earlier in the week. The Merced River in Yosemite Valley is certainly rising towards, and will exceed, flood stage (below), but not nearly to the extent that had been predicted in the previous week.

Early predictions had suggested discharges in the range of 20,000 cubic feet per second, but the latest projection is pointing more towards 9,000 cfs (below). This will raise the river level to nearly 12 feet, and that will inundate some roadways, but nothing like the floods of 1997 when wide parts of the valley floor were under 8-10 feet of floodwaters. That's good news.

There is also good news indicated by the actions of the watermasters at Don Pedro Reservoir on the Tuolumne River. Two days ago, a lot of water was being released from the reservoir, trying to make room for possibly catastrophic river flows. Flows were up to 10,000 cubic feet per second for a while (see some pictures here). This morning, I checked the flow (below), and it has dropped back to the usual level of several hundred cubic feet per second. This means that the dam operators are confident that they can capture and save the runoff and are not worried about the dam being overtopped the way it was in 1997 (the damage from that event is still visible 20 years later). (*see new update below)

Discharge of the Tuolumne River at LaGrange Jan 8, 2017

The river surge will have some benefits: River Hyacinth, an invasive aquatic plant has been choking the channel of the Tuolumne River during the last few years. The surge of the artificial flood has no doubt cleansed the channel of the river in many places. A lot of silt that has been smothering the best spots for salmon eggs has probably been swept way, and new sand bars have perhaps been formed. Although some minor flood damage may have taken place, there is a lot of good too.

River hyacinth in the lower Tuolumne River in 2015. Those mats of green aren't supposed to be there.

The other area of concern is Dry Creek. It is an unconstrained drainage, and for a time it seemed possible to have a record flow of 8,000 cubic feet per second. Those projections have backed off a bit too, but the expected 5,600 cfs will still be the highest runoff that I've seen, and some minor flooding damage will be possible in Modesto. Notice in the diagram below that there are three peaks predicted.

Source: http://www.cnrfc.noaa.gov/graphicalRVF.php?id=DCMC1

I've been thinking about something else today. Will this spell the end of the drought that has afflicted California since 2011? The short answer is no, it will not. The storm is building reservoir levels to more healthy levels, but filled reservoirs are but a single metric in determining droughts. This warm storm has melted the snowpack, and the snowpack is what is critical to sufficient supplies during the dry summer season. The good news is that the storms later in the week will be much colder, and the snowpack may be building up. The storm does nothing about global warming, which will continue to put a "finger on the scale" each year in California towards continued droughts.

Even more concerning is the fact that the storm will only help a bit to recharge the groundwater of the Great Valley. We have developed a huge deficit in groundwater storage during the drought, as agricultural interests have pumped increasing amounts of groundwater to replace the missing irrigation supply. Even if we have the foresight to put water back into the ground, some of the storage space has been lost due to compaction. This becomes obvious when one observes the amount of subsidence of the ground surface throughout much of the San Joaquin Valley (the southern portion of the Great Valley).

Source: http://www.sacbee.com/news/state/california/water-and-drought/article31527953.html

UPDATE (1/8/17 4:50PM): The story on the drop in the discharge on the Tuolumne River is a bit more nuanced than I suggested above. I've been notified that they are trying to modulate the flow with the high discharge in Dry Creek to prevent flooding downstream of the confluence of the two watercourses in Modesto. In other words, flooding occurs on the Tuolumne at about 9,000 cfs. Dry Creek may contribute as much as 6,000 cfs tomorrow, so they've cut back on the flow of the Tuolumne to compensate.

UPDATE  (1/8/17 8:50PM): The Merced River in Yosemite Valley has just reached flood stage at 10 feet (6,600 cfs). The river is expected to rise another 1-2 feet before subsiding.

From https://waterdata.usgs.gov/ca/nwis/uv?site_no=11266500

UPDATE (1/8/17 11:20 PM): Among all the other stories of the day, word comes from Calaveras Big Trees State Park that the beloved "Tunnel Tree" has fallen in the windstorm. This is sad in one way, but it's clear that these kind of "touristy" developments like carving big holes in the base of the tree is damaging to them. We are changing nature for our own amusement instead of appreciating them for what they are. It's an unfortunate parallel that the Orca in the "Blackfish" story died this week as well.

Liveblogging the Deluge: Perspectives on the Biggest Flood in a Decade, Part One

See updates at end of post... BTW, if you are on the scene in places like Yosemite Valley, please send photos or updates! I will gladly post them here.

Printable PDF of current conditions can be found at this link 

It's clear by now that I am fascinated by the current atmospheric river storm that is blanketing the state of California with precipitation from one end of the state to the other. I'm right in the thick of it, in the Great Valley, sandwiched by mountain ranges that will be getting rain amounts measured not in inches, but in feet. On this blog, I've already talked about the last record-breaking storm, the 1997 event that caused unprecedented damage across California, but especially in Yosemite and along the Tuolumne River. I also blogged about the preparations being made in anticipation of the storm: the operators of Don Pedro Reservoir have ramped up the flow of the Tuolumne River to near flood stage to make room for storm runoff. Then, last evening, we had a spectacularly clear view of the Sierra Nevada from the valley floor, covered with snow, and seeming to wait for the coming storm event. From here on, I'll be liveblogging, sort of, the storm (it will be separate posts at times).

Radar of precipitation in Central California as of 8:00 PM Saturday. Source: Intellicast

And now the storm has arrived. Atmospheric river storms are linear streams of moisture-rich air coming northward out of the tropics (they have been called Pineapple Express storms at times). In "normal" front-related storms, the period of precipitation is fairly limited as the front sweeps through the state. Atmospheric river storms are different; they spray the state with storms that can last for days, and in some extreme examples, weeks. They are also warm storms. The snow level can reach very high elevations so that rain falls on the snowpack, melting vast amounts of ice. It all adds up to a potential for the worst kinds of floods in California.

I don't know what all is going to happen in the next few days, but I want to establish some baselines so it can be understood just what the storm means for California and our water situation. We have been in the grip of a crippling drought since 2011, and reservoirs across the state have been at historical, even catastrophic, low levels. The first diagram in this post provides a benchmark to track the changes in the next few days. It's already been a fairly good precipitation year, as some reservoirs already sit at 100% or more of their desired levels. A few are still very low, including especially New Melones Reservoir on the Stanislaus River just north of me. It is only at 27% of capacity. Lake McClure on the Merced River below Yosemite Valley is about where it is supposed to be at 47% of capacity. My special river, the Tuolumne which also flows out of Yosemite National Park, is a bit too close to full at 76% of normal. If the storm dumps too much rain in the park, it has a small chance of overflowing the floodgates in an uncontrolled manner as it did in 1997. That's the reason the dam operators ramped up flows in the last two days.

Source: California Nevada River Forecast Center

It's going to be especially interesting to see how the storm predictions pan out. The flood hydrograph above is the expected outcome in Yosemite Valley. The red dotted line is flood stage (at 10 feet, or around 7,000 cubic feet per second). Earlier predictions for the flood peak have wavered between 15,000 cfs and 24,000 cfs. The high end prediction would be of 1997 magnitude, but even the low prediction would be enough to flood valley roads and possibly close the park. The high flow history at Pohono Bridge in the valley is shown below:

Historic Crests

(1) 23.43 ft on 01/03/1997
(2) 23.43 ft on 01/02/1997
(3) 21.52 ft on 12/23/1955
(4) 20.98 ft on 11/19/1950
(5) 20.10 ft on 12/11/1937
(6) 16.96 ft on 12/23/1964
(7) 13.11 ft on 04/11/1982
(8) 13.01 ft on 01/13/1980

The current outlook is for a peak of 21,590 cfs (19.7 feet).  If it happens, it would be the 6th highest flow ever recorded. As you might expect, I'll be watching this one closely.

Flood hydrograph for Dry Creek. Source: http://www.cnrfc.noaa.gov/graphicalRVF.php?id=DCMC1

The other local river that has my undivided attention is Dry Creek. It's not a well-known waterway outside our region, but it is capable of causing some havoc at times. Although it doesn't have a vast drainage basin (it arises in the Sierra Nevada foothills in the Mother Lode), it has no dams or flood control structures. It is therefore very responsive to variations in storm intensity. I've seen it flowing at 3,000 or 4,000 cfs, but the prediction as of this evening is a bit ominous: it may peak at 8,400 cubic feet per second. Let's be clear what that means: yesterday, the Tuolumne River was flowing at 8,000 cfs, and that's considered very close to flood stage. For the Tuolumne River. A minor tributary to the Tuolumne River may be as big as the Tuolumne, but in a channel that is many times smaller. I will be out and about on Monday to get pictures, but to set a baseline of sorts, here's how the creek normally looks at the Oakdale-Waterford Highway bridge:

Dry Creek on Dec. 17, 2016 just prior to a previous high water event late last year.

So, here is where we stand with the atmospheric river storm in my backyard. We've received about a half inch of rain today, adding towards an expected 4 inches by the end of the week. If things transpire that way, it will represent about a third of the precipitation expected in my town over the course of an entire normal year. We of course are in the driest part of Central California (aside from the desert east of the Sierra Nevada), so literally everywhere else will be getting a lot more. As I've been saying in my previous blogs, be safe out there! Don't travel if you can avoid it, don't try crossing flooded bridges, and don't try walking either. If you are headed into the mountains, imagine being stranded by yourself for a few days and pack accordingly, especially with warm clothing and extra food rations. My distant relatives, the Donners, failed to do that in the Sierra Nevada in 1847, and look how they ended up. If authorities issue a flood warning, take it seriously. They're getting their advice from scientific professionals, and that still means something.

UPDATE: Officials closed Yosemite Valley roads and visitor services as of yesterday, and will reopen after the flooding subsides.
UPDATE: (although more like an addendum) For comparison's sake, here is where the reservoirs of the state were at a year ago:

A huge difference!
UPDATE (1/8, 1:52 AM): Yes, up late, listening to intensified rainfall. Gauge has picked up another .40 inches in two hours.

UPDATE  (1/8, 10:18 AM): Good morning! There was another 0.20" in the backyard gauge this morning, and now we are in a lull between major storms (most of the action is north of here at the moment). Another 2/3 inch is expected later today on valley floor. There is better news in Yosemite; the expected flood is now projected to be less than catastrophic, with a projected high flow of 9,600 cubic feet per second. Yesterday, the projection was twice that. It's still above flood level by 2 feet, but would not cover valley roads. Several more inches of warm rain is expected (~4"), but tomorrow the precipitation will turn to snow, and that is a good development.