Saturday, January 14, 2017

Liveblogging the Deluge: Wrapping Things Up (for now)

A week ago, I looked eastward from my science lab and saw the sun setting on the Sierra Nevada crest from 80 or 90 miles away. It was quite literally moments before the first outliers of the storm arrived and hid the mountains from view. Over the next six days or so, California was pummeled by the worst storm in two decades. Flooding was widespread, and there were some huge changes in my local bailiwick, the drainages of the Merced, Tuolumne, and Stanislaus rivers. I've been able to directly document some out-of-control drainages like Dry Creek, and some barely controlled drainages like the Tuolumne River (short story, flood with Don Pedro dam, 9,000 cubic feet per second; flood without the dam, 45,000 cubic feet per second). I couldn't get up there, but I followed events in Yosemite Valley as the park service prepared for the biggest flood in a long time. One of the most incredible moments of the week was the opportunity that I had to inspect the activity at La Grange Reservoir, where the Tuolumne River was plunging over the dam ramparts at 7,000 cubic feet per second. I also took some video (below) that I wasn't able to post yesterday.



I was out running errands yesterday evening, and as if to bookend the events of the week, the sun once again was shining on the newly fallen snow of the Sierra Nevada crest, this time from Claribel Road between Oakdale and Waterford (the first picture of this post). The storm, the worst in 20 years, was over, and northern and central California began cleaning up the flood damage.

There was an even bigger issue: the California drought. Since 2011, we have been in the grip of the worst drought ever recorded in modern times (megadroughts lasting a century or so are known from the recent geologic past). Three diagrams illustrate the massive changes that have taken place since last year, and since last week.
Reservoir levels Jan 7, 2016
The first diagram (above) shows reservoir storage around the state one year ago. At that time, not a single major reservoir in the state had anything close to normal storage. Most were between 20-36% of capacity, which was barely half of normal in the best of cases. Some were below 15%, including New Melones, at 14%, and McClure at 9%. The picture improved slightly later in the rainy season, but extreme drought conditions still prevailed over 90% of the state.
Reservoir levels, Jan 6, 2017
 We had a good start to the rainy season, with a powerful storm arriving in October, starting things off early. By the beginning of January, most reservoirs around the state were showing marked improvement. Four of them, McClure, Don Pedro, Shasta, and Millerton, were actually above normal for this time of year. Others were doing "okay", not quite to normal, but better than a year ago by a wide margin.
Reservoir levels today. Source: http://cdec.water.ca.gov/cdecapp/resapp/getResGraphsMain.action
By the end of the storm, all the reservoirs were doing very well, with the sole exceptions of Perris and Castaic, both in Southern California, where considerably less rain fell. All the other reservoirs showed large rises in storage. Lake McClure on the Merced River jumped from 46% to 66% of capacity (145% of normal). Don Pedro increased from 76% to 90% of capacity (134% of normal). Although New Melones Lake lags behind other major reservoirs in the state, it still saw a rise from 27% to 35% of capacity (61% of normal).
Source: http://cdec.water.ca.gov/cgi-progs/products/swccond.pdf
Even better news comes from the snowpack, which increased considerably after the warm start of the storm. Prior to the storm, no part of the Sierra Nevada had a normal amount of snow. In the aftermath of the storm, the snowpack ranges from 132% to 197% of normal for this time of year. If not another flake of snow fell this year, we would be at 74% of a full year (not counting melting and evaporation over the next few months)! And we have three more months of rainy season to come, including another atmospheric river storm arriving in the state on Tuesday (it's not thought to be as powerful, but will be falling on fully saturated ground).

Single storms can make a difference, but even the biggest are not drought-enders. We really need two or more consecutive wet years to start making some inroads in our depleted groundwater basins. But the storm happened and it dumped a lot of rain in California. The drought may not yet be ended, but it looks better right now than it did a year ago.

Liveblogging the Deluge: I've Never Seen Anything Quite This...La Grange Dam

Sometimes you just have to say "what the heck?" (or some other expletive). Some things just grab your attention that way. This was my day to say that. I was privileged to see a rare sight.
I was given the opportunity to accompany some MID employees on an inspection of La Grange Dam. And it was no normal day. We are in the midst of the storm runoff that has the entire Tuolumne River flowing over the rampart of the dam. You are looking at 7,000 cubic feet per second flowing over the brink of a dam 200 feet wide, and 131 feet high (Niagara Falls is only 36 feet higher). It was an astounding sight.
La Grange Dam is located on the Tuolumne River about two miles downstream of Don Pedro Dam. It was built in 1893 to divert the Tuolumne into the irrigation canals of the Turlock and Modesto Irrigation Districts. Most of the time the river does not flow over the lip of the dam. If the water isn't going through the canals, it is piped to the 4 megawatt powerhouse a short distance downstream and released back into the river channel. It's only during major runoff events that the dam overflows in this fashion.
La Grange Dam in quieter times (Source: http://www.turlockjournal.com/archives/29341/)

The dam has a unique structure, being composed in large part of locally quarried metamorphic rock blocks (about 25% of the volume of the dam). The rugged texture of the dam face is distinctive. The rest of the dam is composed of concrete. It holds back a mere 500 acre feet (in contrast, Don Pedro Reservoir upstream has a capacity of 2.04 million acre-feet).
Access to the dam is severely restricted, and the reasons are obvious. The cliffs and slopes around the dam site are dangerously steep, and there are no facilities of any kind.
We walked through a tunnel and got a perspective of the dam from just upstream of the brink (above). It was certainly quieter, but all the more menacing. I was imagining the sudden concern of an errant kayaker realizing that something was amiss just ahead.
We climbed to the top of the hill overlooking the dam for a broader view of things.
One can see the remains of a much older irrigation canal on the hill to the left (south) side of the dam. It dates to the Gold Rush days.
This has been an extraordinary week, with the greatest storm to hit California in twenty years. I've seen some incredible sights in my corner of the world (I've been covering events on the Merced, Tuolumne, and Stanislaus Rivers. But of all the strange new things I've seen, this was in many ways the most stunning. I appreciated the opportunity to witness the deluge.

Thursday, January 12, 2017

Liveblogging the Deluge: Following Up on the Dry Creek Flood

Dry Creek in Modesto flooded to the greatest extent in two decades yesterday, with peak flows exceeding 6,000 cubic feet per second. I was out documenting the flood surge, and I managed to get to the Dry Creek Trailhead ahead of the high water around 4:30 or so. The water was rising but as you can see in the picture above, it had not breached the small levee that kept the river in the channel. I know from other reports that the flood hit a short time after I left.
I was out early this morning, and though the peak of the flood had passed hours earlier, the flow was still high, about 4,000 cubic feet per second, and there was a lot of water covering the flood plain. It was an impressive sight.
Now that the flows in Dry Creek are receding, the dam operators at Don Pedro Reservoir will probably start ramping up their releases from the lake. The goal is to keep flows in Modesto to 9,000 cfs or less to prevent flood damage. The reservoir has been accumulating water with inflows around a high of almost 45,000 cfs to the current 26,000 cfs. The lake stands at 812 feet, or 1,805,600 acre-feet, and has risen 26 feet since the beginning of the storm sequence. Since the lake will fill at 830 feet (2,030,000 acre-feet), it is now at 89% of capacity, and more than 130% of average for this time of year. They will need to free up more space for additional storms and spring runoff

Wednesday, January 11, 2017

Liveblogging the Deluge: "Dry" Creek Takes Center Stage Today

Dry Creek in December of 2016 before the current storms
 What happens when a small insubstantial creek that is dry for much of the year...
...gets hit with a flash flood amounting to 6,100 cubic feet per second? Let's find out!
Dry Creek at about 1,000 cubic feet per second on January 9, 2017

Dry Creek (one of many such "Dry Creeks" in California and elsewhere) is a "minor" tributary to the Tuolumne River that has its headwaters in the lower parts of the Mother Lode northeast of Modesto Reservoir. It actually isn't dry as much as the name might suggest because irrigation overflow keeps some water in the channel during the dry season. But it has no dams or reservoirs to control flows, so it has a history of sudden flashfloods during intense storms. I've been here in Modesto for nearly thirty years, and I've seen several events that resulted in flows of 3,000 cubic feet or so, but only once have I seen flows that approached that which took place today. It was in 1997 during some of the worst flooding ever experienced in Northern California. The opening scene in the video that I posted the other day about the 1997 floods shows Dry Creek in Waterford at that time. Compare that scene with the picture below.
Oakdale-Waterford Highway at high water on January 11, around 6,000 cubic feet per second.
There is only one stream gage on Dry Creek, and it is located downstream in Modesto at the Claus Road Bridge. The peak flow was predicted for around 5 or 6 PM, which meant the surge in Waterford upstream would be several hours earlier. I took these first pictures at the Oakdale-Waterford Highway Bridge at about 2 PM, and the river was indeed very high. Compare to the flow on December 9 in the picture above. The entire floodplain was covered by several feet of water.
A few hours later I headed downstream to see if I could get ahead of the flood crest, and I found high water at the Church Street Bridge north of Empire. The view was astounding. In the picture above one can see how entire orchards are under water. And it wasn't standing water, either. The entire channel was flowing rapidly downstream.
I then went just a few miles west to the Claus Road Bridge, and found that the highest flows had not yet arrived! The Dry Creek Trail had been closed because some portions were already under water, and the creek was expected to rise another couple of feet. I walked down to the river edge and found a sheriff's deputy and a crew from the office of emergency services who were using a drone to take video of the coming flood. Modesto friends: let me know if you see the videos posted anywhere!
It started raining again, and it was getting darker, so I headed east again to check out some of the other bridges.
Wellsford Road bridge was the most interesting. The main channel was moving fast, and the muddy water reminded me of running the Colorado River through the Grand Canyon a few years back. Not because of any canyon walls, of course, but because of the surging muddy water with eddies and whirlpools. The flows weren't all that much different; Dry Creek was at 6,000 cfs, and most of the time the Colorado was running at about 15,000 cfs. The big difference is that the Colorado flows at that rate more or less the entire year, and Dry Creek does it once in a generation! I found a bit of information somewhere (source has been forgotten) that suggested that about once every 500 years a flood on Dry Creek could exceed 18,500 cubic feet per second. It would be something to see something like that happen, but such a flood would do incredible damage, and I wouldn't wish such a thing on anyone.
The morning will tell if there has been any serious damage downstream. The dangers of flooding are well-known today, but a number of very nice homes were built decades ago along the lower reaches of Dry Creek near the confluence with the Tuolumne. The dam operators at Don Pedro Reservior work very hard to modulate flows of the Tuolumne River to prevent the combined flows of the two rivers from exceeding 9,000 cubic feet per second. If flows go any higher, water backs up in Dry Creek, causing flooding in the neighborhoods there.
I head to work before sunrise, but I'll probably try to catch a few more photographs in the morning. It will take a day or so for flows to recede.

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...

Tuesday, January 10, 2017

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

Check out some newly "discovered" footage from the floods of 1997!
We've been following developments on the Stanislaus, Merced, and Tuolumne Rivers as the biggest atmospheric storm in a decade or more has been sweeping through California. Many references have been made to the record-setting floods of 1997, and I was reminded that I was actually around back then. I even had a thing called a "VHS video camera" that recorded images on, of all things, magnetic tape. How so very quaint! I finally remembered the tapes, and even more importantly remembered that I had the tapes recorded to a DVD a couple of years ago to assist someone's research on the 1997 floods. I dug it out and isolated my videos of the Tuolumne River in Waterford, CA, and Dry Creek in Waterford and Modesto (it was not very dry at the time).

Some important numbers can be compared to the events transpiring right now. Don Pedro Reservoir is a huge dam upstream of Waterford and Modesto. It has a capacity of 2.04 million acre-feet. In 1997 it was relatively full, but not out of sync with the seasonal guidelines (about 1,690,000 acre-feet, around 83% of capacity; that's the level of the reservoir today, January 9). The storm of 1997 was not normal, however, and awareness was growing that the dam might fill and start flowing in an unconstrained manner. Operators ramped up flows on the river downstream to near-flood level at 9,000 cubic feet per second, and realized eventually that they were going to have to make a difficult choice. They were going to have to flood out a number of homes and ranches in order to make room in the reservoir for the even bigger flood to come. Several feet of warm rain fell on a near-record snowpack, and soon river flows well over 100,000 cubic feet per second were entering the reservoir. The lake level rose at an astounding rate of a foot per hour, and in less than two days, the level rose to 830 feet, overtopped the dam weir and floodgate.

For several hours, the Tuolumne River below the dam was flowing at 60,000 cubic feet per second, the highest such flow ever recorded. This was a disaster for several hundred homes downstream, but had the dam not been there, and had the operators not made the choice to produce an artificial flood, there would have been a flood in Modesto that was twice as large.

To compare to the flood going on right now in 2017, inflow to Don Pedro has been ranging as high as 38,000 cfs, and the controlled outflows have been as high as 10,000 cfs. The lake has reached an elevation of almost 802 feet, but the main part of the storm has passed, so I don't expect major problems on the Tuolumne River (but of course predictions are just that, predictions). Keep your attention on the news until this storm is over with).

And so that is the background to the video above. I was filming what I could from the various bridges before some of them were closed. I had to take a circuitous route to get to town that day to get video of Dry Creek in the La Loma Park area, which was completely inundated. I couldn't even stop, and had to take the video from a moving car (Mrs. Geotripper assisted with the driving in case you were wondering).

So here it is in all the glory of hand-held amateur film-making. Be thankful that it isn't happening again, at least not here (but give a lot of thought to those who are struggling with high water farther north in the Great Valley and along the Truckee River in Nevada).

UPDATE (1/10/17, 12:20 PM): It looks like the inflow at Don Pedro reached 44,905 cubic feet per second yesterday. Lake level reached 802.6 feet, about 1,698,000 acre-feet.

UPDATE (1/10/17, 4:40 PM): Don Pedro Lake level reached 804.9 feet, about 1,723,000 acre-feet. That's about 84.5% full.

Monday, January 9, 2017

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.