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.

The Difference a Year Makes: Liveblogging the "Deluge" (Hint: There isn't one)

This post is both a look back at ten years of Geotripping, but is also an update on snow and precipitation conditions in California right now, and that picture is not pretty. My backyard rain gauge had amassed a mere 1.22" of rain by the beginning of January, and while January had higher than normal precipitation, I only show 4.66" for the rain year, just a bit over 50% of normal (I think we benefited from a few isolated downpours, as Modesto, just 13 miles away is at 3.09"). During the historic drought of 2011-16, three of the dry years were wetter than this.

I walked the Tuolumne River Parkway Trail today, and for the first time in weeks I could see the Sierra Nevada, the peaks that loom high above Yosemite Valley. The sun reflected off a snowpack that was far different than it was a year ago. The snowpack is only 30% of normal (see below). It's late January and there are a few ski resorts that haven't even opened yet (if they'll even open at all).

Source: http://cdec.water.ca.gov/snowapp/sweq.action

If there is any bright spot in this dismal year it is California's reservoirs. Because of the ample rain and snow last year, most of the reservoirs are at healthy levels, more than 100% of normal (see below). One prominent exception is Oroville Reservoir, which was lowered drastically to allow repairs to the spillways that failed during the height of the storms last year. There is at least some comfort to know that we have some resources to weather another drought, at least for a few years. I would have preferred a few wet years to help replenish our depleted groundwater reservoirs. That is a lasting effect of the drought that may not be fixed any time soon.

Source: http://cdec.water.ca.gov/cgi-progs/products/rescond.pdf

The Tuolumne River Parkway is a changed place. During the deluge last year, river flows were maintained at or near flood levels through July. Much of the river floodplain was underwater for months, and hundreds of trees and shrubs were uprooted and carried downstream, in places leaving behind huge masses of dead vegetation. Riverside vegetation really never had a chance to recover and regrow once the water subsided. The hated invasive weed River Hyacinth is gone, but so are many riparian shrubs. The six month flood was necessary to protect human developments on the river, but it didn't do the habitat much good. I'm hoping that the wholesale redistribution of river gravels will do the Salmon and other river organisms some good. I have run across signs of beaver, otter, raccoon, and foxes on the floodplain in recent days.

I've been going through the Geotripper archives to select some of my favorite blog posts of the last ten years. The first half of 2017 was dominated by my observations of the extraordinarily wet year and the flooding, which I called "Liveblogging the Deluge". I wrote dozens of posts all through the first half of the year, and it was hard to pick any particular ones to illustrate here, so I settled on the one I wrote exactly one year ago. It involved the post-mortem of the first of the major atmospheric river storms that battered the state. Many more were to come...

Thursday, January 26, 2017

Liveblogging the Deluge: The Post Mortem...Storms That Made a Difference

The atmospheric river storms of January have finally subsided, and we are looking at kind of a new landscape across California. We had a couple of sunny days, so we headed up the highway to have a look at Don Pedro Reservoir on the Tuolumne River coming out of Yosemite. When we visited on January 5, the lake stood at 786 feet, which translates to 76% of capacity. That was 114% of normal for this time of year, which was a relief after five years of intense drought.

Don Pedro Reservoir on January 26 after two atmospheric river storms, elevation 813 feet (90% of capacity).

When we arrived yesterday, the lake stood at 813 feet, or 90% of capacity, which is 133% of normal. It is only 17 feet below the level of the dam. It could have been higher, but the dam operators have been maintaining constant outflows in the range of 7,000-9,000 cubic feet per second, a level that is just short of flood stage. Had they not done this, the lake could have overflowed and flooded downstream urban areas as happened in 1997.

Source: http://cdec.water.ca.gov/cgi-progs/products/rescond.pdf

It is a similar picture at the major reservoirs all around California. The monster reservoirs, Shasta and Oroville, are at more than 120% of normal for this time of year. San Luis Reservoir, the critical link in the California Water Project, is 103% of normal, and may fill for the first time in five years. A few are still low, most notably New Melones (68% of normal), and Trinity (84% of normal), but they are way up from where they stood before the storm.

Source: http://cdec.water.ca.gov/cgi-progs/products/rescond.pdf

The picture in my corner of the woods is brighter too. The Tuolumne River is running fast and cold, and in many places it covers practically the entire floodplain, and has done so for several weeks now. I believe that most areas downstream are not affected by the high flows (there is a history after all of flooding, and outflow from Don Pedro is regulated so as to prevent it). Instead the river is flushing itself of invasive hyacinth, which has been threatening numerous creatures and plants. Gravel bars are shifting and accumulated silt is being removed, providing better nesting areas for salmon and other fish species. Silt is being redistributed across the floodplain, rejuvenating the soils of the riparian areas. Groundwater aquifers in the vicinity of the river are being recharged.

Tuolumne River in Waterford, about 8,000 cubic feet per second

My rain gauge has been active. My friends in more humid regions may snicker a bit when I talk of how we've had 7.38 inches of precipitation in January. That might not seem like all that much but in 25 years of recording rainfall in Waterford, only two had greater amounts, 7.58" in 1995, and 8.60" in 2011.  We've had a year where that was the total for the entire season (7.26" in 2014). We've already passed the total rainfall normally received in an average year (14.69" so far compared to 13.92" average for the last 25 years).

But the real story? The snowpack.

At the height of the drought, we had a snowpack that was 5% of normal. 5%! It was both unbelievable and appalling.

Source: http://www.sacbee.com/news/state/california/water-and-drought/article124305504.html

This year started out with some good healthy storms, but the January events threatened to undo the progress. On the first of January, the statewide average was 70% of normal, which was an improvement over the last five years.The atmospheric rivers began as warm tropical storms that threatened to melt what snow there was. At first they did, but colder arctic are started to move in and the snowpack began to build. After the first set of storms blew through, the statewide snowpack had improved to more than 100% of normal.

And the snow kept falling! The second atmospheric river storm system brought even more snow, and as of today, the snowpack is nearly 200% of normal. If the trend continues (there is NO guarantee of this), we could be on track for a record snowpack. I don't consider it likely, but it would be nice to start recharging the groundwater aquifers that have been severely depleted in recent years.

Source: http://cdec.water.ca.gov/cgi-progs/products/swccond.pdf

The record snowpack should not be seen as evidence that global warming isn't happening. Average temperatures are defiinitely up and have been for several decades. The thing is, snow is snow whether the temperature is 15 degrees or 30 degrees. A not-at-all unusual heat wave could undo the progress in the snow levels. The sky spigot could turn off. After the record flooding of 1997, February and March both provided less than a quarter inch of rain over the entire month. And the drought will never be truly over, as demand outstrips supply even in plentiful years. And little is being done to replenish declining groundwater aquifers.

All in all, though, I'm happier to have plentiful rain rather than crippling drought!

Liveblogging the Deluge: San Joaquin River National Wildlife Refuge - What a difference a few months made (and Rabbits)

The San Joaquin River at the National Wildlife Refuge in November 2017

Just a few months ago, the San Joaquin River, and its major tributary the Tuolumne River, were in big trouble. The worst drought in California's recorded history had left the rivers at a mere trickle, and many parts of the San Joaquin were dry, despite recent efforts to bring back some sort of minimal flows to stretches of river that had been dry for decades (after dam and irrigation levee construction upstream). The invasive weed River Hyacinth had choked channels, crowding out native vegetation and making life difficult for fish and other organisms.

I hiked the Pelican Nature Trail in the San Joaquin River National Wildlife Refuge back in November, and despite a few early storms, dryness was the overwhelming feeling. Volunteers have put in a vast amount of work replanting former riparian woodlands, but it felt like the river overflow areas wouldn't see water any time soon. The river was flowing at a sluggish couple of hundred cubic feet per second.

The San Joaquin River in the same exact location on February 14, 2017

I returned to the Pelican Trail yesterday to a changed world. A series of atmospheric river storms over the last six weeks have dumped record amounts of precipitation across northern and central California. Watermasters at the reservoirs upstream joyfully let their dams fill with the prodigious amounts of water, but then the storms kept coming and they realized that some of the dams were in danger of overflowing. They ramped up flows out of the reservoirs and the rivers downstream swelled. The Tuolumne River, for instance, has been flowing at near flood levels (~9,000 cubic feet per second) for the last five weeks, and this week the flows were increased to over 11,000 cubic feet per second. Don Pedro Dam is only 2-3 feet below full capacity, and has only about 30,000 acre-feet of capacity (out of 2.03 million acre feet of storage space). The Merced River has been experiencing high flows as well, and water is high in the usually dry San Joaquin riverbed. Yesterday the river at Vernalis, just downstream of my trail, reached official flood state at 34,000 cubic feet per second.

It was rather stunning to stand on one bank of the San Joaquin, the neglected trickle of water from the southern Great Valley, and not be able to discern exactly where, off in the distance, the other bank was located. And there is this: the water level is probably going to rise soon. Yet another intense storm is headed towards California, and there is going to be another week of rainfall and snow in the mountains upstream. Don Pedro Lake, for one, is just about full and it is possible they will have to let additional water through the system to keep the lake from overflowing.

More than a month ago, on January 4, I wrote the first of a series of blogs that I soon called Liveblogging the Deluge. I quite honestly thought it was going to consist of four, maybe five posts as the first atmospheric river storm passed through California. But another storm soon followed, and then another. I look back now and see that I've published 24 posts on the storms, and they keep coming. This has been an extraordinary storm event and, for some people, a scary experience. Nature cares little for human beings and our puny attempts to control it can sometimes result in failure and tragedy. Despite the evacuation of 180,000 people because of an unstable situation at Oroville Dam, we've kind of held things together in the north part of the state, but the system is presently strained to the limits. Levees are showing signs of failure in places and reservoirs are getting dangerously full. It is imperative that residents in California keep their eyes open, and when the warnings come and evacuations are ordered that they comply as quickly and orderly as possible. Making a principled stand to defend your house against a rising flood is dangerous and may be deadly.

By the way, the other strange sight on the Pelican Nature Trail was the prevalence of Desert Cottontail Rabbits. There were perhaps hundreds of them along the trail. I assumed they had been flooded out of their habitat on the flats below and had gathered on the high ground of the levee where they were nibbling at the smallest shoots of grass, or reaching for leaves on the lower branches of the shrubs.

They barely seemed to register my presence. I was stepping only two or three feet away from them before they would move into the brush along the trail. They only scattered rapidly once, when a Northern Harrier flew overhead. Human beings are not the only beings who are affected by the floods.

I'm not going to be able to liveblog the coming storm, as I will be out in the middle of it. We're headed out to the Death Valley region where we will be navigating between storms and flash floods. I expect to have some interesting observations once the storm is past and we are home again. And yes, we will be careful out there. It's not often that one gets to observe rain in the driest place in North America. See you in a few days!

Liveblogging the Deluge: Before and Almost After

Tuolumne River on Feb. 21, 2017, discharge about 16,000 cubic feet per second

There is no doubt that this has been a unique year for the rivers of California, one that could very well not be repeated in many of our lifetimes. A year ago we were in the grips of the worst drought ever recorded, five years running, and then the rains began. And continued. Month after month, one atmospheric river storm after another took aim at California like an out-of-control fire hose. The snowpack reached levels not seen in generations, in some places reaching 200% of normal.

Tuolumne River this afternoon, discharge 3,520 cubic feet per second

And then things got scary. Oroville Dam came uncomfortably close to failure, requiring the evacuation of 200,000 people downstream for a period of time. Don Pedro Dam on the Tuolumne River was not in danger of failure but it came within inches of overflowing uncontrollably, and the emergency floodgates were opened for only the second time in history (the first being in 1997). On January 4, operators at the dam ramped up flows of the river to 10,000-12,000 cubic feet per second (for a day or two, flows reached 16,000 cfs), putting it in a state of official flooding, and the water flows did not begin to recede until only a few days ago. I checked out the river a week back, and the river was down to 6,000 cfs. Today it was 3,520 cfs, and after five months of constant inundation, the floodplain was at long last reemerging. For perspective's sake, the average flow of the river during much of the drought was around 200-500 cubic feet per second.

On Feb. 21, the river was flowing into the large quarry pond on the top left of the picture.

The snowmelt has not actually slowed down, actually. The inflow into Don Pedro Reservoir has remained constantly above 12,000 cfs for much of the last month, but apparently the dam operators are feeling confidant that they can fill the dam without overflowing, and have allowed the lake level to rise slowly from 798 feet to 815 feet (it would be full at 830 feet). This is the delicate dance they must do to maintain flood protection while preserving as much water in storage as possible for irrigation and domestic use downstream.

Today, the river and the pond are separated again. The floodplain in the foreground is once again exposed.

I've been wondering ever since the floodplain was inundated how the channel of the river would be affected by the ongoing deluge. At such high flow velocity, cobbles and gravel have surely been redistributed across the floodplain. It is not yet clear whether the river will find a new channel, but I would not be surprised if that happens. I can see new sandbars that may be blocking old channels in a few places. I wondered if the slough at the base of the metal stairway on my river trail would become a new channel, but it's looking like it will not, but it may be longer than it once was.

The most apparent change will be in the riparian vegetation. There had been a great deal of growth on the floodplain since the last inundation in 1997, and much of that vegetation has been swept away. Whole mature trees are gone, and entire willow thickets. A bit of good news in that regard is the complete absence of river hyacinth. The invasive plant was well established on the upper Tuolumne, but all sign of it has been swept away in the torrent. I hope the same has happened downstream at the confluence with the San Joaquin and in the delta. The hyacinth has choked channels and blocked out native plants and wildlife. Maybe this event will be a reset, and some form of control can be achieved.

The other changes to consider are the animals. The floodplain was a rich habitat for all manner of mammals, reptiles, amphibians, fish, and creepy crawlers. Many have been displaced for months, and their former homes will be highly altered or gone. There will be large tracts of barren gravel. I'll be watching for their return.

The floodplain of the Tuolumne was not a natural river before the flood. Gold mining, dredging, and quarrying had already severely damaged the riparian environment, and altered the natural channel. There were few of the gravel bars needed by the salmon and other native fishes to spawn. I am hopeful that the flood will have made some positive changes.

The deluge is not yet over. There is still a huge amount of snow in the high country, and flows will no doubt remain high for weeks or months to come. The full extent of the changes to the floodplain will not be apparent for some time. I'll be there to report when they are!

Liveblogging the Deluge: The Other Shoe Drops!

Wait...it hasn't rained in weeks. Why am I still talking about "liveblogging the deluge"? This is the case of the other shoe dropping. For months we have had storm after storm, adding up to a record year of precipitation in Northern California, and nearly a record in the central state. The snowpack a week ago was nearly 200% of normal. So the storms have stopped, but now a tremendous amount of snow is about to melt, so we have another round of possible flooding.

This was all brought home to me this last weekend when I took my class on a field trip to Yosemite Valley. We had a short heat wave during the week prior, and the river shot above flood stage on Wednesday and stayed there until Saturday when we arrived. The valley floor was flooded in many places, and the Merced was raging downstream (below).

On Thursday, the river peaked at nearly 12 feet (9,000 cubic feet per second), and was still at 10 feet (6,500 cfs) on Saturday. With a weak storm system passing through over the weekend, the flows backed off a bit, but the next heat wave will started the cycle all over again. For perspective, the average flow at this time of year is about 2,000 cubic feet per second.

Needless to say, the waterfalls were booming. Yosemite Falls were exploding and the echoes were resounding across the valley. It sounded like boulders were falling off the cliffs.

There was a change back home, but for a different reason, I suspect. The Tuolumne River was down for the first time since early January! I took my customary walk along the Parkway River Trail in Waterford, and the water had receded some 2 or 3 feet! I checked the numbers, and indeed the flow had declined in the last week from flood stage at 11,000 cubic feet per second to about 8,500 cfs. My first thought is that the dam operators finally felt confident enough about the flood capacity at Don Pedro Reservoir, and this has to be partly true, as the lake is down to 798 feet after nearly spilling over in January at 830 feet.

A check of the flow data told a different story. For months the outflow has been at 11,000 cfs or so, and inflow at the reservoir has been around 8,000-9,000 cfs. But during the heat wave last week inflows climbed to 11,000-12,000 cfs. The releases have been fairly constant at about the same level, but now the irrigation system is starting to take a fair fraction of the river at LaGrange Dam, thus the drop in river level.

The river is still astounding. The normal channel still lies hidden beneath 10-15 feet of water, and the river is filling the flood plain in a way that hasn't been seen in decades. And it will continue, according to reports, well into the summer. Extraordinary...

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.