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: The First Day of Fall and a River Finally Returns to Abnormal

I was mistaken. Nearly two months ago, I suggested in a post that the abnormally high flows on the Tuolumne River were finally subsiding, and that the great flood of 2017 might finally be ending. This happened because I strolled along the river on a day when the output from Don Pedro Reservoir finally fell below 5,000 cubic feet per second, to around 1,500 cfs. That lasted for an entire day or two. The inflow at Don Pedro was still several thousand cfs, and the effort to build up some emergency flood storage space in the reservoir meant that they ramped up flows to 5,000 cfs, and that level continued for another seven weeks.

Source: https://waterdata.usgs.gov/ca/nwis/uv?11289650

I walked the river again today and saw something I haven't seen in nine months: a river at very close to minimum mandated flow. A quick check of the river gauge on the USGS site confirmed that the river was flowing at a mere 339 cubic feet per second. A look at the table above shows how the flow has been declining over the last week.

The CDEC site for Don Pedro Reservoir is even more informative, showing high flows throughout August and early September. Inflow to the reservoir finally dropped below 1,000 cfs about the 12th of September, and the outflow was then also lowered (about 1,500 cfs is diverted for irrigation which accounts for the discrepancy between output from Don Pedro and the river flow below LaGrange Dam where the diversions take place).

Source: http://cdec.water.ca.gov/cgi-progs/queryDaily?s=DNP&d=22-Sep-2017+20:14

Don Pedro Reservoir remains well above normal in water storage after an extremely wet year of precipitation. It presently holds 1.7 million acre-feet, about 84% of lake capacity, and 126% of normal for this time of year.

The floodplain is a different place now, compared to what it was a year ago. The biggest change is the vegetation. Hundreds, maybe thousands of trees and shrubs have been uprooted and washed away downstream. There are huge piles of branches and tree trunks across the riverbed. Other areas along the streambed have been washed clean of any vegetation at all, leaving vast tracts of barren gravel and pebbles. The invasive and damaging water hyacinth is gone, carried downstream in the many months of flooding. One can only hope that the seeds were carried away as well, although they probably weren't. I'll be pulling any hyacinth out of the river that I see in coming months.

The river is not back to normal, because "normal" disappeared more than a century and a half ago when gold was discovered upstream. The original channel and floodplain was upended in the search for the elusive metal. Trees and shrubs were removed, and every bit of gravel was run through sieves, longtoms, or dredges. After the search for gold ended, quarrying for gravel and sand took over, further altering the floodplain, ultimately forming numerous ponds fed by groundwater seepage.

These days, efforts are being made by organizations like the Tuolumne River Trust to bring about some sort of natural balance on this badly scarred landscape. Adjustments to the channel can help expose the gravel bars that salmon need to spawn, and one can hope that the fall run will be more successful than those of the last five years during the drought. Only the Merced River has a more southerly run of Chinook Salmon. At one time 130,000 salmon cruised the Tuolumne. In the last decade, the run has exceeded 1,000 only once (1,926 in 2013).

Walking the Tuolumne River Parkway Trail in Waterford. This is my backyard.

In the meantime, the flood of 2017 seems to finally have subsided. The river is back to abnormal, and we now await the new storm season. After a monster season in 2017, one has to wonder what the coming year holds in store for the river.

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, 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!

So You Were in Death Valley During Bombogenesis...Did You Get Any Rain?

Explosive cyclogenesis (also referred to as a weather bomb, meteorological bomb, explosive development, or bombogenesis) refers in a strict sense to a rapidly deepening extratropical cyclonic low-pressure area. One of those things hit Southern California a few weeks back, at the very moment that we were exploring Death Valley National Park. It caused some serious flooding problems across the Southland, and we knew we were in the path of it.

It's kind of ironic that during the latter stages of California's staggering five-year drought that Death Valley had more precipitation than normal, and last spring that rain delivered a so-called Super-bloom, one of the greatest wildflower shows in decades (see some of our pictures from last year right here). Then, this year when most all of California was being pounded with storm after storm, leading to record accumulations of snow in the mountains, Death Valley stayed dry. Less than a quarter inch of rain had fallen in the five months before our arrival.

It didn't stay that way, of course. We got doused the night before in Bakersfield, and the rain stayed with us for most of the day. We got a lucky break of several hours as we set up camp at Stovepipe Wells in Death Valley, but the rain began falling again during the night, and it was constant for quite a few hours. Somewhere around 0.5 inches fell on us. That may not seem like very much to those who live in wetter climes, but it is overwhelming for a desert environment like Death Valley, which is lucky to receive 2 inches in an entire season. The desert soils look rocky, but the pebbles often hide a layer of clay and calcite deposits that are largely impermeable to water. Instead of sinking into the gravels, the water runs off, and our campsite turned into a muddy morass.

It wasn't just the campsite. We again had a lucky break as far as morning rain was concerned. There was a hiatus that allowed us to pack up and hit the road in an attempt to see what we could of the park. No roads were closed overnight, but raging torrents had clearly passed through during the hours of darkness.

It has been rare during my 28 years of bringing students to Death Valley that we've seen the mountains draped in rain clouds, so the scenery was quite stunning. Above one can see the view of Grapevine Mountains from our campsite.

Driving the highways demanded constant attention, as puddles covered the roads in several places. The Furnace Creek resort had experienced quite a bit of runoff. They've had quite a year, with a fire several months ago that destroyed the laundry room and several other buildings (below).

We made our way past the resort and headed east towards Ash Meadows National Wildlife Refuge, hoping to miss the brunt of the precipitation that was still falling that morning. Debris was everywhere, but never so bad as to prevent our passage. Many of the roads are carefully designed to let the debris flow over the highway without causing damage. Sometimes it works, but there are limits. The highway at Scotties Castle was completely destroyed by an unprecedented flash flood a few years ago, and has yet to be rebuilt.

The rain did add a special perspective though. The rocks of Death Valley are always colorful, but wetness seems to bring out an intensity of color that is rarely seen most years. A bit of inconvenience and discomfort was balanced by some very pretty scenery as we drove along.

Liveblogging the Deluge: Checking out the Spillway at Don Pedro Reservoir

It's probably not too hard to figure out what happened. I get home from a five day trip only to find that the spillway at Don Pedro Dam has been opened for the first time since the floods of 1997. It's a big event in these parts, an acknowledgement that the reservoir was full and in danger of spilling over in an uncontrollable manner. So I had to go and have a look. Mrs. Geotripper and I had a few hours this afternoon and headed on up the river. We had no idea what to expect, or whether we would be allowed anywhere near the spillway.

We were pleasantly surprised to find that there is some limited access for the public. If you want to have a look, you need to drive Bond's Flat Road to the Blue Oak Campground at Don Pedro (trying to approach from the south side - the Fleming Meadows side -  doesn't work as Bonds Flat Road is closed two miles away from the dam). The campground and day use area is open, and provides a limited view of the spillway and the spray from the water releases.

The spillway opens up into a former meadow that was carved down to bedrock during the floods of 1997. A portion of the flow can just be glimpsed from the viewing area. The spillway is similar to the one that failed at Oroville Dam, but at Don Pedro the slope is more gentle, so uncontrolled erosion of the rock is unlikely (especially since the flow rates are not nearly as high as they were in 1997).

The long concrete structure in the top two photographs is the weir that serves as kind of a last ditch spillway. The crest lies at an elevation of 830 feet, and the water this afternoon had reached 829.5 feet. As a consequence, the outflow through the spillway has been increased to 14,600 cubic feet per second (well above flood level) to start bringing the water level down.

There is a high point in the campground that provides a better look at the spillway from the lake side. On this sparklingly clear day, the view of the valley was also spectacular.

For the first time in twenty years the lake is absolutely full. It is quite a sight!

Just a note, in case you want to see the sights for yourself...stay behind the fences and follow the directions of the authorities. I didn't find out for myself ("But sir, I'm a GEOLOGIST!"), but the ranger told me stories of the people that they had caught and cited. They were rather vigilant.

Liveblogging the Deluge: Big Changes on the Tuolumne River

Source: http://www.capradio.org/articles/2017/02/20/don-pedro-reservoir-spillway-opens-for-first-time-since-97/

I've been away for the last five days, experiencing California's storms from an entirely different perspective, that of being exposed and out in the open country of Death Valley National Park. There will be plenty of information and pictures about our adventures soon enough, but there were plenty of events back home that have been rather significant as well. A great many people have been affected as the waters of the San Joaquin River and its tributaries have risen past flood level.

First and foremost, at Don Pedro Reservoir on the Tuolumne River the emergency spillway has been opened for the first time since the floods of 1997. This became necessary when the lake filled nearly to capacity, and a new storm battered the north state over the weekend. The channel downstream floods at around 9,000-10,000 cubic feet per second, but storm runoff threatened to exceed that level. The dam operators had to make a decision to cause some flooding downstream to avoid even greater flooding if runoff was too high.

Flows were ramped up to around 16,000 cubic per second over the weekend, and have since settled back to 13,500 cfs at the latest reading (below). Rain and snow are still falling in the region, so the concern about flooding remains for the time being. The lake fills at 830 feet, and the current level is 828.82 feet. There isn't much room for error.

Source: USGS (https://waterdata.usgs.gov/ca/nwis/uv?11289650)

People are understandably concerned about Don Pedro Reservoir as they compare notes with the events at Oroville Dam in the last few weeks. Both dams have an emergency spillway that flows over unlined and unreinforced rock rather than a concrete channel.

There are some important differences, however.

First, the emergency channel below Don Pedro is much less steep than Oroville's, and is therefore less subject to the headward erosion that threatened to undermine the spillway at Oroville. Second, the spillway was tested previously, during the floods of 1997. The runoff amounts in that event were almost astronomically higher than any flows expected in this year's event. A forty-foot channel was carved through the meadow, and the flowing waters are unlikely to do anything worse this time around.

Still, these are nervous times. I had my first chance to see the higher flows this morning as I headed to work. I stopped at the head of the Tuolumne River Parkway Trail to have a look. The picture below was taken on February 5th when flows were around 10,000 cfs. Note that the entire trail was above water level.

The picture below shows the same scene this morning with flows closer to 14,000 cfs. As you can see, the entire trail is under water now, which means I'll have to find another place for my birdwatching for a few weeks or so.

One senses that authorities are just barely keeping ahead of events, which is not surprising given the nearly nonstop barrage of atmospheric river storms battering California. The situation has not quite spiraled out of control, and the storms are letting up for a few days, which will allow for more floodwaters to flow into San Francisco Bay. I hope we'll have a breather.