Solstish

Apologies for my long absence; it was a busy summer in Yosemite, and I've been enjoying the recovery. My schedule slows down as the park's does.

Yosemite is truly uncrowded now; I've been hiking where I see no one all day. I went up to Little Yosemite Valley for the night last week, and saw 4 people on the way; in the summertime it'd be 400 people. The campground there was calm and quiet with most nighttime noise coming from a spotted owl and the brightest fires were from Geminid meteors overhead. Half Dome leans completely away from the sun before 5pm and its cold shoulders cool off quickly then. I went up to George Anderson's spring and cabin but no one was there, either.

The Merced has dropped to below average, for just the second short stretch in a year. Yosemite Falls and the others are light but not anemic. There's very little snow at any elevation.

Yesterday was our annual Christmas Bird Count wherein several dozen amateur naturalists spend the day afield accounting for all avians. All-star Michael Ross added the first-ever Say's Phoebes to the count. Thomas Say went to boarding school with John Kirk Townsend (of Townsend's Warbler, for example). Townsend did some of his western natural history work in the company of Thomas Nuttall (of Nuttall's Woodpecker). Nuttall never got to the Sierra but he came to coastal California in 1835 where he bumped into one of his former Harvard students, Richard Henry Dana, Jr. (that's right, "Two Years Before the Mast"). On his second trip to California, Dana made it up to Yosemite and spent time with Galen Clark. Clark, of course, is buried in the Valley's cemetery, the residents of which Michael and I think of as some of the people from our village. Even after all these years we are 4 degrees of separation from the fellow for whom the phoebe is named.

Winter solstice is at hand, when the darkest days will start to stretch and lighten a bit. Here's hoping the Sierra gets Nevada and all of us range in the light soon.

A solstice to remember

Our remarkable year continues to surprise with storms into June. The Merced River has hovered near flood level for several weeks, running 3-5 times usual volume. Only now is it showing a typical seasonal decline, more than a month later than 'normal.' Low elevation tributaries are already drying or dried, but the main stem still runs strongly.

The lower canyon shows an interesting color reversal of early spring's redbuds underlain by white Nemophila or Claytonia, whereas now it's the white of buckeye overlying the purple of Clarkia.

Steve's newest Yosemite Nature Notes video has been released; you can learn something about Yosemite's grizzly bears here. How would your Yosemite visit be different with grizzlies around? Here's a brief travel item on Yosemite in the Huffington Post. Both of these media items have something in common with this blog...

Tioga Pass opens to cars today, but don't expect any services in Tuolumne to open soon. Likewise, hiking will be quite challenging for a while because of lingering snow and high runoff. (Do not take chances with stream crossings!) This IS an exceptional year and we won't see the high country we've become used to.

Post-winter Recovery

Springtime is making its way uphill in the Sierra with redbud peaking in El Portal now while unfathomable snow persists above 7000 feet. It can hardly be said enough: WHAT a winter we've had here! Storms were repeated with good frequency and lots of Pacific moisture, leaving us with a tremendous snowpack. The snowline was a bit higher than historical averages; not much accumulated in Yosemite Valley (though we had lots of rain runoff), but higher elevations have had fantastical quantities. The central Sierra has 175% of usual water content in the current snowpack. Picture the meadows and forests in the May Lake area buried by 6-7 feet of water (not 6' of snow, but 6' of standing water) - that's the nature of how much mature, dense snow is covering the tens of thousands of acres of Yosemite's upper elevations.

<-Bridalveil in flood.

Storm damage has been considerable in/near the park, with Hwy. 41 having been closed for a month by a washout, and crews working hard to repair slope movement on the Big Oak Flat Road below Crane Flat in hopes of getting it re-opened before Memorial Day. Trails at and above the Yosemite Valley level have a lot of downed trees; trail crew sawyers will be very busy for much of the summer to get those cleared. When you visit the Valley, check out the fragments of bark-less logs below Bridalveil or Yosemite Falls from trees that were uprooted and thrown over the falls this winter. Since December there's been a huge deposit of frazil (wist) ice below Yosemite Falls, and we're now in the month when one is most likely to be able to observe wist ice flowing.

The excitement isn't over. Because of the closure of the Big Oak Flat Road, Hwy. 140 has been handling much more traffic. This past Saturday, visitors were waiting over 2 hours in a 3.5 mile-long line of 800+ cars just to get through the stoplight at the Ferguson rockslide detour west of the park. (Easily avoided by coming in before 9am on weekends.) Because of the road construction in the Valley, the main parking at Yosemite Village will be closed for the next two months, and detours are confusing to both new and veteran visitors. It's going to be a very nice improvement once it's completed, but parking and navigating can be challenges on spring weekends now. Half Dome Village and the new lot by Camp Four are best bets. The road crew is already working to clear Glacier Point Road.

But, wait, there's more. The Merced is running almost 4x average flow today. All that snow in the high country seems likely to bring us some degree of 'high water incident' between now and mid-June (sure to cover some Valley trails at least), depending on how the warming progresses. Yosemite explorers should expect a delayed start to summer, with Tioga Road opening late, trails covered by snow and fallen trees, and creeks difficult to cross.

Ice, Ice, Maybe

There's an exceptional accumulation of waterfall slurry ice below Yosemite Falls right now, and the whole amphitheater is closed for safety reasons. The stream of 'frazil' flow meanders dynamically and it'd be possible for someone to get into real trouble with this unstable landscape. We know it's not really 'frazil ice' because this slurry is formed of frozen waterfall mist/droplets, but it's remarkable, whatever we call it.

There's frazil deposition in Royal Arch Creek and Steve B. says there's frazil in Bridalveil and Ribbon Creeks.

There's also a very healthy snowpack at higher elevations, well above average in depth and water content. The Valley has lots of water from recent storms; there's almost a foot of snow on the ground but running water in Sentinel, Eagle, Royal Arch, Ribbon and other creeks. This wet winter bodes well for summertime waterfalls, some groundwater recharge, and perhaps a more normally-timed start to the fire season. We'll have to wait a few months to fully assess the end of the drought.

Meanwhile at lower elevations flowers are blooming in the Merced River canyon: fiddleneck, baby blue eyes, and a galaxy of waterfall buttercups can be found.

High Water 2017

I am quite impressed with NPS preparations for anticipated flooding in the next couple of days; this is much different from the surprises of 1997's flood. Forecasting has been honed and there's institutional memory of the last big one.

As of last evening, all visitors have been evacuated from the Valley. Staff housing in the Half Dome Village area has been evacuated and all other locals are being told to stay put as of tonight. Peak flow is expected late in the day on Sunday. Projections are for about 17,000 cfs at Pohono Bridge, where the Merced exits the Valley. Average river flow for this time of year is about 100 cfs, and because of this week's rain the river is carrying 572 cfs right now. Again, that projection is for the river to increase to 30 times the current flow by tomorrow evening. We had a flood warning in mid-December but the river didn't quite reach 5000 cfs; it needs to get to about 7000 cfs before the water comes up on to a road in the Valley. The river would first gently back up on to pavement at Wosky Pond on Northside Drive.

If we do get to 17,000, this'd make it the 6th biggest recorded volume for the Pohono gauging station. The bigger events were the floods of 1937, 1950, 1955, 1964 and 1997. Five 'big' floods in a century averages to every other decade or so. What some locals parochially call 'The Flood' of twenty years ago was only a little bit bigger than those other four were, and such floods affect far more than just Yosemite. There was no gauging station in 1862, when the Merced surely exceeded its 1997 size in a mega-flood that wrecked the whole state.

All these high water events happen December-February and are due to warm storms, which bring rain to high elevation instead of snow. There's a persistent myth that the 1997 flood was due to rain melting recent snows, but the science says that rain doesn't melt very much snow. The floods happen simply by high snowline causing tens of thousands more acres of watershed to receive rain. Especially in higher terrain with thinner soils and vast expanses of bare granite, that rain just runs off right away and swells the rivers downstream.

I share Muir's enthusiasm for such events; he witnessed and wrote about the flood of December 1871. While I shelter in place, I look forward to seeing the video record collected by the professionals.