Tag: Yosemite National Park

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A good acorn year

The 2023-2024 geomorphic restoration of Ackerson Meadow wrapped up last week with the final filling of a 160,000 cubic yard erosion gully network. The next phase of work will be to establish native plants that will stabilize the meadow for centuries to come. In addition to planting wetland plants in the meadow, we’ll be planting upland trees, shrubs, and grasses in the excavation areas. And one tree that I’m hoping will thrive on the sunny slopes is the California black oak, Quercus kelloggii. There are a few big beautiful specimens of this species around the edge of Ackerson Meadow and a couple of them produced an excellent acorn crop this year. Some acorns were sent to the Park for growing into seedlings that will get planted in a year or so. But we also directly planted a bunch of acorns into the bare dirt slopes. Some of the equipment operators helped; it was a fun way to wrap up the year, putting seeds into the ground that we can watch grow over the coming years.

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My first find of a northwestern pond turtle in Ackerson

While doing topographic surveying in support of the gully-fill restoration at Ackerson Meadow, I found a pond turtle basking in the sun in the section of the gully that was to be scraped clean in the following days by heavy machinery. Yosemite deploys a team of aquatic biologists to search the channel ahead of the machines, finding and removing turtles to safe locations. They’ve found dozens of turtles, but this was my first one! Thanks to Pando for the photo of me and my turtle.

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Great grey owls at Ackerson during restoration work!

Sound on! Video of a juvenile great grey owl calling from the top left of the snag in the middle of the frame.

Photo of a fluffy juvenile (there were at least two visible at once in this area) taken on my phone through my binoculars.

This is an adult hunting the Phase 1 section of Ackerson Meadow that was restored last year. The owl is about 12 feet off the ground and was 20-30 feet away from me.

An owl pellet full of rodent bones. https://en.wikipedia.org/wiki/Pellet_(ornithology)

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The cows came home

A portion of Ackerson Meadow remains in the Stanislaus National Forest, with an active grazing lease. About 300 cattle are gathered here as part of the fall roundup, calf splitting, and prep for the drive down to winter grounds in the Central Valley.

Cowboys and cattle dogs driving cattle down Evergreen Road to Ackerson Meadow. This is part of the longest remaining cattle drive in the state of CA. The calves were separated from their mothers this month, and next month the cows will be herded by horse-mounted cowboys about 50 miles down to their winter pastures in the Central Valley, utilizing highway 120 and its bridges over major rivers for part of the way.

A fence separates the cattle gathering pasture at the left from the wetland restoration project to the right. Cattle will be excluded from the restoration for 3-5 years to allow plants to become densely established. Rewetted portions of unfilled meadow on the right are already thriving with ungrazed plants, whereas the small section of filled gully visible in the lower right is still mostly bare dirt with erosion blanket over it. The pasture to the left has been intensively grazed for a few days. Cattle squeezed their heads under the fence to get at the lush growth on the restoration side.

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Ackerson Phase II is underway

Over the coming months the 7000-foot-long, 12-foot-deep, 100-foot-wide erosion gully in Ackerson Meadow will get filled in. Excavators are clearing out the gully to make way for the haul trucks to dump the fill soil that bulldozers will spread out and pack down in layers. As they move down the gully, the excavators pluck out willows by the root ball and set them aside for replanting in the filled surface. The narrow ribbon of wetland sod that fringes the bed of the erosion channel is similarly salvaged. By filling in the gully up to the level of the surrounding meadow, the human-caused change in the shape of the land (the geomorphology) is returned to its natural state. This restored geomorphology allows water to flow as it once did: spread out across the 1000-foot-wide valley as shallow slow flow rather than confined to a deep erosive torrent in a narrow erosion gully. The restored water flow (the hydrology) will rewet the entire valley, growing dense wetland plants where there is currently cheat grass and sand. That wetland vegetation will hold the soil in place, add organic matter underground, and provide habitat and food for a broad array of wildlife. It’s amazing to see the transformation taking place.

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2024 Tioga Road opening date prediction

Spring has sprung, flowers are blooming, and my thoughts turn to when I’ll be able to drive through Yosemite and see Tuolumne Meadows again!

This year the April 1st measurement of snow water equivalent (SWE) in Tuolumne Meadows is 19.9 inches. My model of the Tioga Road opening date as a function of SWE predicts that the road will open on May 22 this year, with a 50% chance that the actual opening date will fall in the May 16 – 28 range.

This year’s prediction is a full 2 months earlier than when the road opened last year, July 22nd.

As before, I’ve excluded a bunch of years (grey dots and numbers on the graph) because of various management and Park operations issues. So the model and reported averages are all based on the black dots and years only.

Snow data here: https://cdec.water.ca.gov/reportapp/javareports?name=COURSES.202404

Tioga Road opening dates here: https://www.nps.gov/yose/planyourvisit/seasonal.htm

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2023 Tioga Road opening prediction

It’s that time of year again to guess when the Tioga Road will open!

The 2023 Tioga Road opening date prediction is July 8th,

with a 50% chance that the real opening date will fall between June 30th and July 17th.

This is based off of the WHOPPING 62.5″ of snow water equivalent measured at the Tuolumne Meadows snow course for the April 1 report.

This huge winter has presented many challenges, this prediction included. For the first time since I started this in 2018 I need to extrapolate, to make a prediction outside of the range of existing data. I’ve ditched the linear model, since it doesn’t make sense that added inches of Apr 1 snow will have the same effect on road openings from May to July. As a snowpack lingers into June, those extra inches will melt away much faster than they did in April and May. So, I switched to a Gompertz function that has a lower and upper asymptote, which seems like a much better model for how snowpack affects getting a road open.

Snow data here: https://cdec.water.ca.gov/reportapp/javareports?name=COURSES

Past Tioga Road opening dates here: https://www.nps.gov/yose/planyourvisit/seasonal.htm

Data excluded from the model are the grey dots and dates on graph: 1995 and earlier, due to significantly different wilderness and safety regulations; 2020-2022 due to covid impacts to Park staffing and operations.

I’ll post the R code to Github if anyone wants it.