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Re: Sierra Snowpack and Stream Flow Data / Maps

Posted: Sun Apr 14, 2019 5:25 pm
by oldranger
paul wrote: Mon Feb 18, 2019 5:02 pm If you are looking for a quick, overall view for the whole range, rather than local detail, the easiest thing from the state is here:
http://cdec.water.ca.gov/snowapp/swcchart.action
This is updated roughly every working day - no weekends or holidays - and gives a quick visual. The default display is the biggest year, the lowest year, and the current year. At the top you can select from a list of years to include in the graph.
I added 2010-2011 to the graph and this year is remarkably similar. Depending on spring and early summer conditions should be similar this summer. If so then expect snow at 11,000 feet thru july in
central and N. sierra.

Re: Sierra Snowpack and Stream Flow Data / Maps

Posted: Mon May 06, 2019 4:06 pm
by rightstar76
Here's another one:

USDA Forest Service Sierra Snow Depth:

https://www.fs.fed.us/r5/webmaps/SierraSnowDepth/

Re: Comparing conditions to past years

Posted: Tue Jun 11, 2019 9:21 pm
by tomba
To compare snow coverage to past seasons we can use MODIS compare view. Example: https://worldview.earthdata.nasa.gov/?c ... 6876822385

This is A-B comparison. B (right) is today, A (left) is 2011-06-21 (another high snow year). Drag the split image slider left and right to compare. Snow coverage is similar on those dates. Click "A" and "B" in the upper-left tabs, and click the up/down year/month/day arrows in lower left to change the A or B date (or drag the slider at the bottom, or use the left-right arrows between the date slider and the date). Scroll down the panel on the left side and click Aqua or Terra tiles to show/hide the approx. 10:00 or 14:00 views for the selected day to pick the clearer image.

We did a trip to that region early July 2011: viewtopic.php?f=34&t=6282&p=45172#p45172.

Re: Sierra Snowpack and Stream Flow Data / Maps

Posted: Tue Jun 11, 2019 10:38 pm
by wildhiker
I've looked at the modis satellite views a lot, but never knew about the comparison mode. That's amazing! Thanks for sharing. And we should all thank our dedicated civil servants who make these great tools available to everyone for free!
-Phil

Re: Sierra Snowpack and Stream Flow Data / Maps

Posted: Thu Jun 27, 2019 10:55 am
by cantare
I've looked at various snowpack report and visualization links and found they are limited by low-resolution images and difficulty with orientation and interpretation--either in matching photos to desired locations or in deciphering sensor placement and the real-world meaning of tabular technical data ("snow water content", eg.)

This CalTopo resource (arbitrarily centered on a Sierra Nevada overview) combines the latest weekly high-resolution Sentinel image with meaningful road/trail/stream/lake overlays:

https://caltopo.com/map.html?fbclid=IwA ... 0.42&a=mba

If you click the dropdown menu at upper right, the MapBuilder Topo layer under "Additional Layers" has a 0-100% opacity slider that fades a detailed and comprehensive topo map in and out, so you can easily zoom to an area and check current snow coverage at precise points of interest. (I've set it to an intermediate value to start so both layers are visible.)

The MapBuilder Overlay (checkbox) shows basic orienting info (major routes, lakes, streams) at 100% opacity even when you're viewing the satellite image exclusively. You can also fall back to daily low-res MODIS images via the "Base Layer" dropdown if the weekly image is stale, and also check the progress & rate of melting over the past days/months/weeks. I do note that the weekly high-res layer may become subscription-only, but it is freely available as of this post.

Re: Sierra Snowpack and Stream Flow Data / Maps

Posted: Sat Jul 06, 2019 6:33 pm
by Dwwd
Check out the comparison discussion of Caltopo high resolution snow/ice images versus the data original site at Sentinel Hub.(free)
See highsierratopix.com/community/viewtopic.php?f=34&t=19598

I particularly like to compare the current snow year, April 1 amounts, to any historical data from above discussion links with similar (4 closest) April 1 amounts from this Ca Water site. http://cdec.water.ca.gov/reportapp/java ... _1_SWC.pdf. I do not focus on snow depth. Only snow weight. Weight zero on calendar historical date => no snow at sensor elevation/location, provided the sensor is working. White pixel in low res image of lake = ice. Blackpixel = water. Between April 1 and start of summer trips, the spring melt rates (heat waves/colder than normal May + June) does modify the snow out/ice out times to some degree. Hence the need to look at historical data for the four closest similar snow years. Then with the Sentinel data you can follow the high resolution images up to a few days before your trip for final verification.

Re: Sierra Snowpack and Stream Flow Data / Maps

Posted: Wed May 17, 2023 3:26 pm
by fpb56
Why is very old data left on this site all the time?

Re: Sierra Snowpack and Stream Flow Data / Maps

Posted: Thu May 18, 2023 11:44 am
by aaron_in_sf
Do you mean, why are threads and posts from 5 years ago or more still present?

I think the question is rhetorical if so... the historical record is utterly invaluable, but it would be nice if the UI had a clear indication of age :)

Re: Sierra Snowpack and Stream Flow Data / Maps

Posted: Mon Jul 10, 2023 3:34 pm
by JosiahSpurr
On the topic of "Sierra Snowpack and Stream Flow Data / Maps," I'm beginning to get a sense of the importance of "river forecast" if river crossings are potentially going to be part of one's trip. I'd be interested to know how exactly how to predict river flow.

It seems to me that part of a river's flow comes from recent rainfall that can be predicted from a weather forecast.

Assuming no new rainfall, river flow seems mostly a factor of snowmelt (snow melt), I think. And snowmelt is largely determined by the daily solar cycle where the hottest temperatures during the afternoon will cause a "pulse" of snowmelt to flow downstream. And how far away the snow was from the point along the river one might be crossing.

For example:

https://cdec.water.ca.gov/dynamicapp/Qu ... an=25hours

Over the most recent 24-hour period, the So. Fork Kings River at station KBC is at a low point (4,260 cubic feet per second at 14:30 PM). It was at or above 5,500 CFS between 12:15 AM and 3:00 AM this morning. Yet, 24 hours ago, it was 4,490 CFS, 230 CFS more than it is now.

Of course, with that much water, a crossing would be impossible. In the Fall of 2023, the numbers will be much lower. However, would knowing the rise and fall of the So. Fork be applicable on the Middle Fork? There aren't that many CDEC stations (maintained by Kings River Water Association?) that measure river flow.

There's three useful query parameters. Above, s=KBC means the station. Above, span=25hours means the duration (not just hours, days will work). Not shown above is the start time/date, e.g., d=03-Jul-2023 would generate a table from sensors a week ago. Ooops... the d= parameter has to also have a time, e.g., d=03-Jul-2023+12:10

Is there a thread just above river crossings? (Also, be careful of snow bridges that can collapse and send an unsuspecting hiker into a freezing cold, fast flowing stream!)

Re: Sierra Snowpack and Stream Flow Data / Maps

Posted: Mon Jul 10, 2023 5:13 pm
by JosiahSpurr
I am running queries on the CDEC database for just station KBC to get river flow every fifteen minutes and discovered that in April 2018 something(s) happened that caused the flow to exceed 8,000 cubic feet per second. I wonder what happened?

Footnote: I spoke with Lonnie O. Work recently. He said 1969 was the biggest precipitation year ever (he's fifth generation Squaw Valley). The bridge at Boyden Cavern says "1939" in the cornerstone at each end, but, he says in '69 the river wiped out the bridge. Thus, the shiny new green I-beams.

Footnote: Apparently, data collection started April 29, 2015:
"04/29/2015 22:45","--",""
"04/29/2015 23:00","471",""