Slide Canyon Snow Sensor
Notes From The Field
2014 Repairs &
2015 Major Upgrade,
Slide Canyon Snow
Sensor Site
Harrison Forrester
Yosemite NP
Wind Damage - December 2011
Repair - September 2013
Enclosure flooded - April 2014
Enclosure repair – September 2014
Minimum Requirements Analysis
for
Automated Snow Data Collection
Step 1: Problem Statement
Briefly describe the threat to wilderness character that is prompting consideration of
management action in wilderness.
Snow data has been systematically collected in the park since the 1920s. The data collection network
consists of manual snow courses and automated snow sensors distributed across the Tuolumne and
Merced River watersheds. This data is used by water managers outside the park and by the NPS to
assess snowpack conditions and monitor storm events. Automated and real-time snowpack data is
especially valuable in monitoring rain-on-snow events, which have produced large floods in the past.
The ability to monitor current snowpack conditions indirectly contributes to a variety of wilderness
management objectives such as search and rescue operations, anticipating the onset of backcountry
use in the spring, and assessment of hydrologic conditions in meadows receiving overnight stock
grazing (i.e. meadow opening dates). Long-term, uninterrupted snow data records provide important
knowledge about natural conditions in wilderness that are likely to change due to increased radiative
forcing from anthropogenic carbon emissions (i.e. climate warming).
The Slide Canyon snow sensor was installed in 1982. It is located in a remote canyon approximately
½ mile from the maintained trail (Fig. 1). Although lower Slide Canyon does not have a maintained
trail, it is a fairly well traveled cross-country route and arguably one of the most sought after canyons
in the north end of the park. The snow sensor consists of a snow pillow, a hose connecting the
snow pillow to the pressure transducer inside the enclosure, a ground-based instrument enclosure, a
15-foot pole with an antenna, solar panel, snow depth sensor, and an air temperature/RH sensor.
There are no manual snow courses or other snow pillows in the north-central quarter of the park.
Because of this, the Slide Canyon Snow Sensor is particularly important for understanding
hydrologic conditions in a large area of wilderness in the upper Tuolumne River watershed.
From 2013-2014, failures of the snow-sensor pole, and ground-based datalogger enclosure, have
caused numerous stock-supported repair trips to the Slide Canyon Snow Sensor. Wilderness
character is threatened by: 1) increasingly frequent use of the official trail and cross-country route
used to access the snow sensor location (Fig. 1); and 2) unavailability of real-time automated snow
data and interruption of long-term hydrometeorologic records that indirectly facilitate wilderness
management objectives by providing fundamental knowledge about natural conditions in wilderness.
MRA site modification permit - March – June 2015
Tower installation – July 13, 2015
Tower installation – July 13, 2015
Instrument swap – July 21, 2015
Instrument swap – July 21, 2015
Pillow plumbing
Instrument install – August 12, 2015
Soil moisture array
New pressure transducer – CS450
Instrument install – September 10, 2015
Instruments
CR1000 Datalogger
TX320 GOES Transmitter
FTS EON2 GOES Antenna
Judd Depth Sensor
CSI Pressure Transducer
CSI Temp/RH
Vaisala 2-D Ultrasonic
Wind Sensor
• Kipp & Zonen Net
Radiation
• LI200 Pyronometer
• CSI Soil Moisture Array
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Instrument install – September 10, 2015
www.cdec.water.ca.gov - SLI