Tioga Road Weather Station Transect Upgrades
These installations span the existing rain-to-snow transition in Yosemite National Park. The primary purpose of these stations is to monitor changes in snowpack and associated soil moisture along this elevation gradient in order to better understand variability in these quantities in wet and dry years and with climate warming. In addition to research that informs park climate science needs, this system would serve downstream stakeholders such as the Merced Irrigation District by providing near real-time data on snowmelt and soil moisture that is critical to runoff forecasting.
Four locations along the Tioga Road corridor (outside of designated Wilderness and outside of the Tioga Road Historic District) would continue to be instrumented as during the preceding 10 years. These sites are:
1. Across the Big Oak Flat Road from Merced Grove parking area
2. Gin Flat
3. Across the Tioga Road from the old Smoky Jack campground
4. Adjacent to the Olmsted quarry (May Lake pit)
Each site will continue to have up to ten snow depth sensors, three of which would include soil moisture sensors. These sensors will be mounted on U-channel posts driven into the ground and stand 10-15 feet in height (see photo). All installations will be upgraded; this will include replacing the soil moisture sensors, requiring excavation of new soil pits adjacent to the existing installation locations. The new soil pit excavation will be approximately 2 feet square by 4 feet deep.
Remote data transmission at Olmsted Quarry will be made possible by the addition of a 10-15 foot tower equipped with a 14-inch Yagi antenna, 30-watt solar panel (30 x 14 inches), and a battery box (12 x 12 x 12 inches). The tower would consist of a galvanized schedule 80 3-inch diameter pipe secured by a poured concrete base constructed in a 3 foot square by 4 foot deep hole. All work would be done using hand tools. Remote data transmission at all other sites will utilize existing weather towers in the vicinity for mounting solar panels and telemetry equipment.
Stations will be maintained by a consortium of researchers from the U.S. Geological Survey, Scripps Institute of Oceanography, and the University of California Merced.
The purpose of this project is to upgrade existing temporary snow depth and soil moisture sensors at four locations and add remote data access telemetry equipment at each location. This project builds on the previous action covered by CE 2006-084, "Highway 120 Corridor Weather Station Installations and Upgrades". Under the previous CE, these installations were temporary, to be removed annually as feasible, and not equipped with remote data transmission capabilities. In addition to upgrades and telemetry, under this project the sensors remain installed year-round for a period of up to ten years.