Hydrometeorological Monitoring Map
Yosemite National Park contains 21 meteorological stations, 18 of which are automated "real-time" stations, and three that are manually operated. Weather stations measure one or more of the following: air temperature, humidity, wind speed and direction, barometric pressure, precipitation, solar radiation, snow depth, and snow water equivalent. Several stations include parameters important to fire management, including fuel temperature and fuel moisture. Weather stations are managed by the California Department of Water Resources (DWR), the Merced Irrigation District (MID), the Hetch Hetchy Water and Power (HHWP), the National Oceanic and Atmospheric Administration (NOAA), the National Weather Service (NWS), and the National Park Service (NPS). Data from the automated stations is provided by the California Data Exchange Center and the University of Utah's MesoWest portals. Data from the Climate Reference Network site at Crane Flat Lookout is available through NOAA.
Weather and river records constitute the longest continuous environmental records in the park, with more than 100 years of observations at some stations. Why was this information collected originally? To answer water supply, flood, and weather forecasting needs. Over time, data expanded to include fire management and climate change impacts. The longest records come from the cooperative weather station in Yosemite Valley (since 1905), gaging stations at Hetch Hetchy (2011), and the Happy Isles and Pohono Bridge gages on the Merced River (since 1911-1916). Snow courses were added in the 1930s and 1940s, and automated snow-pillows were added to many sites in the 1980s and 1990s. Automated weather stations were installed near the same time.
Yosemite's 21 meteorological stations (shown on map as Met stations)
Snow Courses: Fifteen snow courses in the park are measured monthly from February through May to estimate water stored in the snowpack. (Additional snow courses and weather stations outside of the park boundaries are included on the park's hydrology map to help provide a more complete picture of conditions, particularly of snowpack.)
Yosemite's 15 snow course locations
River Gages: In addition to weather stations and snow courses, there are seven automated river gages: five of those are operated by the U.S. Geological Survey (USGS), one by Hetch Hetchy Water and Power (HHWP), and one by Merced Irrigation District (MID). River gages primarily measure water stage or depth, which is translated into flow (volume per unit time) via a stage-discharge table developed and maintained through regular manual measurements of flow. Some gages report water temperature and turbidity.
Yosemite's seven river gage locations
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