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Streamflow and water chemistry in the Tenaya Lake Basin, Yosemite National Park, California

June 3, 2021

The Tenaya Lake Water Budget Study seeks to quantify and understand the water balance within the principal snow accumulation and runoff yielding zone in the Sierra Nevada Mountains. The Study operates stage sensors and data loggers to record Tenaya Lake inflows, water surface elevation, and outflow, with continuous annual data collection for the 21 square-kilometer watershed located in the alpine zone of Yosemite National Park. The Study began in September 2005 and includes discharge and water quality measurements. Water samples have been collected at several gage locations and analyzed for an extensive panel of dissolved constituents.

Tenaya Lake lies in a glacially-scoured granitic basin. Murphy Creek, Tenaya Creek, and Cathedral Creek are the primary surface inflows to Tenaya Lake. Groundwater flow into and out of the lake is minimal because of the granitic bedrock in the basin. Water primarily leaves the lake either as surface flow over the outlet sill or by evaporation. Streamflow in the Tenaya Lake basin is dominated by snowmelt in late-spring and early-summer. Extensive meteorological information is obtained from a weather station located about 300 meters northeast of Tenaya Lake (California Department of Water Resources, 2021) including snowpack levels, precipitation, and air temperature. The water quality in the Tenaya Lake Basin is pristine as the specific conductance of waters throughout the basin are commonly less than 10 microSiemens per centimeter.

The objective of this report is to provide streamflow and geochemical data into and out of Tenaya Lake over a variety of climatic and hydrologic years. These data are being utilized to quantify the water budget for the Tenaya Creek Basin.

References
California Department of Water Resources, Station Meta Data: Tenaya Lake, https://cdec.water.ca.gov/dynamicapp/staMeta?station_id=TNY, accessed February 17, 2021.

Acknowledgements
The Tenaya Lake Water Budget study has benefited from the support and encouragement of many individuals over a span of 16 years. A field project located in a wilderness area could not have succeeded without their commitment. The study would not have been possible without the support of the Yosemite National Park hydrologists, Jim Roche and Catherine Fong. Snowfall can prevent road access to the Tenaya Lake watershed from early October until late June. Jim and Catherine, together with other NPS staff, Joe Meyer and Mitzi Thornley supported the development and operation continuous, Wilderness compatible stream gages. From 2013 to 2019, Tuolumne Meadows winter over rangers, Laura and Rob Pilewski, visited the snowbound gage sites and collected monthly water samples. NPS hydrology technicians, Rachel Hallnan and Harrison Forester, loaned equipment and provided their time to overcome numerous obstacles. William Carey, a hydrologist with Ventura County, CA, helped to establish the gaging stations and develop the stage-discharge relations. Tim Gordon volunteered for a week each year from 2006 to 2018 to maintain the gages and download the annual stage records. Kristen Poehling and Caroline Andrews, each volunteered for a summer to make discharge measurements and collect weekly water samples for chemical analysis.