Project overview: Address critical knowledge gaps on groundwater resilience in Yosemite to better plan for both municipal use and ecosystem health in times of prolonged drought, early snowmelt, and rain-on-snow events.

How your support helps: High in Yosemite’s alpine country, groundwater quietly sustains life long after the snow has melted. These underground reserves keep streams flowing through late summer and fall, protect rare plants, support meadows, and provide water for wildlife, visitors, and the communities in Yosemite Valley and Tuolumne Meadows. But as snowpack declines and droughts become more frequent, Yosemite and the surrounding areas rely on groundwater more than ever.  

In recent drought years, flows on the Dana Fork — the source of drinking water for Tuolumne Meadows — dropped so low that managers were forced to consider backup supplies. Similar challenges are emerging in Yosemite Valley, where the municipal water system also depends on groundwater. 

Yosemite has already sustained two major droughts in the last 20 years, and this project aims to answer the questions of how long Yosemite’s groundwater can keep buffering these droughts before the next major one hits. By sampling and dating water from streams, springs, and groundwater wells in both Tuolumne Meadows and Yosemite Valley, scientists will create the first detailed picture of the age and origin of Yosemite’s groundwater. The results will show how much water comes from fresh snowmelt versus older reserves, and how vulnerable each source is under prolonged dry conditions. 

This year: In 2026, park scientists will fill critical knowledge gaps on how resilient the park’s water sources are under prolonged drought, earlier snowmelt, and rain-on-snow events. With your support, teams will generate a new dataset of groundwater age, quantify the proportion of water supply coming from snowmelt versus groundwater sources, and produce a summary report with data visualizations and maps to support resource management. These findings will give park managers the science they need to make informed decisions about protecting meadows, preparing for drought, and safeguarding the drinking water relied upon by visitors and staff.

Project partner: Yosemite National Park

 

Photo credit: Nathaniel Abrahams