River Monitoring

River flowing through pine forest
Lyell Fork of the Tuolumne River, Yosemite National Park

NPS photo


The Sierra Nevada Network parks contain the headwaters of seven major rivers. Most of the parks' land area is mid- to high-elevation, where snow is the major form of precipitation. As the winter snowpack melts, it supplies water to park lands through dry summer and early fall seasons. Sierra Nevada snowmelt water flows down rivers and streams to serve as the primary source of water for domestic, commercial, and agricultural use throughout California.

Climate change will have profound effects on the pattern of streamflow in the Sierra Nevada - the timing of peak runoff and the quantity of water through the dry seasons. Warming temperatures raise the elevation of the rain-snow transition zone. As this moves upward in the mountains, more precipitation falls as rain rather than snow. Changes in precipitation type and timing result in a reduced snowpack, earlier snowmelt runoff, and longer and drier summers with less water available during the months it is most needed.

In this project, we monitor hydrology, or the distribution and movement of water and its interactions with the surrounding environment. This monitoring will improve our understanding of the effects of climate change on Sierra river hydrology, contribute to the understanding of relationships between fire and hydrology and guide fire management decisions, and inform managers so they may plan for short-and long-term changes in surface water availability and the effects that may have on wetlands, forests, wildlife, and other park resources.

Scientist in hip waders takes depth measurements in the Middle Fork of the San Joaquin River, Devils Postpile National Monument.
Scientists take depth measurements at a cross-section of the Middle Fork of the San Joaquin River in Devils Postpile National Monument.

NPS photo by: Alice Chung-MacCoubrey

Approach and Objectives

Sierra Nevada Network and Park staff evaluated existing stream gaging stations and selected 14 gages to include in this monitoring project. These gages measure streamflow, or the quantity of water flowing past a gage at a given point in time. The objectives of the river hydrology monitoring project are to:

  1. Detect long-term trends in timing and volume of streamflow using fixed, continuous water stage recording stations at existing stream gages in selected water sheds of the Sierra Nevada Network, and
  2. Record, measure, and/or calculate a set of specific hydrologic measures related to the timing and quantity of streamflow (for example, stage, discharge, number of days to onset of snowmelt, and measures related to low and high flows).

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    Last updated: August 31, 2020