Understanding Greenhouse Gas Emissions from Managed Water Systems
UC Davis researchers, including collaborators from the Tahoe Environmental Research Center (TERC) and the Department of Civil and Environmental Engineering, are partnering with Valley Water to study methane emissions from reservoirs in Northern California. This work applies advanced environmental monitoring techniques to better understand how freshwater systems contribute to greenhouse gas emissions — and how those emissions can be managed.
Why Study Methane in Reservoirs?
Methane is a potent greenhouse gas, and reservoirs are increasingly recognized as important sources. In these systems, methane is produced by microbes in low-oxygen sediments and deep waters, then released into the atmosphere through bubbling and diffusion.
However, measuring methane emissions is challenging. Emissions can vary widely across a reservoir depending on depth, sediment type, temperature, and oxygen conditions. Traditional monitoring methods often miss this variability, leading to uncertainty in emission estimates.
A New Approach to Measuring Methane
This project uses a combination of innovative, high-resolution techniques to capture methane dynamics across entire reservoirs:
- Hydroacoustic (sonar) mapping to detect methane bubbles rising from sediments
- Sediment sampling to measure methane production at the source
- Water column and atmospheric measurements to quantify how much methane reaches the surface
- Integration with environmental data such as temperature, oxygen levels, and stratification
This approach allows researchers to move beyond single-point measurements and develop a whole-reservoir understanding of methane emissions.
Key Findings
Research conducted in multiple Valley Water reservoirs — including Almaden, Chesbro, Stevens Creek, and Uvas — has revealed:
- Methane emissions vary significantly across reservoirs, depending on sediment characteristics and location
- Low oxygen conditions drive methane production, particularly in deeper waters
- Water levels and seasonal changes influence emissions, with higher rates often observed during warmer periods and lower water levels
- Stratification and mixing processes affect how methane reaches the surface
From Science to Management
This research is directly informing how water managers understand and address greenhouse gas emissions from reservoirs. Findings are being used to:
- Improve greenhouse gas accounting and reporting
- Evaluate management strategies such as oxygenation or water level adjustments
- Support decision-making that balances water supply, ecosystem health, and climate impacts
Broader Impacts
The Valley Water collaboration represents a growing field of research at the intersection of freshwater science, engineering, and climate policy. By developing new tools and approaches to measure methane emissions, UC Davis researchers are helping to:
- Reduce uncertainty in global greenhouse gas budgets
- Identify opportunities to mitigate emissions from water systems
- Apply watershed science to real-world infrastructure and management challenges
Connecting to Watershed Science
This work builds on TERC’s broader expertise in understanding how physical, chemical, and biological processes interact in freshwater systems. By extending these approaches beyond Lake Tahoe to managed reservoirs, researchers are advancing a more complete understanding of how water systems influence — and are influenced by — a changing climate.
Together, this research helps ensure that freshwater management strategies are informed not only by water supply needs but also by their role in the global carbon cycle.
For more information email Alex Forrest @ UC Davis.