Julie Zimmerman

Lead Scientist
Freshwater
[email protected]

Julie’s focus in The Nature Conservancy’s California Chapter is to develop collaborative, science-based approaches to water management and river restoration in California, based on principles of decision science. Julie has over 10 years of experience in the area of environmental flows, providing scientific leadership and technical expertise through positions with the Conservancy, the federal government, and academia.

Before joining the Conservancy in California, Julie was the Science Coordinator for the Central Valley Project Improvement Act for Fish Programs with the U.S. Fish and Wildlife Service (USFWS), specializing in environmental flows, water operations, and development of decision support tools for river restoration. Prior to working at USFWS, Julie was a River Ecologist with the Conservancy’s Connecticut River Program and Chesapeake Bay Program. She participated in several projects developing environmental flows for large watersheds in the Northeast, including the Connecticut, the Potomac, and the Susquehanna Rivers. Julie holds an M.S. in ecology from Colorado State University and a Ph.D. in fisheries from University of Minnesota-Twin Cities.

What Julie is working on now:

I’m currently working with academic and agency partners to develop environmental flow recommendations for every stream in California and a companion framework to refine these flow recommendations with local information where necessary. I’m also wrapping up a paper that analyzes flow alteration at all stream gages in the state and beginning another paper that describes an approach for river restoration in the Central Valley that is based on quantifying desired ecological outcomes.


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2020 | Freshwater | Science | Publications & Reports

A functional flows approach to selecting ecologically relevant flow metrics for environmental flow applications

Sarah M. Yarnell, Eric D. Stein, J. Angus Webb, Theodore Grantham, Rob A. Lusardi, Julie Zimmerman, Ryan A. Peek, Belize A. Lane, Jeanette Howard, Samuel Sandoval-Solis

The authors of this paper are engaged in developing flow criteria for California Streams through California Environmental Flows Framework (CEFF) collaboration. The effort is funded by the State Water Resources Control Board. This collaboration is a working group within the California Water Quality Monitoring Council. This…


2019 | Freshwater | Science | Publications & Reports

Cannabis and residential groundwater pumping impacts on streamflow and ecosystems in Northern California

Samuel C. Zipper, Jennifer K. Carah, Christopher Dillis, Tom Gleeson, Ben Kerr, Melissa M. Rohde, Jeanette K. Howard, Julie K.H. Zimmerman

Using a newly developed tool for estimating streamflow depletion from groundwater pumping, this study examined the impacts of ongoing groundwater pumping on streamflow and aquatic ecosystems in the Navarro watershed in rural, coastal California. The study found that common uses of groundwater in the watershed,…


2019 | Freshwater | Science | Publications & Reports

Rapid and Accurate Estimates of Streamflow Depletion Caused by Groundwater Pumping Using Analytical Depletion Functions

Samuel C. Zipper, Tom Gleeson, Ben Kerr, Jeanette K. Howard, Melissa M. Rohde, Jennifer Carah, Julie Zimmerman

Reductions in streamflow from groundwater pumping can negatively impact water users and aquatic ecosystems but are challenging to estimate due to the time and expertise required to develop numerical models often used in water management. This paper develops a new approach – a combination of…


2019 | Freshwater | Planning | Science | Publications & Reports

Conservation Planning Foundation for Restoring Chinook Salmon (Oncorhynchus tshawytscha) and O. mykiss in the Stanislaus River

Prepared by Anchor QEA, LLC (John Ferguson, Elizabeth Greene, and Michelle L. Ratliff), Contributors and Participants: John Cain, Jon Rosenfield, Alison Weber-Stover, Stephen Louie, John Shelton, Tim Heyne, Brian Ellrott, Sierra Franks, Monica Gutierrez, Rhonda Reed, David Swank, Steve Edmundson, Katie Schmidt, Rachel Johnson, Jeanette Howard, Julie Zimmerman, Chris Carr, Daniel Worth, Rene Henery, Ron Yoshiyama, Joshua Israel, Paul Cadrett, Ramon Martin, and J.D. Wikert

Also view Appendix A: Stanislaus Survival Model and and other report Appendices.  


2019 | Freshwater | Science | Publications & Reports

Stream flow modeling tools inform environmental water policy in California

Theodore E. Grantham, Julie K. H. Zimmerman, Jennifer K. Carah, Jeanette K. Howard

Management of California’s vast water distribution network, involving hundreds of dams and diversions from rivers and streams, provides water to 40 million people and supports a globally prominent agricultural sector, but it has come at a price to local freshwater ecosystems. An essential first step…


2018 | Freshwater | Planning | Science | Maps & Webmaps

Rearing habitat objectives to support salmon in the Central Valley

Travis M. Hinkelman, Myfanwy Johnston, Joseph E. Merz, Julie Zimmerman

To restore degraded stream corridors and develop large-scale, sustainable watershed conservation strategies, it is essential for managers to consider—in order to ultimately re-establish—the habitat requirements of keystone species. For example, in order to restore salmon in the Central Valley of California, we need a clear…


2017 | Freshwater | Science | Data

California Natural Flows Database

Julie K.H. Zimmerman, Daren M. Carlisle, Jason T. May, Kirk R. Klausmeyer, Theodore E. Grantham, Larry R. Brown, Jeanette K. Howard, Nathaniel Rindlaub

The Nature Conservancy and the United Stated Geological Survey (USGS) partnered to generate estimates of natural flows (expected streamflow in the absence of human modification) in all the streams and rivers in California (1950-2015). For more details on the methods and results see  Patterns and…


2017 | Freshwater | Science | Publications & Reports

Patterns and magnitude of flow alteration in California, USA

Julie K H Zimmerman, Daren M. Carlisle, Jason T. May, Kirk R. Klausmeyer, Theodore E. Grantham, Larry R. Brown, Jeanette K. Howard

The importance of the natural flow regime to stream and river health has received growing attention in recent years. Understanding natural flows and patterns of flow alteration is an important first step in improving the management of California’s rivers and streams for human and ecosystem…