Cosumnes River Watershed
The Cosumnes River is the last river without major dams on the western slope of the Sierra Nevada. Thus it is one of the few systems in which the ecological impacts of natural variation in seasonal flows can be studied. In addition, the Cosumnes River Preserve occupies large stretches of the river's lower reaches and has sought, by means of levee breaches and other strategies to reinstate seasonal flooding, restore riparian vegetation and improve conditions for native plant and animal species. The Cosumnes flows into the North Delta; and at its downstream terminus is the McCormack-Williamson Tract, a leveed Delta island which has been under consideration for conversion to tidal freshwater habitat.
Cosumnes Research Group
In 1998, the David and Lucile Packard Foundation provided seed money to a group of UC Davis faculty (originally termed the Cosumnes Consortium) to conduct studies to help inform management and restoration decisions on the Preserve and in the surrounding North Delta region. These studies --- conducted in collaboration with The Nature Conservancy, the Bureau of Land Management, and other Cosumnes Preserve partners --- resulted in the collection of baseline data and the development of a research design which became the foundation for a 7-year multi-disciplinary study of the ecological response of river and floodplain to annual and interannual changes in runoff conditions.
Subsequent work proceeded in several phases, and expanded to include focused investigations of the potential for reestablishment of fall flows in the Cosumnes and of restoration options for the McCormack-Williamson Tract.
- Cosumnes Phase I
- Cosumnes Phase II
- Restoration of Fall Flows
- McCormack-Williamson Tract/North Delta Project: Restoration Planning, Design and Monitoring
- McCormack-Williamson Tract/North Delta Project: Modeling of Restoration Scenarios and Science Panel
Cosumnes Phase I
In 2000, with a grant from the California Bay Delta Authority (CBDA/CALFED) the Watershed Center began a 3-year study of the hydrogeomorphic conditions and aquatic biology of the Lower Cosumnes River and its highly regulated neighbor, the Mokelumne River. This effort focused on identifying the hydrologic and geomorphic processes necessary for restoring and sustaining the ecologic integrity of floodplains.
The project included the following elements: upper watershed hydrologic modeling; lower watershed groundwater hydrology; geomorphology of the floodplain; biogeochemistry and nutrient cycling in aquatic and floodplain habitats; ecology of fish and aquatic invertebrate communities, riparian bird surveys; and an analysis of the reestablishment of riparian forests.
Publications
- Patterns In The Use Of A Restored California Floodplain By Native And Alien Fishes
Peter B. Moyle, Patrick K. Crain, and Keith Whitener. July 2007. San Francisco Estuary and Watershed Science. Vol. 5, Issue 3, Article 1.
More reports and publications from the Cosumnes I project can be found at: http://baydelta.ucdavis.edu/reports/crg1
Cosumnes Phase II
Cosumnes I focused primarily on the relationship between hydrologic conditions and aquatic ecosystems. Cosumnes II, also funded by CBDA/CALFED, built on this earlier work, but emphasized the connection between aquatic and terrestrial systems in floodplain environments. This project continued the monitoring of basic ecological and hydrological processes, but expanded to include investigations of: patterns of restoration success, groundwater and vegetation interaction, linking aquatic and terrestrial ecosystems, bird populations as indicators of ecosystem integrity, and data management for ecosystem monitoring.
The Cosumnes II phase of the project ended in 2004. Reports and papers are posted at: http://baydelta.ucdavis.edu.
Publications
- The Role of Stochasticity and Priority Effects in Floodplain Restoration
Wendy Trowbridge. 2007. Ecological Applications, 17(5), 2007, pp. 1312-1324.
Restoration of Fall Flows
During the late 1900's late summer and fall flows declined within the Cosumnes River. These declines in baseflow reduced access to historic spawning habitat for Fall run chinook salmon. This study, funded by the US Fish and Wildlife Service: investigated the loss of baseflow contributions to the river caused by regional groundwater overdraft; documented the seasonal hydraulic disconnection between much of the river and the complex regional aquifer; and estimated the volume of water needed to partially reconnect the river with the aquifer, reduce seepage losses and partially reinstate baseflows.
Publications
- Linked Surface Water-Groundwater Model for the Cosumnes River Watershed: Hydrologic Evaluation of Management Options to Restore Fall Flows
Jeffrey Mount, Graham Fogg, Levent Kavvas, Jan Fleckenstein, Mike Anderson, Zhi Qiang Chen and Eriko Suzuki. September 2001. Report to U.S. Fish and Wildlife Service Anadromous Fish Restoration Program. Cooperative Agreement No. 11332-8-J264. - Managing Surface Water-Groundwater to Restore Fall Flows in the Cosumnes River
Jan Fleckenstein, Michael Anderson, Graham Fogg and Jeffrey Mount. July/August 2004. ASCE Journal of Water Resources Planning and Management. Received the ASCE Best Theoretical Paper Award for 2004.
McCormack-Williamson Tract/North Delta Project: Restoration Planning, Design and Monitoring
The McCormack-Williamson Tract is a North Delta island located immediately downstream of the confluence of the Cosumnes and Mokelumne Rivers. Owned by The Nature Conservancy California, the island offers opportunities for restoration of of critical tidal freshwater marsh and floodplain habitat. There is also the potential that the island could be managed in such a way as to moderate flood flows in the North Delta.
In 2000, the Watershed Center began the research and baseline studies necessary to inform restoration planning and design, and the monitoring of restoration success. This study included analysis of historic geomorphic conditions, characterization of the modern hydrologic and sedimentologic regime, and baseline studies of aquatic and riparian resources.
Publications
- Natural and anthropogenic geochemical signatures of floodplain and deltaic sedimentary strata, Sacramento Delta, CA
Kendrick Brown and Greg Pasternack. 2006. Environmental Pollution 141:2:295-309. - The geomorphic dynamics of an upper deltaic floodplain tract in the Sacramento-San Joaquin Delta, California, USA
Kendrick Brown and Greg Pasternack. 2004. Earth Surface Processes and Landforms 29:1235-1258.
More reports and publications at: http://baydelta.ucdavis.edu/reports/crg1?q=reports/crg1/MWTC
McCormack-Williamson Tract/North Delta Project: Modeling of Restoration Scenarios and Science Panel
In 2002, the Watershed Center began working with The Nature Conservancy California, the California Department of Water Resources and the North Delta Improvements group on an effort to model a range of restoration scenarios for the McCormack-Williamson Tract. This involved expanding and modifying existing hydraulic models, examining the effects of flood flows and other upstream events, evaluating the water quality effects of various scenarios and investigating the sediment-trapping efficiency of levee breaches and other restoration alternatives such as setback levees.
At the request of the Department of Water Resources, the Center also convened a panel of experts to provide advice on North Delta integrated flood control and ecosystem restoration planning. The experts were asked to address such concerns as: mercury, exotics, dendritic channel creation and function, sediment dynamics, ecological processes, geomorphology, terrestrial and aquatic species, water quality and hydraulics.
Publications
- Water Quality Modeling and Monitoring in the California North Delta Area
Raffi Jirair Moughamian. 2005. Thesis submitted in partial satisfaction of the requirements of the degree of Master of Science in Civil and Environmental Enginnering, University of California, Davis.