Yolo Bypass

Methyl mercury (MeHg) cycling and export from agricultural and natural wetlands in the Yolo Bypass.  2007 - 2010

Collaborating Organizations:

California Department of Fish and Game (CDFG); US Geological Survey (USGS)  CA Water Science Center; USGS Biological Resource Division; USGS National Research Program; Moss Landing Marine Labs (MLML); Yolo Basin Foundation; Battelle Marine Sciences Laboratories (MSL); San Jose State and Bachand & Associates / Tetra Tech

Funding Organization:

State Water Resources Control Board Board Project 06-232-555-0 

Project Description:

MeHg is a critical water quality pollutant affecting commercial and recreational fishing within the  San Francisco Bay-Delta (SFB-D) . Wetlands are significant MeHg production sites in the San Francisco Bay Delta and elsewhere; delta wetlands are estimated to produce approximately 40% of the aqueous MeHg present in the San Francisco estuary.  Of the 8 sub-watersheds in the Delta, the wetland-dominated Yolo Bypass (YB) has the highest average annual surface water MeHg concentration, requiring a 70% reduction to meet total maximum daily load (TMDL) goals. 

The primary wetland typs in the YB include rice and wild rice fields farmed annually, fields that undergo crop rotation management, and non-farmed seasonal and permanently flooded wetlands. The purpose of the project was to characterize links between MeHg production and wetland type and management so that TMDL MeHg reduction goals can someday be met.

 Tetra Tech (dba Bachand and Associate) quantified surface water hydrology and loads for the different agricultural wetlands.  They installed equipment for continuous monitoring of flow to and from the wetlands; supported discrete sampling for water quality and hydrologic constituents; and managed hydrologic and water quality data through development of an ACCESS database.  Tetra Tech implemented PFR and CFSTR mass balance reactor models to analyze the data.  Products from those models included quantifying loads onto the system and exported via surface water or groundwater; determination and quantification of net ecosystem production of MeHg; identification of management practices to control MeHg surface exports; modeling soil transport via advection and diffusion and identifying seasonal and diel transport trends; and identifying the importance of transpiration regarding constituent transport in long HRT systems like rice fields and restored wetlands.  Tetra Tech co-authored the final report for this project and three manuscripts that have been published in STOTEN.  Tetra Tech was lead author of two of those manuscripts which identify the importance of transpiration on loading trends and transport pathways of MeHg in wetland systems.

Publications and Final Reports by Bachand & Associates

Bachand, P.A.M., S. Bachand, J. Fleck, F. Anderson, C. Alpers.  2011.  Utilizing Reactor Models to Estimate Transpiration in Aquatic Crops and More Accurately Quantify Constituent Transport and Field Hydrology Utilizing Reactor Models to Estimate Transpiration in Aquatic Crops and More Accurately Quantify Constituent Transport and Field Hydrology.  Under preparation for submittal to Science of the Total Environment for special issue on mercury.

Bachand, P.A.M., S. Bachand, F. Anderson, J. Fleck. 2011.  Transpiration Driven Diel and Seasonal Hydrologic Transport Patterns in the Root Zone of Aquatic Crops and Implications on Soil Biogeochemical Processes and System Management. Under preparation for submittal to Science of the Total Environment for special issue on mercury.

Windham-Myers, LJT AckermanJA FleckM Marvin-DiPasqualeCA StrickerP Bachand, CA Eagles-Smith, D Feliz, G Gill, M Stephenson, CN AlpersIn Press. Mercury cycling in agricultural and managed wetlands: a synthesis of observations from an integrated field study of methylmercury production, hydrologic export, and bioaccumulation. Science of the Total Environment.

Windham-Myers, L., M. Marvin-DiPasquale, J. Fleck, C.N. Alpers, J. Ackerman, C. Eagles-Smith, C. Stricker, M. Stephenson, D. Feliz, G. Gill, P. Bachand, A. Brice, and R. Kulakow. 2010. Methylmercury cycling, bioaccumulation, and export from agricultural and non-agricultural wetlands in the Yolo Bypass. Final Report to the Central Valley Regional Water Quality Control Board. September 2010. 266 p.   (Available from CA. State Water Resources Control Board).

 Publications featured in Speci  and Final Reports by Bachand & Associates

Eight papers are to be published in a special section of the journal Science of the Total Environment presenting the 2007-2008 findings.  Two additional papers were published earlier.  See the list below for the full list of publications from this project.USGS authors are underlined.

Ackerman, JT, CA Eagles-Smith. 2010. Agricultural wetlands as potential hotspots for mercury bioaccumulation: Experimental evidence using caged fish. Environmental Science and Technology. v.44, p. 1451–1457

Ackerman, JT, AK Miles, CA Eagles-Smith. 2010. Invertebrate mercury bioaccumulation in permanent, seasonal, and flooded rice wetlands within California's Central Valley. Science of the Total Environment. v.408, p. 666-671

Alpers, CN, JA Fleck, M Marvin-DiPasquale, CA Stricker, M Stephenson, HE Taylor. In Press. Mercury cycling in agricultural and managed wetlands, Yolo Bypass, California: Spatial and seasonal variations in water quality. Science of the Total Environment.

Bachand, PAM, SM Bachand, JA Fleck, F Anderson, L Windham-Myers. 2013. Differentiating transpiration from evaporation in seasonal agricultural wetlands and the link to advective fluxes in the root zone. Science of the Total Environment. [on-line proof] http://dx.doi.org/10.1016/j.scitotenv.2013.11.026

Bachand, PAM, SM Bachand, JA Fleck, CN Alpers, M Stephenson, L Windham-Myers. 2013. Methylmercury production in and export from agricultural wetlands in California, USA: The need to account for physical transport processes into and out of the root zone. Science of the Total Environment.

Fleck, JA, G Gill, BA Bergamaschi, TEC Kraus, BD Downing, CN Alpers. 2013. Concurrent photolytic degradation of aqueous methylmercury and dissolved organic matter. Science of the Total Environment. [on-line proof] http://dx.doi.org/10.1016/j.scitotenv.2013.03.107

Marvin-DiPasquale, M, L Windham-Myers, JL Agee, E Kakouros, L Kieu, JA Fleck, CA Stricker. 2013. Methylmercury production in sediment from agricultural and non-agricultural wetlands in the Yolo Bypass, California. Science of the Total Environment. [on-line proof] http://dx.doi.org/10.1016/j.scitotenv.2013.09.098

Windham-Myers, L, JT Ackerman, JA Fleck, M Marvin-DiPasquale, CA Stricker, P Bachand, CA Eagles-Smith, D Feliz, G Gill, M Stephenson, CN Alpers. In Press. Mercury cycling in agricultural and managed wetlands: a synthesis of observations from an integrated field study of methylmercury production, hydrologic export, and bioaccumulation. Science of the Total Environment.

Windham-Myers, L, M Marvin-DiPasquale, CA Stricker, JL Agee, L Kieu, E Kakouros. 2013. Mercury cycling in agricultural and managed wetlands, Yolo Bypass, California: Experimental evidence of vegetation-driven changes in sediment biogeochemistry and methylmercury production. Science of the Total Environment. [on-line proof] http://dx.doi.org/10.1016/j.scitotenv.2013.05.028

Windham-Myers, L, M Marvin-DiPasquale, E  Kakouros, JL Agee, LH Kieu, CA Stricker, JA Fleck, CN Alpers, JT Ackerman. 2013. Mercury cycling in agricultural and managed wetlands, Yolo Bypass, California: Seasonal influences of vegetation on mercury methylation, storage, and transport. Science of the Total Environment. [on-line proof] http://dx.doi.org/10.1016/j.scitotenv.2013.05.027