Invasive aquatic vegetation management in the Sacramento-San Joaquin River Delta: status recommendations

Authors: TA, JENNY - University Of California; ANDERSON, LARS - Retired ARS Employee; CHRISTMAN, MAGGIE - Delta Stewardship Council (A CALIFORNIA STATE AGENCY); KHANNA, SHRUTI - Department Of Fish And Wildlife; KRATVILLE, DAVID - California Department Of Food And Agriculture; Madsen, John; Moran, Patrick; VIERS, JOSHUA - Dominican University Of California

Submitted to: San Francisco Estuary and Watershed Science
Publication Type: Literature Review
Publication Acceptance Date: 10/16/2017
Publication Date: 12/1/2017
Citation: Ta, J., Anderson, L.W., Christman, M.A., Khanna, S., Kratville, D., Madsen, J.D., Moran, P.J., Viers, J.H. 2017. Invasive aquatic vegetation management in the Sacramento-San Joaquin River Delta: status recommendations. San Francisco Estuary and Watershed Science. 15(4) Retrieved from https://escholarship.org/uc/item/828355w6. doi: 10.15447/sfews.2017v15iss4art5.
DOI: https://doi.org/10.15447/sfews.2017v15iss4art5

Interpretive Summary: Non-native aquatic weeds float on the water and root in the mud in the Sacrament-San Joaquin Delta, also known as the Californa Delta, located between the San Francisco Bay Area, Sacramento and Stockton in northern California. The Sacramento and San Joaquin Rivers flow into the Delta, providing drinking water for millions of people all the way to Los Angeles, and irrigation water for 4 million acres of farmland producing $25 billion in annual crop value in the Central Valley of California. Aquatic weeds block water flow to the pumps that move water to canals to take it to farms and cities. They also reduce opportunities for recreatonal boating, a major industry in the Delta worth several hundred millions of dollars per year, and even commercial navigation by big freighters that use the Stockton and Sacramento Deepwater Ship Channels. In September 2015,scientists and agencies involved in controlling aquatic weeds in the Delta and managing its water resources gathered to discuss new technologies and collaborations to improve aquatic weed control and to better understand how these weeds interact with Delta ecosystems. The most serious aquatic weed invaders are floating water hyacinth and water yellow-primrose, also known as Ludwigia, with other species such as South American spongeplant. There are also submerged weeds that root in the mud and grow almost entirely underwater, such as Brazilian waterweed, also known as egeria, and curly-leaf pondweed. Other submerged weeds such as hydrilla are not in the Delta currently but pose a major threat. This paper summarizes the verbal presentations made by scientific experts to better understand these aquatic weeds and improve control. The paper shows that control of aquatic weeds with chemical herbicides, removal with backhoes, special boats and conveyor belts, and biological control using insects that eat the weeds, can all be used as part of an integrated weed mangement program to maximize control benefits. The paper goes over the pros and cons of each of these methods. The paper concludes with a series of recommendations for further research and continued improved communication among the Federal, state, regional and local agencies with responsibility for managing aquatic weeds and water resources in the Delta.

Technical Abstract: Widespread growth of invasive aquatic vegetation is a major stressor to the Sacramento-San Joaquin River Delta, a region of significant agricultural, industrial, and ecological importance. Total invaded area in the Delta is increasing, with the risk of new invasions a continual threat. However, invasive aquatic vegetation in the Delta remains an elusive ecosystem management challenge despite decades of directed scientific research and prioritized policy recognition. In this paper, we summarize the current state of knowledge of the history, status, and potential future directions for coordinated research, management actions, and policy to minimize impact to native aquatic species of concern throughout the Delta and its environs. Using cross-cutting evidence from disciplines spanning physical, biological, and social sciences, we present the case for improved coordination between scientists and managers within the existing regulatory and policy framework to improve overall effectiveness of invasive aquatic weed control in the Sacramento-San Joaquin Delta and elsewhere. Remote sensing technology, mechanical, chemical, and biological control, as well as community science networks have all been shown to be effective management tools, but overall effectiveness has been hindered by complex regulatory structure, the lack of a consistent monitoring program, regulations that restrict treatments in space and time, and funding cuts. In addition, new management options depend on continued research and development of new active ingredients for chemical control and testing of biological control agents. The ongoing development and implementation of new strategies for adaptive, integrated management of aquatic weeds, using currently-available management tools, new knowledge derived from remote sensing and plant growth models, and an area-wide, ecosystem-based approach, is showing promise to achieve improved management outcomes and enhance protection of the Delta’s water resources.