An overview of the Delta Region Areawide Aquatic Weed Project for improved control of invasive aquatic weeds in the Sacramento-San Joaquin Delta

Authors: Moran, Patrick; Madsen, John; Pratt, Paul; BUBENHEIM, DAVID - National Aeronautics And Space Administration (NASA); HARD, EDWARD - California Department Of Boating And Waterways; JABUSCH, THOMAS - Sacramento-San Joaquin Delta Conservancy; CARRUTHERS, RAYMOND - Retired ARS Employee

Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2020
Publication Date: 8/31/2021
Citation: Moran, P.J., Madsen, J.D., Pratt, P.D., Bubenheim, D.L., Hard, E., Jabusch, T., Carruthers, R.I. 2021. An overview of the Delta Region Areawide Aquatic Weed Project for improved control of invasive aquatic weeds in the Sacramento-San Joaquin Delta. Journal of Aquatic Plant Management. 59s:2-15. https://apms.org/journal/.

Interpretive Summary: The 27,540-ha (68,000-acre) Sacramento-San Joaquin River Delta of northern California consists of the freshwater floodplain where these two large rivers meet. The original marshlands and tidal channels have been drained and modified into a complex system of canals, sloughs, small lakes, farmland, small towns and cities, and remnant wetlands. The Delta drains into the brackish waters of Suisun Bay, which in turn drains to saltwater in San Francisco Bay. The freshwater Delta provides irrigation water for over $30 billion in crops in the Delta and Central Valley, provides drinking water for 27 million people, supports $300 million in recreational boating, and contains two major deepwater shipping channels. Non-native aquatic plants have invaded the Delta, blocking access to the water for boating and fishing and reducing business for marinas and supporting industries. These weeds also block water flow to pumping facilities, impede flood control systems, create human health hazards, and displace native plants and animals. Water hyacinth, occupying over 2,000 acres of water surface each year, is one of four major floating aquatic weeds in the Delta. Brazilian waterweed or egeria, occupying over 7,000 acres, is one of five major submersed aquatic weeds. Other weeds grow close to the water, such as arundo or giant reed, which forms dense thickets along canal banks and river levees. Control of aquatic weeds in the Delta is conducted mainly by one agency, the Division of Boating and Waterways, California Department of Parks and Recreation (DBW). This agency needed new information and tools to improve aquatic weed control. The USDA-ARS Areawide Pest Management Program provides support for USDA to work with state and local agencies, university researchers and agricultural producers to improve control of major invasive pests through the development and implementation of adaptive integrated pest management (IPM) strategies, achieved through improved collaboration among agencies. The USDA-ARS provided five years (2014-2018) of support for the Delta Region Areawide Aquatic Weed Project or DRAAWP. The objectives of the project were to develop models of how aquatic weeds grow and spread each year in response to water nutrient and temperature factors; to use satellite images to detect aquatic weeds and track control; to test and use control methods that were new to the Delta, including newly-permitted herbicides and biological control agents; and to keep stakeholders and the public informed of project success through online and in-person outreach and by tracking weed control costs through an annual cost survey. The DRAAWP effort led by USDA-ARS has reduced peak annual floating aquatic weed acreage by over 30%, and has reduced weed control costs for agencies other than DBW by 33%-100%. Technology developed for control of water hyacinth and Brazilian waterweed is now being applied to improve control of four total floating and five total submersed aquatic weed species. New knowledge generated by the DRAAWP, combined with expertise leveraged through collaborations, has led to additional projects funded by the State of California, at 10-fold the original USDA-ARS investment, to control aquatic weeds to protect habitat for threatened and endangered fish species.

Technical Abstract: The 68,000-acre Sacramento-San Joaquin River Delta of northern California is the largest freshwater estuary on the U.S West Coast. The Delta provides irrigation water for over $30 billion in crops in the Delta and Central Valley, provides drinking water for 27 million people, supports $300 million in recreational boating, and contains two major deepwater shipping channels. The Delta’s sloughs, wetlands and riparian habitats host 56 listed species. Invasions by non-native aquatic weeds constitute a major environmental challenge. The USDA-ARS Areawide Pest Management Program focuses on integrated, adaptive control of invasive pests, by supporting implementation of new, science-based control solutions. The USDA-ARS Delta Region Areawide Aquatic Weed Project (DRAAWP) was funded from 2014 to 2019 to improve control of floating water hyacinth (Eichhornia crassipes), submersed Brazilian waterweed (Egeria densa), and riparian arundo (Arundo donax). Outputs from the DRAAWP are now informing control of nine aquatic weeds and arundo using integrated chemical, mechanical, and in some cases biological methods. The DRAAWP addresses critical Delta issues, including water resource use and protection, conservation of native species and habitats, and protection of economic activities. The development of decision support tools has led to improved knowledge of aquatic weed growth and dispersal in the Delta, models of watershed nutrients and flow, control prioritization protocols based on remote sensing and economic cost modeling, implementation of the use of new herbicides, release of biological control agents, and improved efficacy tracking. Project benefits include reduced weed coverage and lower control costs for stakeholders.