Bioeconomic modeling of floating aquatic weeds in the Sacramento–San Joaquin River Delta

Authors: JETTER, KAREN - University Of California, Davis; Madsen, John; BUBENHEIM, DAVID - National Aeronautics And Space Administration (NASA); DONG, JUNJUN - University Of California, Davis

Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2020
Publication Date: 9/30/2021
Citation: Jetter, K.M., Madsen, J.D., Bubenheim, D.I., Dong, J. 2021. Bioeconomic modeling of floating aquatic weeds in the Sacramento–San Joaquin River Delta. Journal of Aquatic Plant Management. 59s:98-106. https://apms.org/journal/.

Interpretive Summary: Using data from the economic costs of managing aquatic weeds in the Sacramento Delta, a growth model for waterhyacinth, and herbicide efficacy trials, a bioeconomic model for management of waterhyacinth in the Delta was constructed. From this model, three insights are gained on managing weeds: 1) the rate of weed growth as a huge impact of the ultimate cost of managing waterhyacinth, 2) a delay for the beginning of management in the spring (e.g., from regulatory mandates) significantly increases the cost of management. In particular, a delay from March until June will increase treatment costs by 16.4%, as well as increasing the amount of herbicides to be used, and 3) an increase in herbicide efficacy will reduce subsequent regrowth and retreatment costs.

Technical Abstract: This study develops a preliminary bioeconomic model that links an aquatic weed growth model to an economic model to evaluate the cost of alternative weed management policies in the Sacramento-San Joaquin Delta (Delta). During the past decade the costs to manage both floating and submerged invasive weeds in the Delta was estimated to be at least $60 million between 2013 and 2017. The bulk of the costs are incurred by the California Division of Boating and Waterways (CDBW), whose areawide weed management program is a public good that influences the costs of aquatic weed management for all other public and private agencies on the Delta. One of the main aquatic weeds managed by CDBW is water hyacinth. Normally, weed control activities can begin in March in areas in the southeast portion of the Delta, and in June elsewhere. This study examines the relative costs incurred by CDBW of starting all weed control in March under three different weed growth model assumption, and two herbicide efficacy assumptions. Costs fall by 16.4% under the slowest growth rate model and by 73% under the fastest growth rate model. Environmental concerns over the protection of native fish spawning areas may prevent the earlier adoption of herbicide control; however, the results show that investments in control methods that are both fish friendly and effective at controlling weed populations may reap substantial weed management cost savings.