Reclamation Information Sharing Environment (RISE)

Among irrigation canals of the U.S.’s semi-arid west, dense growths of aquatic macrophytes are a persistent issue – slowing water delivery and decreasing canal capacity. The aim of this project was to design and test the efficacy of a novel ultraviolet (UV) tool for controlling nuisance aquatic plants and determine the environmental constraints on macrophyte density and composition are driven by macrophyte abundance in irrigation canals in Fallon, Nevada. Inventive Resources, Inc. provided a UV-C Treatment device that was designed to provide a lethal dose of ultraviolet light in the range of 254 nm, killing and controlling the invasive aquatic plants in the unlined canal by damaging the aquatic plant cell structure and DNA that prevents it from replicating. The UV treated plants should collapse within a few days and begin the decomposition process in a few weeks depending on water temperature and other environmental factors. The testing of the tool was hampered by drought and the dewatering of the canal in the first year and the rapid decline of plants in the reference and treatment reaches of the canals in the second and final year of treatment perhaps due to large disturbances from wildfire smoke emissions in the region or other conditions. We found that total suspended solids were the primary driver of macrophyte density, suggesting that light availability within the water column drives macrophyte growth.