Virgin

VIRGIN RIVER PROJECT

The Virgin River flows from its headwaters in the Colorado Plateau of SW Utah through the Eastern Mojave Desert of NW Arizona and SE Nevada where it joins the Colorado River underneath Lake Mead. This perennial river is mostly unregulated, so periodic natural flooding is important in maintaining habitat for native riparian vegetation including cottonwood-willow stands and mesquites on drier terraces. Serving agricultural, domestic and recreational needs for St. George UT, Las Vegas and other surrounding communities, this ecosystem also provides habitat to many endangered aquatic and riparian species, such as Virgin spinedace and Woundfin, and the SW willow flycatcher. The floodplain is severely infested by invasive tamarisk (Tamarix spp.), which competes with native plants, transpires substantial water resources, and promotes wildfires.

In collaboration with the USGS, we are evaluating effectiveness of methods for controlling tamarisk, and for promoting recovery of riparian plants and associated wildlife. The recent introduction of the Saltcedar Leaf Beetle, Diorhabda elongata, for suppressing tamarisk in the Virgin River provides the opportunity to conduct intensive evaluation of the beetle's dispersal and establishment process, the responses of target weeds and associated native vegetation, and how wildlife will respond to system recovery. Many collaborators are involved in research on bird nesting and feeding behavior, insect community interactions, plant transpiration, fire modelling and other elements, and we anticipate a 10-year program to characterize and direct the riparian restoration process in this, and other watersheds of the Colorado Basin where tamarisk biocontrol is being implemented.

Tom Dudley collects the Diorhabda elongata, a tiny beetle that feeds on the invasive tamarisk tree on the riverbank in Virgin Gorge, Arizona. The plant is sucking prodigious amounts of precious water out of streams across Nevada and the West and the tiny beetle was released into strategic areas with hope that it will ultimately kill the invasive tamarisk tree.