Eurasian Watermilfoil

Click here for a slide show developed by UC Davis Researcher and USDA employee Erin Donley: Macrophytes and Aquatic Food Webs of the Fall River 

Background and Problem

The Fall River originates from California’s largest network of cold-water springs.  In total, the entire system generates approximately 890 million gallons per day—over one million acre feet annually—of cold, clean water.   For perspective, that’s almost as much water as the entire County of Los Angeles uses per year!  The value of this water to our community—and the environment—is almost immeasurable.  We use the water for agriculture, hydropower, municipal drinking supply, and outdoor recreation. Moreover,  large wild trout thrive in this nutrient rich, spring water.

But over the last 10 years an unwelcome visitor has gradually established roots in the Fall River: Eurasian watermilfoil (EWM), Myriophyllum spicatum L.

EWM threatens our ability to fully capitalize on our most valuable resource: cold, clean, plentiful water.  EWM impedes natural flows, destroys levees, floods crops, degrades wild trout populations, and destroys the natural order of the Fall River ecosystem.  Additionally, PG&E spends tens of thousands of dollars annually trying to keep the problem under control using a mechanical harvester that may actually exacerbate the problem.

Eurasian Watermilfoil (EWM)

Eurasian watermilfoil (EWM) is an invasive, submerged aquatic plant found throughout most of North America.  Over the last 50 years, it’s become one of the most noxious aquatic weeds in the western United States. First identified in the Fall River in 1999, EWM now infests large portions of the lower river.  Although its origins remain unknown, EWM spreads rapidly when plant fragments get redistributed throughout the river by boat props, mechanical harvesting, and other natural methods.  EWM grows extremely fast, forming thick mats in the river that impede flows, disrupt natural foodweb cycles, and out-competes the native aquatic plants that bugs and fish rely on for survival.

Eurasian Watermilfoil (EWM)
2003 Levee Breach

Additional information on Eurasian watermilfoil can be found at the following links:

http://www.cal-ipc.org/ip/management/plant_profiles/Myriophyllum_spicatum.php

http://fallriverconservancy.org/research/