Management of Quagga and Zebra Mussels for Preventing Blockage of Water in Delivery Systems and Protecting Infrastructure
This study is addressing integrated, cost-effective methods for managing and controlling highly invasive quagga and zebra mussels in Reclamation water systems. Research questions include:
* What are the best integrated management options for controlling mussels that block, damage, and corrode these water delivery and irrigation systems?
* How can we protect sensitive, high-value structures such as dams and pumping plants from being colonized?
* How can we maintain the designed water delivery capability when canal linings are being infested with mussels?
* How do we remove quagga/zebra mussels for structures once they have been colonized?
Need and Benefit
Quagga mussels (_Dreissena bugensis_), an exotic noxious mussel, have been recently introduced into the lower Colorado River, presumably originating from contaminated boats in Lake Mead. Related to the zebra mussel (_Dreissena polymorpha_), the quagga is a macrofouler of equal tenacity. It quickly colonizes new areas and rapidly achieves high densities (tens of thousands per square meter). Unlike native mussels that burrow in sand and gravel, these mussels spend their adult lives attached to hard substratum. They can also attach to man-made surfaces made of plastic, concrete, wood, fiberglass, iron, and surfaces covered with conventional paints.
Quaggas (and zebras) have very high reproductive rates. A female is capable of releasing as many as 40, 000 eggs in a season. It is possible for newly spawned individuals to reach sexual maturity and spawn in the same year. Sexual maturity usually occurs when the female reaches about 10-millimeter shell length (usually in its first 12 to 18 months). Veligers (free-swimming larvae) are waterborne for their first two to three weeks when they travel aided by currents to a new site for settlement. In riverine or flowing systems, the distance traveled may be many miles.
Reclamation has thousands of miles of canals and water systems at considerable risk to biofouling damage by quagga and zebra mussels. To date there may be as many as four regions affected. It is anticipated that the mussel veligers can very quickly spread downstream in western water conveyances and colonize them throughout. Their impacts will likely fall into one of three categories:
* Flow restriction in canals or roughening ranging to complete blockage of small diameter (<1-foot diameter.) pipes
* Ecological damage through competition with other aquatic organisms.
Consequently, these mussels seriously threaten basin-wide operations. Quagga mussels have invaded the Colorado River and threaten dams and irrigation facilities throughout that drainage. Control of these mussels will directly support all aspects of Reclamation's mission of enhancing western water supplies, increasing reliability, and saving money.
There are a number of factors which have singly and in combination aggravated the quagga mussel invasion. Until the recent breakout, the known _Dreissena spp._ infestations were essentially confined to east of the 100th meridian. Western irrigation and other man-made water conveyance systems have to this point been unaffected, so there is very limited experience and a lack of knowledge by field operators on how to contend with attached biofouling mussels. Western water systems were designed to disperse water, which serves to spread the problem by transporting veligers (free-swimming larvae) downstream and at times, to other watersheds by interbasin transfer. Additionally, Western United States water systems were designed in the absence of the very concept of such biofoulers. As a result, there is a lack of redundant structural features and operational practices which would lessen quagga mussel impacts.
Technology is needed to remove the threat these organisms impose on our water facility operations and structures. Great advances have been made in the Eastern United States during the past 20 years of _Dreissena spp._ management. These tools need to be evaluated in a western context. However, as it was already mentioned, western water systems have different designs, water chemistry, and operational criteria. Existing management tools may need to be modified or new ones may need to be developed to help us cope with this new problem.
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