Before deciding on a mitigation strategy, it is important to evaluate, in depth, both the environment from which the raw water comes, as well as the asset to be protected. When dealing with a newly introduced species, it is possible that the environment may support the invader for a short period of time after which the population, if not eliminated, will stabilize to a very low level. This has been the case with the introduction of Corbicula fl uminea to the lower Colorado River. Following an explosive growth phase after introduction over 40 years ago, the population now remains at a very low level. The Corbicula present are small by North American standards (mostly around 1 cm in the Colorado River) and are not considered to be a problem in terms of macrofouling (McMahon, 1981, 1983; Strayer, 1999).