Invasive species of milfoil can potentially cause problems in drinking water reservoirs. Potential issues include increased disinfection by-product precursors, alteration of oxygen or pH, clogging of intakes, creation of excessive suspended solids upon decay of plants, encouragement of benthic or attached algae responsible for taste and odor, and shifts in biological structure that favor higher algal biomass in the reservoir.


The overall objective of this project was to improve the understanding of drinking water managers with regard to detecting, mitigating, and controlling the potential impacts of invasive water milfoil in their reservoirs. Specific objectives included a review of the features and impacts of different species of milfoil, assessment of control methods in drinking water reservoirs, evaluation of the extent of the problem, and development of case histories for selected water supplies. A literature review was employed to gather information about milfoil types, ecology, and distribution. Literature surveys and staff experience were used to generate information on control strategies and applicability in drinking water situations. A questionnaire survey was applied to gather information on utility awareness and experience with milfoil. Additional investigations of state databases and discussions with knowledgeable parties were used to expand the results of the questionnaire survey. Case histories were used to assess the range of impacts and responses.