A source-water assessment is a study that defines the land area contributing water to each public water system, identifies the major potential sources of contamination that could affect the drinking water supply, and then determines how susceptible the public water supply is to this potential contamination. Public utilities and citizens can then use the publicly available study results to take actions to reduce potential sources of contamination and protect drinking water. As required by the Safe Drinking Water Act, the State of Colorado has completed source-water assessments for virtually every public water system.