Over 270 million Americans receive drinking water from approximately 161,000 public water supplies. Americans enjoy some of the world's safest drinking water. Nonetheless, drinking water safety cannot be taken for granted. For instance, drinking water that is not adequately treated or that travels through an inadequate distribution system can endanger the health of a community. However, in many cases, public health protection starts at the drinking water source. A community is likely to be at higher risk if it relies on a source that is contaminated. Preventing contamination of drinking water sources depends on the awareness, participation and actions of Federal agencies, state agencies, local governments, interest groups, individual citizens and the business community. Indeed, source water protection is based on the premise that no single entity can effectively be the driver of drinking water source protection efforts in every case. We all need to work together. Source water includes all current sources of drinking water from ground waters and surface waters. However, as the results of source water assessments are used to launch source water protection programs, such programs should not be deterred from comprehensive efforts to protect surface and ground waters that are not now used for drinking water. Source water protection should be a standard part of providing safe drinking water to the public. If not eliminated, risks to source waters should be reduced to minimize risks to public health. Building consensus to do this requires a long and sustained effort. Source water protection means different things in different situations. This is appropriate because the threats to drinking water sources and the means to address those threats are site specific and most effectively implemented at the local level, with assistance from other government and private stakeholders. The Safe Drinking Water Act (SDWA), amended in 1996, promotes a multiple-barrier approach to safeguarding the nation's water supply. This multiple-barrier approach goes beyond the traditional emphasis on treatment to address new challenges and reflects a better understanding of the need for a coordinated source water protection effort. The purpose of this guidance is to promote coordinated efforts that should drive state and Federal actions to assist localities, implement protection actions where a state or Federal program has a specific responsibility, establish tangible measures of state and local source water assessment results and protection actions and institutionalize practical information sharing systems so states and Federal agencies can communicate results and the status of the program. By doing so, EPA and its many partners can more effectively and efficiently maintain and improve the quality of America's drinking water.