After the September 11, 2001, series of coordinated terrorist attacks against the United States, the utmost national mission is ensuring the effectiveness of safeguard measures protecting critical national infrastructure. Security of water reserves is a matter of the highest priority for governing agencies, environmental stakeholders, and the general populace worldwide. Consequently, Executive Order (EO) 13010 designated water infrastructure as one of the eight critical national infrastructures. After the terrorist attacks, the USA PATRIOT Act of 2001 (P.L. 107–56), Homeland Security Act of 2002 (P.L. 107–296, Section 2.4), and Homeland Security Presidential Directive 7 (HSPD-7) designated water infrastructure as one of 18 separate infrastructures vital to the security of the United States. Destruction of groundwater resources and the urban water supply system—through using deadly chemical threats that are difficult to remove, blasting water supply treatment facilities, blasting reservoirs/dams, and exploding petrochemical facilities adjacent to water resources—would likely create mass casualties, cause catastrophic health effects, create chaos in regional or national security, cause irreversible damage to the water system, disrupt the downstream industry infrastructure, and cause economic destruction comparable to that from the use of a weapon of mass destruction (WMD). Based on review of the literature, there is inadequate protection against acts of terrorism on water infrastructure and scarce technology for ensuring safety and security. Such protective measures are urgently needed so that homeland security professionals, managers, engineers, scientists, and experts can incorporate risk assessment in policy making that provides tools for water infrastructure protection, while providing a flexible vehicle for incorporating public input.