sing from natural phenomena. A few very large plants located in urban areas in the United States supply some 75% of the population, and any attack on these could have major implications. Locally the smaller plants are more vulnerable as security measures are lower, but any consequences of attacks on these would be less widespread. Water infrastructure interdependence on other services, such as ICT, also makes it vulnerable, although there is considerable knowledge following the preparations for Y2K that should help mitigate problems. Nevertheless it is more likely that widespread disruption would be effected more easily via cyber attack, disrupting power, communication and control systems. The effects can be demonstrated by the power failure in northeast United States in August 2003, in which a number of wastewater treatment plants failed. That led to environmental pollution and households being advised to boil water due to failure of water treatment plants (Copeland and Cody, 2005). New technologies are emerging for better collection, analysis and use of information related to infrastructure and asset performance, and as this becomes more sophisticated it may also become more vulnerable to security threats. Instrumentation for water service systems has not been as reliable or effective as in many other areas, and terrorist threats could well encourage more investment in the development of effective instrumentation for water infrastructure monitoring and control. The development of novel technologies that are less vulnerable also may well be forthcoming. Other potential consequences arise from threats to maintaining adequate functioning of water infrastructure, due to the inability to finance the services provided, unavailability of the necessary expertise, goods and services, and the inability to provide service to meet the legitimate needs of citizens. Threats to functioning could arise from social unrest and inequality, as exemplified during the apartheid era in South African townships; from environmental fact