75%. In addition there are 21 1400 non-profit non-community water systems, according to the US Environmental Protection Agency (USEPA). The privately owned water systems are in the main small, user-owned or local investor-owned rather than publicly traded corporations; they supply only some 13% of households. In contrast, public water systems serve 86% of households across America. Private companies are subject to rate-of-return regulation by state public utility commissions, which also oversee the publicly owned utilities. The estimated water use in 2000 was 1 544 million m³ per day; use has varied by less than 3% since 1985 as withdrawals for irrigation and power generation have stabilised (Hutson et al., 2005) down from a peak in 1980. Irrigation remains the largest consumptive user; since 1950 it has accounted for 65% of total water withdrawals. Over this period proportionally more water has been withdrawn from aquifers, increasing to 42% of the total in 2000. Irrigated areas more than doubled between 1950 and 1980, remaining stable until 1995; since that year there has been a 7% increase in response to drought conditions, standing now at some 61.9 million acres (Hutson et al., 2005). However, irrigation application efficiency has increased. In 2000, 85% of the population obtained their supplies from public suppliers, up from 62% in 1950, with a corresponding drop in self-supplied domestic usage. Public water supply withdrawals account for some 11% of the total. By contrast, industrial water withdrawals have been decreasing since 1985 (24%), reflecting the changing pattern of industrial activity and the impact of pollution control legislation. California, Texas and Florida accounted for a quarter of all withdrawals, reflecting their usage for irrigation and power generation. It has been estimated that there are some 1 440 000 km of water mains in the United States; on average there are 238 000 water main breaks each year; and, on average, water systems lose between 20 and 30% of supply, and in the INFRASTRUCT