In Arizona, water officials are concerned, though not panicking, about getting water in the future from the Colorado River as its levels decline and the federal government talks about the need for states in the Colorado River Basin to reduce use. Tucson, Goodyear and Scottsdale are the most dependent of Arizona cities on river water delivered through the Central Arizona Project, a $4 billion, 336-mile-long canal system running from the river to the Phoenix and Tucson areas. While all these cities have backup supplies, led by groundwater, to cushion them in the short- to medium-term in the event of river water cuts, their long-term picture is more uncertain.