The concern is that during periods of high precipitation or snowmelt, when normally dry rivers are flowing, the CAP canal might provide a water link allowing non-native fish to reach the headwaters of streams, invading the habitat of native species. Eliminating such hazards can require building expensive fish barriers or other obstacles to non-native fish, resulting in water project delays and additional costs. The 19 largest municipal water providers within the Tucson area are listed in Figure 7-3. Tucson Water, the largest, serves about 80 percent of the total population. About 12 percent of the population is served by private domestic wells and a large number of very small companies.
Different regulations regarding water rates apply to different types of water providers.
Elected officials and the mandate of the electorate control municipal water companies. This can lead to disenfranchisement when the boundaries of the water company and the municipality are different. Also voters within the Tucson city limits who receive water from utilities such as Flowing Wells Irrigation District have the right to vote on Tucson Water issues. Both of these situations prevail in Tucson. Tucson Water's service area extends far beyond city limits, and private water providers operate within city limits.