Even in regions where desalinization has the potential to add water and strict management practices are underway, water is such a vital commodity that water rights of communities, cities and even states are often contested in court. Such legal battles sometimes stem from old agreements about the distribution of rivers and groundwater between municipalities that were drawn up before substantial growth occurred. With population growth requiring water for drinking, domestic use, agriculture and industry, the value of water has increased substantially and old agreements are often extremely prohibitive to growth. Some of the most bitter water disputes occur in the western US, where, as we have seen, southern California relies heavily on water derived via aqueducts from the Colorado River to the east and the Owens Valley in the Sierra Nevada Mountains to the north.
The City of Los Angeles has had brutal showdowns with farmers and environmentalists in the Owens Valley from where it derives about half of its water. The city built the first of two aqueducts from the valley between 1908 and 1913 and the second in 1970. These aqueducts substantially lowered water levels in Mono and Owens Lake and the Owens River and took a terrible toll on farming in the Owens Valley. The impact was so negative that farmers used dynamite to breach the aqueduct and temporarily return the flow to the Owens River. After the second aqueduct was built, a series of litigation began between municipalities in the Owens Valley and ultimately the Sierra Club. The net result has been rulings in favor of the Owens Valley, and some increases in water levels in bodies such as Mono Lake, but ultimately southern California continues to withdraw water at a faster rate than it is being replenished, so the conflict is by no means over.
To the east of Los Angeles, water rights for the Colorado River were defined by the Colorado River Compact of 1922, which divided states bordering the river into upper basin states (in the mountains) and lower basin states (in the plains). The compact also appropriated the annual amount of water each group of states could withdraw from the river. The compact was modified when the Hoover Dam was constructed, at which time the lower basin states (Arizona, California, Nevada) were allocated annual withdrawal amounts. These amounts have led to fierce litigation between Arizona and California, which changed the appropriations in Arizona’s favor. For a long time, only California has completely utilized its quota each year and its surplus was guaranteed by the Secretary of the Interior until 2016. By that time, surging development in Arizona and southern Nevada will require diversion of their quotas from the Colorado and the surplus will no longer be available to California. At some stage, also, upper basin states Colorado and New Mexico may challenge the 1922 Compact to obtain increased quotas of water to fuel growth in these states. At the same time, environmental considerations were not a factor of the original compact. For example, the allocations were not based on estimates of the impact of long-term withdrawal on hydrology and ecosystems. These factors will also likely become significant issues in the future.