Arizona Water History

The history of AZ water is complicated and has many facets. I’m tracking historical data as best possible, but to start I’ve created a brief summary of the groundwater in Metro Phoenix and the situation with the Colorado River’s lack of volume resulting in the “War of the River”.  

Arizona Ground Water

AZ is a dry state and that helps, as such, AZ had to focus on water far earlier than other States.  Salt River Project (SRP), one of our main utility companies, has helped oversee our surface and ground water for more than 100 years.  There has always been significant unsupported “negative press” about our ability to sustain our growth.  But in fact, Arizona has been more water conscious than any other state and Metro Phoenix is located where it is because we have plenty of water. The early Hohokam Indians lived along AZ rivers up to about 1500 AD.  The drainage basin that feeds the Salt River, that flows into metro Phoenix, is huge and a good portion of this basin receives 15 to 20+ inches of rain per year.  This water has been filling the aquifers below Phoenix for eons and more recently, been the source of water for many of the upstream lakes, a prime example is the Roosevelt Dam completed in 1911.  

In 1980, AZ created the Dept. of Water Resources and adopted the 1980 Ground Water Management Act.  Even with a population increase of about 4.5 million people since 1980, our water consumption dropped from about 9 maf/yr to about 7 maf/yr.  Besides implementing conservation measures much of our domestic development has been by taking over water-thirsty agricultural land.  Housing takes about 25% of the water typically used for agriculture.  Other significant conservation examples in the Phoenix area include the Granite Reef Recharge Aquifer and multiple treatment plants for effluent water.   In 1903 the Government dedicated much of the 13,000 sg mile drainage basin that feeds the Salt and Verde Rivers as National Forest to preserve the water.  The 1980 Groundwater Mgmt. Act also required developers working in populated areas (designated as Active Management Areas or AMA’s) to have an “assured water supply” – in many cases this is a 100-year assured water supply and new irrigated agricultural land was banned.  Phoenix has 7.1 maf stored in aquifers and only uses 2.3 maf/yr.

All of the above essentially refer to groundwater, Salt-Verde and Effluent water which accounts for 71% of our water, and of that amount, only 50% is used for domestic purposes.  Metro Phoenix obtains about 29% of its water from the Colorado River via the Central Arizona Project (CAP).  This equates to metro Phoenix only using 15% of the CAP water for domestic use.   The heavy rains and snowpack this year will give us a bit more time to adjust the CO river water situation – and the thought is that with CA not going along with the other 6 States, the Feds might need to intervene.

Water Wars of the West

California stands on the Law of the River. First in Time – First in Line. That’s a long-standing principle and in 1922, an agreement (1) was entered into between all seven states that share the Colorado River to provide CA with 4.5 maf/yr. BUT, what if the agreement was made with incorrect data, no adjustment for evaporation or seepage and a disregard for suggestions that the water flow may be reduced. Add to this, AZ has been conserving water better than any other state and its water consumption is less than it uses in 1957. CA actually dumps enough water into the ocean that all of Phoenix uses annually.
With the recent 23-year drought in the Southwest creating record low water levels in Lake Mead and Lake Powell, the Feds (US Bureau of Reclamation) requested the seven states get together and come up with a plan for a 2 to 4 maf/yr reduction in water from the Colorado River. Six of the states submitted a plan and CA submitted an alternate plan (2). CA only agreed to a minimal reduction. Arizona’s CAP General Manager Ted Cooke said “If everyone continues to take what they’re currently taking from the river over the next two years, Lake Mead’s surface will sit just above the point where it can still flow over Hoover Dam”. (3).
If all states do not agree on a plan soon, the Feds may be forced to step in. For Arizona, what’s at stake is the amount of water that can be delivered via the Central Arizona Project (CAP), but the final plan will have huge impact on all seven states and Mexico. To understand the history, how things developed and where we are today, I will try to start from the beginning. To be continued.

  1. Contract of 1922 –
  2. Plans submitted by CA and 6 other states –