The History of the Central Arizona Project

When you live in the desert, the scarcity of water is always top of mind. The temperatures in Arizona, especially during the summer months, require the consumption of water to stay alive. However, many people do not know or take the time to appreciate where this water comes from. Today, we are taking a deep dive into Arizona’s water history to see where the majority of our water really comes from. 

The year 2020 marks the 52nd year since President Lyndon B. Johnson’s signing of the Colorado River Basin Project Act. At the time, the people of Arizona did not know that the signing of this act would change the way water would be brought into their homes and consumed for the next 52 years. 

In the early 1900s, the Colorado River Compact was signed. This piece of legislation divided up the Colorado River into two parts: the Upper and Lower Basins. Arizona was placed in the Lower Basin group with California and Nevada. The Lower Basin was allotted 7.5 million acre feet of water to split amongst themselves, and has been awarded this amount of water since the compact took effect. Arizona alone receives 2.8 million acre feet out of that original 7.5 million. However, up until 1968, it was unclear how this 2.8 million acre feet of water was being used throughout the state. 

So, in 1968, President Johnson signed the act that authorized the construction of the system that provides 80% of Arizonans with water to this day: the Central Arizona Project (CAP). The construction of CAP officially ended in 1993, producing a 336 mile canal system from Lake Havasu to Tucson. The water within the system is used statewide for agriculture and recreational purposes, and has made CAP the largest supplier of renewable water in the state of Arizona since its completion. 


Without water from the Colorado River, and without CAP to funnel this water to the population, Arizona would be a completely different state; quite possibly a state without any usable water for its population and economy to flourish.