Last week in Part 1 of this series I wrote about what happened to Tucson's waterways and the subsequent mining of groundwater.

In Part 2 I'll talk about the Central Arizona Project, our water resource status today, and critical issues for the future.

I wrapped up last week's column with the observation that by 1970 Tucson's population had grown to more than 260,000 and that unless we wanted to mine underground water down to the last drop, something else had to be done.

Central Arizona Project

That "something else" was truly amazing! In 1938 Parker Dam was completed as one of a series of dams to help control and regulate the once unruly Colorado River.

Parker Dam's primary purpose was to provide reservoir storage for water to be diverted to California, Arizona, Nevada, Utah, Colorado, Wyoming, New Mexico and Mexico.

For four decades lawmakers argued about how to allocate Colorado River water among its claimants, how to manage this critical resource, and the priorities for use of the water in the various states.

Arizona got its act together in the late 1960s and early '70s with, as the Arizona Republic reported, "probably the state's most celebrated bipartisan achievement of the 20th century," which led to the approval of the Central Arizona Project (CAP) to divert water from the Colorado River from Lake Havasu City into Central and Southern Arizona.

Construction of the project, the largest and most expensive aqueduct system ever built in the United States, began in 1973.

Over 20 years workers built a 336-mile diversion canal from the Colorado River to just southwest of Tucson. In 1992 officials "turned on the faucet" to start providing Tucson with water to supplement our limited groundwater.

In 2001, after resolving some CAP water-quality problems, Tucson began blending CAP water and underground water before delivering it to users.

Today and the future

Today, with the population of Tucson exceeding a half-million and growing steadily, we are operating under the Tucson Water Department's Long Range Water Plan 2000-2050.

We have stopped pumping most of the wells where the water table has dropped significantly and where the loss of riparian areas and sinking of the land has been most damaging.

As a result, the water table has begun to rise slightly in some areas. The goal is to "limit our pumping to no more than the rate of natural replenishment (so) we can still use this resource without causing environmental damage."

In an effort to conserve water, Tucson is recharging groundwater supplies by running some of the CAP water into local rivers to seep into the aquifer.

Tucson is also using increasing amounts of reclaimed water (treated wastewater) for irrigation, dust control and industrial uses.

As we look ahead to meeting water demands, we are naturally concerned about possible significant effects of climate change and prolonged draughts.

In a July 29 front-page story in the Arizona Daily Star, reporter Tony Davis writes about how Southern Arizona streams are drying up. Riparian and recreation areas are suffering. Even the mighty Colorado River, the source of our CAP water, is reporting near-record lows this summer.

So Tucson faces real water challenges. Can we conserve enough to make a difference? Could we transport groundwater from less populated areas into Tucson? Could we cover the CAP canal to prevent water losses from evaporation - perhaps with solar panels, as some have suggested? Are artificial snowmaking and cloud seeding applicable to increase fresh water runoff to the Colorado River? Could we desalinate deep-aquifer brackish groundwater or ocean water?

The answers to these questions may determine the future of Tucson.

On StarNet: Read Bob Ring's recent columns at

Sources: "Arizona's Changing Rivers: How People Have Changed the Rivers" (Tellman, et. al., 1997); "Cienega Creek, other S. AZ. streams, increasingly dry" (Arizona Daily Star, Tony Davis, July 29, 2012); "Seeking Freshwater for Tucson" (Desert Leaf, Craig S. Baker, July/August 2012); Water for Tucson's Future: Long Range Water Plan 2000-2005; "Water Supply and Demand in Tucson" (Tucson Citizen, Johnathan DuHamel, June 21, 2009); "What's happened to GOP since Goldwater" (Arizona Republic, Dan Nowicki, Jan. 1, 2009) E-mail Bob Ring at