Deserts have been expanding in the Southwest for well over 100 years, accelerated by climate change. Pumping of groundwater more rapidly than it is replaced is drying up rivers, causing subsidence of the ground, and reducing availability of water for agriculture.

The CAP (Central Arizona Project), which brings water from the Colorado River to the Phoenix and Tucson areas, has allowed these cities to grow beyond the carrying capacity of their historical local water supplies. Now, however, the Colorado River carries a significantly reduced volume of water, and it is no longer a reliable supply. When cutbacks in CAP water occur, agriculture will be hit first and hardest. Although people have tried, nobody has identified a new, secure, certain and abundant water supply that can be developed in time to offset the coming losses.

The University of Arizona students in Charles Lowe’s ecology and evolutionary biology lab, of which I was one, realized in the 1960s that with the coming water shortage, Southern Arizona would lose its appeal as a pleasant place to live or visit. Citizens and industries, including tourism, could move to more sustainable places, and people who could not afford to move would be left behind. This awareness comes from 10,000 years of human history, during which many great civilizations collapsed and disappeared, due to inadequate planning for long-term sustainability.

For local economies, many people suggest that encouraging population and industrial growth will result in higher tax revenues that are needed to adequately support education, police, sheriff, fire and other services. Nevertheless, the last doubling of the population and industry did not accomplish this, and it may have made our problems worse. With the looming water crisis, it makes no sense to encourage increasing the population and industry.

My wife and I built our retirement home in the Tucson Mountains in 2002-2003. Realizing that the water shortages were coming, we built so as to capture all the rainwater that falls on the roof, store it in a 26,000-gallon capacity cistern, treat it, and use it for all household purposes year-round. Together with others — like the UA College of Architecture, Watershed Management Group, Pima Association of Governments Watershed Planning group, Community Food Bank of Southern Arizona, Community Water Coalition of Southern Arizona, and Tucson Water — we recognize that rainwater is a significant renewable resource. By increasing its use, we conserve groundwater, but we must not take so much that we deprive native plants and animals of their needs. They have a right to exist and also are a source of millions of dollars annually in tourism.

Solutions to future water problems could come from several approaches:

(1) Encourage increased water conservation and rainwater harvesting;

(2) Encourage significant global reduction in greenhouse gases, in part by incentivizing use of solar power in homes and businesses, and working with locally owned banks and credit unions to provide low-interest loans or grants to low-income groups;

(3) Develop local up-scaled levels of rainwater harvesting, without depriving the environment;

(4) Change the system of taxation to one that does not encourage population and industrial growth but allows for a level population size with vibrant, interesting, and affordable communities;

(5) Incentivize farms to convert to sustainable practices such as low water-use crops and drip and below-ground irrigation.

Let’s all work together and achieve a sustainable water future.

Charles Cole is a retired evolutionary biologist with a doctorate from the University of Arizona, and is Curator Emeritus, American Museum of Natural History, with 115 scientific publications. Contact him at