Local opinion: Consider safer water alternatives

The Arizona Daily Star recently published a story that the Arizona Water Infrastructure Finance Authority (WIFA) voted to take the first step of asking companies to show how they could import more than 100 billion gallons of water from outside of the state.

Various schemes are being suggested, including reverse-osmosis (RO) treatment of water from the Sea of Cortez in Mexico and “sewer to tap” recycling. I have suggestions to make on both of these schemes.

As a board-certified environmental scientist, I helped to write the new national standards for protecting water systems from terrorism (ASCE 78-24) and presently serve as a volunteer expert to the FBI on water system protection. I have considerable experience in the areas of water management and conservation and have some suggestions for WIFA.

Regarding proposed “sewer to tap” schemes, I urge caution as these will be highly dependent upon computerized controls (SCADA), and therefore vulnerable to hacking by cybercriminals and hostile nation state actors. I am much more comfortable with using highly treated sewage effluent to recharge groundwater as is done in Sahuarita, Arizona, because this provides a safety buffer to our communities since groundwater is treated before distribution in our water systems. Sending recycled sewage directly to our taps entails some measurable risk that makes me uncomfortable.

As far as Arizona’s need for water, I suggest that we seek out “low-hanging fruit” and become more efficient. According to the Central Arizona Project’s (CAP) own data, annual evaporative losses from the CAP open channel system total about 25,000 acre-feet of water, or 8 billion US gallons per year. Our open CAP water conveyance channels can be easily seen throughout Pima County, carrying irrigation water to cotton farmland and elsewhere. Agriculture represents our single largest user of water, and there are many ways that water can be conserved. We should help our farmers to buy the equipment they need for precise water management.

Evaporation from CAP canals represents a remarkable loss of water that should be addressed by CAP operators and our elected representatives. Additional evaporative losses occur from large recharge basins and other components of our water system such as Lake Pleasant, where evaporation accounts for an additional 50,000 acre-feet of water, or 16 billion US gallons per year. Leakage from concrete CAP channels, piping and other components further increases our system water losses. CAP has historically considered these losses to be “nominal,” but times have changed, and global warming, population growth and competition for Colorado River water from other states makes reexamination of past practices essential.

Finally, Arizona’s copper mines do not recycle much of their process wastewater, and stipulating mandatory recycle could save additional millions of gallons per year. On average, Arizona’s copper mines consume approximately 5 million gallons of fresh water per day, so hundreds of millions of gallons of water per year could theoretically be conserved by better practice during mining.

Only after we have evaluated all sources of water loss in our system should WIFA consider spending public money to pursue expensive schemes.