PHOENIX – When rain hits the roof of Greg Peterson’s home, almost half flows directly into a giant cistern to be used to water his garden and most of the rest goes into an underground pipe carrying it to his fruit trees. What remains pours onto trees placed strategically beneath the eaves.
Peterson uses these rainwater harvesting systems in order to live and promote an environmentally conscious lifestyle. But a lower water bill is a nice benefit.
“I’m fully in support of rainwater harvesting,” Peterson said. “It’s the best way for individuals to water their yards.”
The process of collecting rainwater is nothing new; people have done it for generations. But if one lawmaker has his way, harvested rainwater may eventually be recognized and regulated as an official water source.
Sen. Steve Pierce, R-Prescott, authored a bill calling for a committee to study the impact of large-scale rainwater harvesting on current water sources, including the aquifers and surface water, as well as the environment.
SB 1522 involves what it calls macro-rainwater harvesting, which rather than collecting water from the roofs of homes would involve large projects to collect rainfall.
Pierce and supporters of the bill hope that the study would prove that macro-rainwater harvesting would help overcome annual water deficits that parts of Arizona experience.
Yavapai County Supervisor Carol Springer, who helped generate the legislation, said macro-rainwater harvesting has immense potential for the future of Arizona.
“The rainwater is a resource that is being wasted and it’s a renewable resource,” Springer said. “There are many places in the state where this problem exists – mainly rural – that don’t have access to surface water rights.”
Pierce’s original bill, which won Senate approval, would have required the Arizona Department of Water Resources to create rules and regulations for large-scale rainwater collection. The bill would provide a credit allowing those who use harvested rainwater to recharge aquifers to pump out half of what they put in.
The bill was amended in the House to call for a study by a committee consisting of both House and Senate members and other stakeholders to more fully understand the impact of large-scale rainwater harvesting on aquifers as well as surface water supplies. If the measure clears the House, the Senate would have to concur with the change or resolve the differences in a conference committee.
Sandra Fabritz-Whitney, acting director of Arizona Department of Water Resources, said that the study would be a fair and necessary first step in the process.
“We are not opposed to the idea, but we need to understand the impact and if it has possible detrimental impact on water users,” Fabritz-Whitney said. “The study is a compromise, and we’re fine with that.”
It’s no coincidence that the main architects of the bill are from Prescott, where the long-term health of the aquifer is a concern. The Arizona Department of Water Resources would like to see the Prescott Active Management Area remove no more groundwater than is recharged by 2025.
Doug McMillan, a senior project manager at Civiltec, a Prescott engineering firm, said the ADWR goal could easily be met by capturing a mere 3 percent of the rain that falls each year. Based on his research, 98 percent of rainwater is lost to evaporation and transpiration, leaving only 2 percent to reach the aquifer. McMillan said recharging the aquifer through macro-rainwater harvesting could be a win-win situation.
“We need more water going into the aquifer, and this could do that,” McMillan said. “It could also lessen the burden on the Verde River, which in turn protects the wildlife that depend on that river.”
Springer said she’s confident that rainwater harvesting can solve Prescott’s water challenges without dramatically affecting natural processes.
“This is a small percentage of rainwater we’re proposing,” Springer said. “Most of the rainwater will go where it’s always gone, into the ground, lost through evaporation, or go to the plants.”
But according to Bruce Hallin, manager of water rights and contracts at Salt River Project, the science behind the concept isn’t as sound as it needs to be.
“There are a lot of unknowns and unproven science,” Hallin said. “From our perspective more analysis is necessary to determine what is true and good science.”
In addition to a potential impact on the aquifer, Hallin said he’s concerned about the consequences of collecting rain before it reaches surface streams, potentially taking away water belonging to users down river.
Springer and McMillan said the proposed time frame is long enough and that the time has come for such a study.
“When most people turn on their taps, they don’t think about where that water comes from, and we can’t wait until the tap is dry to find a solution,” McMillan said. “We need to be looking generations ahead.”