Yet in the early 1900s, many regional rivers--now mostly quiet and desiccated, such as the Santa Cruz--always had flowing water, supporting dense forests of willow, cottonwood and mesquite. However, decades of floodplain development, the introduction of invasive species and, in particular, groundwater pumping powered by gasoline turbines destroyed these habitats.
"That has not only sparked endangered-species issues and made Tucson an uglier place. It also struck at the heart of the agriculturally based river community that we had here with the Tohono O'odham Nation," said Julia Fonseca, environmental planning manager for the Pima County Flood Control District. "At San Xavier, there was a community of people who lived there and farmed for thousands of years. When they couldn't divert the Santa Cruz River anymore, they lost their way of life."
Pima County's Sonoran Desert Conservation Plan is the blueprint for preserving what's left of riparian areas and reconstructing some of what has been lost. The plan uses a variety of measures, including government acquisition of sensitive lands and the introduction of effluent (treated sewage) to riverbeds in order to recharge aquifers.
While some may balk at the notion of using effluent on such projects during a prolonged drought, experts said there are a number of reasons why people should support the conservation and restoration of water-dependent ecosystems.
Frank Postillion, principal hydrologist with the Pima County Flood Control District, said letting effluent loose in rivers "kills about four birds with one stone"--in a good way.
Last year, the Lower Santa Cruz Managed Recharge Project replenished 22,100 acre-feet of water in the aquifer, while at the same time providing for riparian restoration, recreation and education, he said. About 53,750 acre-feet of effluent flowed into the Santa Cruz River.
"When you do multi-purpose recharge, you accomplish the goals of recharge and replenishing the aquifer, in addition to providing riparian habitat for water fowl and other types of creatures," Postillion said. "You're really maximizing what you're doing here."
The effluent is purified naturally as it seeps into the ground, improving the overall quality of the water.
In terms of pure self-interest, property values increase when riparian areas are nearby, and people often enjoy such environments for recreation, Fonseca said.
Another reason to support these projects is that 80 percent of animals are dependent upon riparian areas for at least one part of their life cycles--whether to find food, for shelter or for mating, said Dave Weedman, aquatic habitat specialist with the Arizona Game and Fish Department. Yet, according to such sources as the Arizona Riparian Council and the Tucson Audubon Society, between 90 and 96 percent of the state's riparian areas have been lost over the past century.
Even the areas that are still technically wet are much changed from 500, 100 or even 50 years ago, said Tom McMahon, a fisheries specialist with the Arizona Game and Fish Department. "Yeah, there may be water, and we can call it a riparian area, but is it the same as it was? No," he said.
Dropping water tables kill some native animals and plants, the roots of which can't reach down far enough to drink. Then, invasive species often do a number on the remaining flora and fauna.
Just say "salt cedar," also known as tamarisk, to any biologist or birdwatcher, McMahon said, and you'll likely get an earful: "It almost oozes salt into the ground around it, and really makes it unpleasant for any other species to germinate. It just takes over."
Fonseca gave one more reason why people, rightly or wrongly, shouldn't fear preservation projects might be pinching their water supply: Regulations give the lowest priority to those who want to maintain riparian areas through something called an in-stream flow water right.
"State laws that surround the use of groundwater--they don't recognize that there is an inherent right for groundwater-dependent ecosystems to exist or have access to water," Fonseca said. "Our state laws are based on predominantly human uses."
The in-stream flow water right can be issued by the state to protect surface water and its surrounding environment. But Arizona has been slow to implement programs recognizing the connection between groundwater and water that's on the surface, even though courts have ruled there is one, Fonseca said.
"So, yes, you can have your surface water right, but the state can also permit a groundwater pumping well over here, near the stream," she said. "And they won't say you can't do that." The well sucks up water, lowering the water table. Even a small dip can cause a stream to dry up.
The ability of pumps to sip the water out from underneath those holding surface-water rights could end soon. Pima County Flood Control District and other agencies have charged the Arizona Department of Water Resources with not doing enough to preserve these rights and want regulatory changes.
The matter will be considered by the Governor's Regulatory Review Council this month.