From Gandy, we spring-hop our way north, and at each stop Sada whips out his sieve. Splashing through water sprinkled with duckweed, Sada retrieves a detritus-eating leech, a largish pond snail and a creeping water bug, which he takes care not to touch. "Its bite is extremely painful, like being stuck by a red-hot needle," he matter-of-factly volunteers. Sada also finds a springsnail known as Pyrgulopsis kolobensis. It isn't rare, but its presence is a sign of hydrological stability. "You always find kolobensis near a spring's source," he says. "They don't like variable environments."
Springsnails are sometimes referred to as the "guardians" of springs, which suggests that they perform some vital function. And no doubt they do; among other things, their appetite for algae and microbes probably helps keep benthic communities healthy. "But to us humans," Sada says, "their most important role may be as indicators of environmental conditions." The presence of springsnails means that water flows have remained constant for a very long time. In addition, springs with springsnails are biologically richer, supporting a larger number of endemic species than springs without snails. When a springsnail population starts to decline, says Sada, it's time to pay attention.
Sada tells Wilson about an experiment he and a colleague recently conducted at Travertine Springs in Death Valley. In essence, the two scientists turned one of the spring brooks into an outdoor laboratory, mapping out the microhabitats occupied by aquatic invertebrates. Then, using the pipes and valves in a nearby springhouse, they throttled back the brook's flow for a few hours at night, measuring changes in ecologically important indicators like the velocity of the current and the depth, temperature, and chemical composition of the water. Once they analyze the data they collected, Sada says, they hope to start answering the question now on everyone's mind: What is likely to happen biologically as a spring's flow slows?
Everyone knows what happens when a spring dries up completely, Sada continues; springsnails and other aquatic organisms die. But what happens to these organisms if the water flow drops by, say, 10 percent? What about 20 percent, 40 percent, 60 percent? "At present," Sada says, "no one knows."
Beneath the shade of giant cottonwoods, we lunch at Miller Spring, where Wilson reminisces about the battles fought here against non-native species -- for a time, the spring was overrun by rainbow trout -- and the agreement with the landowner to control cattle access with fencing. The springsnails and least chub should now have an improved chance at survival, Wilson says, as long as their habitat stays wet. "These are truly aquatic species," she adds. "They are basically trapped in this system, so if the water goes, they go."
Before we leave, Sada makes a final pass with his sieve while Wilson and I stare into the spring pool, hoping to spot a least chub. Thanks, in large part, to the ruckus kicked up by the Southern Nevada Water Authority, these sprightly fish and other small spring dwellers are beginning to intrude into public consciousness. The question remains: Will that matter? Like all creatures, Sada observes, "Humans must make use of water and other resources to survive. The problem is, we have a penchant for using these resources to depletion. The challenge is to use them in a sustainable manner. Sustainable is an overused word, but there's just no good substitute for it.. "
J. Madeleine Nash is a freelance journalist and science writer based in San Francisco, California.
This coverage is supported by contributors to the High Country News Enterprise Journalism Fund.
For more information:Suck this, Vegas!
Squeezing water from a stone
Southern Nevada Water Authority Web site
Great Basin Water Network