Once upon a time, they say, cotton was king in the South. Out West, in the expanse of arid land known as the Great Basin, it's water that rules; and it rules just as sternly today as it did 100 years ago. In the West, where craggy mountain ranges and expansive desert flats seem to unfurl forever, there's plenty of room for everyone, but only enough water for some. In northern Nevada, the Truckee River provides much of that precious water. The Truckee originates at Lake Tahoe, tumbles down the eastern slopes of the Sierra Nevada, flows through Reno and Sparks, and finally spills into Pyramid Lake-one of the last vestiges of ancient Lake Lahontan, which once covered a much larger area. A portion of the river is diverted at Derby Dam, just east of Reno, and conveyed via the Truckee Canal through the primarily agricultural communities of Fernley and Fallon.

Along its relatively short journey, the Truckee's water is in great demand. Reno and Sparks need it to support their booming growth. Farmers in Fernley and Fallon need it to coax alfalfa, melons, and other unlikely bounty from the desert soil. Recreationists want it for rafting, fishing, and swimming. Environmentalists, sportsmen, and Native Americans want it to support wildlife populations and sustain the viability of Pyramid Lake and its cutthroat trout fishery. It goes without saying, then, that the Truckee River is a closely watched and, sometimes, bitterly contested resource.

One bone of Truckee contention was recently resolved by the Truckee River Water Quality Agreement, which settled long-standing litigation between the Pyramid Lake Paiute Tribe (PLPT) and a number of entities including the U.S. Environmental Protection Agency, the Nevada Department of Environmental Protection (NDEP), and the municipalities of Reno and Sparks. In the settlement, which addressed the PLPT's claim that discharge standards for upstream waste water treatment plants were inadequate during drought flows, the U.S. Department of the Interior and the cities of Reno and Sparks agreed to purchase a total of $24 million worth of water rights along the Truckee Canal, thereby removing some of the surrounding land from agricultural use. According to the agreement, the water cannot be sold or committed to development. Its sole purpose is to be stored and released to meet water quality standards and increase flows to Pyramid Lake.

From a water quality standpoint, leaving that water in the river may be a good thing. But no one is sure just how good it is, and that's where DRI enters the picture. Led by DRI hydrogeologist Alan McKay and Washoe County hydrologist Michael Widmer, a team of DRI researchers is trying to assess if and how irrigation activities in the Fernley region affect the Truckee's water quality. Of special concern is the lower Truckee, between the communities of Wadsworth and Nixon (see map), where ongoing monitoring conducted by DRI over the last 25 years has shown a marked increase in total dissolved solids, or TDS. This leads to increasing salinity, which is bad news for the fish and wildlife in and along the river and also for Pyramid Lake, the ultimate sink for the river's impurities.

There is a long-held hypothesis that the flood irrigation practices along the Truckee Canal may contribute to salinity problems in the lower river. Flood irrigation is just what it sounds like: instead of using sprinklers to deliver water to field crops such as alfalfa, farmers simply open gates and flood laser-leveled land with water. While it's an easy and inexpensive way to irrigate, it may result in excess water deliveries to some fields. This excess water then has two primary paths it may follow: as surface returns to downstream users; and/or as infiltration into the soil and groundwater.

"The predominant theory," explains McKay, "is that, as irrigation water infiltrates, it picks up naturally occurring salts in the earth and returns to the river, via groundwater, carrying more salt than when it left the canal. The Washoe County Regional Water Commission has generously funded us to do a physically based study to verify if this is how the system really works."

If groundwater really is contributing to the TDS problem, then it's possible that removing $24 million worth of water from agricultural use might help improve water quality in the lower Truckee. The PLPT would like to have that scientifically proven to give more weight to its battle to enhance water quality and to increase flows in the lower river. For the county and municipalities, the motivation is a little different. If they can quantify the improvement in water quality as a result of purchasing those water rights, they might be able to trade those pollution savings and use them to reduce structural treatment costs at the wastewater treatment facility. It's called "pollution swapping"-increasing output from one source in exchange for lessening output from another. "Reno's limiting factor for growth isn't water quantity, but water quality," explains McKay. "The cost of treating water to the current standards is very high. By showing that they have improved water quality in one area by a certain amount, they may be able to negotiate, say with NDEP or the Tribe, more lenient standards in another area."

Pollution swapping is becoming an increasingly common strategy to achieve water quality objectives, but to implement it, the reduction of contamination has to be measurable. In this case, where the pollution is in the form of dissolved salts carried via groundwater, firm numbers are hard to come by. "This is non-point-source pollution," says McKay, "meaning that it's diffuse. It's not discharging through a pipe or a specific point into the river. There aren't many precedents for negotiating these kinds of swaps, and the County is hoping our study results will help them do it."

Pollution carried by groundwater presents some special challenges to researchers, and unraveling the puzzle requires experts in several disciplines. For example, DRI's Dr. Eric McDonald and Kurt Cupp will be mapping the area's subsurface geology to determine if viable sources of salts exist for the water to pick up. DRI's Dr. Scott Tyler and William Albright will focus on the seepage and infiltration processes at work beneath irrigated and non-irrigated areas, including leakage from the unlined Truckee Canal. Douglas Guerrant of Broadbent and Associates is determining water budgets for the study area, and Dr. Burkhard Bohm of Plumas Geohydrology is the project's lead geochemist. Drs. Greg Pohll and John Tracy, along with David McGraw of DRI, will eventually integrate all their findings into computer models. With the foregoing in mind, McKay also notes that the study provides a useful model for partnerships among DRI, the consulting community, and public agencies.

Right now, researchers are at work drilling a series of wells that should demonstrate the direction of groundwater movement between irrigated areas and the lower Truckee. By doing very precise water quality analyses of the groundwater and the river, they hope to relate the changes found downstream with what's found in the groundwater.

The County, as it turns out, is not the only agency to recognize the importance of unraveling the relationship between groundwater and river quality. The project has also gotten a considerable boost from the U.S. Geological Survey's Water Institute Program, the U.S. Department of Agriculture, and the State of Nevada's Applied Research Fund. "This additional funding was implicit recognition that the project, as designed by the County Water Commission, really was a good idea," says McKay. While the County's concern primarily focuses on TDS inputs at the river, the additional funding is allowing researchers to investigate the subsequent effects of the increased salinity and associated nutrients on the river ecosystem-specifically, the impact on the river's algae population.

"Algae that attaches to a stream's rocks and gravel are a common problem in western rivers, consuming oxygen needed by spawning fish. The existing computer models used to predict algal growth and oxygen consumption under various conditions don't take into account groundwater inputs, and the information we'll get from the study can really help improve these models," points out McKay.

In fact, McKay says that the resulting computer models may be one of the project's more scientifically gratifying, and farthest-reaching contributions. In arid regions around the world, agriculture very often results in salinity problems and in the need to convert land to other uses. "We're hoping this study can provide a model for how to approach this sort of problem and give other arid regions a scientifically valid, cost-effective way to make land-use decisions."

Needless to say, where water is king, a lot depends on such decisions. Safe and clean water sources will always be crucial to people living in arid regions, be it the Great Basin or the Gobi Desert. The study underway at DRI will help everyone better understand those sources-a vital first step to making sure they're available for future generations.

Jackie Allen

Next Story