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From its beginnings at Lake Tahoe to its terminus in Pyramid Lake, the Truckee River is one of the most litigated, adjudicated, and studied little rivers in America. And virtually since the day DRI was founded in 1959, its scientists have been involved in some form of research somewhere along the Truckee River system, unraveling its complex ecology and assessing its response to 150 years of heavy human impacts. (See “DRI’s Long History with a Short River.”) Today the Institute’s presence in the Truckee River Basin is greater than ever, spurred by a new focus on water quality that has grown out of a partnership of local, state, and federal government agencies dealing with water quality challenges. That focus is also oriented toward the future, seeking new knowledge for maintaining the river’s environmental quality while meeting increasing demands for water resources. Barely more than 110 miles long, the Truckee drops 2,400 feet from Lake Tahoe to Pyramid Lake, getting used and re-used for rafting, fishing, swimming, kayaking, power generation, drinking, flushing, lawn-watering, light industrial processing, and agriculture along its course. The Truckee Meadows, the collective name for the valleys containing Reno, Sparks, and surrounding urbanization, is in the transition zone where the alpine Sierra Nevada foothills coalesce into the high desert of the Great Basin. And the area, itself, is in its own transition.
DRI scientist Alan McKay, who heads up a large part of DRI’s Truckee River studies, says development and other human influences—along with some natural conditions—affect the river’s water quality along its entire length. McKay, a DRI associate research hydrologist who has served as the interim director of DRI’s Division of Hydrologic Sciences for two years, says the biggest issue for water quality compliance on the Truckee is the amount of total dissolved solids entering the river from urban and agricultural sources, and ending up in Pyramid Lake. “A major challenge to future growth in the Truckee Meadows is the ability to treat salinity, the amount of total dissolved solids (TDS) we’re putting into the river,” McKay says. The Clean Water Act of 1972 sets limits on the amount of salts and other pollutants allowed in the water through a mechanism referred to as the Total Maximum Daily Load, or TMDL. TMDLs present serious challenges to both Nevada and California along the entire length of the river, McKay says. “The
old philosophy for managing river water quality was ‘dilution is
the solution for pollution,’” says McKay. “But TMDLs
have changed that. The concern is about how many tons actually end up
in Pyramid Lake, not the concentration of salts or other pollutants in
the river water as the seasonal flow volume changes during the year.” He says local
waste water treatment operators do an excellent job limiting the nutrients
that support the growth of algae in the river, though there may be some
river management techniques that could reduce that impact further. But
the treatment process for removing salinity from wastewater is difficult
and very expensive.
“The
conventional wisdom was that the surface water returning from irrigation
in the Fernley-Wadsworth area was responsible. But the crop there is mainly
alfalfa, and the growers don’t use much, if any, fertilizer. Further
research finally showed that surface water return flow from irrigation
is responsible for just a small amount of the salinity.” This management option was one element of the Truckee River Water Quality Agreement of 1997 that settled long-standing litigation involving the Pyramid Lake Paiute Tribe, the U.S. Environmental Protection Agency (EPA), the state of Nevada, and the cities of Reno and Sparks. The hard facts and real numbers to support the assumed benefits of this trade-off, however, were lacking, but the research challenge to develop that knowledge played directly to the strength of DRI’s hydrologic sciences capabilities. Hydrogeologist Michael Widmer of the Washoe County Department of Water Resources recalls the Washoe County Regional Water Planning Commission requested competitive proposals to study groundwater’s role in the river’s salinity in the Wadsworth area and selected DRI for the project based on its strong qualifications. Today, Widmer is the County project manager for the study and a collaborator in the research. “DRI had the experience and a great deal of knowledge about the river as well as some good ideas for approaching the problem,” he says. “The County is very serious about meeting water quality standards, but we have lacked a thorough understanding of the geochemistry in the watershed and the interaction of the river with the groundwater east of the Truckee Meadows.” The study’s goals were ambitious: investigate those physical processes that govern the potential sources of fluid and solutes to the river. This included developing a baseline conceptual model for the current conditions in the Fernley area, identifying the origins and sources of high levels of TDS in the groundwater, determining their influence on the TDS loading of the river, and, finally, developing a sophisticated groundwater flow and transport model that could predict the impact of various land-use scenarios on TDS mass loading to the Truckee River.
After more than two and a half years of intense field work and complex analysis by DRI, County researchers, and several private consultants, the conclusions suggested a window of opportunity for Washoe County. Groundwater carrying natural mineralization was, indeed, responsible for most of the salinity loading on the lower Truckee River, and, further, a significant portion of that groundwater was being driven by irrigation activities in the river’s watershed. “This is an outstanding example of ‘science meets policy,’” says McKay. “We’re now working with the County on the next phase to assess the extent of the pollution trading potential identified in those results. If the County acquires enough irrigated acreage and removes it from production, will the associated reduction in high TDS groundwater return provide opportunities for infrastructure expansion in the Truckee Meadows?” This follow-on project is now underway through a collaborative effort that includes DRI and private consultants ECO-Logic and TetraTech. McKay says the river’s research legacy reveals a piece-meal approach to its various, but related problems. Now, however, he and his fellow researchers would like to “tie it all together, approach it from beginning to end, assessing the hydrology, ecology, and socio-economic aspects of the entire river basin. The goal would be to synthesize all information to provide a better decision-making tool for local and state river management.” McKay also believes DRI’s Truckee River research has broader implications. “The
Truckee River, all by itself, contains elements of most of the water quality
management challenges facing local governments across the western United
States. DRI’s experience here can be used to benefit many other
communities across this region.” |
