8 • November/December 2005 • Southwest Hydrology

Lake Mead Dyed RedDoug Karafa – Clean Water Coalition, and Robin Lee and Rhys McDonald – Brown and Caldwell

More than a few heads were turned last fall when Brown and Caldwell released red dye into Lake Mead as part of a Clean Water Coalition (CWC) dye tracer study. The CWC comprises the three agencies responsible for wastewater treatment in the Las Vegas Valley: Clark County Water Reclamation District and the cities of Las Vegas and Henderson. The CWC is investigating mixing patterns, flow characteristics, and water quality in Lake Mead in order to identify a new outfall location for treated effluent from the Las Vegas Valley.

Wastewater from the coalition agencies currently is treated and released into Las Vegas Wash, which flows into Lake Mead. Over the years the wash has suffered significant erosion from high effluent flows. Nutrients from the wastewater have increased algae growth in the lake, and lower lake levels in recent years have led to more frequent eutrophication at the confluence of the wash and lake.

In response, CWC is researching a proposed wastewater discharge pipeline into Lake Mead to reduce flows in Las Vegas Wash and allow wastewater to be released at depth in cold water over a larger area where it is less likely to cause algae blooms.

The Brown and Caldwell dye tracer studies in Lake Mead were conducted from September to November 2004 to validate fate and transport numerical modeling studies of discharge from the proposed pipeline. The tests consisted of surface and 23 meter- deep subsurface releases at

ON THE GROUND

Near right: November 2004 aerial photos of Boulder Island surface release from 10:30 to 18:00. Far right, top: map showing tracer release sites. Far right, middle: composite dye concentration contour map from the October subsurface release. Far right, bottom: composite profiles of dye concentration at depth illustrate that the plume remained trapped in the thermocline during the October release but mixed vertically during the November release.

see Mead, page 38

two potential discharge locations: near Boulder Island (Boulder Basin) and near Sand Island (Las Vegas Bay).

Five gallons of rhodamine WT fluorescent dye were released during each test. Substantial effort went into injecting it so as to create distinct plumes that remained at target depth in a patch of sufficient breadth and thickness to measure and track remotely.

To meet the needs of model validation, each plume was tracked for approximately 30 hours following release, during which time near-synoptic data sets were collected. A towed, remote-operated vehicle was used to measure the dye concentration using in-situ fluorometers and to map the plumes by moving through the water column along horizontal and vertical transects while recording depth, water quality parameters, and dye concentration.

Color aerial photographs also documented the trajectory and dispersion of the surface dye plumes. The first overflight took place immediately after tracer release, followed by flights two, five, and nine hours after release. The surface plumes were typically visible only the first day after release due to dilution and dispersion.

Results validated the computer modeling

analysis and revealed the important role that lake structure plays in the fate and transport of a plume. In late summer, when the thermocline was well defined, the surface plume stayed on the surface and the subsurface plume remained trapped within the thermocline, moving horizontally with ambient currents. During the fall, vertical mixing was the dominant factor in dispersing the plumes. Cooler air temperatures, particularly at night, cause surface waters to sink, driving down the depth of the thermocline and producing a relatively uniform and unstable density structure above it. The surface plume remained intact near the surface during the day and sank and dispersed vertically during the night. Shortly after release, the subsurface plume spread vertically both above and below the release depth, eventually dispersing throughout the water column above the thermocline after about 20 hours.

The modeling predictions indicate a significant decrease in algae growth with the proposed pipeline. The modeled predictions as validated by the tracer study are part of the work supporting Boulder Islands as the preferred outfall location in the Environmental Impact Statement (EIS), scheduled to be completed by mid-2006.

Contact Rys McDonald at rmcdonald at brwncald.com or visit www.cleanwatercoalition.com.

38 • November/December 2005 • Southwest Hydrology

Engineers, Geologists, EnvironmentalScientists, and Decision Analysts

Costa Mesa, CA (949) 642-0245Scottsdale, AZ (480) 348-1283Please visit for career opportunities - EOE

www.geomatrix.com

Regional Groundwater Studies

Water Resources Engineering

Groundwater Modeling

Watershed Management

Subsidence Analysis/Geohazard Evaluations

Conjunctive Use

Water Quality Evaluations

Environmental Assessments

Resources Department. The award is presented to individuals who have made outstanding contributions to advancing or facilitating the role of geoscience in the areas of education, research, public service, and public policy in New Mexico.

John Hawley is well known in the New Mexico water community, having worked for decades in the state, including 20 years at New Mexico Tech, where he is now emeritus senior environmental geologist. The award recognized his technical expertise in New Mexico geology and hydrogeology and his professional and scientific integrity and contributions to public service and policy.

The other recipient of the Earth Science Achievement Award was New Mexico State Senator Carlos R. Cisneros.

Visit wrri.nmsu.edu.

National Water Research Institute Mourns DirectorIn August, the National Water Research Insitute of Fountain Valley, California announced the death of Ronald B. Linsky, who served as executive director of the institute for its entire 15-year existence.

Through his work at the institute, Linsky promoted the importance of a reliable water supply for all. He was known for his cutting-edge ideologies that promoted technological advances to ensure the integration of water reuse, desalination, and conservation into long-term strategies to enhance sustainability of water resources for future generations.

The National Water Research Institute was founded in 1991 by a group of Southern California water agencies in partnership with the Joan Irvine Smith and Athalie R. Clark Foundation to promote the protection, maintenance, and restoration of water supplies and to protect the freshwater and marine environments through the development of cooperative resesarch.

Visit www.nwri-usa.org.

Mead, continued from page 8People, continued from previous page

10 • November/December 2005 • Southwest Hydrology

Restoring Fossil Creek: A Collaborative EffortMichele James – Fossil Creek Project Coordinator, Northern Arizona University

A tributary to the Verde River in central Arizona, Fossil Creek has had the vast majority of its flow diverted to power plants since the early 1900s. That changed on June 18, 2005, when the Arizona Public Service Company (APS) decommissioned the Childs and Irving hydroelectric facilities and stopped diverting much of the creek’s base flow. Fossil Creek once again flows freely. On top of that, multi-agency efforts have restored the creek’s native fishery.

The Childs Power Plant was built in 1909 on the banks of the Verde River and was one of the first hydroelectric power plants in the West. Electricity generated there was used by the mining industry in the Jerome area, and by large irrigation companies and individual farmers in the Verde Valley

to run pumps to irrigate thousands of acres of land. In response to increasing power demands, the Irving Power Plant was built in 1916 at Fossil Creek. Power for these plants came from diverting almost

the entire discharge of the Fossil Springs complex—nearly 46 cubic feet per second. In their heyday these power stations supplied all the electrical needs of Yavapai County and generated nearly seven

ON THE GROUND (continued)

Fossil Creek, before and after project decommission.

20 Years of Enriching Our Desert Life

November/December 2005 • Southwest Hydrology • 11

megawatts of electric power combined.

With more than 60 springs located along a 1,000-foot reach, discharging at a near-constant temperature of 72 F, Fossil Creek is one of Arizona’s rare warm water streams, and has the greatest spring-water discharge in the Mogollon Rim region. The water contains high concentrations of calcium carbonate and dissolved carbon dioxide, resulting in travertine precipitating on rocks, leaves, and other objects in the channel. The encrustations resemble fossils, accounting for the creek’s name. Travertine also forms dams that can quickly build to many feet in height; deposition of travertine at a rate of almost one foot per month was recorded at Fossil Creek in 1996 when the Irving Power Plant was shut down for maintenance.

Restoring Full FlowWork to return full flows to Fossil Creek began in the late 1990s when several conservation organizations and the Yavapai Nation intervened in the relicensing of the Childs-Irving facilities. The conservation organizations and APS recognized the unique opportunity to restore the Fossil Creek ecosystem to its original condition and APS decided the benefits of restoration outweighed the benefits of continued production from the plants. The resulting settlement agreement included the surrender of license, removal of the majority of the project facilities by the end of 2009, and the restoration of full flow.

Protecting the NativesFossil Creek is one of the few streams in Arizona retaining viable populations of six native fish species: headwater and roundtail chub, desert and Sonora sucker, and longfin and speckled dace. In the mid-1990s the Bureau of Reclamation entered into consultation with the U.S. Fish and Wildlife Service (FWS) about the effects of operating the Central Arizona Project on threatened and endangered fish. The ensuing agreement required construction of a fish barrier in Fossil Creek to prevent non-native fish from migrating up from the Verde River.

The barrier was constructed in 2004 approximately five miles upstream from the confluence with the Verde River. Multiple agencies also collaborated to restore the 12 miles of Fossil Creek above the barrier to a native fishery. Biologists from Reclamation, FWS, Arizona Game and Fish, and the U.S. Forest Service removed native fish from the creek and kept them in holding tanks until after the application of a piscicide to eradicate non-native fish including green sunfish, smallmouth bass, catfish, and yellow bullhead. After the piscicide dissipated, the native fish were returned to the restored creek.

Pre- and Post-Restoration ResearchNorthern Arizona University scientists and engineers have been working at

Fossil Creek for the last five years, gathering baseline data about the physical, biological, and social conditions of Fossil Creek prior to the return of full flows. This work will continue to track changes now that full flows have been restored.

Visit www.watershed.nau.edu/FossilCreekProject. Contact Michele James at michele.james@nau.edu.

References.....................................................Marks, J.C., G.A. Haden, E.C. Dinger, and K. Adams,

2005. A survey of the aquatic community at Fossil Creek, Arizona. Dept. of Biology and Merriam-Powell Center for Environmental Research, Northern Arizona University. Heritage Fund Report submitted to the Arizona Game and Fish Department, Heritage Grant I03003.

Overby, S.T., and D.G. Neary, 1996. Travertine geomorphology of Fossil Creek. Hydrology and Water Resources in Arizona and the Southwest: Proceedings of the 1996 meeting of the Arizona Section, American Water Resource Association and the Hydrology Section, Arizona-Nevada Academy of Science, April 20, 1996, pp. 9-12.

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