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Lake Mead Science Symposium Concurrent Sessions
LAKE MANAGEMENT
Session Chairs:
Kent Turner and Chris Holdren
Wednesday, January 14, 2009 * 1:15 pm to 5:00 pm * Room 2081:20 – 1:40 pm
Boulder Basin Adaptive Management
Turner, Kent-1; Orphan, Lynn-2; and Karafa, Doug-2 (1) NPS Lake Mead National Recreation Area (2) Clean Water Coalition.The Boulder Basin Adaptive Management Program (BBAMP) manages the treated effluent of Las Vegas to meet water quality objectives for the Las Vegas Wash, Lake Mead and the Colorado River downstream. Currently three municipal wastewater discharges are permitted into Lake Mead: 150 MGD from Clark County Water Reclamation District, 91 MGD from City of Las Vegas and 40 MGD from City of Henderson. Discharges are conveyed through the Las Vegas Wash, which also conveys Las Vegas storm water.
The Clean Water Coalition (CWC) was formed in 2002 by the dischargers to plan alternatives to their effluent discharges to Las Vegas Wash. The CWC proposed through an Environmental Impact Statement for a new effluent diffuser system to include a diffuser pipeline.
Through the EIS process, NPS, BOR and FWS developed mitigation requirements documented in the record of decision and biological opinion. These include a selenium management plan for the Las Vegas Wash, a Fathead Minnow study to predict impacts to Razorback Suckers in Lake Mead, and implementation of an adaptive management program for the BBAMP. The BBAMP outlines a monitoring program and as management process to ensure that project goals related to water quality and resource protection are met.
The BBAMP is managed by a core management team of the CWC, SNWA, Reclamation, NPS, and FWS. The main functions were assigned to four technical advisory teams comprised of representatives from local, state and federal agencies with responsibility for water resources, water quality and use of Lake Mead, the Las Vegas Valley watershed, and the Colorado River downstream.
1:45 – 2:05 pm
Development and Application of a Three-Dimensional Water Quality Model to Lake Mead
Hannoun, Imad, A.-1; Preston, Al1; Kavanagh, Kristen, B.-1; List, E., John-1; Orphan, Lynn-2; Turner, Kent-3; Roefer, Peggy-4, (1) Flow Science Incorporated, (2) Clean Water Coalition, (3) NPS Lake Mead National Recreation Area, and (4) Southern Nevada Water AuthorityThe three-dimensional Estuary, Lake and Ocean Model (ELCOM), coupled with Computational Aquatic Ecosystem DYnamic Model (CAEDYM) were applied to the simulation of water quality in the entire Lake Mead. Eight years of extensive field measurements of water quality parameters in the reservoir were used as inputs to the model, and to provide comparisons between the model results and field data. Good agreement was obtained for various modeled parameters including temperature, salinity, perchlorate, nutrients (nitrogen and phosphorus), and chlorophyll a. The model will be used as an integral part of an adaptive management plan for the lake. It is anticipated that the model will be used to evaluate various future lake operating scenarios and assist in management decisions for optimizing the various uses of the reservoir under the adaptive management plan. The presentation will show comparisons between the model and the field data. It will also provide animations that will highlight the complex limnological processes within the reservoir, including the inflows from the Colorado, Virgin and Muddy Rivers and Las Vegas Wash, and the outflows through Hoover Dam and the various water supply intakes. The model results proved to be a valuable resource for understanding the interactions between the various reservoir processes and for defining the seasonal characteristics of the reservoir.
2:10 – 2:30 pm
Water Quality, Endocrine Disruption, and Fishes in Lake Mead: Reconnaissance Analysis of Competing Risks as Inputs for Developing Adaptive Management Plans
Linder, Greg and Little, Edward E., USGS/BRD, Columbia Environmental Research CenterCompeting risks play a critical role in developing adaptive management plans for natural resources. For water resources, the analysis and characterization of competing risks relies on a wide spectrum of analytical tools to evaluate hazards and risks associated with anticipated uses of water resources. For waters of the lower Colorado River that are stored in reservoirs such as Lake Mead on the Arizona-Nevada border, a wide range of water quantity and water quality challenges confront resource managers. These issues are often interdependent and complicated by competing uses of source waters for sustaining biological resources and for supporting a range of agricultural, municipal, recreational, and industrial uses. USGS is currently conducting a series of interdisciplinary studies on water quality of Lake Mead and its source waters. In this case-study we examine selected constituents potentially entering the Lake Mead system, particularly endocrine disrupting chemicals (EDCs). A number of potential EDCs have been detected in Lake Mead, and several substances have been identified that are of concern because of potential impacts to the aquatic biota, including the sport fishery of Lake Mead and endangered razorback suckers that occur in the Colorado River system. To identify potential linkages between EDCs and species of management concern, the risk analysis and characterization in this reconnaissance study focused on effects (and attendant uncertainties) that might be expressed by exposed endemic populations. In addition, risk reduction measures potentially of interest to resource managers are considered relative to emerging contaminants in treated effluents, interdependencies among biological resources “at risk”, and uses of reservoir waters derived from multiple inflows of widely varying qualities.
2:35 – 2:55 pm
Nutrient Budgets for Lake Mead
Holdren, G. Chris, U.S. Bureau of ReclamationAvailable information on nutrient concentrations, tributary inflows, and outflows for Lake Mead were used to develop nutrient budgets for the lake. As expected, the Colorado River, which contributes approximately 96% of the annual inflow to the lake, was the largest single source of nutrients. Las Vegas Wash contributes less than 2% of the total inflow but contributes more than 5% of the total phosphorus and more than a third of the soluble orthophosphate entering the lake. The Virgin and Muddy Rivers combined contribute less than 1% of the annual phosphorus load to the lake, with virtually no contribution during the summer growing season as a result of upstream water diversions. As a result, algal productivity in the relatively shallow upper reaches of the Overton Arm may be fueled by sediment resuspension.
3:25 – 3:45 pm
Initial Management Response to the Quagga Mussel Invasion of Lake Mead and the Lower Colorado River
Dingman, Sandee J., NPS Lake Mead National Recreation AreaQuagga mussels, closely related to zebra mussels, were first discovered at Lake Mead on January 6, 2007, the first detection of this species in the western United States. These invasive freshwater mussels were expected to cause, and indeed have started to realize, major impacts to biological resources, submerged cultural resources, marinas, water intakes, boats and recreational use in the Lower Colorado River System and, when spread, pose similar threats to other western waters. The National Park Service's Lake Mead National Recreation Area led a three month interagency initial response effort focused on assessment, containment, treatment, and long-term management of the quagga mussel infestation in Lakes Mead and Mohave. This effort culminated in an Initial Response Plan. When no treatment or eradication methods were found to be feasible, the efforts focused on containment of spread to other watersheds. Highlights of this initial response effort as well as lessons learned the hardway will be shared in this presentation by the Initial Response Coordinator.
3:50 – 4:10 pm
Whole Lake Manipulation for Controlling Quagga Mussels in Southern California Reservoirs
Taylor, William D. and DeLeon, Ricardo, Metropolitan Water District of Southern CaliforniaSince quagga mussels were first reported in Lake Mead in January 2007, they spread from the Colorado River throughout the 250 mile storage and conveyance system of the Metropolitan Water District of Southern California and into San Diego County to within a few miles of the Mexican border affecting the water supply of 18 million people. Metropolitan has been developing numerous approaches to manage the mussels in the conveyance side of the system for trash racks, pumping plants, aqueducts, pipelines, etc. During 2008, Metropolitan conducted two whole lake experimental manipulations designed to kill mussels in the reservoirs. The first strategy relies on enhancing lake stratification, a natural process that can lead to anoxia and mussel death in the hypolimnion. The second strategy was to draw down the reservoirs to kill mussels in the upper reaches through desiccation. The intent of the combined approaches was to reduce mussel populations and disrupt reproductive cycles. The approach took advantage of operational options available in engineered systems that can be used to manipulate lake processes. Both Lake Mathews and Lake Skinner developed anoxia that successfully killed hypolimnetic mussels at depths inaccessible to divers for cleaning. Also, Low oxygen conditions appeared to stress mussels above the kill zone and interfere with spawning. Desiccation will clearly kill mussels. Risks associated with these whole lake manipulations include increasing availability of nutrients to algae blooms and taste-and-odor events, manganese releases from sediments, fish kills and water quality conditions incompatible with treatment plant processes.
4:15 – 4:35 pm
Interagency Response to Quagga Mussel Invasion at Lake Mead: Detection, Prevention, Control, and Monitoring
Gerstenberger, Shawn-1; Turner, Kent-2; and Wong, David-1 (1) University of Nevada, Las Vegas and (2) NPS Lake Mead National Recreation AreaQuagga mussels (Dreissena bugensis) were found on January 6, 2007 in Lake Mead and constitute one of the first occurrences of dreissenid mussels (quagga and zebra mussels) in the western United States. Multiple agencies have expressed concerns about protecting drinking water quality, water delivery infrastructure, ecosystem health, endangered species, recreational activities, and identifying ways to reduce the spread of this invasive species. To address these issues, a small working group was established shortly after quagga mussels were discovered and has grown rapidly to include about 80 individuals representing over 25 agencies. Significant progress has been made by combining efforts, providing current data to the group, standardizing methodology and carefully examining the objectives and requirements of the different agencies. The results of these efforts will be compiled and integrated into an interagency quagga mussel plan targeting the long term monitoring of veligers, juveniles and adults. Based on group discussions, we will primarily focus on 18 stations in Boulder Basin, the most heavily monitored area of Lake Mead. This program can be implemented by lake managers and stakeholders to scientifically monitor the long-term quagga mussel development and its ecological consequences on water quality and food webs in Lake Mead.
4:40 – 5:00 pm Panel Discussion