Columbia River Basin: Integrated Land-use, Lakes and Streams (ILLS) Study
The Columbia River embodies a hydrologic continuum, from the headwater streams, through the lakes and marshes that feed the larger streams and tributaries, to the main stem of the Columbia River itself, and ultimately to the Pacific Ocean. The health of any part of the river system is, therefore, dependent on the combination of these elements – the transport provided by the flow of water through the system, the spatial distribution and form of the individual sources, the transformation of water-borne contaminants that occur within the system, and the concomitant biological uptake of these contaminants.
Working in partnership with the Columbia River Inter-Tribal Fish Commission (CRITFC) and the Yakama Nation, this project is creating a computer model and a modeling framework to allow the fate and transport of contaminants on the Columbia River system to be better understood and treated as necessary. The modeling framework is being applied to the fate and transport of methyl (bioavailable) mercury in the Columbia River Basin.
The Tahoe Climate Information Management System (TahoeClim)
Kelly Redmond (DRI), Geoff Schladow
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[/cryout-pullquote] Weather and climate are well understood to be very important as primary drivers of atmospheric, ecological, limnological, biological, geological, hydrological and economic processes affecting the basin in myriad ways. Within the Tahoe Basin a heavy and steady demand for such information exists, and a large amount of data and information already exist, but are not fully validated, processed or available from any single authoritative source. A joint collaboration between the Western Regional Climate Center at DRI in Reno and the UC Davis Tahoe Environmental Research Center (TERC) will develop an accessible archive of historical and current meteorological and climatological data for the Tahoe Basin. The Tahoe Climate Information Management System (TahoeClim) will include all past and present observations from the principal weather and climate networks operating in the basin and NASA space-borne thermal infrared imagery. A variety of specialized sites on and near the lake, and in and near the basin, will likewise be incorporated, including a small number to be added or augmented during this project. The data flow and management system will be established to allow the continued assimilation and archiving of real-time data in the future. The data sets will include direct measurements from in situ locations, interpolated and infilled data on fine grids, three-dimensional hourly fields of data from the last five years, and synthesized information in the form of products, many of which can be generated directly by the users and therefore be more responsive to their needs. The intended audience encompasses the public, managers, politicians, the press, educators and students, but will meet the more stringent demands and standards of the environmental research community.
Potential for Pathogen Growth, Fecal Indicator Growth and Phosphorus Release under Clam Removal Barriers in the Lake Tahoe Basin
Stefan Wuertz, Mitsunori Odagiri, Geoff Schladow
The project seeks to measure the impact of clam barriers – rubber sheets that are spread on the bottom of Lake Tahoe to create anaerobic conditions to kill Asian clams – on the survival and re-growth of fecal indicator bacteria (FIB) and potential bacterial pathogens, and the release of soluble reactive phosphorus (SRP) from the anaerobic sediments that are produced through the treatment. The project is motivated by recent in-lake pilot [cryout-pullquote align=”right” textalign=”left|center|right” width=”33%”]
[/cryout-pullquote]experiments that demonstrated that barriers, when properly designed and installed, are effective at killing Asian clams in near-shore areas but that the anaerobic, relatively warm, and nutrient-rich conditions that are produced under the barriers may result in undesirable water quality impacts. Experiments testing the hypothesis that elevated FIB levels observed in preliminary experiments at Marla Bay and Lakeside Marina are due to bacterial re-growth and not actual contamination with fecal waste of human or non-human origin will be conducted in laboratory-based microcosms designed to mimic environmental conditions at the bottom of the lake. The simultaneous SRP measurements are intended to quantify release rates of phosphorus under anaerobic conditions (internal nutrient loading). The goals of the project are to (1) establish if FIB can re-grow under low oxygen conditions underneath clam barriers positioned in the lake, (2) perform spiking experiments with fecal material to track the fate of FIB and two relevant bacterial pathogens, Campylobacter jejuni and Salmonella enterica, and (3) quantify the release rates of phosphorus from the sediments associated with Asian clam growth in Lake Tahoe. This information is critical to helping agencies make an informed decision about both the benefits and risks of using bottom barriers to contain the spread of priority invasive species, and will be required as part of permitting associated with large-scale deployments of this technology.
Development of a risk model to determine the expansion and potential environmental impacts in Lake Tahoe
Sudeep Chandra (UNR), Marion Wittmann, John Reuter, Francisco Rueda (U. Granada), Geoff Schladow
In the last 40 years many private and public resources have been expended to restore Lake Tahoe’s fragile ecosystem and water clarity. Recently, the expansion of an invasive species, the Asian clam, was documented in the southeastern part of the lake. Further, this summer there were dense, filamentous algal blooms co-located with Asian clam beds. These blooms occurred in less than 10 meters of water were detected by local homeowners, residents and lake visitors and reported to local agencies. The rapid expansion of Asian clam in one year combined with the demonstrated potential to alter the ecology of the lake via 
unprecedented levels of algal biomass in the near shore, represents a major new threat to lake Tahoe. This proposal is motivated by concerns of agency staff requests for assistance in developing control methods, predicting likely future locations for clam colonization, and assessing the impact of clams on both a local and entire-lake scale. The objectives are to develop a longer-term risk assessment of Asian clam growth, spread and impact.
Measuring the Ability of Floodplains to Treat Urban Runoff
Stefan Wuertz, Adrienne Aiona, Yujie Jin, Geoff Schladow
The project seeks to measure the mechanisms and the efficiency of fine particle removal from urban stormwater using floodplains. The project is based in the Cold Creek/Trout Creek floodplain, and utilizes the Cattlemans detention basin and the floodplain immediately downstream of it. Experiments separating the role of biofilm processes and 
gravitational settling will be conducted within the detention basin, and on the floodplain downstream of the basin in response to both natural overflows of the basin and pumped flows of urban stormwater. The goals of the project are to (1) quantify the effects of gravitational settling and biofilm processes in the removal of very fine (<20 micron) particles from urban stormwater and to (2) determine the elemental composition of both the stormwater itself and the particulate material to assess the potential for negative impacts to the resident floodplain biota and their food webs. This information will be used to help calibrate and validate a two-dimensional floodplain model that will enable floodplains to be designed to optimally treat urban stormwater.
Potential of Floodplains to Retain Fine Sediments
Stephen Andrews, Fabian Bombardelli, Geoff Schladow
Goals:
- Develop, calibrate, and validate a two-dimensional hydrodynamic/water quality model to quantify the removal efficiency for fine sediment and nutrients in the Trout Creek and Upper Truckee River watersheds.
- Determine the features of flood plains that have the largest effect on fine sediment and nutrient removal (e.g., residence time, vegetation density and distribution, turbulence sources).
- Use the model to design methodologies to maximize the efficiency of flood plains as best management practices (BMPs).
- Evaluate the basinwide potential and costs of flood plains as BMPs.
Lake Tahoe Carbon Budget
Bridget Tracy, Geoff Schladow
In recent decades, concern about global warming has encouraged scientists to look more closely at ecosystems’ role in carbon (C) storage and efflux with the atmosphere. Lakes are hotspots for biogeochemical processing of the global carbon load. The dynamic nature of the water which constitutes this ecosystem type makes the process of determining carbon balances more difficult than for many terrestrial ecosystems, but no less important.
This project will build a whole-lake carbon budget for Lake Tahoe. By measuring the amount of dissolved and particulate and organic and inorganic carbon entering the lake, via precipitation, streams, urban runoff and atmospheric deposition, and the amount leaving the water column, by outflow, atmospheric exchange and sedimentation, a carbon budget can be constructed. Experiments quantifying loads entering and exiting the lake will be used to understand the Lake’s role in processing carbon and its potential to act as a carbon sink. In particular, findings will be compared to estimates for surrounding forested areas, in order to understand the Lake’s role with respect to the entire watershed. This information will be used to help understand the role of Tahoe and other oligotrophic lakes in global carbon cycling and to provide a baseline from which to assess potential changes in the Lake’s ability to act as a carbon sink with the climate warming and increased use by visitors and residents.
Sediment Resuspension and its Implications for Near-shore Water Quality at Lake Tahoe
Krisin Reardon,Geoff Schladow
We are developing a process-based understanding of the source and fate of fine particles in the near-shore zone. This requires quantification of the contributions of different forcing mechanisms to sediment resuspension. The specific aims of this research are to conduct field measurements on sediment resuspension and transport; to implement a three-dimensional hydrodynamic lake model coupled with a wind-wave model and a sediment resuspension model; and to investigate linkages between the physical processes associated with sediment resuspension and transport to water quality variables such as water clarity and dissolved oxygen
Lake Clarity Model for Lake Tahoe TMDL
Goloka Behari Sahoo, Geoff Schladow
Lake Tahoe is world renowned for its natural beauty and spectacular cobalt-blue color. However, long-term monitoring and research since 1968 show that its clarity, expressed as Secchi depth, has declined by 10 m between 1968 and 2009. The declining clarity is attributed to the influx of nutrients (phosphorus and nitrogen) and fine inorganic particles (particle sizes ranging 0.5 to 16 mm in diameter) to the lake. If the loss of clarity continues at its current rate, there will likely be a change of lake color and trophic status. Therefore, public concern for the clarity of Lake Tahoe is high with local, state and federal agencies and policy-makers developing science-based restoration plans. Central to plans to improve Lake Tahoe’s water clarity is the Tahoe Total Maximum Daily Load (TMDL) program. The Tahoe TMDL (1) quantifies the source and amount of fine sediment and nutrient loading from a variety of activities and land-uses within the major categories of urban watershed, forest upland, atmospheric deposition, stream channel/shoreline erosion and groundwater, (2) uses a customized Lake Clarity Model (LCM) to link pollutant loading to lake response and (3) develops the framework for an implementation plan to achieve an annual average Secchi depth of approximately 30 m as required by existing water quality standards. A watershed model was used to address the generation of pollutant loads over the land surface and through groundwater contributions, as well as to predict the resulting impact on stream water quality. Given the unique features of Lake Tahoe and its oligotrophic nature, a customized model that focused on Secchi depth was needed. The Lake Clarity Model (LCM) is the customized model based on the UC Davis Dynamic Lake Model with Water Quality (DLM-WQ).
Tahoe Water Quality Toolbox
The Lake Tahoe TMDL program has spearheaded the development of a series of models that can be used for water quality planning. The Tool Box was intended to incorporate models and other tools that can be used by agencies, resource managers, planners, scientists, engineers, and EIP project implementers to help plan for achieving basin-wide load reduction goals.
Effect of Climate Change on Lake Tahoe
Goloka Behari Sahoo, Geoff Schladow
Meteorology is the driving force for lake internal heating, cooling, mixing, and circulation. The trends in air temperature, precipitation, percent of total annual precipitation falling as snow, and snowmelt timing indicate that the Sierra Nevada range is warming and that the Tahoe basin is warming faster than the surrounding region. Continued global warming will affect the lake thermal properties, water level, internal nutrient loading, nutrient cycling, food-web characteristics, fish-habitat, aquatic ecosystem, and other important features of lake limnology. The impact of climate change on a deep and large lake (Lake Tahoe (CA-NV)) was investigated using a suite of models and bias-corrected downscaled climate dataset generated from of the two emissions scenarios (B1 and A2) of the Geophysical Fluid Dynamics Laboratory (GFDL) Global Circulation Model. Our results indicate a shift of snow to rainfall during the 21st Century along with an onset of earlier snowmelt. Combined, these changes could affect water supply and the winter recreational sport industry. The lake may fail to mix completely by the middle of this Century due to lake warming. Under this condition bottom dissolved oxygen would not be replenished leading to the significant release of ammonium-nitrogen and soluble phosphorus from the sediment. Both these nutrients are known to cause increased algal growth in the lake and would likely result in major changes to the lake’s water quality and food web. Lake warming also increases water loss through evaporation, resulting in less available water for downstream domestic supply, agriculture, and recreation.