2015 Tahoe Science Conference – Poster Abstracts

The influence of stormwater, lake level management, and boat waves on Lake Tahoe’s nearshore transparency
Michael Alexander, U.S. Forest Service, Russell Wigart, El Dorado County
The geographic position and physical setting surrounding Lake Tahoe combined with its exceptional size, depth, and transparency promises long standing prominence with residents and visitors. Urbanization is threatening ecological values of the region and resulted in a decrease in offshore transparency. Nearshore processes are not as well understood as the offshore and there is limited in-lake science statistically differentiating between natural and anthropogenic nearshore turbidity plumes. We investigated the influence of stormwater, lake level management, and boat waves on Lake Tahoe’s Southern nearshore transparency by measuring stormwater turbidity, lake bed sediment, and wave height. During one winter and three summer seasons we measured daily morning and evening lake turbidity and horizontal black disc transparency from piers in South Lake Tahoe. By reviewing rain, lake level, and summer boating intensity between 2012 and 2014 we found nearshore transparency was significantly degraded by stormwater during wet weather, boating during summer dry weather, and that the management of lake level dominated interannual variability in nearshore transparency. Improved nearshore transparency will be realized if urban infiltration facilities accommodate 25 mm rain events and if summer nearshore lake bed sediment is buffered from resuspension by boating.

Continuous Turbidity Monitoring in LTIMP streams in Lake Tahoe
Nancy Alvarez, Dan Riddle, U.S. Geological Survey, Nevada Water Science Center
The Lake Tahoe Interagency Monitoring Program (LTIMP) has provided streamflow, nutrient, and suspended sediment data for use in annual load calculations and trend analyses for several streams in the Lake Tahoe Basin since 1980. During water year 2015, the U.S. Geological Survey, in cooperation with Tahoe Regional Planning Agency, California Tahoe Conservancy, Lahontan Regional Water Quality Control Board, and UC Davis, enhanced the stream monitoring program by installing and operating continuous real-time turbidity stations co-located with gaging stations at five streams to improve load estimates of suspended sediment, fine sediment, and total phosphorus. Turbidity is measured every 15-minutes at Upper Truckee River, and Trout, General, Blackwood, and Ward Creeks. Discrete water-quality samples are manually collected at the five streams at a monthly frequency and during run-off events. Continuously measured turbidity and streamflow will be used in regression models to establish relations with suspended sediment, fine sediment and total phosphorus concentrations. Continuous turbidity also documents and improves loading estimates during rapid or extreme changes in water quality that can occur during run-off events. Such changes are difficult to measure by collection of discrete samples or predicted based solely on streamflow. Based on provisional 15-minute data collected over two hours during a storm event at Ward Creek in May 2015, turbidity increased from <1 to about 990 formazin nephelometric units (FNU) while streamflow increased from 17 to 38 cubic feet per second. This demonstrates the functionality or utility of the continuously measuring system at this site.

Is Lake Tahoe Terminal?
Robert Coats, Hydroikos Ltd., Jack Lewis, Retired, U.S. Forest Service, Pacific Southwest Research Station
Since 1980, the Lake Tahoe Interagency Monitoring Program (LTIMP) has measured discharge and sampled water quality at up to twenty stations in Tahoe basin streams. Measured constituents have included total and fine suspended sediment and various forms of nitrogen and phosphorus. To identify the best load calculation methods for estimating each constituent, we resampled synthetic data sets and part of the historic record. Synthetic data sets were generated using turbidity, discharge, and time of year as explanatory variables. In general regression methods were more accurate than interpolating methods for suspended sediment, fine sediment, and total phosphorus. Simple rating curve estimates of load were improved by including lagged discharge and/or day number as predictors. Improvement was the greatest when turbidity was available as a predictor. Interpolating methods were more accurate for total Kjeldahl nitrogen and dissolved constituents. The composite method, a hybrid of regression and interpolation, appears to improve upon interpolating methods and should improve upon regression when serial correlation is present in the residuals. Using the best models, we recalculated total annual loads for all constituents and stations over the period of record, removing known biases due to historic changes in sampling and laboratory methods to the extent possible. We regressed total loads against total annual and maximum daily discharge, and tested for time trends in the residuals. Significant long-term downward trends were identified in some constituent loads and streams.

Development of a WEPP online watershed interface to predict effects of watershed management on runoff, and sediment and phosphorus delivery in the Lake Tahoe Basin
Mariana Dobre1, Erin S. Brooks1, William J. Elliot2, James R. Frankenberger3, Roger Lew1
1) University of Idaho, 2) US FS Rocky Mountain Research Station, 3) USDA-ARS National Soil Erosion Research Laboratory
Forest and land managers need hydrologic models to evaluate the effects of different management practices on both water quantity and quality. Such tools exist, however, their applicability is limited by the user’s proficiency in using the models, availability of data for the interest region, and the time required to download the data and set up the necessary input files. We enhanced an online GIS interface to the process-based Water Erosion Prediction Project (WEPP) model with input files developed specifically for the Lake Tahoe Basin. To run simulations of surface runoff and erosion, users only need an internet connection and minimum information about the location of interest. The interface remotely accesses national databases to download USGS 30-m National Elevation Data, USGS topographical maps, USGS land cover and NRCS soil data specific for the study area, and uses additional data and algorithms stored on a server to automatically create all the model input files. Users can choose between hourly and daily historical and future climate files developed for eight major SNOTEL stations within the Basin. The model allows users to assess the long-term effects of forest management practices on runoff and erosion from specific hillslopes and at the watershed outlet. Consistent with the current efforts in the Basin to reduce phosphorus transport to the Lake, our recent improvements to the model have focused on enhancing the interface with a phosphorus component that allows users to evaluate the effect of forest managements on phosphorus delivery to the lake.

Montane peatlands (fens) as gauges for drought and climate change in California
Judith Z. Drexler (1); Justin Huntington (2), Rich Niswonger (3), and Lorraine Flint (1)
(1): US Geological Survey, California Water Science Center, Sacramento, CA; (2) Desert Research Institute, Reno, NV; and (3) US Geological Survey, Menlo Park, CA
Fens are montane peatlands, which store carbon and rely on steady groundwater discharge to persist in the landscape. Here we present two studies on fen sustainability. In the first, we studied five fens in the Sierra Nevada and two in the southern Cascade Range over 50-80 years using aerial photography and climate analysis. Over the study period, the Sierra fens decreased by 10-15% in area, but little change occurred in the Cascade fens. The climate analysis showed that Sierra fens are highly vulnerable to long-term increases in minimum air temperature and decreases in snowpack. Such changes resulted in decreases in groundwater discharge, which ultimately led to contraction of fen boundaries over time. In the second, we studied Landsat-derived normalized difference water index images (NDWI) for a subset of the same fens. NDWI is used to evaluate the liquid water content of vegetation and soil, with the common range being between -0.1 (lowest) to 0.4 (highest). We analyzed NDWI images acquired during July 1-August 30th from 1984-2015 for two Sierra fens and one Cascades fen. NDWI values were all negative from 2013-2015, indicating that the fens are responding to the current severe drought in California. In the Sierra fens, NDWI drought values were the lowest on record (as low as -0.1845), whereas in the Cascades fen, the NDWI drought values were among the ten lowest values (between 0 and -0.1400). These studies suggest that groundwater systems in the Sierra are more responsive to hydrologic changes, especially water shortage, than the groundwater systems of the Cascades. Initiation of studies along a fen network could provide rare insights into the impact of drought and climate change in California.

Nitrogenous air pollutants and atmospheric nitrogen deposition in the Lake Tahoe Basin
Mark Fenn1, Andrzej Bytnerowicz1, James Sickman2, Michael Bell3
1USDA Forest Service, Pacific Southwest Research Station, Riverside, CA; 2University of California, Riverside, CA; 3National Park Service, Denver, CO
Nitric oxide (NO), nitrogen dioxide (NO2), ammonia (NH3), and nitric acid (HNO3) were measured with passive samplers on a network of 34 sites in the Lake Tahoe Basin in summer 2010. NH3 and NO dominated, comprising 38.2 and 35.4% of total reactive N gases, respectively. Highest NH3 concentrations were west of the Basin on the Sierra Nevada slopes indicating the effects of pollution sources in the California Central Valley. However, local NH3 emissions contributed to elevated NH3 on the southwestern side of the Basin. The highest concentrations of total reactive N gases were measured near the western shore of the Lake indicating effects of local motor vehicle emissions. On a subset of 10 sites (megasites) N deposition was measured with ion exchange resin collectors. Nitrogen deposition in throughfall was low (1-2 kg/ha/yr) on the northern and western sides of the Lake, but was moderately elevated (> 5 kg/ha/yr) on its southern and eastern sides. Throughfall deposition of NH4-N was 60% greater than deposition of NO3-N indicating the importance of reduced forms of N. Nitrogen concentrations in lichen tissue were above the ‘clean-site threshold’ at 5 megasites and throughfall N deposition at 3 megasites was above the critical load at which epiphytic lichen communities become dominated by eutrophic species. Values for δ15NO3 in bulk deposition and throughfall samples were more enriched along the south and southeastern portions of the Basin where deposition is also highest likely due to NOx emissions from motor vehicles in the urbanized regions surrounding South Lake Tahoe.

What is the Future of the Sensitive Plant, the Tahoe Star Draba?
Gail Ferrell, Truckee Meadows Community College
The sensitive plant, Tahoe Star draba, is found only in the greater area of the Lake region in Nevada and California. The viability of this species depends on healthy populations in the Lake Tahoe and Mt. Rose regions. At this time, conservation plans are not required for such plants, but would potentially help to eliminate habitat degradation and physical injury to sensitive plants.
The management of sensitive plants on Forest Service lands is codified by the National Forest Management Act of 1976. Recent changes in requirements to winter recreation management on federally managed forest service lands have the potential to improve protection and minimize impacts to sensitive species. While only scant research has been done on the effects of winter recreation on the sensitive plant Tahoe Star draba, the need exists for more research to address impacts by winter recreationists on sensitive plants, particularly outside ski resorts.

Due to a March 29, 2013 United States District of Idaho Court ruling, the United States Forest Service must manage and account for impacts by snowmobiles on Forest Service lands. One result is an opportunity for change in winter forest management of sensitive plants.
A new Winter Travel Management Plan is currently in process in the Lake Tahoe Basin Management Unit of the United States Forest Service: a process that should take a minimum of three years to complete. Will there be additional safeguards for the sensitive plant, Tahoe Star draba, at the conclusion of this Winter Travel Management Plan?

Winter Travel Management on Six forests including the Lake Tahoe Basin Management Unit
Gail Ferrell, Truckee Meadows Community College
A fundamental change in travel management planning for winter recreation is now taking place in our national forest units. This change is the result of a March 29, 2013 United States District of Idaho Court ruling that required the United States Forest Service to manage and account for impacts by snowmobile use. The ruling eliminated what had been an exemption for the analysis of the impacts of snowmobiles in the 2005 Travel Management Rule by the United States Forest Service.
In addition to the 2013 court ruling, Snowlands Network, et. al. settled out of court with the United States Forest Service (USFS) in a lawsuit that required the USFS to analyze impacts, including social and environmental, of motorized, snowmobile use on the environment and other forest visitors, namely skiers, snowshoers and family snowplayers. The result is now taking place on six forests in Nevada and California. The process is referred to as Winter Travel Management and is taking place on the Tahoe, Stanislaus, Eldorado, Plumas, Lassen and the Lake Tahoe Basin Management Unit of the USFS.
The Winter Travel Management process is an involved and lengthy process involving the many stakeholders of winter recreation on public lands. At the conclusion of the multi-year planning process, a set of guidelines, rules and restrictions will be in effect for 20 years on each respective forest that guide winter recreation on each of the respective forests.
Note: Dr. Gail Ferrell is on the Board of Directors of Snowlands Network

Rosewood Creek Restoration, Area A
Brian Fitzgerald1, Meghan Kelly2, Domi Fellers2, Rick Susfalk1
1) Desert Research Institute, 2) Nevada Tahoe Conservation District

Rosewood Creek is a small, urban creek in the northeastern part of the Lake Tahoe Basin. In a mid-elevation section of the creek, a deep head cut was previously found to have steeply incised banks characterized with lower than average bank stabilization above Highway 28. In an effort to improve the sensitive environmental zone and mitigate suspended sediment and nutrient delivery into Third Creek and ultimately into Lake Tahoe, the Rosewood Creek project to restore Area A was constructed during the summer of 2013. The new construction was allowed to stabilize for approximately one year, in order to minimize sediment mobilization before water was diverted to the new channel. The overall objectives of this research were to utilize pre-construction monitoring to assess the impact of Rosewood Creek suspended sediment and nutrient delivery out of the restoration area, and to quantify the ability of the restoration project to alter the mass and particle-size distribution of suspended sediment after construction. In-situ monitoring was conducted between November 2010 and July 2015. Data collected at each site included continuous measurements of water discharge, turbidity, specific conductivity, and water temperature. Discrete water samples were collected by an automated vacuum sampler and were analyzed for total suspended solids (TSS), particle-size distribution, and nitrogen and phosphorus species. Particle-size distribution was used to assess the relative importance of suspended sediment loading as finer-sized particles remain entrained in stream flow and suspended in the nearshore regions of Lake Tahoe for a longer period of time, and are more likely to adsorb nutrients on their surface, compared to coarser-sized particles.

Evaporation Estimates for Lake Tahoe: Review, Challenges, and Future Opportunities
Justin Huntington1, Chris Pearson1, Dan McEvoy1, Simon Hook2, Geoff Schladow3, Tom Mathis3
1) Desert Research Institute, 2) NASA/JPL, 3) UC Davis
Evaporation from Lake Tahoe is the largest outflow component of the water budget. Average annual evaporation estimates from past studies range from ~ 2 to 4 feet per year. Given that Lake Tahoe has a small storage depth (six feet per year) relative to the depth of evaporation, better understanding the range of evaporation for historical periods is important for current operations as well as predicting lake stage under changing climate. This presentation provides a review of previously published evaporation estimates and respective methods, highlight challenges associated with each method, and focuses on future opportunities for operational estimation using a combination of in-situ and modeled hydrometeorological data, and satellite based surface temperature observations.

Sources of fine suspended particles (< 20 µm) in stormwater runoff from the Lake Tahoe Basin
Hyun-Min Hwang, Matthew Fiala, Ralph Townsend, Russell Wigart
1) Texas Southern University, Houston, TX, 2) Tahoe Environmental Research Center, Incline Village, NV, 3) El Dorado County, CA
Urban runoff is a primary vector that delivers fine suspended particles into Lake Tahoe. To mitigate water clarity decline, major sources fine particles and their contributions need to be assessed more accurately. Sources of fine suspended particles stormwater and snowmelt runoff collected in the Lake Tahoe Basin were identified and apportioned using source-specific compounds and a chemical mass balance model. Time-series stormwater and snowmelt runoff samples were collected from two traffic roads (Pioneer Road and Cattleman Road) using autosamplers between 2012 and 2014. The amount of fine suspended particles was typically peaked in the first flush and declined exponentially. It indicates that if the first flush can be separated from the rest of the runoff, size of treatment facility can be minimized that helps reduce management costs. Fine suspended particles were separated using a 20 µm sieve and analyzed for elements and organic markers using ICP-MS and GC-MS, respectively. Chemical mass balance model showed that soil from nearby surface areas is a primary source (up to 62 %). Organic marker distribution patterns in the samples from these two sites with asphalt pavement were very different from those in samples from concrete pavement, indicating the presence of asphalt pavement wear particles. Wear particles of asphalt pavement account for up to 20% of fine suspended particles. The contribution of traction sand was less than 15% in all samples that is much lower than expected. This study provides a critical dataset required to develop more efficient winter time road management practices.

Comparison of Role and Effects of ‘Animal Engineers,’ beavers and elephants, in broadly different ecosystems
Charles Levitan1, Alan Gardiner2, Montana Schwarz2, and Caden Goss1
1) Sierra Nevada College, Incline Village, NV, USA, 2) Southern Africa Wildlife College, Hoedspruit, South Africa
Animals may have roles beyond membership in energetic pathways or even trophic cascades. As ecosystem engineers, they may fundamentally change the physical form of an ecosystem, enabling the addition of an entirely new ecological community to the ecosystem. In this study we compare ecosystem engineering by the African elephant (Loxodonta africana) and the North American Beaver (Castor canadensis). Elephants southwest of Kruger Park, in the Lowveld of Mpumalanga, South Africa, have begun damaging vegetation recently, perhaps due to increased populations and restricted migratory impetus. Our vegetation census shows they have selectively predated an iconic emergent tree, the Marula (Sclerocarya birrea), a habitat for many raptors. Damage was spatially clustered as shown by Gi-Bin autocorrelation and Getis-Ord General G and Moran’s. Damage type was distinct among tree species (Fig. 3; Χ2 = 96, p<0.001), For example, only Marula and Terminalia were uprooted. There was no preference for Marula bark by diameter, but there was a decided absence of young Marula, which indicates they may be uprooted and dispersed. Beaver habitat preference the North Lake Tahoe area, in the Incline and Third Creek watersheds, was not strongly dictated by topography, but the horizontal extent of tree harvest was negatively correlated with valley incision. Tree selectivity was high among all trees, but low among deciduous trees. Extent of damage was anecdotally associated with the season of animal activity; beavers were noted to travel and carry trees over longer distances on snow-covered slopes. We conclude that animal engineers’ effects are guided by their idiosyncratic dietary preferences, with the actual engineering dependent on their food species’ ecological role.

On the Fens: Monitoring the Effects of Livestock Use in Northern Sierra Nevada Fens
Scott Markwith (1,2), Kyle Merriam (2), Michelle Coppoletta (2)
1) Florida Atlantic University, Department of Geosciences, Boca Raton, FL, 2) USDA Forest Service, Sierra Cascade Province, Quincy, CA
Fens are an unusual wetland type that accumulates organic material as peat and supports many rare wetland plant species of management interest. However, these systems have only recently been documented in many areas of the Sierra Nevada. Following an inventory and condition assessment of these unique wetlands on the Plumas National Forest, resource specialists found that many fens are currently being grazed by livestock even though there is relatively little information about the effects of livestock use on these wetland ecosystems. To evaluate the effect of livestock use on fens, a monitoring program was established in 2007 in fenced and unfenced fens on the Beckwourth Ranger District in the Old House and Woodsy meadows. Each meadow includes two fens, one fenced to exclude grazing and one nearby fen subject to grazing, for a total of four sampled fens. Both the Old House and Woodsy meadows fenced and grazed monitoring pairs include pre-treatment (i.e. prior to exclusion of grazing), and one, three, and five years post treatment monitoring. The monitoring was conducted in accordance with methods developed for the USDA Forest Service Pacific Southwest Region meadow monitoring program, and consists of 125 10-cm x 10-cm frequency frames per fen along 25-m transects. The analysis found variation in species, functional group, and ground cover measures with livestock use within fens.

Western Pearlshell Mussel (Margaritifera falcata) Pilot Relocation Monitoring
Erin Miller, Shana Gross, U.S. Forest Service, Pacific Southwest Region
The western pearlshell (Margaritifera falcata) is a freshwater mussel that inhabits cold creeks and rivers with clean water and host salmonids in the Western US. These mussels have an average lifespan of 60 to 70 years. Many historic populations have been drastically reduced in size from dense beds to a few isolated individuals. Threats to populations of this species include anthropogenic impacts on watersheds including, channel modification, introduction of exotic species, and the decline of host fish. The only known historic populations that are persisting in the Lake Tahoe Basin are found in the Upper Truckee River (UTR) and the Truckee River. Reach 5 of the UTR Restoration Project will dewater and fill in a 7,400 foot reach that currently contains about 11,500 individuals of M. falcata. A pilot relocation effort was initiated in 2014 that relocated 927 mussels into 37 plots in seven reaches. The objective of the pilot work was to identify suitable relocation methods and site habitat characteristics that will successfully support the translocation of mussels to be relocated from Reach 5 in 2015 and 2016. Success has varied by plot within reaches, however all sites had a large number of plots with ≥75% mussels remaining. Larger mussels had a higher probability of being found in subsequent monitoring. Eighty-two percent of the relocated tagged mussels increased in weight and 29% increased in length between fall of 2014 and spring of 2015. Of the mussels that increased in weight, 33% increased in length and 51% decreased in length.

Optical Properties of Aerosols from Smoldering Laboratory Combustion of Wildland Fuels
Joshua Molzan, Nicholas D. Beres, Adam C. Watts, Vera Samburova, Hans Moosmüller
Desert Research Institute, University of Nevada-Reno
During combustion, gases and particles, called aerosols, are formed and emitted. Dominant categories of emitted aerosol are black carbon (BC) and organic carbon (OC). BC is strongly light-absorbing and OC may contain light-absorbing components, which are known as brown carbon (BrC). Aerosol light absorption in the solar spectral region (300 nm – 2300 nm) is key for understanding the direct aerosol radiative forcing (that is, do aerosols make the earth look darker (heating) or whiter (cooling)?) caused by carbonaceous aerosol, which is largely determined by three parameters: aerosol single scattering albedo (SSA), asymmetry parameter, and the albedo of the underlying surface. Optical properties of BrC from biomass combustion are not well known. It is therefore necessary to investigate the optical properties of carbonaceous particles from combustion of fuels found globally, including from the drought-stricken and fire-prone Western United States.

Here, we describe a project to aid the development, tuning, and verification of satellite SSA retrievals to better characterize biomass burning aerosol properties, sources, radiative forcing, and photochemistry, and to improve understanding of their impact on air quality. We will utilize Desert Research Institute’s Biomass Combustion Chamber to generate aerosols from different wildland fuels, including those found in the Western United States. Coupled to sensing instrumentation – such as an integrating nephelometer to measure aerosol light scattering, a photoacoustic instrument to measure aerosol light absorption, and various other instruments – we will be able to increase the qualitative and quantitative understanding of radiative forcing and satellite retrievals of absorbing carbonaceous aerosols.

Long-Term Fuels Accumulations Following Mechanized Thinning and Prescribed Fire: Implications for the Lake Tahoe Basin
Shannon L. Swim, Roger F. Walker, Dale W. Johnson, Robert M. Fecko, Watkins W. Miller
Department of Natural Resources and Environmental Science, University of Nevada, Reno, Nevada
Forest thinnings implemented through cut-to-length and whole-tree harvesting followed by underburning were evaluated for their long-term influences on downed and dead fuels accumulations in pure, uneven-aged Jeffrey pine (Pinus jeffreyi Grev. & Balf.). Fuel loading was quantified as dry weight per unit area segregated by timelag categories, specifically 1+10-hr, 100-hr, and 1000-hr size classes, plus the total across categories augmented with measurements of fuel bed depth. Immediately following treatment implementation, every fuels measure was lower in the burned stand portions except for the 1000-hr fuels within the whole-tree burned combination, indicating a rapid onset of new fuels deposition following prescription fire in this stand portion, which contained somewhat smaller trees than those in the remaining acreage. A linkage between initial mortality attributable to the prescribed fire and final 1000-hr fuels was established but also reflected a cumulative effect of both the thinning and fire treatments. Over the course of the study, diminished decomposition coupled with elevated litterfall in the 1+10-hr and 100-hr timelag categories led to either smaller reductions or greater increases in all fuels measures in the burned stand portions and most notably so in the whole-tree burned combination, which was the only treatment combination to incur an increase in total fuels. These findings advance the understanding of the likely long-term impacts of density management and prescription fire on post-treatment fuels accumulations in Jeffrey pine and similar dry site forest cover types.

Cold Desert Vegetation Response over 35,000 Years of Climate Change
Robin J. Tausch1, Robert S. Nowak2, and Cheryl L. Nowak2
1) Emeritus Scientist, US Forest Service Great Basin Ecology Laboratory, Reno NV 89521
2) Department of Natural Resources & Environmental Sciences, University of Nevada Reno
We used the functional plant type richness for trees, shrubs, grasses, and forbs from 154 plant taxa for the analysis of 52 fossil woodrat midden strata from a western Great Basin study area. These strata spanned an 800 m elevation gradient and the last 35,000 years. Functional plant type richness was relatively stable in each of four time periods (vegetation states). Significant changes in functional plant type richness occurred during the transitions between time periods. These vegetation transitions at 26.0 kCY, 15.0 kCY, and at 8.0 kCY also coincided with transitions in climate between recognized major climate periods. The states of relative stable taxa richness, and the significant transitions between them, represent a form of long-term state and transition model of the vegetation change in the western Great Basin over the last 35,000 years. There is also a predominant unidirectional trend of increasing aridity over the last 15,000 years that has preferentially decreased the richness of forbs compared to shrubs, increasing the importance of shrubs over time. Periods of colder climate represented a hiatus in forb loss, rather than a reversal of the trend of increasing aridity. Climate warming expected over the rest of this century will continue to favor woody vegetation over herbaceous species, at least until invasive species displace shrub species following wildfire. The decreasing richness of herbaceous species, particularly the reduction in forbs at the 8.0 kCY transition, may have provided opportunities for these invasive species to establish in the Great Basin during the last century.

Tracking the water cycle with real world data around Incline Creek watershed
Aaron Vanderpool, Andy Root, Sierra Nevada College
Water evaporates, condenses, and falls as precipitate in a continuous cycle. In our Sierra Nevada College hydrology class, 301/305 2015, we learned about each stage of the water cycle and how to quantify and relate it into real world situations. We also learned water management, western US water law, and the impact humans have on water resources. We deployed a weather station and sensors around the sub-watersheds of the Incline Creek watershed. For our final project, we put everything together into hydrological models in an attempt to simulate actual conditions.

Responsible Winter Management Strategies and its Effect on Water Quality and Permit Compliance at Lake Tahoe
Russell Wigart, Brendan Ferry, County of El Dorado
Annual and Seasonal Fluxes of Particulate Matter from Atmospheric Deposition to Lake Tahoe: Assessment from a Long-Term Passive Monitoring ProgramThe County of El Dorado (County) believes they have found through research the golden ticket to improve stormwater quality and help save Lake Tahoe clarity. The County has been leading the Lake Tahoe Basin in the advancement of Winter Management Strategies in the effort to protect the famed clarity of Lake Tahoe for many years. Lake Tahoe has a Total Maximum Daily Load (TMDL) for Fine Sediment Particles (FSP) less than 16 microns in diameter and is designated as an Outstanding National Resource Water. The County has been researching effective means to reduce sediment particles and believes it has identified simple cost effective measures to meet restoration objectives aimed at improving Lake Tahoe’s renowned clarity. This presentation will focus on the science and process used to change winter sand (abrasive) specifications for public safety and its evolution from a very “dirty” source to one that is environmentally responsible with much less pollutants of concern. The presentation will also discuss the reasoning and rationale behind FSP source control as a means to cost effectively reduce critical pollutant loading to Lake Tahoe and methods that can be implemented to control these such as sweeping, sanding and anti-icing. This presentation will focus on advanced winter management strategies, public safety enhancement, pollutant source control, cost effective load reduction opportunities, and technological advancements including road sanding and sweeping operations. Science behind particle size distribution (PSD) and comparisons between abrasives will also be discussed. For road systems it is imperative that simple yet highly effective solutions be implemented in order to meet the needs of this dynamic and changing environment. The County believes these modifications are the most effective means.

Annual and Seasonal Fluxes of Particulate Matter from Atmospheric Deposition to Lake Tahoe: Assessment from a Long-Term Passive Monitoring Program
Anna Ya-Chun Tai, L.-W. Antony Chen, Xiaoliang Wang, Alan C. Heyvaert, Heather Holmes, Joseph Knue, and Mi Zhang
Desert Research Institute, University of Nevada, Reno
Concerns have been raised about the declining water clarity at Lake Tahoe over the past few decades due to nutrient and sediment particle inputs. Contributions from atmospheric deposition of particulate matter (PM) have been suggested to be substantial, yet inadequately quantified. This study established three long-term monitoring sites (July 2013 – August 2014) to measure 24-hr, size-resolved dry and wet PM deposition in near-shore, offshore-background, and upper watershed conditions in the Lake Tahoe Basin. The objectives are to: 1) investigate spatiotemporal variations of PM deposition flux, 2) obtain deposition velocity using mass deposition flux and PM concentration measurements, and 3) estimate annual number deposition flux (NDF) via dry and wet processes. Dry deposition was quantified on passive substrates using a scanning electron microscope, while wet deposition was analyzed by laser diffraction spectroscopy. The results show higher NDF_dry and greater monthly variability at the near-shore than the offshore and upper-watershed sites, suggesting substantial impacts of nearby beach, traffic, and construction activities. Seasonal NDF_dry and NDF_wet (1–20 µm) were consistent across all three monitoring sites, characterized by higher NDF_dry in fall, winter and summer but higher NDF_wet in spring when precipitation occurred more frequently. The annual NDF_dry+wet is, estimated between 4.31×10^19 and 8.61×10^19 particles/year, in the same order of magnitude with a previous estimate of 7.4×10^19 (<16 µm) particles/year by the Lake Tahoe Total Maximum Daily Load (TMDL) using an independent approach. Comparison of the NDF_dry with conventional eddy correlation measurements was also examined through short-term collocated monitoring.