Thursday, November 14
1:30 pm – 3:00 pm
Agenda subject to change.
Updated 7 November 2019
★ Denotes that the lead author is a student.
Moderator: Kiyoko Yokota
SUNY Oneonta, Oneonta, New York
|1:35||So You Want to Deploy a Lake Monitoring Buoy: Essential Considerations for Successful High Resolution Data Collection
Kiyoko Yokota1, Paul H. Lord1, and Sarah Coney2
1Biology Department & Biological Field Station, State University of New York College at Oneonta, Oneonta, New York; 2State University of New York College at Oneonta, Oneonta, New York
Continuous lake monitoring buoys, or lake data buoys, once mainly developed and used by academic researchers, are gaining popularity within the greater lake management community, including such stakeholders as municipal utility operators and individual lake associations. In addition to these stand-alone, site-specific buoy-based monitoring programs, regional lake monitoring networks are rapidly expanding their capabilities with automated sensors and loggers connected to buoys. These networks and stand-alone systems are converging with each other with standardized protocols. We will present an overview of various types of buoy-based lake monitoring equipment. A three-year case study from Otsego Lake, a glacial mesotrophic lake (maximum depth ≈ 51 m or 168 ft) in Central New York State, will be discussed as an example of a relatively deep-water deployment that requires winterization in fall and re-deployment in spring.
|1:55||Collecting “More and Better Data” on a Low-Power Budget – Hybridizing Technologies to Maximize Measurement Frequency and Analytic Capabilities at the Edge of Environmental Sensor Networks
Michael R. Kelly, Vincent W. Moriarty, Eli M. Dow, John Ma, and Harry R. Kolar
IBM Research, Albany, New York
Effective real-time environmental monitoring depends on having sufficient data (quantity and quality) and being able to autonomously analyze that data in the field to detect exceptional conditions. Such systems may use the results of these analyses to improve the future collection of data and possibly for alerting water managers or scientists of such conditions. The current state of the art in environmental measurement considers recording measurements at 15-minute intervals “high-frequency”. While this frequency of measurement indeed provides insights beyond what monthly, daily, or even hourly measurements may provide in what are often dynamic natural systems, it remains insufficient for effectively characterizing ephemeral or otherwise rapidly changing aspects of these systems, for example, the emergence and dissipation of harmful algal blooms (HABs). For decades, dataloggers have been utilized for reliable, accurate, and low-power environmental data measurement and collection. However, their storage and analytical capabilities have typically restricted their usage to data logging and rudimentary analyses of the collected data. While higher functionality computing systems can be used to collect significantly more data and efficiently process and analyze that data in very sophisticated ways, these systems generally consume significantly more electrical power than dataloggers. We will present a method of combining these two technologies to exploit the best attributes of each system. Examples from the Jefferson Project at Lake George will be shown whereby such low-power solutions have been employed to achieve both large, high-quality data set collection and sophisticated autonomous analytical capabilities, in the field.
|2:15||Assessing Change in the Overturning Behavior of the Laurentian Great Lakes Using Remotely Sensed Lake Surface Water Temperatures
Cédric Fichot1, Katsumi Matsumoto2, Benjamin Holt3, Michelle Gierach3, and Kathy Tokos2
1Department of Earth and Environment, Boston University, Boston, Massachusetts; 2Department of Earth Sciences, University of Minnesota, Minneapolis, Minnesota; 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California
The region of the Laurentian Great Lakes has experienced significant atmospheric warming over the past decades, and lake surface water temperatures (LSWT) have been shown to respond to this regional change in climate. Questions remain, however, as to how climate-driven changes in LSWT might affect the overturning behavior of these lakes. Situated in the mid-latitudes, the five Laurentian Great Lakes (Superior, Huron, Michigan, Ontario, Erie) all experience complete overturning in the spring and fall as lake temperature moves past the 4 °C threshold, the temperature of maximum density for freshwater. It is well known that overturning does not happen everywhere all at once and generally starts along the shallow margins and progresses offshore. Nonetheless, the spatial and seasonal patterns of overturning in each lake remains poorly characterized and the inter-annual variability is largely unknown. Here, we used remotely sensed LSWT collected over the past two decades to assess the seasonal evolutions of the 4 °C surface isotherm, in an effort to better characterize and understand the overturning timing and behavior of these lakes (spring and fall), and to identify any potential long-term changes. The results revealed important differences in overturning timing and behavior between the five lakes seasons and years, and point toward significant climate-driven changes in Lake Michigan and Ontario.
|2:35||Linking Land to Water – Development of the NHDPlus High Resolution and Applications to Estimate Streamflow, Habitat Characteristics, and Water Quality
Stephen S. Aichele
US Geological Survey, New Cumberland, Pennsylvania
The US Geological Survey maintains, in cooperation with States and other Federal agencies, the National Hydrography Dataset (NHD), the Watershed Boundary Dataset (WBD), and data from the 3D Elevation Program (3DEP). Since 2004, the USGS has collaborated with the EPA to produce the NHDPlus, a product integrating these three datasets into a single catchment-based representation of the landscape to link the characteristics of the contributing watersheds to bodies of surface water. Until recently, NHDPlus was only available at the 1:100,000 scale, dividing the conterminous US into approximately 2.7 million catchments. The NHDPlus High Resolution (NHDPlus HR), which is nearly complete for the conterminous US and under development in Alaska, is being generated from the best available data, including the NHD at 1:24,000 scale and elevation data derived from lidar where available. The NHDPlus HR will provide substantially more discretization than the previous product.
This presentation will review development of the NHDPlus HR and associated pre-computed catchment characteristics, as well as some key differences between the two NHDPlus products. The balance of the presentation will describe applications of the dataset to modeling and prediction with an emphasis on streamflow, water quality, temperature, and aquatic habitat.
Moderator: Kirsten Nelson
New Hampshire Department of Environmental Services, Concord, New Hampshire
|1:35||Lake Iron Nodules – An “Index Mineral” to Assess the Impact of Sulfate on Surface Water and Sediment Quality Over Time (Pre-1800s to Today) in New England Lakes, Ponds and Rivers
Higgins Environmental Associates, Inc., Amesbury, Massachusetts
Prior to the 1800s, bog and lake iron nodules were widespread in freshwater lakes, ponds and rivers of New England. The purpose of my research and field assessments was to establish what happened to this once abundant iron mineral resource in New England.
My research included review of pre-1800s historical records and mining surveys and more recent published literature on lake iron nodule formation.
Field work that I have completed since 2010 has documented that the current occurrence and spatial extent of lake iron nodules is more limited than the historic, pre-1800s range.
This difference in occurrence over time correlates well spatially with mapped wet and dry deposition areas for sulfates and nitrates (a.k.a. “acid rain”) in New England. My findings indicate that sulfate impacts to New England’s fresh water and sediments would have a stronger negative impact on the natural biogeochemical cycling of iron and formation of lake iron nodules. While atmospheric sulfate impacts to surface waters has decreased and dissolved organic carbon content and “browning” of fresh water continues to increase, historical sulfate impacts to sediments and other point and nonpoint sources of sulfate impacts to water quality remain in urbanized areas of New England.
In conclusion, through historical research, field assessment and published literature reviews, I am proposing that lake iron nodules in New England have sufficient characteristics to serve as an “index mineral” to evaluate the impact of sulfate on the quality of surface water and sediment over time (pre-1800s to today) in New England.
|1:55||D.O.D. – The Dynamics of Dredging
Aquacleaner Environmental, Buffalo New York
When one first hears the word “Dredging” many cringe, believing it’s a nasty eight letter word, due in part to the perceived stigma that some associate with the process. In addition, people anguish having to navigate the various governmental agencies they’ll have to work with, just to see a project through to fruition.
Initially conceived to facilitate the deepening of waterways for commercial & recreational boating, its benefits have evolved to include the suppression of IAS & the reclamation of shorelines.
On the administrative side, there is a vast amount of negativity and nervousness associated with obtaining a dredging permit from the appropriate jurisdictional agencies because the information they require is often viewed as tenuous and confusing. Some in the scientific community have concerns relative to this activity due in part to the types of disruption both in the water and upland they envision.
This presentation will discuss the dynamics of dredging including:
Moderator: Dick Osgood
Lake Advocates, Duluth, Minnesota
|1:35||Using Aluminum Chlorohydrate (ACH) as a Demonstration Project to Treat an 8 Acre Eutrophic Stormwater Pond in Verona, Wisconsin
Marty Cieslik1, Richard Wedepohl2, Dave Marshall3, Harvey Harper4 and Kevin Connors5
1City of Verona, Wisconsin; 2Lake Management Consultants, Madison, Wisconsin; 3Underwater Habitat, Daleyville, Wisconsin; 4ERD, Orlando, Florida; 5Dane County Land Conservation Director (Retired), Madison, Wisconsin
An 8.3-acre stormwater management pond built in 2004 for the Verona Technology Park has become an integral part of Wisconsin Brewing grounds. Consistent algae blooms are a concern for this dog friendly local brewery limiting the ponds use due to poor water quality and potential liability issues associated with Cyanobacteria toxins. Emphasis on meeting TMDLs in the Madison Lakes region lead to this project demonstrating the use of aluminum compounds to enhance phosphorus reduction goals. Alum (4.4% aluminum) was originally intended to be used, but some logistical problems, along with the inability to put in desired levels due to low alkalinity for a one-time treatment, lead us to use Aluminum Chlorohydrate (12.4% aluminum). This allowed us to apply 22 mg Al/L without concern for pH depression since this product is highly hydrolyzed and produces floc which is further along the aging process. Floc formation was quick, and part of the pond was then covered with floating floc that broke down over a couple of days. A small number of fathead minnows were found dead, having been caught in the more “sticky” ACH floc which raised some concern although the numbers were minimal. Given new EPA standards on aluminum and new state regulations on use of use of additives in stormwater ponds, there were some concerns that needed to be addressed to allow use of this product.
|1:55||Aqual – P®: A Nutrient Inactivation Technology for PO43- and NH4-N
Vertex Water Features Inc., Pompano Beach, Florida
Aqual-P® is an aluminum modified zeolite (natural clay product) that contains alkaline-earth metals in its structural framework. Zeolite has a natural affinity for NH4-N meaning that an application of Aqual-P® has the capacity to adsorb both soluble reactive phosphorus (SRP) and NH4-N. Aluminum salt is the active ingredient that binds to PO43- while the zeolite portion binds to NH4-N via “molecular sieving.” Applied as a fine grain powder in a slurry, the product settles relatively quickly to the lakebed where it can form a cohesive capping layer. Aqual-P® has been found to work under anoxic conditions and does not depress lake alkalinity and therefore, does not require a buffer. It has been subjected to testing for potential toxicity covering a wide range of expected sediment application rates. Aqual-P® has been used in the wastewater treatment industry for removing both PO43- and NH4-N; it has also been used to treat incoming stormwater (applied as a granular in porous sacks) and to reduce internal nutrient recycling. This presentation provides a literature overview of Aqua-P® and compares it to other nutrient inactivation technologies. It also will cover some field trials using Aqual-P® on a variety of stormwater ponds in the US.
|2:15||★ Improving Phosphate Adsorption to Prevent Freshwater Bodies Eutrophication Using a Circular Economy Approach
Carlo Belloni1, Raimonda Buliauskaitė2, Prashanth Kumar1, and Leon Korving1
1TU Delft RST/FAME and Wetsus, European Centre of Excellence for Sustainable Water Technology, Leeuwarden, Friesland, The Netherlands; 2Aquacare, ‘s-Hertogenbosch, Noord Brabant, The Netherlands
Removal of phosphate (oP) from freshwater bodies is an important part of the process to prevent eutrophication. Adsorption is a suitable method in terms of performances and economics. Iron oxide-based adsorbents represent in this sense a cheap option, with good affinity towards oP. Lot of studies have already been done on oP adsorption experiments with iron oxides-based adsorbents, often neglecting the regeneration of the medium and recovery of oP, which is a key point to make the process economically convenient. Two different iron oxide-based systems for oP recovery have been applied in eutrophicated marsh water as part of the third stage of the George Barley Water Prize in Canada. These systems treated up to 32 m3/day at low temperatures, managing to reach oP concentrations below 20 ppb, while recovering a pure oP product that satisfies fertilizers requirements for 100–200 $/kg. Difficulties in regeneration affected to some extent the performances during the application. Both the fundamental research and applied experiences learn that important factors for future application are selectivity, regeneration of the adsorbent to make it reusable and recovery of the phosphate to prevent waste. The presentation will translate practical challenges to fundamental insight and show possibilities for further improvement such as adsorbent selection, surface modification and improved regeneration procedures.
|2:35||Shoreline Stabilization and In-Lake Nutrient Management With Anionic Polyacrylamide
Applied Polymer Systems, Woodstock, Georgia
Sediment, nutrients, and other particulate matter can enter our water resources through erosion, stormwater, agricultural runoff, construction, mining, and other land disturbing activities. Fine particulates are a point of attachment for nutrients and contaminants such bacteria, metals, pesticides, and endocrine disruptors. Turbidity resulting from particulate matter and associated contaminants can have detrimental environmental effects on receiving waters causing ecological, economic, and human health related problems.
Anionic polyacrylamides (PAMs) have been used since the 1950s to safely treat drinking water and prevent soil erosion. This versatile, environmentally safe material flocculates a wide range of dissolved and particulate matter from sediment and inorganic nutrients, to metals and bacteria. In the past decade, these materials have been utilized as a stormwater management tool to either prevent harmful particulate from entering stormwater, or to remove it once it has entered the water. Anionic PAMs have proven highly effective in erosion control and water treatment applications and using polymer enhancement in conjunction with other stormwater best management practices (BMPs) has resulted in 75–85% reductions in inanimate phosphorus as well as > 95% reductions in total suspended solids (TSS) and NTUs. This presentation will focus on anionic polyacrylamide applications for preventing contaminants from entering water bodies as well removing turbidity and phosphorus from ponds and lakes.
Moderator: Euan Reavie
University of Minnesota Duluth, Duluth, Minnesota
|1:35||★ Sedimentological and Limnological Evolution of a Recreative Lake Located in a Former Asbestos Mining Region: Insights From Paleolimnology
Olivier Jacques1,2 and Reinhard Pienitz1,2,3
1Département de Géographie, Université Laval, Québec, Québec, Canada; 2CentrEau, Quebec Water Research Centre, Université Laval, Québec, Québec, Canada; 3Centre for Northern Studies (CEN), Université Laval, Québec, Québec, Canada
The Bécancour River basin in southern Quebec (Canada) has been impacted by more than a hundred years of asbestos mining activities in the Thetford Mines region. Several recreative water bodies located downstream from the city are suffering from high sediment loads and eutrophication. In order to allow an efficient management of the lakes, we completed paleolimnological investigations to evaluate the extent of their deterioration and identify catchment disturbances that influenced their present-day condition. Here we present the results of a multi-proxy study of a sediment core collected from Lac à la Truite. The sedimentary record from this lake indicated severe perturbations associated with the complete draining of Lac Noir, a former lake of Thetford Mines excavated for mining purposes between 1955–1959. Radiometric 210Pb dating revealed an extreme increase in the sediment accumulation rate following this event. Analyses of loss-on-ignition, carbon (C) and nitrogen (N) content, grain-size, and X-ray microfluorescence indicated that the post-1960 sediments were enriched in fine-grained mineral matter and had higher metal concentrations as compared to older sediments at the bottom of the core. Changes in the δ13C and C/N ratios and the predominance of diatom taxa (class Bacillariophyceae) typical of nutrient-rich waters (e.g., Cyclostephanos invisitatus, Cyclotella meneghiniana) also showed that the 1955–1959 event lead to a rapid eutrophication of the lake. Results from our study illustrate that the asbestos mining activities had dramatic impacts on Lac à la Truite and suggest that major restoration efforts will be needed to improve its ecological condition.
|1:55||★ Establishing the Timing of Stable Pb Deposition in Maritime-Canadian Lakes
Dewey W. Dunnington1, Ian S. Spooner2, Joshua Kurek3, Chris E. White4, and Graham A. Gagnon1
1Centre for Water Resources Studies, Department of Civil & Resource Engineering, Dalhousie University, Halifax, Nova Scotia, Canada; 2Department of Earth & Environmental Science, Acadia University, Wolfville, Nova Scotia, Canada; 3Department of Geography and Environment, Mount Allison University, Sackville, New Brunswick, Canada; 4Nova Scotia Department of Energy and Mines, Halifax, Nova Scotia, Canada
Establishing age-depth models for lake sediment cores is essential to determine the causal relationships that form the basis of many paleolimnological investigations critical to lake management. 210Pb dating is an essential tool to establish recent (< 150 years) lake sediment age-depth models, however the cost, interpretability, and turnaround time required to measure 210Pb in lake sediments is often a barrier to the inclusion of paleolimnological data in lake management studies. Stable Pb is present in measurable concentrations in many lake sediments, is rapidly and cost-effectively measured, and often follows a regional pattern of increase following aerial deposition of particulates from industrial development. To establish the degree to which stable Pb can be used as a reliable stratigraphic marker in lake sediments, we measured stable Pb concentrations in 20 210Pb-dated sediment cores in Quebec, New Brunswick, and Nova Scotia, Canada, using X-Ray Fluorescence Spectroscopy. Pb concentrations ranged from non-detect (~2 ppm) to 250 ppm, with a substantial increase observed between 1900 and 1930. Peak lead concentration dates were variable, but generally occurred between 1970 and 1990. Lakes with an earlier rise in stable Pb concentration tended to have historical coal-fired activity nearby (within 5 km), and one lake had Pb mining within the catchment, which led to a Pb concentration controlled by watershed disturbance. For most lakes, the timing of the initial increase was within the range of 210Pb age-depth model error, suggesting that this marker could be used to construct or validate age-depth models in recent lake sediments.
|2:15||The Impacts of Acid Deposition and Landscape Re-greening on Organic Carbon Stocks in Sudbury, Ontario Lakes Over the Last ~200 Years: Evidence From Paleolimnology
Carsten Meyer-Jacob1, Andrew M. Paterson2, Andrew L. Labaj1, and John P. Smol1
1Paleoecological Environment Assessment and Research Lab, Department of Biology, Queen’s University, Kingston, Ontario, Canada; 2Dorset Environmental Science Centre, Ontario Ministry of the Environment, Conservation and Parks, Dorset, Ontario, Canada
Metal mining and smelting operations have dramatically altered the landscape near Sudbury, Ontario, since the discovery of nickel-copper sulfides in the Sudbury Basin in the late-1800s. Over decades, very high sulphur dioxide emissions caused lakes to acidify and damaged vegetation near smelters, resulting in severe soil erosion. However, emissions reductions and landscape-restoration efforts in the 1970s have shown positive results. For example, Sudbury lakes are recovering chemically, with dramatic increases in lake-water organic carbon (OC) levels (i.e., lake browning). Given the importance of organic carbon to the overall functioning of aquatic ecosystems, through its influence on physical and chemical properties of water, our study aims to: a) determine the specific influences of acid deposition, changes in vegetation cover (initial loss and recovery following restoration), and climate change on aquatic OC stocks (water column and sediment) in Sudbury lakes over the last ~200 years; and b) estimate the potential for additional OC storage through continuing restoration activities. Using elemental carbon analysis and sediment visible-near infrared spectroscopy, we measured changes in sediment OC burial and lake-water OC trends in eight Sudbury lakes over the last ~200 years. We report that lake-water OC concentrations declined by ~50% compared to pre-industrial levels during the 1900s. Following emissions reductions in the 1970s, OC concentrations started to slowly recover, but remained ~30% below pre-industrial values by the 2000s. Our findings confirm the widespread “re-browning” of lakes in former high acid deposition regions, but also suggest that OC levels could exceed pre-industrial values with complete recovery from acidification in response to ongoing climate change. In contrast to lake-water OC dynamics, long-term trends in sediment OC burial are more complex, and appear to be driven primarily by local watershed disturbances rather than regional changes.
|2:35||★ Tracking the Long-Term Effects of Metal and Sulfate Deposition From Past Mining Operations on Sedimentary Chironomid and Cladoceran Assemblages
Brigitte Simmatis1, Kathleen M. Rühland1, Marlene Evans2, Andrew M. Paterson3, and John P. Smol1
1Paleoecological Environmental Assessment and Research Laboratory, Department of Biology, Queen’s University, Kingston, Ontario; 2National Water Research Institute, Ontario Environment and Climate Change Canada, Saskatoon, Saskatchewan; 3Dorset Environmental Science Centre, Ministry of Environment, Conservation and Parks, Dorset, Ontario
Lakes are socially, ecologically and economically valuable resources that are common on the Canadian landscape. Unfortunately, long-term monitoring records do not often capture the environmental conditions of lakes prior to anthropogenic change. Paleolimnological techniques use biological, physical and chemical information stored in lake sediment archives to extend our knowledge of past conditions and offer a long-term perspective on the cumulative effects of multiple stressors on biological communities. In smelting regions, characterizing past biological communities can further our understanding of the long-term effects of mining, smelting, and remediation, as well as other factors that may influence the trajectory of ecosystem recovery (such as climate change). Little is known about the long-term effects of metal contamination and acidification on sedimentary invertebrate assemblages, and previous studies have primarily focused on rivers or broad taxonomic groupings. Here, we will examine trends in past biological assemblages (Branchiopoda: Cladocera, Diptera: Chaoboridae and Chironomidae) preserved in lake sediments to provide a regional perspective of change in the Sudbury, Ontario area. In addition, we will examine responses of invertebrate assemblages over the past ~200 years from a dated sedimentary record from Phantom Lake (Flin Flon, Manitoba). The biological response to past smelting-related stressors varies depending on whether the lakes became acidified, as in Sudbury, or not, as in Flin Flon. This work will expand on our understanding of how mid-trophic level organisms respond to environmental degradation from long-term smelting activities, spatial trends in common invertebrate indicator assemblages in mine-affected regions, and recovery trajectories in affected systems.
Moderator: Reed Green
US Geological Survey, Little Rock, Arkansas
|1:35||Monitoring and Calibration of a Three-Dimensional Hydrodynamic Model for Lake Arrowhead, California, Prior to Initiating Indirect Potable Reuse Through Surface Water Augmentation
Ali Saber1, David E. James1, Imad Hannoun2, Tracy Vermeyen3, Meghan Thiemann4, and Jeffery Pasek5
1Civil and Environmental Engineering, University of Nevada, Las Vegas, Nevada; 2Water Quality Solutions, McGaheysville, Virginia; 3US Bureau of Reclamation, Denver, Colorado; 4US Bureau of Reclamation, Boulder City, Nevada; 5City of San Diego, San Diego, California
A multi-year monitoring and modeling effort was conducted to evaluate lake mixing and transport processes prior to planning for surface water augmentation at Lake Arrowhead, California, a warm climate high-altitude lake. Data from a wide range of instrumentation including, multiparameter water quality profiles, four weather stations, two acoustic Doppler profilers, six Lagrangian drifters, and two thermistor strings, combined with utility water withdrawals and high-resolution bathymetry were used to calibrate the hydrodynamic model. If approved, an extensively researched non-toxic dye tracer will be used to validate the model.
Findings to support model calibration include: Lake level varied 3.2 meters during the study period. Water inflows occurred primarily during winter storms. Mixing and transport were primarily wind driven. Small differences in water quality indicators were found across the lake’s four major bays. Lake stratification began in late February, peaked in July and ended with December overturn. Hypolimnetic hypoxia below 4 mg/L occurred during stratification. Reoxygenation rapidly occurred following turnover. Mountainous terrain generated a spatially variable wind field, with slower southwesterly prevailing wind speeds near the south shore and higher southerly and southeasterly wind speeds on the north shore. The calibrated AEM3D hydrodynamic model, simulating one year on a 30 × 30 × 0.5 meter grid, successfully reproduced the lake’s energy and water balances and its temperature profiles. Correlations of water column velocity profiles and prevailing winds were investigated and subsequently used to estimate water column mixing intensity. ADP and Lagrangian drifter data were used to validate velocity profiles.
|1:55||The Impact of Weather Model Resolution on a Hydrodynamic Model of Lake George
Guillaume Auger, Campbell D. Watson, Eli M. Dow, Michael E. Henderson, Harry R. Kolar, and Lloyd A. Treinish
IBM Research, Yorktown Heights, New York
Algae growth and spatial distribution depend on water temperature and the hydrodynamics. Impacts of climate change on lakes’ water temperature and ecosystems have been assessed using weather prediction models to force lake hydrodynamics. Due to various constraints, weather models provide outputs on a grid at 9 km resolution, which was shown to suffice for the Great Lakes. Despite outnumbering the large lakes, the smaller ones have received less attention.
To fill that gap, we performed a sensitivity analysis of weather simulation resolution (3 km and 0.333 km) and show the consequences on the hydrodynamics of Lake George, New York, for a time period of one month. Our results show that using finer resolution weather leads to more accurate water temperature and heat content at two locations in the lake with coarser resolution weather forcing inducing reduced heat in the lake and an underestimation of thermocline depth.
The net long wave radiation makes up most of the heat difference between fine and coarse resolution, where the finer resolution case yielded an average increase of heat flux density of 7 W/m2. High resolution weather forcing led to a doubling of downward heat mixing in the first 5 meters during the stratification period, explaining the increase of heat and deepening of the thermocline.
Our research shows that using coarse weather model to force the hydrodynamics of Lake George leads to inaccurate forecast of water temperature, in one-month time. Consequently, prediction of phytoplankton concentration would be inaccurate as well.
|2:15||Simulating the Effects of Destratification System Expansion Using Coupled Bubble-Plume and Water-Quality Models
Kevin Bierlein, Christine Hawley, and Jean Marie Boyer
Hydros Consulting Inc., Boulder, Colorado
Cherry Creek Reservoir is a polymictic flood-control reservoir near Denver, Colorado. A compressed air destratification system was installed in 2007 with the goal of eliminating anoxia and reducing summertime chlorophyll a concentrations below the site-specific standard of 18 µg/L, which is assessed as a July – September average. The system consists of 116 circular diffuser heads each operating at a flow rate of 2.4 SCFM, and was operated during the standard assessment period from 2008–2013.
Data analysis shows that the destratification system has not effectively maintained oxygenated conditions at the bottom or had the desired effect on summer chlorophyll a concentrations, as the standard was exceeded in 4 of the 6 years from 2008–2013. A coupled bubble-plume and water-quality model was used to assess the existing destratification system and determine the potential impact of an expanded destratification system on summer chlorophyll a concentrations. Several potential system expansions were considered that included additional diffuser heads (up to a total of 580 heads) and/or increased airflow to each diffuser head (up to 24 SCFM/head). The coupled model results indicate that a larger destratification system would reduce chlorophyll a concentrations, but the reductions would not be enough to bring the reservoir into compliance with the site-specific standard in all years. The effectiveness of this type of system for reducing chlorophyll a concentrations was found to be limited by the shallow reservoir depth, large surface are over which mixing is required, and high external nutrient loading.
|2:35||Combining Waterbody Morphometry With Estimates of Nutrient Loading and Flushing Rate to Examine Lake and Reservoir Susceptibility to Eutrophication
W. Reed Green1, Anne B. Hoos2, and Alan E. Wilson3
1US Geological Survey, Lower Mississippi-Gulf Water Science Center, Little Rock, Arkansas; 2US Geological Survey, Nashville, Tennessee; 3Auburn University, Auburn, Alabama
Estimates of nutrient loads and flushing rates were combined with measures of waterbody morphometry in lakes and reservoirs to aggregate waterbodies of similar Secchi depth and chlorophyll a concentration. Aggregation was completed for 320 lakes or reservoirs greater than or equal to 0.1 km2 located in the eastern United States, Alabama, and parts of Mississippi and Tennessee, and were previously included in the US Environmental Protection Agency National Lake Assessment Program in 2007 and 2012. Waterbodies were categorized by type (natural lakes (n = 95), headwater reservoirs (n = 165), and downstream reservoirs (n = 60)), and waterbody types were assessed independently. Recursive partitioning and model-based boosting were used to create four-node partition trees to aggregate waterbodies into five endpoints along a gradient of lowest to highest values relative to Secchi depth, chlorophyll a concentration, according to shared nutrient loading and morphometric characteristics. Trophic state designations were assigned relative to the median value within each of the five endpoints. These partition trees were then used to place all other waterbodies that were not included in the National Lake Assessment Program into one of the five Secchi depth or chlorophyll a aggregates. Results will aid water-resources management in prioritizing lake and reservoir protection and restoration efforts based on the susceptibility of these waterbodies to eutrophication relative to nutrient loading and morphometric characteristics.