Bear Lake Sediment Study Alan Steinman and Mary Ogdahl Annis Water Resources Institute Grand Valley State University
Outline Study Site Description Management Issues - TMDL Internal Loading Measurements Summary/Implications
Bear Lake: 410 acres 6.9 ft: mean depth 11.8 ft: maximum depth Polymictic Mean HRT = 78 days Bear Lake Muskegon Lake Lake Michigan
Eutrophic Bear Lake Water Quality Mean TP = 44 µg/l (turnover) Chl a = 10-65 µg/l (summer) Suffers from nuisance algal growth caused by elevated phosphorus (P) - Muskegon Lake Area of Concern (AOC) - Michigan 303(d) list Total Maximum Daily Load (TMDL) for P
What is a TMDL? Total Maximum Daily Load Required by Clean Water Act and U.S. EPA for water bodies not meeting water quality standards Establishes the allowable loadings of pollutants for a water body Identifies pollutant reductions necessary to restore and maintain water quality
Phosphorus Loads to Bear Lake External P Load = 1,839 lb/yr Internal P Load = 1,548 lb/yr* *Based on Sediment TP (Nürnberg 1988, CJFAS): TP release rate (mg/m 2 /d) = -4.18 + 3.77(TP) Total P Load = 3,387 lb/yr
Bear Lake TMDL MDEQ: need to reduce mean TP concentration from 44 µg/l to 30 µg/l Requires a total reduction from 3,387 to 1,313 lbs/yr: - 848 lbs/yr from watershed (50%) - 1,226 lbs/yr from internal loading (80%) Internal load target = 322 lbs/yr http://www.michigan.gov/documents/deq/wb-swas-tmdl-bearlake_258228_7.pdf
Study Goals & Objectives Goal: Develop a strategy to reduce internal P loading to meet TMDL requirements Objectives: - Determine accurate internal loading rates - Develop Feasibility Report for Best Treatment
Sediment-Water Interactions Water Sediment SRP bioavailable Uptake Release Diffusion Resuspension (anoxic) alum Precipitation (Oxic: Fe) PP particulate Sedimentation SRP bioavailable Mineraliz n PP particulate
Strategy Collect sediment cores from 4 sites over 3 seasons - spring, summer, and fall, 2011; summer 2012 Measure internal P loading under oxic and anoxic conditions Measure diel DO concentrations at 2 sites - summer 2011; spring and summer 2012
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Total Phosphorus Release Rates Season Bear Lake Aerobic TP Flux (mg P/m 2 /d) Bear Lake TP Flux (mg P/m 2 /d) Mona Lake TP Flux (mg P/m 2 /d) Spring 2011 Summer 2011 Fall 2011 Summer 2012 0.0 ± 0.0 0.4 ± 0.2 1.9 ± 0.9 0.8 ± 0.7 6.7 ± 3.4 11.4 ± 3.4 0.0 ± 0.1 0.6 ± 0.3 4.2 ± 1.4 0.3 ± 0.5 3.9 ± 2.1 ---
Total Phosphorus Release Rates Season Bear Lake Aerobic TP Flux (mg P/m 2 /d) Bear Lake TP Flux (mg P/m 2 /d) Mona Lake TP Flux (mg P/m 2 /d) Spring 2011 Summer 2011 Fall 2011 Summer 2012 0.0 ± 0.0 0.4 ± 0.2 1.9 ± 0.9 0.8 ± 0.7 6.7 ± 3.4 11.4 ± 3.4 0.0 ± 0.1 0.6 ± 0.3 4.2 ± 1.4 0.3 ± 0.5 3.9 ± 2.1 ---
Total Phosphorus Release Rates Season Bear Lake Aerobic TP Flux (mg P/m 2 /d) Bear Lake TP Flux (mg P/m 2 /d) Mona Lake TP Flux (mg P/m 2 /d) Spring 2011 Summer 2011 Fall 2011 Summer 2012 0.0 ± 0.0 0.4 ± 0.2 1.9 ± 0.9 0.8 ± 0.7 6.7 ± 3.4 11.4 ± 3.4 0.0 ± 0.1 0.6 ± 0.3 4.2 ± 1.4 0.3 ± 0.5 3.9 ± 2.1 ---
Dissolved Oxygen and Temperature 11 ft August 4, 2011 mid-day 4 8 ft 4
NIGHT (11 ft) Diel Dissolved Oxygen August 16-17, 2011 4 4 (8 ft) NIGHT
Modeled Annual Internal TP Load - 5 Scenarios - Scenario Hypoxic Area General Explanation 1. Aerobic: entire lake 0 ha Most conservative estimate; unlikely 2. : depths > 10 ft 47 ha Very conservative estimate 3. : depths > 9 ft 296 ha Generally conservative estimate 4. Polymictic lake estimate * N/A Moderate estimate 5. : entire lake 1,518 ha Most liberal estimate; unlikely * Nürnberg et al. 2012
Modeled Annual Internal TP Load - 5 Scenarios - Scenario Hypoxic Area General Explanation 1. Aerobic: entire lake 0 ha Most conservative estimate; unlikely 2. : depths > 10 ft 47 ha Very conservative estimate 3. : depths > 9 ft 296 ha Generally conservative estimate 4. Polymictic lake estimate * N/A Moderate estimate 5. : entire lake 1,518 ha Most liberal estimate; unlikely * Nürnberg et al. 2012
August 16-17, 2011
Modeled Annual Internal TP Load - 5 Scenarios - Scenario Hypoxic Area General Explanation 1. Aerobic: entire lake 0 ha Most conservative estimate; unlikely 2. : depths > 10 ft 47 ha Very conservative estimate 3. : depths > 9 ft 296 ha Generally conservative estimate 4. Polymictic lake estimate * N/A Moderate estimate 5. : entire lake 1,518 ha Most liberal estimate; unlikely * Nürnberg et al. 2012
August 16-17, 2011
Modeled Annual Internal TP Load - 5 Scenarios - Scenario Hypoxic Area General Explanation 1. Aerobic: entire lake 0 ha Most conservative estimate; unlikely 2. : depths > 10 ft 47 ha Very conservative estimate 3. : depths > 9 ft 296 ha Generally conservative estimate 4. Polymictic lake estimate N/A Moderate estimate 5. : entire lake * Nürnberg et al. 2012 Nürnberg et al. 2012: 1,518 ha Most liberal estimate; unlikely AA (days/season) = -36.2 + 50.2 log (P season ) + 0.762 z/a 0.5
Modeled Annual Internal TP Load - 5 Scenarios - Scenario Hypoxic Area General Explanation 1. Aerobic: entire lake 0 ha Most conservative estimate; unlikely 2. : depths > 10 ft 47 ha Very conservative estimate 3. : depths > 9 ft 296 ha Generally conservative estimate 4. Polymictic lake estimate N/A Moderate estimate 5. : entire lake 1,518 ha Most liberal estimate; unlikely
Estimated Annual Internal TP Load (lbs/yr) 1. All Aerobic 2. > 10 ft 3. > 9ft 4. Polymictic Lake Estimate 5. All MDEQ 1,548
Estimated Annual Internal TP Load (lbs/yr) 1. All Aerobic 2. > 10 ft 3. > 9ft 4. Polymictic Lake Estimate 5. All MDEQ 169 1,548
Estimated Annual Internal TP Load (lbs/yr) 1. All Aerobic 2. > 10 ft 3. > 9ft 4. Polymictic Lake Estimate 5. All MDEQ 169 224 1,548
Estimated Annual Internal TP Load (lbs/yr) 1. All Aerobic 2. > 10 ft 3. > 9ft 4. Polymictic Lake Estimate 5. All MDEQ 169 224 513 1,548
Estimated Annual Internal TP Load (lbs/yr) 1. All Aerobic 2. > 10 ft 3. > 9ft 4. Polymictic Lake Estimate 5. All MDEQ 169 224 513 1,166 1,548
Estimated Annual Internal TP Load (lbs/yr) 1. All Aerobic 2. > 10 ft 3. > 9ft 4. Polymictic Lake Estimate 5. All MDEQ 169 224 513 1,166 1,931 1,548 TMDL internal load target = 322 lbs/yr
Best Treatment? Develop Feasibility Report for Best Treatment Internal P loading already close to or exceeds TMDL reduction target No need to address internal loading
Summary Internal loading in Bear Lake is highest in summer but overall rates are relatively low TMDL estimates for internal loading are too high (perhaps by 3-7 fold) TMDL needs to focus more on external P loading reductions
Acknowledgements Maggie Weinert, Sara Damm, Brian Scull, Rick Rediske, Eric Tidquist, Whitney Nelson, Scott Kendall, Rick Rediske, Kurt Thompson, and James Smit Project partner: Muskegon River Watershed Assembly Questions? Funding: Michigan steinmaa@gvsu.edu Department of Environmental Quality