mead lake tmdl critique alicia allen and nick grewe
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MEAD LAKE TMDL CRITIQUE
Alicia Allen and Nick Grewe
Mead Lake
Shallow eutrophic lake Mean depth 1.5 m, maximum depth 5 m
Drains 248 km2 of west central Wisconsin South Fork Eau Claire River is the primary
source of surface water inflow Mead Lake was placed on 303(d) list in 1998
due to sediment and Phosphorous In 2008 was updated as a result of habitat
degradation, pH exceedance, and excess algal growth in the summer
Issues
Sediment enters from South Fork Eau Claire River
Phosphorous bound to sediment particles transfers Phosphorous to lake bed
Severe algal blooms during growing season (May-October)
Removal of CO2 through photosynthesis raises pH
Goal
Reduce sediment loading Reduced sediment will decrease
Phosphorous load Reduced Phosphorous will decrease algal
blooms Algal bloom control will address pH
exceedance and degraded habitat Improve for recreational purposes
Water Quality Standards
Wisconsin has no numeric criteria for Phosphorous and sediment
Narrative criteria: The following should not be present in such amounts as to interfere with public rights in waters of the state Substances that will cause objectionable deposits on
the shore or in the bed of a body of water Floating or submerged debris, oil, scum, or other
materials Materials producing color, odor, taste, or unsightliness
93 ppb P- site-specific target developed using criterion
Water Quality Standards
pH standard: “The pH shall be within a range of 6.0-9.0, with no change greater than 0.5 units outside the estimated natural seasonal maximum and minimum” Based off the designation of Mead Lake as
fish and other aquatic life uses TMDL was not based off of this standard,
but was checked against it at the end
Background of Study
2 year study (2002-2003) of water quality in Mead Lake and South Fork Eau Claire River
Focused on external loading of suspended sediments and nutrients from river, internal P fluxes from lake sediment, and in-lake water quality
South Fork Eau Claire River Continuous flow monitoring Bi-weekly and storm event water quality
sampling TSS, total N, total P, soluble reactive P
Background of Study
Mead Lake Bi-weekly testing at 3 locations from May-
September Total N, Total P, soluble reactive P,
chlorophyll In-situ testing for temperature, DO, pH, and
conductivity
Study Findings
Trophic State Index
YearSecchi
(m)Chla (ug/l)
TP (ug/l) TSISD
TSICHL
A TSITP
2002 0.52 50.8 130 69.2 64.5 65.8
2003 0.7 76.2 125 65 67.6 65.5
TSI>50 = Eutrophic
River accounted for 54% of Total P load to Mead Lake
Exceedance of WQ criteria for pH generally correspond to chlorophyll levels > 70 ug/L
Sediment Load
(tons)
YearSeasona
l Annual2002 428 7742003 189 609
Land Use Modeling
Modeled using SWAT Simulated runoff, sediment, and P loading Utilized to assess the effectiveness of
reducing phosphorous and sediment loads to Mead Lake
Used Detailed land management information 2002 farm survey of 74 farms 1999 land use survey
3 crop rotations were used Calibrated for flows and load data using 2002
values
Land Use
Land CoverArea
(hectares)Area
%Cropped Farmland 10,383 41.38
Forest 7,964 31.47Grassland/
Pasture 2,690 10.72
Wetland 2,423 9.66Urban/
Impervious 1,214 4.84
Farmsteads 242 0.97
Water 172 0.69
Conclusions
ScenarioSeasonal Total P
Load (lbs)
P Load Reduction
(%)Baseline 5,500 Reducing soil P (25 ppm) 4,730 14%Reducing Soil Erosion (50% reduction in USLE) 4,730 14%Reduce manure P by 38% (animal dietary changes) 5,280 4%Combination: reducing soil P, soil erosion control and manure management 4,015 27%
Winter Rye Little change 5%
Continuous pasture (rotational grazing) 4,345 21%
Change in P export due to different management and land use changes
Lake Modeling
Modeled using BATHTUB Used various P loading scenarios to predict
changes in Total P Chlorophyll Secchi transparency Algal bloom frequency
Calibrated using 2002 data and compared to collected 2003 data
Conclusions
30 % reduction in external P load decreases Total P by 24%
Loading Capacity
TMDL Load Capacity = WLA + LA + MOS WLA = Wasteload Allocation LA = Load Allocation MOS = Margin of Safety
WLA = 0 because no point sources Load Capacity = LA + MOS
Load Allocation
Phosphorous 30% reduction in seasonal P load = 3850 lb 35% reduction in annual P load = 8600 lb
Sediment 30% seasonal decrease = 233 tons 30% annual decrease = 826 tons
Only focused on external P load. Internal load will be addressed after external load is controlled and funds become available
Margin of Safety
Load reduction goals greater than what is needed Seasonal- 200 lb MOS Annual- 480 lb MOS
MOS from non-point source control programs not incorporated into SWAT model Implementation of Conservation Reserve
Program (CRP) Barnyard BMP implementation- barnyard
runoff not incorporated into the model
Implementation
Utilize preexisting programs Federal, state, and county Use existing employees
Funding from public and private investors Public includes: WDNR, Mead Lake District,
Clark County Land Conservation Department
Additional BMP funding available Volunteer water quality monitors
Suggested Further Treatment Methods
Three methods for reducing internal P loading Alum Treatment:
Treat lake bottom before going anoxic and releasing P
Floc generation leads to P binding and becoming unavailable for plant uptake (aluminum phosphate)
Only administered after external loading controlled
External P would cover alum bed
Suggested Further Treatment Methods
Aeration Prevent stratification and anoxic layer Lines placed in deep holes to bubble air Operation costs may be high due to
electricity demands Siphoning
Siphoning water from bottom before going anoxic
Where does it go? Dry years may not have enough flow
Continued Monitoring
Data collection to begin 5 years after implementation
Water quality monitored for 2 years at South Fork Eau Claire River
Lake water quality data collected Assume same time period?
Update land use data Run updated SWAT and BATHTUB
Expensive
Critique of TMDL
No set 303(d) standards for WI Advantage
Each lake will have unique characteristics No standard allows for tailored goal based on
feasibility Disadvantage
Difficult comparison between lakes No “blue print” for TMDL More analysis required to develop specific goal
Critique of TMDL
Not including barnyard runoff in SWAT Runoff from livestock is a major source of
phosphorus Land use data from 74 farmers Load allocation may be underestimated No reason as to why it was omitted from SWAT
Assuming BMPs will be enough to address MOS MOS may be off due to barnyard runoff exclusion
Only 10 months of bi-weekly water quality data for calibration Is this data really representative of average loads?
Summary
Load Capacity (%
Reduction)
Sediment
(tons) Phosphorous
(lb)
Seasonal 233 (30) 3850 (30)
Annual 826 (30) 8600 (35)
Will also decrease pH and algal blooms significantly Seasonal loads have the most impact, but including
annual load capacity will address all time periods Inclusion of barnyard runoff into SWAT would have
better represented load reduction results. As of 2008, TMDL approved.