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.