lake independence phosphorus tmdl critique stephanie koerner & zach tauer bbe 4535 fall 2011
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Lake Independence Phosphorus TMDL Critique
Stephanie Koerner & Zach Tauer
BBE 4535 Fall 2011
Watershed Description
Pioneer-Sarah Creek Watershed
851 – acre lake / 7631 – acre watershed
North Central Hardwood Forest ecoregion
Deep lake – max depth: 58ft
15 miles West of Minneapolis
Uses: Recreation
Aesthetic viewing
Contains portion to Municipalities Medina
Independence
Loretto
Watershed Shoreline
Receives 7,631 acres of runoff
Uses of shoreline: Agriculture
Commercial
Park and Recreation
Residential
298 animal units are on the shoreline, mostly of Horses on Single Family Property.
History of Watershed
Prior to 1850 the surroundings were predominantly Forests and Wetlands.
July 4, 1854 settlers found the lake giving it’s name Lake Independence for the day it was found.
Area slowly developed with lakeshore homes and agriculture
Drainage systems were then put in place which drastically changed the hydrologic system
Recently seasonal lake homes on the lake were converted to year round homes
Water Quality
Monitored biweekly from 1990 except in 1992
Phosphorus and chlorophyll data show no significant trends of improving or declining since 1990 but Secchi disk data showed a reduction in clarity.
Water Quality – Aquatic Vegetation
Curlyleaf pondweed and Eurasian watermilfoil cause water clarity and recreational problems from the lake.
Curlyleaf pondweed grows under ice and forms dense growth by late spring and dies in mid July causing increase in nutrients.
303(d) Listing
Total phosphorus concentration exceeded 40ppb 11 of 12 years from 1990 to 2003. Calculated from a minimum of 9 samples a year
Placed on 303(d) list as impaired waterbody for its recreational uses in 2002.
Modeling
MINLEAP, BATHTUB and Canfield and Bachman models were. MINLEAP quantified the feasibility of the target goal
Canfield and Bachman estimated TP reduction to achieve target
BATHTUB estimated nutrient flows from subwatersheds
Canfield and Bachman was used based on field monitoring and computer model which resulted in 2,381 lbs/yr assuming normal precipitation.
Model predicted reduction of 1300 lbs/yr to reach 36ppb.
MINLEAP
Calculated with “typical” nutrient inflows to unimpaired lakes in central Minnesota
Target concentration is likely attainable.
BATHTUB with GIS
GIS for Livestock Contribution
Bachman and Canfield
Sources of phosphorus
TMDL
TMDL = WLA + LA + MOS
TMDL Continued
Seasonal Variability
MOS – 35 lbs/yr was incorporated into TMDL for rainfall Variability
Final Phosphorus TMDL
Non-degradation Policy Future land development requires to meet strict guidelines
to protect water quality and prevent increases in runoff and nutrient loading.
Public Participation
Funding for the study was provided by the Three Rivers Park District and Lake independence Citizens Association provided many hours of volunteer work.
Efforts between the Three Rivers Park District, local municipalities, and MPCA the diagnostic feasibility evolved into the Lake Independence Phosphorus TMDL Estimated associated costs, expected effectiveness,
predicted longevity, and technical feasibility.
Target goal, WLA and LA were discussed by a large group of stakeholders.
Committee met monthly for two years
Decided WLA and LA would be based on source instead of municipal or subwatershed basis.
Implementation
Reducing movement of phosphorus into Lake Independence.
45% reduction (1081lbs/yr)
872 lbs/yr decrease from each identified external source
209 lbs/yr decrease of internal loading due to reduction of external sources.
Source Implementation Plan
Continue water quality monitoring program
Water sample collection
Inflow monitoring during and after implementation
Cost and Implementation
Ranked in highest priority, Time lines, Estimated costs, responsible parties and tasks are explained Goal reduction and possible reduction
Agriculture – Buffer Strips 300 acres can be installed
$150,000 to $500,000
Goal reduction 284lbs possible reduction 288lbs
Animal Waste – BMPs 33 feedlots
$330,000 to $825,000
Goal reduction 378lbs possible reduction 435lbs
Urban Development – urban runoff Goal reduction 146lbs possible reduction 202lbs
Failing Sewage Treatment – inspections $500,000
Goose Removal – reduce goose population $2,500
Loretto Wastewater Treatment
Example of Implementation Plan
Critique
Overall capable reduction
Effort and time put behind implementation plans
Local involvement was helpful
Useful and long record of data
Water Quality was not monitored for the year of 1992 but was not explained.
Sediment cores were used from four other lakes in the area of Lake Independence but not from the lake to estimate historical phosphorus loads.