Lake Independence Phosphorus TMDL Critique

Lake Independence Phosphorus TMDL Critique

Stephanie Koerner & Zach TauerBBE 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.