Medicine Lake Excess Nutrients TMDL project: Water Quality Standards

Transcription

1 Medicine Lake Excess Nutrients TMDL project: Water Quality Standards Steering Committee Meeting #1 November 18 th, 2008

2 Water Quality Standards Water quality standards the fundamental benchmarks by which the quality of surface waters is measured (Minn. Rules Chapter 7050 and 7052 govern program)

3 Water Quality Standards Water quality standards consist of 3 major components: 1. Beneficial use classifications for waterbodies 2. Numeric and narrative criteria that protect those beneficial uses 3. Nondegradation requirements to provide extra protection to high quality waters

4 1. Beneficial Use Classifications Use Class Class 1 Class 2 2A 2Bd 2B 2C 2D Class 3 Class 4A Class 5 Class 6 Class 7 Beneficial Use Drinking Water Aquatic life and recreation Cold water fisheries, trout waters Cool and warm water fisheries, drinking water Cool and warm water fisheries Indigenous fish and associated aquatic community Wetlands Industrial uses and cooling Agriculture and wildlife uses Aesthetics and navigation Other uses Limited resource value waters

5 1. Beneficial Use Classifications Protection of aquatic life: healthy, diverse, and successfully reproducing populations of aquatic organisms (including fish and invertebrates) are maintained Protection of recreation: conditions suitable for swimming and other forms of water recreation are maintained for all surface waters (except wetlands and Class 7 waters)

6 2. Numeric Water Quality Standards Sets a specific concentration for a certain pollutant in water that will allow maintenance of beneficial uses All use classifications have numeric standards associated with them (except Class 6 other uses) Ideally, if the numeric standard is not exceeded, the beneficial use will be protected

7 2. Narrative Standards prohibit unacceptable conditions in/on water floating solids scum visible oil film nuisance algal blooms are sometimes called free forms protect aesthetics

8 Lake Nutrient Criteria Development Considers regional patterns & distributions; Varying uses of lakes & differences among deep & shallow lakes; Consider fishery (aquatic life) requirements; Shallow lakes emphasis on plant communities relative to P, chl-a, & Secchi; Use of sediment cores to re-affirm regional patterns & estimate background; Accounts for lake user perceptions;

9 Due to regional diversity in lake and watershed characteristics one single TP value could not be adopted for the state

10 Trophic Status of Lakes the typical trophic status range of reference lake data represents a starting point for establishing criteria Trohpic Status = overall health or level of productivity of the lake Reference Lake = representative lake in minimally impacted watershed

11 Carlson Trophic Status (TSI)

12 Natural Background Conditions and Regional Patterns 55 Lakes Study conducted in Minnesota included lakes from the major ecoregions Surface and deep cores were taken in all lakes Core-sections corresponded to circa 1750, 1800, 1970, and 1993 Diatom reconstructions of ph, chloride, color, acid neutralizing capacity, total phosphorus, trace metals and organic contaminants were conducted

13 User Perceptions Defining the relationship between user expectations and lake water quality measurements important Methodology involves the use of an observer survey and water quality data from the ecoregion data set and Citizen Lake-Monitoring Program. Cross-tabulating water quality measurements against observer survey categories provides a basis for calibrating nuisance criteria.

14 User Perceptions Data Minnesota Lake Water Quality Assessment Report: Developing Nutrient Criteria (Sept. 2005)

15 Minnesota s Lake Eutrophication Criteria. Ecoregion TP Chl-a Secchi (classification) ppb ppb meters NLF Lake trout (Class 2A) NLF Stream trout (Class 2A) NLF Aquatic Rec. Use (Class 2B) CHF Stream trout (Class 2a) CHF Aquatic Rec. Use (Class 2b) CHF Aquatic Rec. Use (Class 2b) Shallow lakes WCP & NGP Aquatic Rec. Use (Class 2B) WCP & NGP Aquatic Rec. Use (Class 2b) Shallow lakes

16 Photo by: Terrie Christian President, AMLAC