1. Tiered Aquatic Life Use Model
Christy Pickens, Physical Research Scientist
Water Quality Control Division
Colorado Dept. of Public Health and Environment
30 July 2003

2. Purpose of Model
The tiered aquatic life use framework is a conceptual model predicting the response of aquatic communities to increasing human disturbance.
The conceptual model is a draft framework for using biological assessment information to refine designated aquatic life uses.

3. Purpose of Model
EPA developed the TALU model for a nationally consistent approach.
Scientifically defensible benchmarks
Common framework for communication and evaluation- public, stakeholders, across political boundaries
Protection for excellent quality waters
Achievable goals for incremental restoration
Nationally consistent approach. Example- 305(b) reports. 305(b) reports are sometimes not consistent when compared across the nation…
Scientifically defensible benchmarks- We all know the credible data issues…

4. Purpose of Model National ALUS Workgroup
Biological Condition Gradient (BCG) focus of workgroup in 2001.
Human Disturbance Gradient (HDG) focus of workgroup in 2002.
Workgroup recommendations going forward to EPA this spring with the conceptual models, implementation options, case examples.
The first step EPA took to develop guidance on use of biological assessments to help refine designated aquatic life uses was to build upon the expertise and practical experience of existing State and Tribal water programs. A workgroup was established for this purpose and includes representation from States and Tribes that have strong, well established biological assessment programs and have adopted numeric biological criteria into their water quality standards.

5. TALU Model Basics
Bioassessments help states develop expectations for acceptable biological conditions.
This is accomplished through the technical process of developing aquatic life goals, aquatic life uses (ALUs).
Biological assessments allow various levels of ALUs.
Using several types, or tiers, of ALUs allows states and tribes to allocate limited resources to waterbodies in proportion to their need for protection.

6. ALUS Integrity ALUS is determined by assessing:
Response variable (biological condition) to determine impairments and full support
Stressors (physical and chemical conditions) to determine impairment
The assessment of these variables is where the BCG and the HDG come into play.

7. TALU Conceptual Model

8. TALU Model Basics
The tiered system of use designations provides for different levels of protection and reflects the choices implicit in reconciling the “ideal” (represented by least impacted reference conditions) with the “reality”, the ongoing effects of two centuries of intensive human use of the state’s land and water resources.

9. TALU Model Basics Key Points to Emphasize: Framework is conceptual
Number of tiers to be determined by State
“Best Fit” approach recommended
The framework may be quantitatively defined by many possible methods
BCG is a quality gradient, not a classification
Framework is conceptual- it does not replace existing use classifications or categories in State and Tribal WQS. It is intended to be used as guidance to assist States and Tribes in thinking how to use biological assessments and criteria to refine their designated ALU.
There is no expectation for States and Tribes to establish 6 tiers. The purpose of the number of tiers is to provide a highly resolved biological condition gradient as guidance to the States and Tribes. The ultimate number and content of the tiers is a State determination.
The list of attributes is intended to organize and record the current state of our understanding and observation concerning changes in key characteristics of an aquatic community in response to increasing levels of human disturbance. It should not be thought of as a check list. The workgroup will be developing recommendations for methods for determining “best fit” of data- weighing the importance of and signal-strength of the different attributes as they pertain to a specific waterway.
Again, this is a conceptual model- it is not constrained to any one method. Needs to be applicable to programs that use RBPs, IBIs, RIVPACS, etc…
The biological condition gradient is a quality gradient- the upper end of the scale reflecting “natural conditions” corresponding with the CWA integrity objective. The BCG is not a model for classification of natural systems such as ecoregions or bioregions. The BCG would only be applied to waterbodies once they have been appropriately classified; e.g. the first tier characterizes the natural expectations for a waterbody unimpacted or minimally impacted by human activities. If the natural expectation for a stream includes naturally low dissolved oxygen concentrations and high suspended sediment load, then that would be the top tier (tier1) for that waterbody

10. TALU Model Basics Human Disturbance Gradient (HDG)
Biological Condition Gradient
(BCG)
The 2 components of the model…

11. TALU Model Basics
From Karr…

12. TALU Model Basics

13. Human Disturbance Gradient
TALU Model Basics
Human Disturbance Gradient

14. TALU Model Basics HDG Layout
Six tiers (A-F)
Six major stressor classes
Habitat Structure
Flow Regime
Water Quality
Toxics and Bioengineered Chemicals
Energy Sources
Biotic Interactions
Look at handout marked TALU From Bob Hughes, Dynamac Corp. A HDG for permanent, unconstrained, desert streams and rivers.

15. TALU Model Basics HDG Layout
Six major disturbance classes
Landscape Character
Riparian Condition
Barriers
Channel Morphology (map scale)
Atmospheric Deposition
Biotic Interactions

16. TALU Model Basics HDG Rationale
Essential for determining reference sites and minimal disturbance
Necessary for metric and index development and evaluation
Often represents half the variability in biological response scores
Easier to assess than large suite of stressors
Assists in diagnosing stressors
Source of most manageable stressors
Critical for stream protection, BMPs and restoration
Self explanatory
HDG is also very useful for selecting candidate metrics that are responsive to the major stressors
Often, such simple variables such as %urban land use can incorporate half the variability in a biological response
If general patterns are deemed important, it is often much easier to assess land use than to attempt to assess all possible chemical, physical, and biological stressors. For ex. Published studies on many areas of N. America show that 10-30% urbanization or 15-50% agriculture results in marked declines in IBI scores.
Knowledge of land use helps us screen particular disturbances that are useful for diagnosing possible stressors, or the effect of the proximity of those disturbances.
It may be easier and more direct, to mange land use, instead of multiple stressors separately.

17. Draft Model Tiers – 6 levels
TALU Model Basics
Draft Model Tiers – 6 levels
Natural structure and function of biotic community maintained
Minimal changes in structure and function
Evident changes in structure and minimal changes in function
Moderate changes in structure and minimal changes in function
Major changes in structure and moderate changes in function
Severe changes in structure and function
From the biological response to the HDG levels of disturbance, the workgroup derived these 6 basic tiers, or levels of the conceptual model.

18. TALU Conceptual Model

19. TALU Conceptual Model www.brainybetty.com
Tiers in depth. Remember that we can have more or less.

20. HDG Concepts
Human disturbance gradient does not necessarily imply degradation.
Human disturbance gradient addresses two basic questions:
What is the departure from expected condition as a result from human activities?
What is the impact of this departure from expected condition on the biotic community?
BMPs will need to be incorporated into the framework. Scale issues need to be addressed (temporal and spatial).

21. Biological Condition Gradient
TALU Model Basics
Biological Condition Gradient

22. TALU Model Basics

23. Biological Condition Gradient (BCG)
TALU Model Basics
Biological Condition Gradient (BCG)
BCG is a quality gradient, with the upper end of the scale reflecting “natural conditions” corresponding with the CWA integrity objective.
BCG is not a model to be used for classification of natural systems, such as ecoregions. BCG would only be applied once they have been appropriately classified.
BCG provides consistency among states using different approaches.
As previously mentioned…

24. Biological Condition Gradient (BCG)
TALU Model Basics
Biological Condition Gradient (BCG)
The first tier of the model characterizes the natural expectations for a waterbody unimpacted or minimally impacted by human activities.
The subsequent tiers show the response of the biological community to increasing human disturbance.
As previously mentioned…

25. TALU Model Basics 10 Major Attributes BCG Layout
Taxonomic composition and tolerance
Attributes I-V
Regionally Endemic through Tolerant
Non-Native taxa
Attribute VI
Organism condition
Attribute VII
Ecosystem function
Physical-biotic interactions
Attributes IX-X
See handout marked TALU 101, Greg Pond – Kentucky Division of Water. Within each of the 6 tiers of biological condition, these attributes are laid out.

26. BCG Attributes

27. BCG Attributes

28. BCG Attributes

29. BCG Attributes

30. BCG Attributes

31. BCG Attributes www.brainybetty.com
Development of BioAxis is on-going - always evolving based on evolving science

32. BCG Attributes EX

33. ALUS Tiers Provide Consistency
the various state/tribal assessment and analytical approaches illustrate OBSERVATION AND MEASUREMENT- constrains the development of precision accuracy and knowledge if EPA were to attempt to standardize at level of ‘METHODS’--Thus BioAxis serves as a common backdrop illuminating the basic theory behind why the various methods work
Standardization - common language of biological conditions- so that a BioAxis ‘B’ in Kansas can be related to a BioAxis ‘B’ in Oregon- regardless what methods are used to do the assessment and quantitative work-up.
Management context is state-specific- the number of quantitatively distinguishable management tiers is a function of
1. the level of rigor of the methods and the overall size and quality of the state database. States/tribes NOT obliged to quantitatively manage for all 6 tiers!! But should be able to relate individual site or reach conditions to any one of the 6 tiers by expert judgement following BioAxis decision rules and to relate management categories to positions on the gradient. a 1 b 2 c 3 d 4 e 5 f 6
Natural
Degraded
Susan P. Davies, MDEP

34. TALU Model Thinking ahead…
How can we transition from describing what we see to establishing thresholds?

35. Designated Aquatic Life Uses in Vermont
natural/
minimally altered 1
Class A1: Excellent - Biota within the range of the natural condition
Threshold criterion A1 2
Class B1: Very Good - Minor changes to structure and function; tolerant/intolerant forms within the range of reference condition.
Biological
Condition
Threshold criterion B1
Class B2/3: Good - Moderate changes in the relative proportions of tolerant, intolerant, taxonomic and functional components. 3
Threshold criterion B2/3
Biocondition Gradient Tiers 4 5
Non-Support: Fair-Very Poor
highly altered
Not meeting CWA 101a uses for protection & propagation of aquatic life 6
Human Disturbance
Low
High

36. This slide illustrates some of the distinctions we wish to keep in mind during the reference condition courses. In some regions, we might find places where human disturbance is relatively minor or minimal, and we might use data from these places to describe a reference condition that approximates biological integrity. In these places we might want to set goals that approximate biological integrity (i.e. uses that meet the objective of the CWA). In other regions, we might find no places with minimal human disturbances; we might use data from places that are least disturbed to describe a reference condition that we expect to be attainable, at the upper end of existing conditions, meeting the goal of the CWA. In still other regions, human disturbance might be so extensive that we might want to describe a reference condition that falls outside the range of existing condition; the condition at least disturbed sites might not be acceptable. Establishing a reference condition outside the range of existing conditions might require approaches other than the use of reference sites in that region.