Report Card Scoring

Several options under consideration for scoring and aggregating data

Why turn data into indices?

• Integrate multiple measures into thematic scores

• Evaluate overall trends and compare locations

• Simplify communication with decision makers and the public

Four Main Steps

• Select and group indicators

• Transform measured data into unit-less scores

• Aggregate scores from multiple indicators into a summary index

• Define breakpoints to bin index scores into descriptors of condition (grades or colors)

Central Coast RegionPreliminary Indices

1. Human Health WQ Index2. Aquatic Life WQ Index3. Toxicity Index4. Bioassessment Index5. Biostimulatory Risk Index6. Habitat Index7. Riparian Index

Indicators within Indices

Example from the Central Coast Region1. Human Health Water Quality Index

Fecal ColiformE. coliPathogensNitrate

Toxic chemicals

Indicators within Indices

Example from the Central Coast Region2. Aquatic Life Water Quality Index

AmmoniaNitrateOrtho-phosphateDO departure

Toxic chemicals

TurbidityTotal dissolve solidsTotal susp. sedimentpH departure

Scoring Approach 1

Scoring into categories using multiple thresholds

If the mean > 20 then the color = Dark RedIf the mean > 10 and the mean <= 20 then the color = RedIf the mean > 5 and the mean <= 10 then the color = Orange If the mean <= 5 then the color = Yellow If the mean <= 1 and the max < 5 then the color = Green If the mean <= 0.3 and the max < 1 then the color = Blue

This is the approach used on the CCAMP website

Scoring Approach 2

Quotient MethodDivide measurement by a standard

Pro: + scientific consensus behind standards

+ capture magnitude of excursion

Con: - no fixed upper end to scale

- appropriate standards must be available

Scoring Approach 3

Magnitude and Exceedance Quotient (MEQ)

Combines two terms that express number of threshold exceedances and magnitude of exceendance.

Derived from Canadian Ministry of Governments method

Canadian CCME WQ Index

Factor 1: Scope

Factor 2: Frequency

Factor 3: Amplitude

Canadian CCME WQ Index, cont.

CCME WQ Index

Quadratic mean (or root mean square) gives greater weight to larger values, thus emphasizing excursions.

Canadian CCME WQ Index, cont.

Pro: + widely excepted (esp. for drinking water)

+ considers scope, frequency, amplitude

Con: - resolution to detect differences among sites or times depends heavily on standards selected

- Not as useful for characterizing “healthy” because it only looks at failed tests- Scope is susceptible to site variability in number of analytes tested (best for very consistent study design)

MEQ: modifications to CCME

We are scoring all tests, not just failed tests. This provides a “good” end to the scoring tool

We eliminated the scope term (how many analytes fail) because we have inconsistent data availability across sites.

We do the calculations at the level of the analyte so that each analyte can also be scored

Calculating MEQ

Factor 1: Frequency

Calculate rate of exceedance (frequency) for each individual analyte (from CCME)

F1

F1

Calculating MEQ, cont.

Calculate unitless sample magnitudes:Magnitude = concentration/threshold

Calculate normalized sum of magnitudes

NSM = Σ magnitudes / sample count

Scale from 0 – 100= NSM / (0.01*magnitude average+0.01)

Calculate magnitude (amplitude) for each individual analyte (from CCME)

Calculating MEQ, cont.

•

MEQ = 100 – √ exceedance2 + magnitude2

1.414

Combine exceedance and magnitude factors and scale to 100 (modified from CCME)

Aggregate scores into an index1. Number of standard excursions per site

2. Means: arithmetic, geometric, harmonic, quadratic

3. Worst case

4. Weights and penalty factors

5. Regression of simple to comprehensive indices

6. Empirical formulae