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Design a Sampling Effort
What We Do With Fish and Macroinvertebrates
What is the reason for sampling? The answer to this question will tell you what type of sampling design you need:
- Sampling for water-quality assessment when a biological index already exists
- Sampling for developing a sound biological index
- Visit EPA's Office of Water guidance on Elements of a State Water Monitoring and Assessment Program and Office Research and Development Aquatic Resources Monitoring Web site.
Sampling Designs for Water-Quality Assessment
Entire State
Sampling the entire state to report on conditions can
take a number of years. Some strategies use a targeted design
to sample different basins throughout the state each year, until
they are all sampled. Other strategies use a probability,
or random sampling design, that is designed to avoid taking
too many samples but still provide statistically reliable results,
such as the
Maryland Biological Stream Survey 
.
USEPA's EMAP has an excellent website on
Monitoring Design and Analysis, focusing on probablistic sample
design and analysis. Please visit these websites to learn more.
Ecoregions
An ecoregion framework is a characterization tool appropriate
for describing an ecosystems natural potential and variability,
as well as its typical response to various human disturbances.
Ecoregions are a good organizating and interpretive framework that
characterizes and depicts ecosystem patterns, identified region-specific
disturbances and risks to ecosystems, and provides a reporting
framework for interpreting research and assessment results.
See how ecoregions are used in the
Florida non-point source bioassessment program .
Watershed
A watershed is the land that drains into a specific
point in a body of water. Watershed management is a wise means to
protect the waters by looking at all of the influences within a
watershed. This way, the additive, or cumulative, effects of watershed
problems can be anticipated, and long-lasting solutions found. Most
States, like
Illinois ,
use the watershed approach for establishing their state-wide monitoring
programs.
Suspected Problem
This is usually an "upstream/downstream" approach to see if a suspected source of a problem makes conditions worse downstream. Another approach, "before/after" sampling, checks whether specific changes made near the waters (development, roads, etc.) changed the quality of the waters. Most states and other programs use this approach for specific problems and their sources.
Sampling Designs for Developing a Sound Biological Index
Biological Index Development
Development of biological indexes require that the component "metrics" of the index are tested. These tests are based on ensuring that the metrics give a reliable signal, or change, when water quality is altered from human influence. This must be done before the indexes can be used for water quality assessment.
Learn more by visiting the Multimetric Index page.
Reference Condition Development
Reference conditions are the ideal condition from which test samples can be compared. The amount of difference among the reference condition and test samples provide an accurate measure of watershed health. Reference conditions are often developed for waters similar to one another with regard to geology, drainage size, and elevation. This reduces the chance that natural variability will influence the results too much.
Learn more about these methods and approaches by visiting the following websites:
- Biological Criteria: National Program Guidance
- Summary of State Biological Assessment Programs
- USEPA's ORD Western Ecology Division Monitoring Design and Analysis
-
ITFM Final Report:
Technical Appendix F: Ecoregions, Reference Condition
and Index Calibration
-
ITFM Final Report: Technical
Appendix G: Multimetric Approach for Describing Ecological Conditions