Table 2.1 Features Useful for Developing Indicators
Lake or reservoir dimensions
Extent of stratification and mixing (Froude number, lake number)
Dissolved Oxygen - Balance between production and consumption;
Oxygen status (profile, deficit rate, anoxic factor)
Water clarity - Light attenuation (color, inorganic particles, organic
Nutrient and Chemical Values
Ambient concentrations (compliance, toxicity, eutrophication status (8.0,
26.7, 84.4 g L-1 Total Phosphorus and 661, 753, 1875 g L-1 Total Nitrogen
(geometric means) for oligotrophic, mesotrophic, and eutrophic systems,
respectively (OECD, 1982))
Loading rates and permissible limits (Total Maximum Daily Load)
Indicator species (pollution tolerant/intolerant) - pitfalls include ambiguity
and relation to community structure/function
Biotic diversity (e.g., Shannon and Weaver, 1949; Wilhm, 1967)
Morphoedaphic Index - Fish harvest (Ryder, 1965)
Trophic State Index (TSI, Carlson, 1977)
Index of Biotic Integrity (IBI, Karr et al., 1986)
EPT Index - based on the abundance of selected orders of pollution-
sensitive insect larvae (Ephemeroptera (mayflies), Plecoptera (stoneflies),
and Trichoptera (caddisflies)). EPT Index is the sum of the number of
families within these orders.
While there is obvious overlap in these two lists of indicators, using concepts from both may
enable identification of specific problem sources (via compliance monitoring) and an overall assessment
of environmental health (cumulative effects even within established standards and criteria). Recent
discussions suggesting water quality standards for metals toxicity may need reconsidering (due to site
specific and metal specific responses to water quality) (Renner, 1997) are also indicative of a need to
carefully consider the development and application of indicators.
Using perceptions of water quality problems, as defined by users and quantification of problems
using indicators applied on a regional basis, is a good start in problem identification. An example of a
program that utilizes a similar approach is the Tennessee Valley Authority's (TVA) Assessment
Program. Specific techniques for using water quality indicators have also been developed by the U.S.
Department of Agriculture Soil Conservation Service (Terrell and Perfietti, 1989).
2.1.3 PROBLEM SOURCES
Problem identification includes consideration of the source(s) of the problem so that application
of enhancement techniques can be targeted for maximum benefit. Often more than one source exists.