assessment (compliance documentation), trend detection (documenting change, both positive and
negative), early warning (anticipate future conditions), or diagnosis (identify the causative agent) (Cairns
et al. 1993). Indicators may be developed from morphometric features, physicochemical constituents,
specific nutrient and chemical concentrations, biota, and integrative values (Table 2.1).
An earlier definition (Hunsaker and Carpenter, 1990) suggests indicators may be defined as "...
a characteristic of the environment that, when measured, quantifies the magnitude of stress, habitat
characteristics, degree of exposure to the stressor, of degree of ecological response to the exposure."
This definition seems applicable to 18 indicators listed in the U.S. Environmental Protection Agency's
"18 Environmental Indicators of Water Quality" which allows for an approach that detects "problems"
that would not necessarily be detected with traditional compliance monitoring. These indicators are
good, as a first cut laundry list of a total range of concerns. The first 4 are for water supply
engineers/public health officials. Metrics for these indicators may include variables not measured by
lake professionals. These 18 indicators are:
1. Population served by drinking water systems violating health-based requirements
2. Population served by unfiltered surface water systems at risk from microbiological
3. Population served by community drinking water systems exceeding lead action levels
4. Drinking water systems with source water protection programs
5. Fish consumption advisories
6. Shellfish-growing waters approved for harvest for human consumption
8. Species at risk of extinction
9. Rate of wetland acreage loss
10. Designated uses: drinking water supply, fish and shellfish consumption, recreation, aquatic
12. Surface water pollutants
13. Selected coastal surface water pollutants in shellfish
14. Estuarine eutrophication conditions
15. Contaminated sediments
16. Selected point source loadings to surface water and groundwater
17. Nonpoint source sediment loadings from crop land
18. Marine debris