ENVIRONMENTAL INDICATORS FOR WATER RESOURCES MANAGEMENT

Water is a vital substance, essential for most life processes and as a liquid flow resource is the connector of all components of ecological and life systems. It is the environmental integrator. As a resource, water is both a natural component of nature and a commodity, or resource, that may be used by people for the benefit of society. This use is called management. Water has inherent characteristics that allow it to maintain processes and thus provide services; this inherent character is called the carrying capacity. Examples of carrying capacity may be waters ability to assimilate wastes, or dissipate excessive heat, or support a given amount of life. If the effects of such activities become large in magnitude and exceed the carrying capacity of water, it becomes srtessed and its capabilities to provide the services may cease. If ecosystems become stressed and impaired those that are dependent on ecosystems likewise become stressed, including human beings. As the liquid that connects all components of ecosystem there are symptoms, called environmental indicators, that may be used to assess the stress level of water; much like there are indicators that are employed to assess stress levels in human systems, e, g, pH, content of chemicals, presence of microbes. Indicators must represent or be correlated with effects of management. In addition these indicators must be relevant, acceptable, measurable, timely and sensitve. To asses effects of management and potential irreversible impact on water systems some reference for comparison is most helpful. One approach in flow water systems is the "input-output" model. Here an indicator is chosen and measured prior to an activity and measured again following the activity; this provides an index of impact and degree of stress.