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Source: ENVIRONMENTAL MONITORING HANDBOOK, PART 1, WATER Water quality guidelines (or criteria) are the scientific and technical information used to provide an objective means for judging the quality needed to maintain a particular environmental value. Knowledge-based management decisions made on the basis of this scientific knowledge are far more preferable than those resulting from pressure by narrowly focused lobby groups. A number of water quality guideline compilations are now available (e.g., USEPA, 1986a; CCREM, 1991; ANZECC, 1992). With few exceptions, these are broadly similar in their approach and in the threshold values they recommend. However, the recently released Australian and New Zealand water quality guidelines mark a radical departure from conventionally derived water quality guidelines (ANZECC ARMCANZ, 2000a). This chapter seeks to define the information and knowledge required by water managers and environmental protection agencies in deciding whether a particular water body has good or bad water quality. The important role of water quality guidelines in the water resources management process is covered first. The types of water quality guidelines are then discussed, focusing first on the human uses of water (e.g., drinking, recreation, irrigation). The main part of the chapter relates to guidelines for aquatic ecosystem protection. USE OF GUIDELINES IN THE SUSTAINABLE MANAGEMENT OF WATER RESOURCES The sustainable use of a water resource involves managing both the quantity and quality of the resource. This chapter will focus mainly on water quality aspects and only briefly cover other aspects of water resources management. A later section contains a short discussion of flow and habitat considerations. 1.3 Water environments are naturally quite variable systems, particularly in flow and ecosystem types. Therefore, any process that seeks to manage a water resource adequately must be responsive, flexible, and adaptable (Walters, 1986). A key objective of modern water management is to maintain the ecological integrity of the resource. However, the knowledge base and mechanisms to underpin this new ecosystem-based management approach are poorly developed (Boon et al., 1992; Sparks, 1995; Hart et al., 1999). It is now generally well recognized that most water bodies are closely linked to their catchment and that activities within the catchment can influence the quality of such water bodies (lake, reservoir, river, or estuary). Thus integrated catchment and waterways management is essential if the quality of particular water resources is to be maintained in the future. Water resource management must address community needs and wishes, and to achieve this, the community must be involved in the management process. Technical and scientific information is essential but not sufficient for the successful management of rivers. Water management involves difficult trade-off decisions often between incompatible objectives, such as ecosystem protection and additional water for irrigation. It is vital that the decision-making process is as transparent as possible if such decisions are to be accepted by the community. Figure 1.1 shows the main steps involved in the water resource management process (Hart et al., 1999). These are discussed briefly below. Knowing the system: A good scientific and technical understanding of the aquatic system is essential if it is to be managed effectively. In particular, information is needed about the condition of the catchment, the water resource itself, the present water quality and stressors likely to degrade the quality, and uses of the water resource. Management goals: Clearly, it is essential in any management process to decide why the system is being managed. At the highest level, the goal of managing a natural resource is to improve community well-being through sustainable use and protection of the natural environment. Effective management of a nation’s water and aquatic resources is crucial to the continued viability of society. Environmental values (or beneficial uses): Identification of the community needs and wishes for the water resource (e.g., agricultural water supply, swimming, fishing, and protection of the ecosystem) provides the first step in defining the environmental values of a particular water body. The major environmental values considered in most guideline documents are: - Ecosystem protection - Drinking water supply - Recreational water use - Agricultural water use (e.g., irrigation, stock watering, aquaculture) - Water for industry Stressors are the physical, chemical, or biologic factors that can cause an adverse effect on an aquatic ecosystem. Toxic stressors include heavy metals and toxic organic compounds, salinity, and pH. Nontoxic stressors include nutrients, turbidity and suspended particulate matter, organic matter, flow, and habitat. Water quality objectives are established in terms of key indicators of quality that provide a means of identifying and measuring change in the environmental values. They can include physical, chemical, radiologic, microbial, or biological measures of water quality. Broadly, three types of indicators of environmental quality exist: - Indicators that are normally present in the water and can be monitored usefully for a change in concentration, quantity, or quality (e.g., salinity and nutrient and heavy metal concentrations) - Indicators that are not normally present but which if detected in certain concentrations or quantities can be used to identify a change (e.g., concentrations of pesticides and other toxic organic compounds) - Indicators that are normally present but the absence of which reflects a change Guidelines provide an objective means for judging the quality needed to maintain a particular environmental value. Normally they are described in terms of the key indicators of quality. Management actions: Water quality objectives defined by the preceding process will require actions to maintain and/or attain the desired quality and therefore achieve the environmental values identified by the community. Programs or strategies that might be developed to achieve these objectives could include control of waste. 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