Abstract
D.Phil.
South African water resource management policies as well as the country's water law have been under review over the past three to four years. The Water Law Principles, which were established as part of this review process, indicate a commitment to sustainable development of water resources and the protection of an ecological "Reserve". Such policy goals highlight the limitations of conventional water quality management strategies which rely on stressor monitoring and associated regulation of pollution.
The concept of an assimilative capacity is central to the conventional water quality management approach. Weaknesses inherent in basing water management on the concept of assimilative capacity are discussed. Response monitoring is proposed as a way of addressing some of the weaknesses. In fact, the inadequate use of biological indicators and techniques in monitoring and evaluating the quality of resources has been identified as a major factor responsible for the continuing decline in the health of natural resource systems. With advances in environmental monitoring over the last decade, it has become clear that biological techniques and protocols need to become part of monitoring in order to allow effective assessment and protection of aquatic
resources.
One way of incorporating response measures into resource assessment is through the use of toxicological assays. As an example, a toxicological assessment of the environmental risk associated with an organic pesticide (fenthion) is presented. Acute and chronic assays were conducted with a spectrum of test organisms. These toxicological response results provided an ability to predict the ecosystem response that can be expected from certain concentrations of fenthion in the environment.
Theoretically, it would be possible to design a risk assessment experiment for every new
anthropogenic substance. However, in terms of cost and time, it would not be practically feasible to execute such experiments. To overcome this problem, a method has been developed to derive water quality criteria for toxic substances using existing toxicological data. This provides water resource managers with a readily available set of values to guide them in decision-making. It is demonstrated how available acute and chronic toxicity data can be synthesised into acute and chronic water quality criteria for the protection of aquatic life. As these criteria are intended to extend protection to ecosystems country-wide, they are very conservative by design.
Although a set of numeric water quality criteria provides an important tool to water quality
managers, the limitations associated with the use of these criteria must be recognised.
x
Limitations relate either to the design of toxicity experiments or to the use of a chemical-specific approach alone in water resource management. In order to overcome these limitations, three broad supporting technologies are proposed, namely whole effluent toxicity (WET) testing, sitespecific adjustment of water quality criteria, and in-stream biological assessments.
Whole effluent testing aims at evaluating the toxic effects of an effluent on organisms. In doing so, acute and chronic toxicity testing (and thus biological responses) becomes part of effluent regulation. An effluent control programme that incorporates toxicity-based standards and compliance criteria is proposed.
One of several approaches that can be used for deriving site-specific water quality criteria is the
calculation of a water-effect ratio. It is demonstrated that the water-effect ratio method could
result in significant adjustments to the national water quality criteria. Although more
development and local testing would be required, such site-specific criteria could be in the
interest of both ecosystem protection and economic development.
In-stream biological assessments introduces a type of response monitoring which provides
insight into the overall integrity of aquatic ecosystems. A comprehensive biomonitoring
programme is designed. To adhere to the objectives of this programme, specifications have been
developed for the selection of sampling sites, the selection of biological and habitat indicators,
and the management of the resulting data. This programme is referred to as the River Health
Programme (RHP).
The ultimate aim of any monitoring programme is to provide useful data. Such data must
contribute to effective decision-making. To ensure that the RHP becomes truly operational as
a management information system, a step-wise procedure is proposed for linking the collected
data with management actions. It is demonstrated how following of this systematic and iterative
procedure would facilitate ongoing learning and improvement of the individual steps (e.g. data
collection and assessment, goal setting, selection and implementation of management actions)
as well as the overall procedure.
As a final step, the dynamics that influence the transition of any new technology from scientific
development to operational application are explored. The RHP is used as a case study and
theoretical models from the field of the management of technology are used to provide valuable
insights. Four key components of the RHP design are analysed, namely the (a) guiding team, (b)
concepts, tools and methods, (c) infra-structural innovations and (d) communication. These key
components evolved over three broad life stages of the programme, which are called the design,
growth and anchoring stages.