Wetlands provide a range of benefits to society, and yet in South Africa wetlands continue to be affected by human activities. Considerable effort is now being directed towards rehabilitation of degraded wetlands and the construction of artificial systems to treat effluent and stormwater. At the same time, wetlands provide potential habitat for vectors or intermediate hosts (collectively referred to in this document as 'invertebrate disease hosts': IDHs), of parasites implicated in the transmission of such important diseases as malaria and schistosomiasis (bilharzia). The present review considers, for the 2 major IDHs (mosquitoes and schistosome-transmitting snails), the type of habitat required by the water-dependent life stage and the ways in which wetland degradation, rehabilitation and creation may affect the availability of suitable habitat. General practical measures for minimising pest species, particularly mosquitoes, are included. This review also highlights other issues that require research and testing in the South African context, including: the IDHs implicated in less well-known diseases (both of humans and animals) and the control of mosquitoes and schistosome-transmitting snails through biomanipulation. We conclude that in regions of the country where the diseases are prevalent there is the likelihood that wetland rehabilitation and creation could inadvertently encourage the IDHs responsible for transmitting malaria and schistosomiasis. Assessment of the potential risks and benefits of a proposed wetland modification needs to be undertaken in a holistic manner using an adaptive framework that recognises the critical need to balance human and environmental health. Possible ways of controlling IDHs both in an environmentally-and socio-friendly manner need to be investigated using a multidisciplinary approach engaging invertebrate biologists, health care officials, wetland scientists and also sociologists and economists.

More than half the river-lengths of rivers in southern Africa dry up occasionally or – more commonly – seasonally. Here we review the literature on water quality (WQ) in non-perennial rivers (N-PRs), with emphasis on river management and southern African systems. Hydrological regimes cover a spectrum from relatively predictable and unvarying in perennial rivers, to unpredictable and highly variable in non-perennial rivers, which are complex, continually shifting mosaics of flowing water, standing-water pools and terrestrial habitats. N-PRs are uncommonly difficult to manage because they represent a limited source of water that is renewed unpredictably and is competed for by local people as well as being required by wildlife. Groundwater, and therefore its chemical and physical features, contributes significantly to base flow and to the maintenance of pools remaining in the bed when the river is not flowing. Water chemistry reflects catchment geology except in polluted systems. Salinity varies temporally, and spatially over three dimensions, and is the variable controlling the composition of the biotas of many N-PRs. Hydrological regimes are seldom predictable with any certainty; WQ varies naturally over time and space; groundwater often determines the WQ of surface water, especially in pools; and WQ in non-perennial rivers and pools may be affected by activities far upstream in the catchment. As yet we have no more than a sketchy understanding of the extent to which data on any one system can be applied to any other. Until we have a better understanding of these systems, the following basic principles should guide the management of WQ in N-PRs: (i) Rivers need to be assessed on a case-by-case basis. (ii) Understanding of the groundwater regime, including its chemistry, is crucial. (iii) Effluents need to be controlled by conservative effluent standards set for both ground and surface waters. (iv) Flows may need to be augmented at certain times of the year.

As part of the determination of the ecological Reserve for rivers in South Africa (National Water Act, 1998), flow requirements are assessed for maintenance low flow, drought low flow and flood conditions. Since water quantity and water quality are often closely linked, it is necessary to ensure that in setting the recommended flow regime, the appropriate water quality will be attained. This paper presents a simple method (based on solute rating curves) for predicting the instream concentrations of chemical constituents that will arise from different flow regimes. The method uses monthly mean flow (discharge) at a given site plotted against monthly median concentration of each chemical constituent. This is carried out for both the reference condition (the natural, or least-impacted state) and for the present state. The flow-concentration relationships obtained are used to predict the expected monthly concentrations under the recommended flow regime. The computed concentrations can be compared with the reference condition and present state values to assess the degree of river modification. This paper outlines the modelling protocol to be followed, considers the limitations and assumptions inherent in the approach, and the application of the resultant information. It is concluded that the modelling method is a useful screening tool for identifying sites where, without reduction of pollution, the water quality component of the Reserve is unlikely to be attained under the recommended flow regime.

Linking the potential effects of altered water quality on aquatic biota, that may result from a change in the flow (discharge) regime, is an essential step in the maintenance of riverine ecological functioning. Determination of the environmental flow requirement of a river (as well as other activities, such as classifying the resource) is known in South Africa as determining the "ecological Reserve". This paper describes the philosophy behind the incorporation of water quality concerns in, as well as the constraints that are likely to be in operation during a Reserve determination. Three simple, predictive tools that have been developed for routine use in ecological Reserve assessments are described in this paper. Flow-concentration modelling can be used to predict the water quality that is likely to result from a given, prescribed flow regime. The Biotic Protocol attempts to provide an assessment of the likely implications of the predicted water quality for aquatic macroinvertebrates. Concentration time-series modelling can be used to rank complex flow scenarios with regard to potential consequences for water quality. Finally, a framework is presented for incorporating predictions of water quality and the implications for the aquatic biota in ecological Reserve assessments.

Chichester, 1999, 283 pp. ISBN 0-47198547-3. This book resulted from a 1-day meeting on Water Quality: Processes and Policy, held during the Royal Geographical Society -Institute of British Geographers Annual Conference in 1997. It brings together a total of 15 chapters, describing the processes that cause impairment of freshwater (and to a limited extent, coastal waters), and policies that have and can be implemented to address such impairment. The question of water pollution is considered from a number of different perspectives. Following a brief foreword and introduction, the book is divided into three sections. Section one examines the problem of water pollution on a global scale, and concludes that reduced water quality, especially in developing countries, is reaching crisis proportions. Section two, entitled 'Science for policy', presents several chapters on the science that is required in order for the processes that affect water quality to be understood, quantified and, ultimately, the results used for formulation of policy. This section describes modelling methods that have been used to simulate the movement of various chemical constituents (e.g. pesticides, nitrogen) through soil and water, and examines the effect of increased inputs and changes in catchment landuse on receiving waters. Two chapters are also included that examine the question of bacterial contamination of nearshore waters, and the implications for bathing. Another instructive chapter examines some of the factors that influence the computation of annual riverine loads of sediments, nutrients and metal pollutants. The final section of the book is entitled 'Linking science and policy'. A wide range of topics are covered in this section, from the importance of massive algal blooms in Australia in spurring on scientific research and development of policy, to integrated management of rural drainage basins in the UK. Of particular interest is the chapter on the economics of water pollution abatement. Overall, this section serves to illustrate (amongst other points) the contrast in enforcement of water quality standards or regulations in developed and developing countries.The strength of this book lies in the multi-disciplinary focus that has been applied to the question of water quality. As such, it includes consideration of the problem from different angles, including the economic, sociological and legal aspects. Because of the complex nature of many water quality problems, it is essential that they be tackled in a multi-disciplinary manner, and this book is useful in facilitating that goal. At the same time, however, one of the major criticisms is the fact that many of the chapters have been written by specialists for specialists. Terminology has frequently been employed with no accompanying explanations for readers that are non-proficient in that field. A little extra care in this regard would have gone a long way in making this book more readable. Despite this criticism, Water Quality: Processes and Policy offers interesting insights ...