This book contains the Proceedings of the Symposium on Perspectives in Southern Hemisphere Limnology which was held from 3-13 July 1984 in Wilderness, South Africa. It can be asked why this Symposium was necessary at a time when conferences, symposia and other gatherings of learned people abound. Limnologists in the Southern Hemisphere have for some time been pointing out that limnological theory and inland water management practices have been developed almost exclusively in Northern Hemisphere temperate latitudes. Most of the land masses of the Southern Hemisphere fall within lower latitudes, 0 from 20-40 S, where the climate tends to be dry, with low cloud cover and with high levels of incident radiation and high water temperatures. Wide extremes are experienced in both rainfall and runoff, which occur mainly in summer. Sedimentary geological structures give rise to dispersive soils and highly turbid waters. Physiological, behavioural or developmental adaptations in the floral and faunal components are necessary to cope with desiccation and low visibility.

Limnology - the study of inland waters - had its genesis in Europe about the turn of the century. The studies of Fore1 on Lake Geneva were of seminal value at this time. It prospered under the early guidance of Thienemann, Naumann and Wesenberg-Lund in Europe and, soon transplanted, of Birge and Juday in North America (to name just a few early spirits). Now, liminology is a respectable scientific discipline taught at many universities, and limnologists are recognized as important contributors to our understanding of how this fragile spaceship functions. All this acknowledged, it must also be acknowledged that limnology is not yet a globally comprehensive science. To be sure, much is known about globally applicable processes, and the structural elements of aquatic ecosystems worldwide, but limnological emphases, interests and concerns remain essentially European and North American in balance. Much is known about lakes and rivers in less than one fifth of the world's land area (northern temperature regions); rather little is known about inland waters elsewhere.

Our understanding of the ecology of running waters has come a long way during the past few years. From being a largely descriptive subject, with a few under tones concerned with such things as fisheries, pollution or control of blackflies, it has evolved into a discipline with hypotheses, such as the River Continuum Concept (Vannote et a/. 1980), and even a book suggesting that it offers opportunity for the testing of ecological theory (Barnes & Minshall 1983). However, perusal of the literature reveals that, although some of the very early studies were concerned with large rivers (references in Hynes 1970), the great mass of the work that has been done on running water has been on streams and small rivers, and information on larger rivers is either on such limited topics as fisheries or plankton, scattered among the journals, or not available to the general limnologist. The only exceptions are a few books in this series of publications, such as those on the Nile (Rz6ska 1976), the Volga (Morduckai Boltovskoi 1979) and the Amazon {Sioli 1984), and the recent compendium by Whitton (1984) on European rivers, among which there are a few that rate as large.

This ia a synopsis and review of the major rivers of the world.