River Mixing

River Mixing J. C. Rutherford NIWA Ecosystems, New Zealand Quantitative predictions of the rates of mixing of tracers (principally neutrally–buoyant tracers) in rivers are needed in a variety of situations including the preliminary design of outfalls, the impact assessment of discharges, water resource planning, and research on biological processes in rivers. River Mixing describes the theoretical basis for commonly–used mixing models, in order that the mixing equations being used are easily understood, and the correct mixing model is chosen for any given problem. Information from a variety of sources is collated to provide the user with a book which contains all the important elements: the theory; the models and solution methods for important river mixing problems; and the methods for determining mixing coefficients. Guidance is given when making rapid calculations for important mixing problems, and recent progress in the understanding of vertical and transverse mixing is discussed. The emphasis is placed on simple models which are invaluable for making rapid and relatively inexpensive appraisals of a mixing problem, although the more complex models, which may be used once a preliminary analysis has been completed, are also described. Covering all the key elements, River Mixing is essential reading for practising engineers, research scientists and technical managers of water resources.