An Agenda of Problems for the Future

Past trends having been examined, there are two traditional aspects of prediction that will help define an agenda, albeit speculative, of problems for the future. For example, interpolation is a conventional way of specifying what is needed to cover any outstanding gaps in past achievements, and extrapolation suggests what would follow from the trends already established. These represent essentially “smooth” developments in a subject. For instance, the growth of interest in the problems of impounded river sections, which represent a convergence of river-like and lake-like problems, is a fairly predictable development. It is obvious that new pollution problems will emerge, but this does not mean that modeling for the purposes of solving these problems will be conducted in any radically different fashion. That is to say, the pollution problems may have different physical, chemical, and biolog­ical attributes, but it is hard to imagine that the procedure of model develop­ment would be radically different from that of Figures 6 and 7 or that the models developed would be essentially different from that of Table 1. Indeed, as with all matters of prediction, it is just as difficult (if not impossible) to speculate about significantly abrupt changes in the development of a subject as it is to predict abrupt changes in the behavior of a system.