Deterministic Methods in Systems Hydrology presents the basic theory underlying the multitude of parameter-rich models which dominate the hydrological literature. Its objectives are to introduce the elements of systems science as applied to hydrological problems; to present flood prediction and flood routing as problems in linear systems theory, clarifying the basic assumptions and evaluating their accuracy; and to review and to evaluate some deterministic models of components of the hydrological cycle, with a view to assembling the most appropriate model of catchment response, for a particular problem in applied hydrology. The material is developed in two parts: the first four chapters present the systems viewpoint, the nature of hydrological systems, some systems mathematics and their application to direct storm runoff. The final four chapters cover linear conceptual models of direct runoff, the fitting of conceptual models to data, simple models of subsurface flow and non-linear deterministic models.