SEARCHING FOR SIMPLICITY IN HYDROLOGY

The use of simplification as a route to scientific insight is reviewed with examples from hydrology and analogies from other sciences. The d iscussion covers a number of types of simplification: (a) simplificati on of the governing equations; (b) reduction of the state space, i.e. the number of dependent variables; (c) reduction of the solution space , i.e. the number of independent variables; (d) reduction of the param eter space, e.g. by freezing a slowly varying parameter; (e) simplific ation of the driving function e.g. Fourier analysis. The importance of scale is stressed and the possibility of apparent paradoxes between d iffering scales is noted. The complementary nature of deterministic an d stochastic approaches is also discussed.