On the Systems Approach in Hydrology

There is a long felt need for a general theoretic frame work for hydrologic systems research which imbeds dynamical, structural, spatial and behavioral aspects of modeling with predictive powers. Many of these problems can be effectively studied by systems analysis. The process of system modeling for large-scale, nonlinear, time-lag systems can be rationalized by suitably identifying and modeling subsystems. When computers are used as modeling tools methods of formulating the problem, choice of the computer used, and choice of performance criteria greatly influence the results. This in turn imposes certain limits on the validity of computer simulated models. These aspects are discussed by studying the nature of hydrologic systems and the nature of the associated inverse problems and requirements for validating the models.