Document Type


Publication Date

January 1966


As demands upon available water supplies increase, there is an accompanying increase in the need to assess the downstream hydrologic system. At Utah State University this problem is being approached by electronic analog simulation of the hydrologic system. Modeling concepts are based upon the development of basic relationships which describe the various hydrologic processes. Within a system, these relationships are linked by the continuity -of-mass principle which requires a hydrologic balance at all points. Once established, the model is applied to any particular geographic unit by determining the appropriate constants of the hydrologic equations. The analog computer is ideally suited to the solution of the many time-dependent differential equations which are encountered in the hydrologic systems. The complexity of a hydrologic model depends to a large extent upon the magnitude of the time and spatial increments utilized in the model. In this study the mathematical development was based on the concepts of relatively small increments of space and large time increments. The model is, therefore, applicable to in-basin probelms involving a time increment of, for example, one month. To test individual equations and to verify the model, the Circle Valley subbasin of the Servier River system in Utah was simulated. Close agreement between computed and observed outflows was achieved on both a monthly and a total annual basis.