A SURFACE AND GROUND WATER MODEL FOR THE CONJUNCTIVE USE OF A STREAM-AQUIFER SYSTEM (COLORADO)

SAMSON, an acronym for underbar S tream- underbar A quifer underbar M odel for underbar M anagement by underbar S imulati underbar ON, is a computer model designed to simulate a stream-aquifer system with management and allocational constraints. It can make comparative studies of water allocation in a river basin that include natural elements such as a main river and its tributaries, and manmade elements such as canals, reservoirs, and wells. The model enables the user to predict the response of a river basin to different configurations of structures and to different water resources management strategies. It evaluates the effectiveness and legality of augmentation plans and addresses the conjunctive use of surface and ground water management opportunities.; SAMSON consists of two major components: the decision (allocation) model and the physical model. The allocation model distributes the surface and ground water in the river basin for daily operations among the water users according to some specified rules of operation. It deals with the decision processes of the agencies or individuals in charge of the operations of the system. It thus makes decisions for every day, regarding all diversion amounts at all diversion points (e.g., canals, reservoir outlets, and wells) in the entire study area. The rules of operation may be determined by existing water use practices, water law, availability of water, and other operational procedures imposed by the user.; The physical model consists of many modules, linked together by a strict logical structure. Using the results of the allocation model, it predicts the new state of the basin based on physical laws that govern the movement of the water both above and below the ground surface. In this way, it provides a physical and analytical solution to the individual hydrologic processes. Most of these processes are modeled on a daily basis, with the exception of aquifer system conditions, which are modeled on a weekly basis.; An application of the model is made to the South Platte River from Denver to the Nebraska border. It could be used as a management study tool for this agricultural basin.