CRDSS_Task1_15-7_ReviewStreamAquiferSimulationModelSAMSON

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CRDSS TASK MEMORANDUM 1.15-7 Water Rights Planning Model Review of the Stream-Aquifer Simulation Model SAMSON 1.0 ISSUE The purpose of this task memorandum is to generally describe the computer model SAMSON developed by the Colorado Water Resources Research Institute at Colorado State University and to summarize the model's functionality related to the CRDSS project based upon the Level One decision criteria presented in CRDSS Task Memorandum 1.15-2. In order for SAMSON to be considered as a candidate for the CRDSS water rights planning model, it must satisfactorily meet the requirements of the evaluation criteria. 2.0 DISCUSSION/ANALYSIS SAMSON was designed to simulate a stream-aquifer system with management and allocation constraints. The model was developed to simulate the physical and operational behavior of the South Platte River system and has not been applied on any other river basin. The Northern Colorado Water Conservancy District was a participant in the application of SAMSON to the South Platte River; however, there has been no current use or maintenance of the model by the District or by the Research Institute. SAMSON uses a daily time-step for simulation of a stream-aquifer system and is classified as a watershed management model rather than a river basin simulation model. Two main components are used in the SAMSON model. The first component simulates the physical processes such as precipitation, evaporation, transpiration, and the movement of surface and ground water including infiltration. The second component is the allocation model which distributes surface and ground water in the system to water users according to specified operation rules. SAMSON attempts to incorporate the entire physical processes of the hydrologic cycle on a daily basis. It can be used to evaluate the effectiveness and legality of augmentation plans and management strategies for the conjunctive use of surface and ground water supplies. The model determines the available flow at diversion nodes, river outflows at the downstream boundary of the system, the amount of water recharged to the alluvial aquifer, ground water return flows, and the amount of water consumed by evaporation and evapotranspiration. Because SAMSON is a watershed management model, the data requirements for the physical component of the model are very extensive and not readily available for all river basins. The data input requirements for water rights are very complex and are not very efficient if a large number of water rights are simulated. Only simple reservoir operations can be modeled, and multiple ownership accounts in reservoirs cannot be simulated. Detailed water right exchange operations cannot be simulated by SAMSON. 1 A275 05.10.94 1.15-7 Fosha, Hyre