An existing simulation model of the Weber Basin (GRES Model) was used as a basis for creating an equivalent model on the Water Evaluation and Planning (WEAP) system. The GRES Model was developed by the Utah Division of Water Resources (UDWR) and simulates the historical water allocation from 1950 to 2006. Using the GRES Model and additional information obtained from UDWR staff, two different WEAP models were created. The two models differed only in how water is transmitted to the service areas. End-of-month reservoir storage and other outputs from the GRES Model were compared to the two WEAP models. The two models turn out to be almost equal. The simplest version of the two WEAP models was selected and named the WEAP Weber Basin Model. The WEAP Weber Basin Model is basically a historical simulation of water allocation in the Weber Basin and shows that the storage level in most reservoirs, except Causey, does not reach the buffer zone. This result indicates the historical water security of the basin and also the security in the foreseable future. The WEAP Weber Basin Model was also modified. Two scenarios consider demand growth (i) with, and (ii) without applying water conservation. These modifications were applied to one of the service areas which serves purely municipal and indusrial demands. The inflow to the system was populated by randomly reshuffling the historical flows. This is assuming that the historical flows will repeat in a random order in the future. Hence the inflows to the streams in 2006 were assigned the historical inflows of 1968 and so on. The result from the WEAP Weber Basin Model without conservation (with growth) shows that most of the reservoirs, with the exception of Pinveview and Willard Reservoirs, do begin to draw from the buffer zone towards the end of the simulation period. Different storage carryover policies tested show that the reliability of the system decreases while its resilience increases when more and more of the water in the buffer zone is carried over between time steps. Applying conservation seems to reduce the shortages created when different storage carryover policies were implemented compred to the model that did not apply conservation.