The vast influx of population began pouring into the Las Vegas Valley in the 1940's the hydrologic regime of the Valley has undergone significant change. This domestic irrigation of vegetation together with wastewater return flows has caused a perennial stream leaving the Valley through Las Vegas Wash. This study was implemented to determine what is happening in the shallow ground-water zone (0 to 300') within the Valley, its flow, and the main sources of contamination. Results of this study have been divided into three volumes. This publication, the third volume, 'Simulation Modeling of the Shallow Ground-Water System in Las Vegas Valley,' discusses the problems and water level fluctuations in the shallow ground-water system.