Hydrogeologic Framework and Numerical Simulation of Groundwater Flow in Bellevue, Washington

Abstract

hough the city of Bellevue, Washington is the fifth-most populous and fourth-fastest growing community in Washington, groundwater studies encompassing the city are noticeably few. Population growth, urban development, and recent drought have highlighted the need for a more detailed and comprehensive understanding of Bellevueís groundwater system. In response, this study developed a conceptual hydro-geologic model and numerical groundwater flow model of Bellevue and its immediate vicinity to provide a basic understanding of the groundwater flow system. The numerical model was implemented in MODFLOW-NWT, and focuses on the unconsolidated sediments present in the study area. The study area covers the Bellevue city limits and adjacent areas between Lake Sammamish and Lake Washington. Simulation of the groundwater flow system indicates that precipitation falling on the study area is the only significant source of recharge to the unconsolidated sediments. Approximately half of all recharge enters the groundwater system directly, while the other half runs off into surface water bodies before leaking into the groundwater system. All kettle lakes in the study area lose water to the groundwater system under steady state conditions. Most of the study area is drained by streams occupying the center of the study area which deliver water to Lake Washington.