UC San Diego

The higher variability of surface-water supplies due to a changing climate has motivated an increased reliance on groundwater for urban, industrial, and agricultural purposes. This is particularly evident in California’s San Joaquin Valley (SJV) where overexploitation of the underlying aquifer system threatens the quality and availability of future groundwater resources as well as lead to large magnitude land subsidence threating critical infrastructure. Direct observation of these reservoirs on policy relevant scales, however, has remained elusive. The three principle chapters of this dissertation explore the extent to which geodetic tools and data can be used to better characterize regional subsurface processes such as groundwater recharge, flow, and extraction. Chapter 1 provides the motivation of this research and an introduction to the data used in the subsequent chapters. Chapter 2 presents a new methodology for combining interferometric synthetic aperture radar (InSAR) and Global Positioning System (GPS) displacements. Chapter 3 explores the efficacy of seasonal surface displacement time series for characterizing locations of groundwater recharge and flow in the SJV. Chapter 4 describes a method for analyzing networks of groundwater level records and how they relate to an extension of Chapter 3 results.