UCLA

The mechanisms, magnitudes, and the effects of large-scale lacustrine changes can vary drastically over both time and space. These changes can alter the surrounding lithosphere, the interconnected natural systems, as well as the ever-growing connections to human water use. The timing of these changes can occur over several decades, or in some extreme cases these lacustrine changes can occur intra-annually (e.g. seasonal reservoir fluxes) or inter-annually (e.g. initial reservoir impoundments). The first portion of this dissertation work examines the magnitudes and effects of these changes at the Grand Ethiopian Renaissance Dam (GERD) in Ethiopia. Here, the mechanisms behind these changes are related to direct anthropogenic impacts (e.g. dam building and riverine impoundment). To this end, I examine the elastic deformation (Chapter 1) and subsurficial stress responses (Chapter 2) to several different impoundment and seasonal operational cycles at the GERD. Large hydrologic loads can impart notable stress on the surrounding crust and upper mantle, and, as such, I examine these stresses at the GERD and discuss the main drivers of potential reservoir triggered seismic events. The spatial patterns and amplitudes of the stress tensors and hydrologic-induced deformation are closely linked to both the size and timing of reservoir fluxes, and an improved understanding of the magnitude and extent of the stresses and deformation provides useful information to water managers in order to better understand the effects from many different impoundment and operational strategies. Lastly, this work examines the magnitude of water level changes for all waterbodies >1 km2 within the contiguous United States (CONUS) as derived from spaceborne lidar altimeter data products (Chapter 3). Here, the mechanisms behind these changes are related to both direct and indirect anthropogenic impacts and are quite diverse across the landscape. A more thorough understanding of the spatiotemporal differences in the magnitude of these changes provides the foundation needed to appropriately assess the varying mechanisms behind, and the effects of these changes. There is a notable spatial data gap of in situ water level measurements within the CONUS. To that end, remote sensing analysis provides a means to fill in those data gaps in order to glean a better understanding of the spatiotemporal water level changes across the entirety of the CONUS.