Interferometric synthetic aperture radar (InSAR) technology allows for detailed monitoring of levee and delta subsidence, while polarimetric SAR (PolSAR) can detect levee seepage. The dissertation first reviews the history of microwave remote sensing and its basic principles before focusing on case studies of land subsidence (Chapter 1). Northern California’s Sacramento-San Joaquin Delta has an exemplar earthen levee system that protects the area from flooding. The region supports part of the water supply for 25 million residents and contributes billions to the state’s economy from agriculture. However, historical drainage for farming has caused continued subsidence of Delta islands, and threatens their vulnerable levees. Aging flood infrastructure needs to be closely monitored as metropolitan areas globally face increasing inundation risk from sea level rise. To augment traditional ground survey, InSAR is shown to efficiently quantify elevation change along levees with continuous spatial coverage (Chapter 2). Evidence of settling from historic breaks is investigated using a vertical velocity map and time- series of cumulative displacement from data acquired by the UAVSAR (Uninhabited Aerial Vehicle SAR) L-band instrument, during 2009-2015. Previous field studies lack continuous subsidence maps across islands that display local complexities (Chapter 3). Traditional lidar surveys, land cover, elevation, and soil organic matter datasets are compared to explain small- scale subsidence. Threats to levee infrastructure include seepage, which occurs when water moves below the structure, weakening structural integrity. Seeps can be detected using PolSAR, which is sensitive to changes in dielectric constant and surface roughness. Since wet soil has a much higher dielectric constant than dry soil, seepage is shown to be detectable with a polarimetric ratio. The California Aqueduct in the San Joaquin Valley is chosen as a dry testbed to investigate polarimetric seep signatures, and the procedure is also applied to Twitchell Island in the Delta (Chapter 4). The potential to combine SAR and GIS visualization makes instruments like UAVSAR optimal to study deltas. UAVSAR’s airborne capability can be utilized during disasters to detect structural damage and flood extent (Chapter 5). UAVSAR is also the prototype for the upcoming NASA-ISRO satellite, and detailed monitoring and response will be attainable for flood infrastructure globally.

The North China Plain (NCP), which encompasses the Hebei, Tianjin, and Beijing provinces, is known as the breadbasket of China and the country’s largest producer of wheat and maize. The NCP relies heavily on groundwater for agriculture, with 60% of its water supply relying on this resource. Such overreliance can result in groundwater depletion and water scarcity, as has been observed in many cases around the world. Land subsidence is often considered as a consequence of groundwater depletion, which has not been quantitatively confirmed, though such aquifer compaction can lead to public safety issues and water management problems by decreasing the holding capacity of important aquifers. In this study, we employed the commonly used Gravity Recovery and Climate Experiment (GRACE) data with well records to validate the groundwater depletion that has already been reported in the NCP, and found similar rates of -2.03 cm/yr water loss for 2002-2014. To quantify the effects of land subsidence, we used NASA’s Ice, Cloud, and land Elevation (ICESat) satellite to measure changes in land elevation in the NCP (5-8 cm/yr). The spatial patterns of groundwater depletion and land subsidence measured from the datasets do not exhibit a one-to-one match, which is to be expected for such processes, but both show the low-lying plains of north China to be a significant area of depletion/subsidence. The seasonality observed from the ICESat data is shown to be sensitive to vegetation height change during the growing season, and interpolated points showed increase subsidence in areas of winter wheat cropland. As confirmed by previous studies, the southern areas of Hebei province are experiencing the most significant groundwater depletion, land subsidence, and contain the most productive cropland, which is of concern to water management in the area and the future of agriculture for northern China.

A substantial and rapid expansion beginning in the late 1990s of Siling Co, the largest endorheic lake on the central Tibetan Plateau (TP), has caused a measurable deflection in the region adjacent to the lake. Current broad-scale measuring of this flexural response is mainly derived from DInSAR processing techniques. The underlying lithospheric response to large lake loads in this region is not well understood, with the focus on either a viscoelastic or an elastic response. This thesis intends to use a more efficient LiDAR remote sensing technique to measure the deflection in the vicinity of Siling Co, and to investigate the mechanisms of the observed lithospheric response. A lake-adjacent deflection rate and Siling Co water load variations are calculated utilizing the Geoscience Laser Altimeter System (GLAS) onboard NASA’s Ice, Cloud and land Elevation Satellite (ICESat) and the joint NASA/USGS Landsat series of earth observing satellites. A downward deflection rate of ~5.6 mm/yr for the first 4 km of lake-adjacent land is determined from the GLAS instrument and this response is compared to the flexural outputs from a spherically symmetric, non-rotating, elastic, and isotropic (SNREI) Earth model in order to better understand the underlying mechanisms of the lithospheric response to the extreme change in Siling Co loads. The modeled elastic response is ~6.7 times lower than the GLAS derived flexure, thereby providing further evidence that a completely elastic lithospheric response cannot explain the deflection in this region, and that a viscoelastic response is more likely. The relationship between the modeled elastic response and the GLAS derived flexure is applied to a long-term lake load change dataset to create the longest-running flexural response curve as caused by the last ~40 years of Siling Co load variations.

In the era of "Anthropocene", lakes as essential stocks of terrestrial water resources are subject to increasing vulnerability from both climate change and human activities. There has been a widespread recognition of the need for further enhancing our monitoring and understanding of lake dynamics under complex human-environment interactions, particularly in populated and rapidly developing regions. To address this pressing need, this dissertation highlights the Yangtze River Basin downstream of China's Three Gorges Dam (TGD), one of the world's most populous areas and a critical eco-region, which hosts the largest cluster of freshwater lakes in East Asia. The TGD, thus far the world's largest hydroelectric project, initiated water impoundment in June, 2003. Existing studies document that individual lakes in this region have recently experienced dramatic changes under the context of enduring climatic drought, continuous population growth, and extensive human water regulation. However, spatial and temporal patterns of lake dynamics across the complete downstream Yangtze basin are poorly characterized; and the underlying changing mechanisms remain largely unclear. With an emphasis of the controversial TGD impacts, this dissertation presents a comprehensive investigation integrating remote sensing, spatial statistics, and hydrological modeling to (1) understand the recent lake dynamics across the downstream Yangtze Basin before and after the initial TGD operation and (2) diagnose the driving mechanism from inducing factors of both climatic variability and major anthropogenic activities, i.e., the TGD operation and human water consumption.

A widespread net decline in lake inundation area was revealed across the downstream Yangtze Basin during 2000-2011 from daily optical imagery acquired from the Moderate Resolution Imaging Spectroradiometer (MODIS). The decreasing trend was tested significant in all seasons, leading to an evident phase drop of the average annual lake cycle before and after the TGD operation (hereafter referred to as "post-TGD decline"). The most substantial decline appears in fall, which intriguingly coincides with the TGD water storage season. Regional lake dynamics exhibits contrasting spatial patterns, with decrease and increase of aggregated lake area within and beyond the Yangtze floodplain, respectively. Decreasing lakes in the floodplain, whose elevations are below the natural Yangtze level maxima, pose further puzzling of TGD's impacts on the lake system.

To investigate the underlying mechanism driving the post-TGD lake decline, a diagnostic approach was proposed based on the conceptual chain where the impact of an inducing factor (e.g., TGD's regulation) usually starts from the Yangtze flows, then propagates to the downstream Yangtze levels, and eventually the surrounding lake inundation areas. Using in situ measurements and hydrological modeling, daily Yangtze level changes were first quantified along the complete downstream range, as a combined result of i) TGD's flow regulation and ii) Yangtze channel erosion due to reduced sediment load. Derivative impacts on lake inundation areas were then assessed as empirical functions of lake-outlet level changes. Results uncover an altered inundation regime of the downstream lake system by TGD's water regulation, manifested as evident lake area decrease in fall and increase in spring and winter. As the most substantial influence, reduced lake area in fall explains ~18-83% of the observed post-TGD decline across the downstream Yangtze Basin. Concurrent Yangtze channel erosion slightly reinforced the area decrease in fall while counteracting ~34% of the area increase in winter. Human water consumption accumulated through the local river network led to constant Yangtze level decrease, which completely counteracted TGD-induced lake area increase in winter. However, human water consumption only adds minor contribution (< 6%) to the post-TGD lake decline due to slow increasing rates during 2000-2011. The major proportions of seasonal post-TGD lake declines were tested to be largely triggered by the decadal climatic drought across the downstream Yangtze Basin; however, the quantified anthropogenic impacts are evident and anticipated to increase in the coming decades due to chronic Yangtze channel erosion and continuous population growth.

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.

The boreal forest circles the high northern latitudes but it is far from a continuous carpet of evergreen trees. Rather, the boreal forest is a patchwork of land cover types in constant flux as they recover from wildfire and then are burned again. This fast turnover of land cover makes the boreal forest particularly susceptible to rapid change in response to climate. Furthermore, the boreal forest is an important component of the climate system that pumps heat into the atmosphere and significantly raises northern hemisphere temperatures year-round. As both a major component of the climate system and a sensitive indicator of climate change, the boreal forest is in a feedback loop. The direction of that feedback loop, positive or negative, depends largely on the strength of the land-atmosphere exchange of heat and momentum driven by forest cover and its spatial structure. That spatial structure has yet to be comprehensively measured.

This dissertation used newly available, high resolution, satellite based forest cover data to quantify the heterogeneity of the boreal forest in North America. First, at the local scale, the pattern of forest cover patches within fires were found to be larger, more regularly shaped, and clustered than in unburned forest. The heterogeneity metrics also returned to pre-fire levels relatively quickly. At the continental scale, the landscape heterogeneity maps were analyzed by region, with respect to the northern extent of trees, and disturbance regimes. The boreal forest regions had smaller, more complicated forest patches, and no single dominant forest cover class which was significantly different than the temperate forests that border the region to the south. When compared to two preexisting maps of the boreal treeline, the patch cohesion metric indicated that the tundra ecoregion extended further south into the forested Central and Eastern Canada. Based on this finding, a new patch cohesion-based treeline was drawn which divides the boreal forest and tundra in a standard and repeatable way. Lastly, fires and lakes had the opposite influence on the heterogeneity metric contagion. Fires tended to decrease heterogeneity in the landscape because they were larger than the preexisting forest patches while lakes were smaller and broke up the landscape increasing heterogeneity. The heterogeneity maps produced as a part of this dissertation will continue to provide insight into the spatial pattern of the boreal forest in the future.

Water is a key resource in arid Central Asia (CA) and is heavily affected by climate change and human activities. Temperature across the region has increased drastically especially in the mountain region while precipitation change is less homogeneous. The increased temperature has caused increased melting of glacier and snow which has a large contribution to the runoff in rivers. Human activities such as agriculture irrigation and reservoir management also affect water availability. In the Soviet era, agriculture in CA expanded continuously and large amount of water was extracted from rivers for irrigation. This has caused the catastrophic decline of the Aral Sea. In the post-Soviet era, countries in CA have reorganized their agriculture structure to be self-sufficient. It is important to understand how these changes affect water availability in CA especially under climate change. This dissertation uses lakes as proxy indicators of water availability and assesses how climate and human activities have affected lakes in CA. Seventeen lakes located in three former Soviet republics and western China from seven basins are examined using remote sensing and hydrologic modeling to estimate their changes in area, water level and volume. Agriculture area changes in these basins from seven countries are also examined using remote sensing. It is found that 1) lakes located in the mountains have generally expanded due to the melting glaciers and snow; 2) lakes located in the lowlands have remained relatively stable due to the relative stability of agriculture area; 3) reservoirs exhibit different seasonal patterns due to their major function as power generation reservoirs release water during the winter while irrigation reservoirs release water during the summer; 4) agriculture area in the former Soviet Central Asia republics is highly dependent on precipitation due to the lack of efficient irrigation infrastructure while agriculture in China has continuously expanded due to the adoption of drip irrigation and groundwater extraction. In conclusion, climate is the more dominant factor affecting water availability especially in the mountains causing the lakes to expand while agriculture irrigation has offset some of the surplus in the lowlands causing the lakes to remain relatively stable.

Lakes are unique in the land surface due to their well-known anomalous intrinsic properties – unusually large heat capacity, stark albedo contrast with water’s phase change and sun’s position. They also exhibit a wide spectrum of extrinsic properties – related to their occurrence, distribution and abundance. That they are ubiquitously besprinkled over most land surfaces with such intrinsic (extrinsic) anomalous (spectrum of) properties makes them a low-hanging fruit to observe from space and tease out in-land climate change signatures from local to global scales. In this dissertation, I explore four aspects in our current understanding of lakes and their connection to climate change, and I show that: 1) Long-term lake changes are multi-directional in nature as a rule and not exception; 2) Lake evaporation calculations using global data can be improved by ~5% at seasonal scales and ~50% (i.e. 5-10X better) in the energy gap to turbulence scales (i.e. ~30 minutes), compared to 5 other state-of-the-art mass-transfer methods, by virtue of a century-old misunderstood body of work by Robert E. Horton that is based on kinetic theory of gasses; 3) Long-term trends can be separated from correlation noise up to 1-sigma better than current practice in terms of both statistical power and confidence by combining a portfolio of 16 methods from two families of trend detection tools from Econometrics (parametric) and Hydrology (non-parametric); 4) Building upon the results of 1-3, a quasi-analytical water albedo model, and derived lake and climate variables from many sources (including Google Earth Engine datasets) can help us characterize lake changes up to sub-daily and sub-meter (micro-topography) scale, under the assumption of regional hydro-climate homogeneity at 0.25 degree spatial resolution (an unavoidable caveat governed by rain gauge density) for millions of Arctic Boreal Zone (ABZ) lakes. Collectively, these results I demonstrate at continental scale spanning whole of Canada and Alaska, ~10 million lakes, carve a pathway for a high-fidelity understanding of local-to-global scale climate change signatures on ~100 million lakes, which are, due to their intrinsic and extrinsic characteristics, our best in-land sentinels of climate change.