Global satellite-based measurement of river and reservoir dynamics
Creators: name: Hou, Jiawei
Publisher: name: The Australian National University
Year: 2020

description: Knowledge of the dynamics of rivers and reservoirs is important to help manage the impacts of climate change and anthropogenic activities on water resources, which are intimately tied to human well-being, economic wealth and environmental health. However, ground-based measurements only capture a small fraction of water bodies, and in situ observed data are generally not publicly shared in most countries for a variety of reasons. Satellite remote sensing technology provides promising new opportunities to measure global water availability at different time and space scales. The objective of this study was to develop a global monitoring capacity to measure rivers, lake, and reservoir dynamics using satellite observation. In pursuit of this objective, I propose approaches to measure river discharge, river morphology, and lake (reservoir) storage based on remote sensing data. Satellite gauging reaches (SGRs) that can predict river discharge based on optical remote sensing are shown to be applicable to many rivers globally, especially in South America, Africa, and Asia. The river discharge prediction capability of SGRs in a certain river reach can be explained by its unique river morphology characteristics. Hydromorphological attributes, including spatial and temporal river width, flow regime and river gradient were produced for 1.4 million Australian river reaches, and can be used to improve river routing in models to better estimate river discharge. Finally, storage dynamics for 6,743 reservoirs worldwide for the period 1984-2015 were reconstructed based on satellite observations. The results indicate that some storages, particularly in southeastern Australia, central Chile, the USA, and eastern Brazil, have declined, accompanied by reduced reservoir resilience and increased vulnerability. Others have increased, mainly in the Nile Basin, Mediterranean basins and southern Africa. Multi-decadal changes in rainfall and hence streamflow were found to be the main reason for these changes. The techniques and data produced in this study provide components for a global monitoring capacity. The approaches developed can be used to process near real-time observations continuously. In future, the storage estimation method developed may be extended to lakes and wetlands. This study emphasizes the importance of increasing, or at least maintaining, the number of global gauging sites, which not only provide the historical context and current status of water resources under climate change, but also provide an indispensable basis to train remote sensing data in order to create a global water availability picture. Collaboration among different counties is urgently needed to share in situ river, lake, and reservoir data to tackle current and future water crisis, a challenge people worldwide face together. Considering the essential role of water resources for human well-being, new satellite missions are required that are specially designed for simultaneously measuring water extent and elevation in rivers, lakes, reservoirs, and wetlands at high spatial (e.g. 10 meters) and temporal (e.g. daily) resolution over the next decades.