Droughts and Floods in a Changing Environment: Natural Influences, Human Interventions, and Policy Implications

Abstract

Hydrological extremes, in the form of droughts and floods, have huge impacts on a wide range of sectors including, most prominently, water availability, food security, and energy production, among others. The expectation of heightened drought and flood risk under climate change, coupled with burgeoning population growth and rapid economic development, poses unprecedented challenges for societies to boost resilience to these natural hazards, mitigate their extreme impact, and develop effective and actionable solutions towards sustainable development. The objective of this dissertation is to advance our understanding of these hydroclimate risks and their societal impact in a changing environment through a coupled human and natural system (CHANS). Chapter 2 and 3 diagnose the changing characteristics of droughts and floods from a climate perspective. Chapter 2 compiles the first Global Drought and Flood Catalogue (GDFC) to provide long-term, consistent and robust estimates of drought and flood hazards. This state-of-the-art catalogue acts as a basis for us to understand current risks and how they may change in the future. Based on GDFC, Chapter 3 develops a novel statistical framework to examine the often overlooked but important risk of coincident droughts and floods. Chapter 4 and 5 focus on the human dimension of the CHANS. Using a physical framework, Chapter 4 conducts attribution analysis to disentangle how climate variability and human interventions (e.g., water use, irrigation, reservoir operation) intensify or mitigate the recent California drought. Taking a further step, Chapter 5 aims to incorporate human behaviors and decisions – which are currently unrepresented – into a large-scale hydrological model to investigate how individuals’ decisions and their behavioral heterogeneity affect the dynamics of the CHANS. Chapter 6 develops a hydro-economic model to identify possible solutions and optimal development pathways towards better management of water-related trade-offs (i.e., energy production and irrigation in California) and environmental sustainability (i.e., groundwater depletion). The integrated modeling platform developed in this thesis can be used to balance trade-offs among conflicting objectives and quantify the potential space for improving current water management strategies, especially under severe hydrological extremes.