Understanding the climate-land-sediment relationships in the context of coupled nature-human
system (CNHS) of high mountain watersheds
Advisor: Professor Ximing Cai
ABSTRACT
In high mountain watersheds, the intricate interdependencies between climate change, land use
evolution, and sediment dynamics have profound implications for both ecosystems and human
societies. Global warming has markedly altered climatic regimes, exacerbating the water cycle and
intensifying hydrological responses. Concurrently, anthropogenic activities have driven significant
land use changes, further entangling the relationship between climate and land, with far-reaching,
synergistic impacts on sediment yield and watershed management. Understanding these complex
interactions within the framework of coupled nature-human systems (CNHS) is imperative for
developing sustainable management strategies, especially in fragile, high-altitude environments.
This dissertation tackles these challenges through a multi-faceted methodology framework
exemplified by a case study in the upper Lancang River Basin (LRB) situated in the southeastern
Tibetan Plateau. The projection of climate-vegetation cover-land use interrelations, grounded in
statistical methods and integrated with hydrological simulations, examines the synergistic impacts
of climate change and land use modifications on hydrological processes, providing a quantitative
analysis of how these factors interact to shape watershed dynamics. To further delve into the
intricacies of the CNHS, the dissertation introduces a novel modeling framework, in which a
coupled Cellular Automata-Agent-Based Model (CA-ABM) is bi-directionally integrated with a
hydrologic-agronomic model (SWAT+), enabling explicit modeling of land use decision making,
the feedback between natural and human systems, and the effects on environmental outcomes.
Ultimately, this framework is extended for future land use projection, emphasizing the feedback
mechanisms and coevolutionary dynamics between human behaviors and environmental emergent
properties, and exploring adaptive land use decision behaviors and policies that can mitigate
adverse environmental consequences while promoting sustainable development.
With an emphasis on the dynamic interactions between natural processes and anthropogenic
activities, this dissertation addresses synergistic and coevolutionary features of climate-land sediment
dynamics in high mountain watersheds in the context of CNHS. By illuminating the
feedback mechanisms and emergent properties, this work offers critical insights for policymakers
and environmental managers aiming to fortify the resilience and sustainability of river basin
systems amid ongoing climatic and land use transformations.