Human–Water Feedbacks under Climate Change on a Tourism-Dependent Island: An Integrated Assessment of Water and Energy Balances on Green Island, Taiwan

Small islands are particularly sensitive to climate change due to limited storage capacity, strong dependence on external energy supplies, and close coupling between human activities and environmental processes. On tourism-dependent islands, fluctuations in population, climate variability, and infrastructure constraints can generate complex feedbacks between human water use, hydrological processes, and ecosystem stress. Green Island, a volcanic island off the southeastern coast of Taiwan, provides a representative case where water-related challenges arise not from a lack of total precipitation, but from the highly episodic nature of rainfall associated with typhoons, during which large volumes of rainwater are rapidly lost through runoff and coastal discharge. This research investigates human–water feedbacks on Green Island by integrating analyses of water balance, energy balance, and climate change impacts within a system-oriented framework, with particular attention to how tourism-driven water and energy demand interacts with hydrological processes under changing climatic conditions and how these interactions may reinforce system vulnerability over time. The water system is conceptualized as a coupled human–natural system, incorporating precipitation inputs, surface and groundwater storage, water treatment and distribution, sectoral water use, and environmental losses such as evapotranspiration and rapid runoff, while human responses to hydrological variability—including infrastructure design and water management practices that limit rainwater retention and reuse—are treated as key drivers shaping feedback dynamics. In parallel, the energy system assessment examines baseline residential demand, seasonal tourism-related electricity use, reliance on diesel-based power generation, and the potential integration of renewable energy sources. Climate change is treated as a cross-cutting driver influencing both hydrological processes and human behavior, as projected increases in rainfall intensity, extreme events, heatwaves, and typhoons are expected to further amplify mismatches between water availability and effective water use. Methodologically, the study integrates hydrological data, energy statistics, climate information, and ecological observations within a conceptual system framework, and employs system dynamics modeling using Vensim at a supporting level to structure causal relationships and explore feedback mechanisms rather than to produce deterministic predictions. By reframing water sustainability as a challenge of retention, reuse, and adaptive management rather than absolute scarcity, this research aims to support more resilient and resource-efficient water governance pathways for small island systems under climate change.