Impacts of Land Use Change on Catchment Hydrological Variables under Climate Change

Climate change is altering precipitation regimes and temperature conditions, thereby modifying hydrological processes and water availability at the catchment scale. At the same time, land use change driven by human activities reshapes land surface characteristics, imperviousness, and energy balance, further influencing evapotranspiration and runoff generation. Understanding the combined effects of climate variability and land use change is therefore essential for assessing future hydrological responses and supporting sustainable water resources management. This study investigates the impacts of land use change under climate change on key hydrological variables in the Mudan Reservoir catchment in southern Taiwan, with a particular focus on changes in evapotranspiration and runoff.

Historical land use data from multiple periods are first compiled into a consistent land use database with unified classification schemes and spatial resolution. Land use transition patterns, temporal trends, and spatial hotspots of change are analyzed to characterize historical land use dynamics. Future land use scenarios are then simulated using the Patch-generating Land Use Simulation (PLUS) model, which integrates land expansion analysis and patch-based cellular automata to capture both transition mechanisms and realistic landscape patterns. These simulations provide spatially explicit land use projections at different future time horizons, serving as a foundation for hydrological analysis.

Climate forcing is derived from statistically downscaled AR6 climate projections provided by the Taiwan Climate Change Projection and Information Platform (TCCIP), representing future changes in precipitation and temperature. A long-term catchment water balance framework is established to quantify major hydrological components, including precipitation, evapotranspiration, and runoff. The relationship between land use composition and hydrological partitioning is examined, with particular emphasis on the evapotranspiration-to-precipitation ratio (ET/P) and runoff response under different land use conditions. A simplified land use–ET/P relationship is developed and applied in conjunction with future land use scenarios and climate projections to assess changes in evapotranspiration and runoff.

The results provide insights into how land use change and climate change jointly influence hydrological variability in reservoir catchments. By explicitly linking human-driven land use dynamics with climate-induced hydrological change, this study contributes to a better understanding of coupled human–natural systems and offers scientific support for reservoir operation and adaptive water resources management under a changing climate.