Decoding urbanization effects on the water cycle: a multi-faceted analysis of balance, magnitude, and memory

ABSTRACT The effects of urbanization on water cycle dynamics are a global concern as cities expand worldwide. This study aims to investigate these effects on Korea's largest campus catchment, Seoul National University Gwanak campus (∼2.9 km2), reflecting urbanization levels similar to the megacity of Seoul. We examined changes in water cycle components (i.e., precipitation, runoff, and evaporation) between pre- and post-urbanization periods (1960–1964 and 2008–2012) through complementary features: water and energy balance, the magnitude and temporal memory of the components. These were identified by the Budyko framework, its integration with the Storm Water Management Model, and power spectral analysis. Compared to the pre-urbanization period, post-period results showed (1) a shift in the Budyko curve from the water and energy limit lines, (2) dryness intensified (decreased) in spring and winter (summer), (3) ∼38% reduction in the integrated-model-derived evaporation due to greater imperviousness and lower vegetation-coverage, (4) the observed precipitation and the integrated-model-estimated runoff increased by ∼15 and ∼75%, and (5) the memory of the observed precipitation got slightly stronger, while that of the others showed no significant difference. This study pinpoints that urbanization, even at a large campus scale, significantly alters the dynamics of water cycle components.