Effects of urbanized campus on the water cycle characteristics: Case study on the Gwanak Campus of Seoul National University in South Korea

Studies on the alteration of the water cycle caused by climate change and urbanization are ongoing worldwide. However, the evaluation of altering water cycle at the scale of a university campus has been poorly conducted. Indeed, trajectories in developing and urbanizing a campus share many similar aspects to those of a city. Under changing climate conditions, understanding how an urbanized campus has changed the water cycle characteristics so far is pivotal for informing pathways to be a sustainable and climate-resilient campus in the future. This study therefore aims to analyze the effects of an urbanized campus on the water cycle features, as a case study on the Gwanak campus of Seoul National University in South Korea. Our study area with ~250 buildings is located in the hillside of Mt. Gwanak where the Dorim Stream begins, and has more than 30,000 floating population which is almost equivalent to a small city. We collected hourly meteorological variables (temperature, wind speed, relative humidity, precipitation, and potential evapotranspiration) observed at the roof of Building 35 in the upper zone of the entire campus since May 2021. The SWMM model was applied to quantify the water cycle index (surface runoff, infiltration, evaporation, and potential evapotranspiration). By using the complementary observed and simulated data, we employed the Budyko framework to investigate how the water balance in our study area differs between pre- and post-urbanization periods. In addition, we conducted power spectral analyses on the time series of precipitation and surface runoff to identify how hydrologic responses of the study area have shifted due to urbanization. Regarding the water balance ratios, we found that the campus urbanization from 1960s significantly increased surface runoff as well as decreased evaporation and infiltration. Detailed analyses and implications will be presented.