The effects of climate change on the water resources of the Geumho River Basin, Republic of Korea

• The impact of climate change on water resources was assessed.
• LARS-WG was used to downscale data from five GCMs used in two rainfall runoff models.
• There were considerable changes and uncertainty in runoff and the aridity index.
• The results indicate that climate change will likely lead to lower water resource levels.

Assessments of the variation and vulnerability of water resources due to climate change are essential for future planning in agriculture. In this study, the impacts and uncertainty associated with climate change on water resources in the Geumho River Basin were measured based on the relative change in the mean annual runoff and the aridity index. Statistically adjusted and downscaled multi-ensemble General Circulation Model (GCM) predicted rainfall and temperature data for three representative concentration pathways (RCPs) (RCP2.6, 4.5 and 8.5) were applied to two lumped parameter conceptual rainfall runoff models. The results revealed considerable uncertainty in the projected temperature, rainfall, potential evapotranspiration (PET), runoff and aridity index (AI). Additionally, temperature and rainfall were predicted to increase significantly in the future. The PET was projected to increase by a mean (range) of 9% (7–12%), 18% (9–30%) and 25% (8–49%), while the mean annual runoff was projected to change by a mean (range) of 1% (−33 to 40%), −9% (−47 to 27%) and −4% (−44 to 35%), in the 2030s, 2060s and 2090s, respectively. The AI was projected to decrease in the future, particularly for the RCP8.5. Overall, the results of this study indicate that climate change will most likely lead to lower water resource levels than are currently present in the Geumho River Basin.