Abstract
This paper investigates the historical and future trends in water balance components and their impacts on streamflow. The trend analyses were applied to the daily climatic and hydrologic variables from 109 subbasins in Korea during the historical period and future period obtained by a multimodel ensemble of 13 global circulation models (GCMs) of the Coupled Model Intercomparison Project, Phase 5 (CMIP5). A calibrated hydrologic model, the precipitation-streamflow modeling system (PRMS) model, was applied to obtain hydrologic data. The results revealed apparent trends in streamflow, with increases in spring and decreases in the other seasons during the historical period. The reduction (or increase) in the amount of streamflow was counterbalanced by the reduction (or increase) in precipitation, groundwater, and soil moisture, which was mainly impacted by the increase (or reduction) in actual evapotranspiration. However, opposite trends are projected for the future period for streamflow and water cycle components, in which spring and winter are projected to have increasing trends mostly counterbalanced by the decreasing trends in precipitation and groundwater. The reasons for the reduction in streamflow include elevated evapotranspiration compared to precipitation, reduced soil moisture, and a significant decrease in groundwater recharge. In addition, the results of the seasonal variability among basins revealed higher variability in summer for the historical period and in winter for the future period, with maximum variability in the Sumjin River basin, indicating that streamflow fluctuated more strongly in the Sumjin River basin during the historical and future periods.
Highlights
Water demand is increasing worldwide; a reliable water supply is not always available
Variation in temperature patterns caused by climate change could impact the temporal and spatial distribution of water resources [39]
This figure shows the increase in mean seasonal temperature for all subbasins (26 subbasins for the Han, 33 subbasins for the Nakdong, 21 subbasins for the Geum, 15 subbasins for the Sumjin, and 14 subbasins for the Youngsan River basins) with respect to the reference period
Summary
Water demand is increasing worldwide; a reliable water supply is not always available. This concern becomes more challenging based on the increasing water demand due to population growth and climate change. It is necessary to understand how the water cycle components affect streamflow or are expected to impact streamflow in the future to overcome probable water scarcity by intelligent water resource management. An increase in temperature is reported for all seasons of the year, precipitation is projected to increase globally and in many basins; a decrease in precipitation is expected in many other regions [6]. Climate change can result in significant changes (increase or decrease) in water cycle components due to changes in temperature and precipitation [7,8,9]
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