Assessment of Climate Change Impact on Future Groundwater-Level Behavior Using SWAT Groundwater-Consumption Function in Geum River Basin of South Korea

Abstract

This study was to evaluate the groundwater-level behavior in Geum River Basin (9645.5 km2) of South Korea with HadGEM3-RA RCP 4.5 and 8.5 climate change scenarios and future groundwater use data using the soil and water assessment tool (SWAT). Before evaluating future groundwater behavior, the SWAT model was calibrated and validated using the daily inflows and storage of two dams (DCD and YDD) in the basin for 11 years (2005–2015), the daily groundwater-level observation data at five locations (JSJS, OCCS, BEMR, CASS, and BYBY), and the daily inflow and storage of three weir locations (SJW, GJW, and BJW) for three years and five months (August 2012 to December 2015). The Nash–Sutcliffe efficiency (NSE) and the coefficient of determination (R2) of two dam inflows was 0.55–0.70 and 0.67–0.75. For the inflows of the three weirs, NSE was 0.57–0.77 and R2 was 0.62–0.81. The average R2 value for the groundwater levels of the five locations ranged from 0.53 to 0.61. After verifying the SWAT for hydrologic components, we evaluated the behavior of future groundwater levels by future climate change scenarios and estimated future ground water use by Korean water vision 2020 based on ground water use monitoring data. The future groundwater-level decreased by −13.0, −5.0, and −9.0 cm at three upstream locations (JSJS, OCCS, and BEMR) among the five groundwater-level observation locations and increased by +3.0 and +1.0 cm at two downstream locations (CASS and BYBY). The future groundwater level was directly affected by the groundwater recharge, which was dependent on the seasonal and spatial precipitations in the basin.

Evaluation of Land-Use Changes Impact on Watershed Health Using Probabilistic Approaches

“…The groundwater level data observed by the National Groundwater Information Center (GIMS) groundwater level observation stations were collected. Five sites (BYBY, JSJS, BEMR, CASS, and OCCS) in the GRB were selected (Figure 1a) [31]. The flux tower DY, operated by K-water, is in the upper GRB within the forested area [31].…”

“…Five sites (BYBY, JSJS, BEMR, CASS, and OCCS) in the GRB were selected (Figure 1a) [31]. The flux tower DY, operated by K-water, is in the upper GRB within the forested area [31]. The DY daily ET (mm) and soil moisture (%) data were collected from April 2011 to December 2019.…”

“…Accordingly, this study evaluated WH by considering all hydrologic and water cycle factors for watershed management focusing on water quantity. This study utilized the SWAT verification and calibration results of Lee et al [31] to evaluate hydrologic WH. The evaluation results were analyzed with respect to the following four factors: ET, SQ, SW, and GWQ.…”

“…This study validated and calibrated SWAT before simulating the hydrology and WQ according to the land-use trend from 1985 to 2019. For the hydrologic validation and calibration of SWAT for the GRB, the parameters proposed by Lee et al [31] were applied. As shown in Table 1, validation and calibration were conducted for two dams (YDD and DCD), and three weirs (SJW, GJW, and BJW).…”

Assessment of Long-term Groundwater Abstraction and Forest Growth Impacts on Watershed Hydrology Using SWAT

“…The difficulties come from complex factors that are not clearly understood or defined (Jung & Kim, 2017) and the lack of hydrological data in small rivers where stream drying usually occurs. Jung, Lee, Lee and Kim (2019) considered stream drying phenomena by applying five different factors, groundwater abstraction, afforestation, watershed development, road development, and soil erosion, and ranked their contribution rates to the loss of runoff. The results demonstrated that groundwater abstraction and forest growth had a relatively higher influence on stream drying than did other factors.…”