Impact of Groundwater Abstraction on Hydrological Responses during Extreme Drought Periods in the Boryeong Dam Catchment, Korea

Abstract

Groundwater withdrawal results in a significant depletion of groundwater storage due to the frequency and intensity of droughts and increasing irrigation demands. To ensure the sustainable use of groundwater resources, it is necessary to accurately simulate the groundwater behavior of catchments using a surface–groundwater integrated runoff model. Most of the existing catchment runoff models have been applied to surface water management; thus, integrated runoff analysis studies that consider the interaction between surface water and groundwater are required. Due to the intensive agricultural sector in Korea and the position of rice as the staple in the Korean diet, more than 50% of groundwater abstraction is used for irrigation. Therefore, it is very important to understand the hydrological interrelationships between agricultural areas and the entire watershed. This study aimed to compare and analyze the groundwater levels in the mountainous areas and paddy field areas in the Boryeong Dam catchment through a surface–groundwater integrated runoff simulation using the Catchment Hydrologic Cycle Assessment Tool model, and to compare the hydrological responses in wet years (2010–2012) and dry years (2014–2016). The maximum difference in the monthly groundwater level in the dry years compared to the wet years was 1.07 m at the forest catchment and 0.37 m at the paddy catchment. These results indicate that the impact of drought on the groundwater level of paddy catchments is not significant compared to the forest catchments; however, drought slows the recovery of the groundwater level before the rainy season, thereby limiting the agricultural groundwater use in the catchment.

Hydrological Effects of Agricultural Water Supplies on Paddy Fields using Surface–Groundwater Integrated Model

“…The water storage volume of the Boryeong Dam in 2015 decreased to 18.87% due to the extreme drought that occurred in the central region of Korea. The drought in the central region continued, and the water storage rate reached 8.29% in 2017, which is the lowest water storage level since the construction of the Boryeong Dam [23,24].…”

“…Figure 1a shows the location of the three rainfall gauging stations: one water level station at the outlet of the Boryeong Dam, and two agricultural reservoirs over the catchment [25]. Figure 1b shows the Boryeong Dam catchment divided into three sub-catchments, SC_1, SC_2, and SC_3, according to the previous study [24]. The CAT system for the Boryeong Dam catchment was constructed by dividing the catchment into three subcatchments and then dividing the paddy field areas of each sub-catchment.…”

“…The subcatchments' information, such as the areas, slopes, and impervious area ratio, were calculated as the input data of CAT using the DEM map with 30 × 30 m resolution and of the land use map of the National Geographic Information Institute [26]. Figure 2 shows the Samsan Reservoir and the Hwasung Reservoir, which are agricultural purpose reservoirs located in the upstream of Ungcheon Stream in the Boryeong Dam catchment [25], which are located in the SC_2 sub-catchment according to the catchment division of the previous study [24]. In this study, the SC_2 sub-catchment, in which the agricultural reservoirs are located, is the target area for the streamflow simulation using CAT.…”

“…The daily precipitation, streamflow, and meteorological data from 2000 to 2019 were already collected for a previous study [24]. The daily precipitation data were gathered from the three rainfall gauging stations operated by K-water [23].…”

“…The groundwater elevation changes in P_Samsan and P_Hwasung according to the application of the Samsan Reservoir and Hwasung Reservoir were compared for the WET and DRY periods. Figure 14 indicated that the increase rate of the groundwater elevation due to the operation of the agricultural reservoirs was higher in the WET period than in the DRY period because the rate of groundwater abstraction was lower in the drought period than that in normal period in the catchment [24].…”