Long-term prediction of groundwater recharge by climate changes in the Gosan agricultural area, Jeju Island of South Korea

Abstract:

<span">Evaluation of long-term changes in groundwater recharge due to the climate changes is needed to secure the sustainable use of grounwater. In Jeju Island, which is composed of various formations of porous volcanic rocks, groundwater is a sole resource for water supply because of its hydrogeological characteristics. Therefore, preservation of the groundwater resource is an essential issue in the island. Prior to establishing a management plan for maintaining the groundwater resources in Jeju Island, long-term estimation of influencing factors are necessary. The Gosan study <span">a<span">rea is located in the western part of the island, where extensive agricultural activity has been performed and groundwater is a main source of supply for watering crops. In this study, we estimated the recharge changes for 100 years (2000~2099) in the Gosan agricultural area based on two climate change scenarios (RCP 4.5 and RCP 8.5) by using the HELP3 (Hydrologic Evaluation of Landfill Performance) program. The estimated component of water budget in this study are as follows (averaged in 2000~2014), precipitation: 1.28x10⁸ m³/yr; ET: 6.49x10⁷ m³/yr; runoff: 5.84x10⁶ m³/yr; and recharge: 5.27x10⁷ m³/yr. Over the 100 years of the estimated period, precipitation will have a highest increase among other meteorological parameters to be 6.16x10⁹ m³ (RCP4.5) and 6.34 x10⁹ m³ (RCP8.5). Increase in recharge by RCP8.5 scenario (2.75 x10⁹ m³) will be less than that by RCP4.5 (2.77x10⁹ m³) because ET by RCP 8.5 (ET: 3.34x10⁹ m³; runoff: 2.27x10⁸ m³) is estimated to be higher than ET by RCP4.5 (ET: 3.15x10⁹ m³; runoff: 2.35x10⁸ m³). Jeju volcanic island is known to have higher recharge proportions to the precipitation due to the distributed highly porous volcanic rocks. Therefore, variations in precipitation by climate changes would greatly affect the groundwater resource of the island.

Acknowledgement: This work was supported by the research project of "Advanced Technology for Groundwater Development and Application in Riversides (Geowater+)" in "Water Resources Management Program (code 11 Technology Innovation C05)" of the MOLIT and the KAIA in Korea.