Aquifer Storage and Remote Recovery by Vadose Zone Injection of Flash Flood in Jeju Volcanic Island, South Korea

Groundwater artificial recharge is a promising technology to address the threat to water supplies posed by climate change. A groundwater artificial recharge project is being conducted at a site adjacent to Hancheon stream in a high-elevation area in the northern part of Jeju Island. The artificial recharge system directs water from seasonal flash flooding into a volcanic aquifer through vadose zone injection. The seasonal variation in precipitation under monsoon climate is getting severe like less annual rainy days and more heavy rainy days under similar amount of annual precipitation. Jeju volcanic island is composed of permeable geologic structures such as clinker and scoria and less permeable geologic structures such as tuff and fine-grained volcanic materials. The Hancheon site has a very thick and permeable vadose zone which is good condition for source water injection and natural filtration of it during migration to main aquifer. Injection tests were performed at multi-depth to quantify vadose zone permeability to decide recharge well depth. Injection characteristics indicate that the clinker zones more than 35 meters from the reservoir bottom would be suitable for the recharge capacity of 15000m3/day. A new method named Jeju-friendly aquifer recharge technology(J-ART) is conceptually designed based on these hydrological, meteological, and geological properties. This artificial recharge system using reservoir adjacent to the stream could reduce threat of flood and secure groundwater resources to Jeju island.