Aquifer-Circulating Water Curtain Cultivation System To Recover Groundwater Level And Temperature

Groundwater temperature, which generally ranges 14 to 16 degree of Celsius all year long, can be said to be 'constant' compared to the amplitude of daily variation of air temperature or surface water. Water curtain cultivating method utilizes this 'constant' groundwater temperature to warm up the inside of greenhouse during winter night by splash groundwater on the roof of inner greenhouse. The area of water curtain cultivation system have increased up to 107.5 square kilometers as of 2006 since when it is first introduced to South Korea in 1984. Groundwater shortage problem became a great issue in a concentrated water curtain cultivation area because the pumped and splashed groundwater is abandoned to nearby stream and natural recharge rate is reduced by greenhouses. The amount of groundwater use for water curtain cultivation system in South Korea is calculated to be 587 million cubic meters which is 35% of national agricultural use of groundwater. A new water curtain cultivation system coupled with aquifer circulating of the splashed groundwater and greenhouse roof-top rainwater harvesting is developed and applied to field site in Nonsan-si, Chungnam province to minimize groundwater shortage problem and recover groundwater level. The aquifer circulating water curtain cultivation system is consist of a pumping well and a injection well of 80 m deep, groundwater transfer and splashing system, recovery tank and rainwater collecting waterway. The distance between injection and pumping well is 15 m and an observation well is installed in the middle of the wells. To characterize hydrogeological properties of this site, hydraulic test such as pumping tests and tracer tests with dye tracer, thermal tracer and ion tracer. Once the integrated system is constructed in this site, hydraulic head in all the wells and temperature of air, recovery tank and groundwater in all the wells are monitored during the operation for 3months in winter season. Hydraulic test and tracer tests revealed that the well is producible enough for 2,000 square meters green house and that highly permeable fracture zone around 20 m deep is well connected between the wells. Circulating operation kept the groundwater level 3 m higher than that in case of conventional operation. The recharge rate of the splashed water into the injection well was 43% resulting in recharging 4,750 cubic meters of water during winter season. The relation between temperatures of air, recovered water, injection well and observation well is quite linear whereas temperature in pumping well remains fairly constant which means the cooled groundwater temperature was almost recovered during transport from injection well to pumping well. Finally, it is found that the newly developed aquifer circulating water curtain cultivation system is effective in recovering groundwater level and temperature and good for sustainable energy saving cultivation system for winter time.