An advanced tool to determine agriculture groundwater usage for irrigation to greenhouse facilities

Introduction: With the development of agricultural technology, it is possible to cultivate crops in winter at the greenhouse facility cultivation complex, and as the crop cultivation period has increased, the use of groundwater has increased. When calculating the amount of groundwater used, the utilization period should be increased according to the cultivation period. Materials and Methods: As a result, the groundwater use calculated by the conventional method is applied to the annual use period of ۲۷۰ days for the whole action and ۱۸۰ days for the answer action, so the value less than the actual groundwater use for the year is inevitably calculated. Therefore, it is necessary to estimate the irrigation water demand for each crop in consideration of the cultivation period when the groundwater use is calculated in the facility cultivation complex that grows the four-season crops. The purpose of this study was to calculate monthly cultivation crops and cultivation periods through Gwang-ju Meteorological Agency's climate data in South Korea, land cover map, field survey, and residents' survey to estimate the irrigation water demand by crops in the area around Yeongsan River where facility cultivation complex is concentrated. Results: Based on the results of the calculation of crop evaporation (irrigation water demand) using the crop coefficients presented by the Rural Development Administration and FAO, it was analysed that irrigation water used is ۲,۱۱۴×۱۰۰۰ m۳/year for rice, ۳,۳۵۳×۱,۰۰۰ m۳/year for field crops, and ۶,۶۴۹×۱,۰۰۰ m۳/year for water dropwort. As a result, water dropwort uses irrigation water twice more than field crops. In addition, except for rice, which mainly uses surface water, the difference in usage amount occurred more than twice as compared to the groundwater use calculated by the existing groundwater use method. Therefore, if the facility cultivation complex that grows four seasons of crops water demand calculation method is applied to the irrigation water required by the crops rather than the conventional groundwater usage calculation method, it will not only calculate the exact amount of water but also establish proper water supply measures and facility maintenance. The high agriculture productivity in the command area and poor performance of the irrigation system clearly justifies the role of shallow tubewell has played in the command area. Since the irrigation facility is Agency Managed and O&M of the surface system is carried out by the Government, the investment cost on the tube well and their O&M is entirely contributed by the farmers. The deficit water fulfilled by the tubewell and total cost associated to it is considered to be the total economic loss due to irrigation system inefficiency. Finally, the amount of irrigation water required by the crop during the growth period was calculated by multiplying the monthly crop evaporation amount to the monthly cultivation area. However, it is difficult to calculate the amount of groundwater used as a crop factor by repeating the operation of filling and subtracting water and running water in order to prevent temperature maintenance and dobok (bending) during cultivation. Therefore, in the case of dropwort with a large amount of groundwater, irrigation water demand was separately calculated monthly through field surveys on cultivation area, cultivation period, and cultivation methods and interviews with local residents. Conclusions: It will be helpful in establishing measures and maintaining water supply facilities. If research on crop factor estimation is activated in the future, it will be possible to more accurately estimate the demand for irrigation water for all crops.