Assessment of Groundwater Availability for Rice Farming in Tuban Regency, East Java in 2018-2022

A study has been carried out on deficit, surplus, percentage of groundwater availability and Oldeman climate type classification in Tuban Regency, East Java in 2018-2022 with the aim of increasing the productivity of rice plants in the area. This process begins with data collection, including rainfall, air temperature, coordinates and height of rain posts, as well as physical soil data which is used to calculate rice ETC (Evapotranspirasi Tanaman/Plant Evapotranspiration), deficit, surplus and ATS (Air Tanah Tersedia/Groundwater Available). The method used in this calculation is the Thornthwaite and Mather method. From data analysis, it was found that the smallest deficit of 0.1 mm occurred in Medalem in June, while the largest deficit occurred in Ngimbang in November amounting to 279.6 mm. The smallest surplus of 0.9 mm was recorded in Sumurgung in April, while the largest surplus of 313 mm occurred in Jenu in January. Groundwater availability reaching 100% generally occurs in November-April, while 0% ATS occurs in June-September. and the Oldeman climate patterns in Tuban Regency are C3, D3, D4, and E3 respectively.