Modeling the Water Balance of Agricultural Land in the Determination of the Growing Season in Buru Regency

This study aims to determine the value of surplus and water deviation of agricultural land in Namlea District, Buru Regency. The study was conducted in Namlea Subdistrict, Buru Regency, Maluku Province. Materials used, questionnaires, climate data, air temperature, precipitation, humidity, solar rays 10-20 years. Tools used, computer equipment, writing stationery and location maps. To obtain the surplus value and water deficit of the land used data on the average amount of monthly precipitation and the average monthly temperature using the calculation of the Thornthwaite method. The calculation of the groundwater balance is carried out using a bookkeeping system. The data used are monthly potential evapotranspiration values, climate station data, monthly average rainfall, and rainfall at a 50 percent chance level. The observation parameters calculated in this study are rainfall, evapotranspiration, and determination of land water balance. The results of this study showed that the difference in rainfall and evapotranspiration in Namlea District was highest in June at 85.40 mm, and the lowest in October at -99.83 mm. This value indicates that the evapotranspiration value is greater than the average monthly rainfall value during the period 2010 – 2019. Namlea Subdistrict experienced potential water loss for evaporation (APWL) in May of 35.30 mm, in August to November of August of 65.26 mm, in September of 156.24 mm, in October of 256.07 mm and in November of 303.45 mm. The land water balance in Namlea Subdistrict, namely rainwater deviation, occurs in May, then August to November, while the water surplus occurs in December to July, and continues in June and July. Namlea district annual runoff is 854.01 mm. Regarding agricultural irrigation development policies, this study recommends that it is necessary to pay attention to weaknesses in each food crop sub-sector.