Water Balance in Rice Intensification Program in Bali Province, Indonesia

The wasteful use of irrigation water is a serious challenge that deserves attention, because of the long-term threat of global climate change. Periodic irrigation or rotation technique was one method that in addition to making the soil healthy, it also saves the use of irrigation water through water balance technology. The objective of this paper is to discuss the management of water stream through technology of water balance in Bali Province, Indonesia to be used for the consideration of a policy by local government to support the program of one river one management. The research on water balance was conducted in the Yeh Ho watershed which was located in the Tabanan district, Bali Province stretching from the Batukaru mountains in the north to the Indonesian Ocean in the south. In the north it was bordered by Buleleng regency, in the east it borders Badung regency and in the west with Pupuan sub-district Tabanan regency. The length of the Yeh Ho river from the Pasut coast (Indonesian ocean) to the slopes of Mount Batukaru ± 75 km. Water treatment consisted of irrigation continuously, irrigation ago 4 days and irrigation intermittent 8 days. In order to obtain three water balance models in each part of the region are as follows: 1). I + Ch = P + Pt + P 1 + C; 2). I + Ch = P + Pt + P 2 + C; and 3). I + Ch = P + Pt + P 3 + C. Where: I = Irrigation (measured and observed was shallow ground water), Ch = Rainfall, P = Evaporation, Pt = tillage, P 1 = Irrigation continuously, P 2 = Irrigation 4 days and P 3 = Irrigation once every 8 days and C = Reserve. Results of the research showed that water supply in the watershed Yeh Ho with continuous irrigation, water used of 28,700 m ha leaving water reserves 62,700 m ha. Irrigation once every 4 days drains 25,200 m ha of waterleaving 66,100 m ha of water reserves and 8 days of irrigation consumes 22,100 m ha leaving 69,200 m ha of water . The observations showed that with continuous irrigation leaving 4.0% water, once every 4 days irrigation 15%, once every 8 days irrigation 46.3%. The availability of water and its dwastribution was increasingly limited, so the use of water for agricultural irrigation especially paddy rice needs to be done wwasely so that excess irrigation water can be used to generate income through other businesses that mutually support the agricultural sector.