Discharge analysis for a system approach to river basin development with Subak Irrigation schemes as a culture heritage in Bali

Abstract Paddy terraces in Baliare important cultural landscapes. Traditionally, the flow within a river basin has been managed using a traditional technology called Subak irrigation. These schemes are based on the cropping patterns and indigenous water management, which are organized by the respective Subak associations. Unfortunately, this traditional technology is facing challenges: water shortage and competition with other water users. In order to sustain agriculture production of Subak irrigation schemes in the Yeh Ho River Basin, the available discharge in Yeh Ho River was analyzed in this study in light of the supply to the Subak irrigation schemes within the river basin. By using the Weibull formula, the historic supply data of several diversion weirs were analyzed independently. Based on this analysis it was possible to determine the water balance of the Subak irrigation schemes behind each diversion weir. Therefore a system approach was developed based on the managed flows within the river basin and the characteristics of the Subak irrigation schemes. The conclusion is that the discharge in the river will remain the most important factor to sustain the characteristic paddy terraces of these Subak irrigation schemes. Keywords river basin, Subak irrigation, Subak association, paddy terrace, weir, water distribution unit, continuous flow