Efforts to preserve the sustainability of subak irrigation system in Denpasar city, Bali Province, Indonesia

Subak as an irrigation system in Bali is estimated to have existed before the IX century and up to now subak has consistently maintained the continuity of traditional irrigation management and operation of the irrigation system. Subak is a socio-agrarian and religious based on the philosophy of Tri Hita Karana rooted in Hindu philosophy. The challenge of subak in general is that the shrinking of the subak area, the farmers are unable to achieve a decent living, the age of the farmers is over 40 years, the financial burden that farmers bear in doing subak activities is very heavy. The condition is also very much felt in the city of Denpasar as the capital of the province of Bali. The Government has determined to preserve subak as a cultural heritage to realize Denpasar as a Heritage City. The conservation effort is carried out through: maintaining the subak area through local regulations as green open space (RTHK), providing various assistance such as: exempting subak areas from taxes and providing insurance assistance in case of crop failure, assistance for ritual implementation, irrigation channel repair assistance, production facilities, agricultural equipment assistance, incentives for subak managers, providing assistance in realizing subak as ecotourism, plan to provide scholarships for the children of subak farmers

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

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

Water Potential in Petanu River Estuary and Model of Water Resources Management for Sustainable Agriculture in Gianyar Regency Bali Province

Water needs in the province of Bali from year to year increase along with the rise of population and tourism activities. A study conducted by the Ministry of Environment (2009) stated that Bali is already experiencing water deficit during the dry seasons since 1995 as many as 1.5 billion m3 / year. To overcome this water deficit issue, it will require researching on the potential water resources in Bali. Along the Petanu River, there are 25 irrigation weirs on a 4475.5 ha of land. Research was carried out in in Saba village, Gianyar Regency, Bali, along The Petanu River up to its estuary. The data collected from the research included primary and secondary data, namely: water quality, water quantity (water volume) in Petanu River estuary, precipitation, climate, and environmental conditions of the Petanu river. The data collected from the research site and the secondary data, the water quality was tested on the reseacrh site and in the laboratory before it was analyzed. The model used to detect water presence (the water system) along the Petanu River up to its estuary was procesed using a software called RIBASIM (River Basin Simulation). The result showed that there is a potential water source (water volume) on the estuary of the Petanu River estuary during the dry season as much as 6.16 million m3 and during the rainy season as much as 43.79 million m3. Water quality in terms of physics (smell, taste, temperature, color, turbidity and salinity), meet the quality standards of class IV (for irrigation). Based on the simulation results on the RIBASIM software, the water resources in the Petanu River estuary can potentially be managed as irrigation water for horticulture agriculture along the coast of Saba. The potential water sources can be contained by building dams / reservoirs that are placed ± 300 m from the shoreline of Saba village in Gianyar regency. The water management model for the water sources in Petanu River to support sustainable agriculture can be put to use through water and soil conservation by controlling land use and cropping patterns that involve the community using the subak system

Water Potential in Petanu River Estuary and Model of Water Resources Management for Sustainable Agriculture in Gianyar Regency Bali Province

Water needs in the province of Bali from year to year increase along with the rise of population and tourism activities. A study conducted by the Ministry of Environment (2009) stated that Bali is already experiencing water deficit during the dry seasons since 1995 as many as 1.5 billion m3 / year. To overcome this water deficit issue, it will require researching on the potential water resources in Bali. Along the Petanu River, there are 25 irrigation weirs on a 4475.5 ha of land. Research was carried out in in Saba village, Gianyar Regency, Bali, along The Petanu River up to its estuary. The data collected from the research included primary and secondary data, namely: water quality, water quantity (water volume) in Petanu River estuary, precipitation, climate, and environmental conditions of the Petanu river. The data collected from the research site and the secondary data, the water quality was tested on the reseacrh site and  in the laboratory before it was analyzed. The model used to detect water presence (the water system) along the Petanu River up to its estuary was procesed using a software called RIBASIM (River Basin Simulation). The result showed that there is a potential water source (water volume) on the estuary of the Petanu River estuary during the dry season as much as 6.16 million m3 and during the rainy season as much as 43.79 million m3. Water quality in terms of physics (smell, taste, temperature, color, turbidity and salinity), meet the quality standards of class IV (for irrigation). Based on the simulation results on the RIBASIM software, the water resources in the Petanu River estuary can potentially be managed as irrigation water for horticulture agriculture along the coast of Saba. The potential water sources can be contained by building dams / reservoirs that are placed ± 300 m from the shoreline of Saba village in Gianyar regency. The water management model for the water sources in Petanu River to support sustainable agriculture can be put to use through water and soil conservation by controlling land use and cropping patterns that involve the community using the subak system

Non-Revenue Water (NRW) and its handling for a drinking water supply system in Kedewatan zone Gianyar Bali

Non-Revenue Water (NRW) is a common issue of drinking water supply system. NRW can be detrimental that should be addressed properly including NRW rates, NRW caused, and a guidance for preventing and reducing NRW. The water loss measured through water balance that calculated the percentage for differences the water distribution (m3) with the water recorded (m3) on the bill. Infrastructure Leakage Index (ILI) used to calculate the physical water loss based on the standard target matrix of IWA (International Water Association). The causes and handles of NRW were analysed based on a step test result, Ultrasonic Flow Meter (UFM) test result, and interviewing PDAM staffs. The result of NRW rates reach 986,884.92 m3/year (65.53 %). The ILI index was 69.98, and the water pressure was 17.2 m. As a result, this zone included D category, that has high of water loss rate > 200/s/connection/day. In this zone, the causes of water loss are categorized into the physical and non-physical water loss, and the mitigation must be carried out according to the type of water loss occurred. PDAM Gianyar should investigate the possibility of non-physical water loss so that can reduce the level of water loss and the ILI value. The further research can be conducted an evaluation of the whole network with the purpose of NRW can be calculated maximally

Sidan Reservoir Operation Model for System Analysis of Ayung River Basin with RIBASIM

Bali Province in the next ten years is feared to experience a shortage of clean water. One effort that can be done to anticipate a shortage of clean water is by constructing Sidan Reservoir. Sidan Reservoir is located in the upstream of the Ayung River Basin. Sidan Reservoir is prioritized to meet raw water needs and it is also calculated to meet the needs of irrigation water in the downstream of the reservoir. The initial stage in this study is to analyze the availability of water as an inflow to Sidan Reservoir using the rainfall-runoff model of the ITB water balance method. Synthetic discharge as the results from the rainfall - runoff model are analyzed as Q90 dependable discharge. Furthermore, it analyzes raw water needs and irrigation water needs as an outflow from Sidan Reservoir. After the inflow and outflow are known, Sidan Reservoir operation simulation is carried out in four scenarios with RIBASIM software. Based on the results of the rainfall-runoff model from 2008 to 2017, the results of the inflow calculation to Sidan Reservoir is obtained in the form of Q90 dependable discharge of 3.45 m3/ sec. The raw water needs up to 2033 is 2.092 m3/ sec, besides that it can be used to meet irrigation water needs of 0.35 m3/ sec. The simulation results of Sidan Reservoir operation model based on the second scenario obtained a dependability level of 91.7%, the third scenario obtained a dependability level of 100%, and the fourth scenario obtained a dependability level of 87.5%. The third scenario with 100% dependability is the optimum result. The verification results of the RIBASIM model with observational discharge data at the control point namely Mambal Weir showed good model accuracy and the error rate was relatively small with the smallest correlation coefficient of 0.50