Role of reservoir operation in sustainable water supply to Subak irrigation schemes in Yeh Ho River Basin

A Subak irrigation scheme, primarily in Bali, Indonesia concerns an irrigation system of which the construction, operation and management are based on agreed principles of technology, management of agriculture and religious community. Subak systems have been well known since the 9th Century. As a manifestation of the Cultural Landscape of Bali Province the Subak schemes are since June, 2012 included in the World Heritage List of UNESCO. These systems are managed by a Subak Association based on the Tri Hita Karana philosophy - harmony between human beings and God, harmony between people and nature, and harmony between people and people. The problem of insufficient water in the dry season developed in the Yeh Ho River Basin. Because of this the main objective of this study was to develop an optimal reservoir operation strategy in relation to the water supply of the Subak irrigation schemes, capable to support agricultural productivity at upstream, midstream and downstream level. Based on a Generic Algorithm the RIBASIM model was applied using the dependable 80% of discharge and shifting the start of land preparation. The results provide evidence that the cropping pattern of the fifth scenario results in an overall optimal agriculture production of the Subak schemes. The recoverable flow considered in the river basin scheme model plays an important role in the optimisation. Nevertheless, if a normal hydro-climate occurs, the other scenarios, especially the first scenario, can be applied as well. This reflects the applicability of the Tri Hita Karana philosophy on harmony among people and harmony among people and nature.</p

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

Evaluasi Pola Operasi Waduk Tamblang di Kabupaten Buleleng Provinsi Bali

Bendungan Tamblang dibangun untuk memenuhi kebutuhan irigasi dan air baku di Kecamatan Sawan dan Kecamatan Kubutamban Kabupaten Buleleng. Waduk ini berada di aliran Sungai Tukad Daya dan direncanakan mempunyai total tampungan sebesar 6,137,228 m3 sedangkan tampungan waduk efektif sebesar 4,199,646 m3. Fungsi Waduk Tamblang adalah untuk irigasi sebesar 584 ha serta penyediaan air baku sebesar 306 liter/detik. Simulasi operasi Waduk Tamblang menggunakan alternatif debit andalan 80% dan 90%. Data pendukung berupa data curah hujan harian, data debit permukaan aliran Sungai Tukad Daya dan data klimatologi dianalisis untuk mengetahui curah hujan andalan R50 dan R80, debit andalan, evapotranspirasi potensial, curah hujan efektif, kebutuhan air irigasi (KAI), serta kebutuhan air baku pada Kecamatan Sawan dan Kecamatan Kubutambahan. Operasi waduk disimulasikan ke dalam lima alternatif dengan keandalan inflow Q80 dan Q90. Hasil simulasi operasi Waduk Tamblang terjadi surplus pada simulasi alternatif 4 dan alternatif 5. Pola tanam alternatif 4 yaitu padi-jagung-kacang tanah dan alternatif 5 yaitu padi-buncis-bawang-kedelai dan ini sudah disesuaikan pada pola tanam eksisting. Hasil simulasi alternatif 4 dan 5 ini dapat memenuhi kebutuhan air baku dan air irigasi dengan persentase terlayani 100%

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

Pemodelan Sumur Resapan Sebagai Upaya Penurunan Risiko Banjir Kota Denpasar pada DAS Badung

Badan Penanggulangan Bencana Daerah Provinsi Bali pada tahun 2013 menyatakan bahwa beberapa wilayah Denpasar terendam banjir karena tingginya curah hujan pada daerah pemukiman sehingga terjadi genangan di beberapa area. Dampak kejadian banjir dapat dikurangi dengan membangun sumur resapan. Sumur resapan mampu menurunkan debit dan limpasan hujan dengan cara meningkatkan kapasitas infiltrasi di daerah aliran sungai. Perencanaan sumur resapan dianalisis dengan menerapkan remote sensing pada DAS Badung yang terdapat di wilayah Denpasar. Selanjutnya dilakukan perhitungan banjir dengan software HEC-HMS dan perencanaan sumur resapan berdasarkan SNI 03-2453-2002. Hasil analisis sumur resapan pada sub DAS Badung dapat menurunkan debit banjir kala ulang 50 tahun sampai 50,70% dan volume limpasan banjir 74,09%. sehingga penerapan pemanenan air hujan dengan sumur resapan dapat dijadikan salah satu referensi sebagai bentuk penerapan konservasi sumber daya air dalam upaya penurunan risiko bencana banjir di Kota Denpasar

Analisis Perubahan Penggunaan Air Bersih Sebelum dan Sesudah Terjadi Kenaikan Tarif PDAM di Kabupaten Bangli

Di tahun 2013 Pemerintah Kabupaten Bangli serta PDAM Kabupaten Bangli sepakat untuk membuat kebijakan baru terkait dengan kenaikan tarif air bersih di Kecamatan Bangli dan Tembuku. Penelitian ini bertujuan memunculkan trend perubahan sebelum dan sesudah kenaikan tarif PDAM sebesar 118%, sehingga dapat dijadikan landasan pengambilan keputusan PDAM Bangli selanjutnya. Penelitian ini menggunakan metode simple random sampling dengan mengambil secara acak sampel yang diteliti tanpa melihat strata yang ada, dan sampel tersebar sebanyak 80 sampel di Kecamatan Bangli dan sebanyak 75 sampel di Kecamatan Tembuku. Hasil analisis menunjukkan penggunaan air bersih mengalami trend penurunan sesudah kenaikan tarif yaitu 25.28% berdasarkan survei dan 25.31% berdasarkan ketetapan PDAM di Kecamatan Bangli. Sedangkan di Kecamatan Tembuku menunjukkan trend sebaliknya yaitu meningkat sesudah kenaikan tarif sebesar 14.08% berdasarkan survei dan 14.07% berdasarkan ketetapan PDAM. Perubahan penggunaan air bersih rata-rata per orang/hari tersebut dipengaruhi kebutuhan air berdasarkan jumlah anggota keluarga di setiap rumah per bulan

Water supply system in Titab village and Telaga village, Busungbiu district, Buleleng regency

The rate of population growth in Titab and Telaga Village, Busungbiu District, Buleleng Regency in 2007-2010 reaches 0.75%, which affects the level of water demand needed for daily needs. One of the efforts to meet the needs of raw water for drinking water, among others, by the development of a potable water supply system infrastructure. Based on the facts, it is necessary to design Water Supply System (SPAM) in Titab and Telaga Village with Titab Reservoir spring with 350 l/dt of debit which is expected to give standard of quantity, quality, continuity of service for Titab and Telaga Village which is 5 km from the dam. In order to maximize the service to the community in Titab and Telaga Village, it is necessary to know the use of drinking water for each household. The next analysis is the calculation of projected drinking water needs over the next 20 years. Planning and calculation of water distribution using WaterCad i8 Software. From the result of projection analysis, the drinking water requirement in Titab and Telaga Village based on the fact of household drinking water usage in 2037 is 5,568 lt/sec. While the effort to maximize water supply network services is by projecting drinking water needs in Titab and Telaga Village based on the fact of household drinking water usage. With the help of WaterNet Software, it will simplify the distribution network planning of drinking water in order to produce integrated drinking water network system to meet the needs of clean water in Titab and Telaga Village

Role of reservoir operation in sustainable water supply to Subak irrigation schemes in Yeh Ho River Basin; Dissertation, UNESCO-IHE Institute for Water Education, Delft and Wageningen University.

A Subak irrigation scheme, primarily in Bali, Indonesia concerns an irrigation system of which the construction, operation and maintenance are based on agreed principles of technology, management of agriculture and a religious community. Subak irrigation schemes are an example of water resources management, distribution and supply of irrigation water in a perfect vision on social welfare in the river basin. The decisionmaking process in a Subak irrigation scheme takes into account political, economic, social and cultural (religious) elements. Multifunctional ecosystems in a sustainable way of agriculture are implemented in the Subak irrigation schemes, particularly in the technology of such systems. On June 29, 2012 the UNESCO World Heritage Committee formally added the Subak systems as a manifestation of the Tri Hita Karana philosophy to the World Heritage List. Subak systems have been well known since the 9th Century. These systems are managed by a Subak Association based on the Tri Hita Karana philosophy - harmony between human beings and God, harmony between people and nature, and harmony between people and people. This philosophy underlies every activity of the Subak farmers. For managing the Subak irrigation schemes, Subak Associations and farmers pursue the Subak regulation called Awig-awig Subak as the togetherness consensus that in the past was announced by the King, nowadays by the Head of the Regency. Paddy terraces in Bali create important cultural landscapes. Traditionally, the flow within a river basin has been managed using the Subak irrigation system technology. Unfortunately, this traditional technology is facing challenges: problems of water shortage and competition with other water users, that make it complicated to sustain the agriculture production of the Subak irrigation schemes. In the middle of the twentieth century, as consequence of ongoing population growth and land conversion, Balinese farmers were having difficulties in meeting the ever-growing demand for rice. In addition, the problem of insufficient water in the dry season developed. In order to increase the irrigation water supply in Yeh Ho River Basin the Government constructed the Telaga Tunjung Dam, based on the cultivated hectares of paddy fields (sawah). However, since the dam was build the downstream river flow was reduced quite significantly and the process of water sharing among the Subak irrigation systems was changed. Due to this, there are serious conflicts on the water sharing among the farmers within Yeh Ho River Basin. Therefore, the main objective of this study was to develop an optimal reservoir operation strategy in relation to the operation of the Subak irrigation systems, capable to support agricultural productivity at upstream, midstream and downstream level. Detailed objectives of study were to: • identify the type of river basin and to evaluate the land use; • identify the contribution of the existing hydraulic structures in the main river system in supplying water to the Subak irrigation schemes; • identify and analyze the reliability of discharge in the main river system and the inflow to the reservoir; • analyze and determine the optimal outflow from the reservoir based on the needs of the Subak irrigation schemes within the river basin; • simulation of the reservoir operation and operation of the related Subak irrigation systems based on the needs of the Subak irrigation schemes at upstream, midstream and downstream level to achieve optimal productivity of agriculture in a sequence time of operation related to the cropping patterns of the Subak irrigation schemes; • to formulate recommendations on the future operation of the reservoir and related Subak irrigation systems. Initially the study presents a literature review to portray centuries of experience with ancient Subak irrigation system management, in which Participatory Irrigation Management (PIM) is represented by three linked elements: PIM in irrigation system operation and maintenance; PIM with respect to socio-culture and economics of agriculture; PIM in light of a religious community. While there have been dynamic changes in human civilization, there are concerns how the values of the Tri Hita Karana philosophy can be applied consistently. The lessons learned are based on natural resources of topography, especially in the paddy terraces landscape, water resources and soils based on the principles using the Tri Hita Karana philosophy that influences all activities of participatory irrigation system management related to those three linked elements in Bali. As associations for irrigation system management, Subak Associations have been already naturally adapted to Participatory Irrigation Management (PIM). The technological and socio-agricultural elements, the application of local cropping patterns and indigenous water management are regarded as the building blocks, which have been further developed in this study as scenarios of Telaga Tunjung Reservoir operation and supply to the related Subak irrigation systems. Using the Weibull formula, the historic supply data of several diversion weirs were analyzed. This analysis was able to determine the water balance of the Subak irrigation schemes behind each diversion weir. In line with this, a system approach has been applied based on the managed flows within the river basin and the characteristics of the Subak irrigation schemes. Irrigation and drainage (irrigation-drainage) of Subak irrigation schemes concern an operational approach, which has been adapted naturally to the topography, soil and water resources of Bali. Irrigation and drainage of terrace systems became an essential element in water distribution. Subak farmers have been able to operate and manage irrigation and drainage from one scheme to another for more than a thousand years. They did also know when irrigation water reached from the highest level to the lowest level of the paddy terraces within the schemes in a river basin. In order to sustain the agriculture production of Subak irrigation schemes there was a need for study based on farmer's perspective related to irrigation and drainage from one scheme to another. This research took place during the cultivation periods by observing the water levels at the inlet and outlet of a paddy terraces block, followed by an analysis of the trend and the amount of water being drained. Latosol soil is the soil layer of the study region. It is one of two types of volcanic soil cover, which is the oldest of soils in Bali. The soil characteristics of Latosol can be categorized by silty clay with medium until high plasticity and brown to yellowish colours. The average value of bulk density is 0.91gr/m3 , the particle density 2.58 gr/m3 , the porosity 0.65, the average hydraulic conductivity 9.7 x 10-4 cm/hour or 2.7 x 10-9 m/s. The average root zone permeability of the paddy terraces is 75 cm/hour. The results prove that the Subak farmers irrigate for saturation of the root zone before land preparation, which requires a large amount of water. In order to achieve an optimal scenario a technical system analysis was needed. Two common techniques have been applied, namely simulation and optimisation. The RIBASIM (RIver BAsin SIMulation) model was applied to identify the best distribution of water resources in the Yeh Ho River Basin. The focus of this study was to obtain the highest productivity related to the operation of the Telaga Tunjung Reservoir and the Subak irrigation systems with several weirs. The approach by representing the Yeh Ho River Basin with the RIBASIM model offered the possibility to find optimum results for the agriculture production. However, there was reduced availability of water for irrigation from upstream sources and from the river. The river basin simulation uses the 80% dependable discharge, and the simulation and optimisation of the Subak schemes in Yeh Ho River Basin. While the period of land preparation is critical with respect to the water needs the scenario analysis and optimisation have been based on shifting of the starting time of land preparation (nyorog). The results show that especially in the upstream and midstream of Yeh Ho River the allocation of irrigation water to the Subak irrigation schemes experienced a deficit since the water of Gembrong Spring was primarily withdrawn for domestic use, and the distribution of water from the spring was not based on applying the agreement on water sharing in practice. Therefore the first step in improved water supply would have to be to really apply the agreement about it in practice. When this will be done effective operation of the Telaga Tunjung Reservoir does not necessarily completely solve the problem of water shortage in the river basin. However, when a cropping pattern based on the fifth scenario will be applied the water deficit and yield reduction will be quite limited. The results further show that the cropping pattern of the fifth scenario would result in an optimal overall agriculture production at 100% and feasibility of farming of 2.3 of the potential field level production for the Subak schemes. The recoverable flow considered in the RIBASIM model plays an important role in the simulation and optimisation of Yeh Ho River Basin. Two values have been applied, being 62% for the average and 21% for the minimum recoverable flow. This is supported by the Tri Hita Karana philosophy on harmony among people that overall could be applied in the schemes in accordance with the cropping pattern of the fifth scenario, so that agricultural productivity will be optimal. Nevertheless, under normal hydro-climatological conditions it is also possible to apply the other scenarios, especially the first scenario. This reflects the applicability of the Tri Hita Karana philosophy of harmony among people and harmony of people and nature. At last, it is important how Subak farmers are able to maintain harmony within the irrigation systems. This research started quantitatively at the river basin scale and at paddy terraces block scale by composing the Yeh Ho River Basin with the Subak irrigation schemes in it. The fieldwork was done by orientation on the water sources and hydraulic structures of and within Yeh Ho River Basin. Then a closed paddy terraces block with inlets and outlets that relatively easy could be studied was analysed. These studies were based on the third element of the Tri Hita Karana philosophy that is the material subsystem in relation to the natural elements. This aspect implies that every paddy block of one farmer has one inlet and one outlet and that the boundaries of the Subak schemes are naturally clear. These observations were conducted during two wet and dry seasons (April 2013 - April 2015). In addition data on agriculture production within Subak Caguh upstream of Telaga Tunjung Reservoir and Subak Meliling downstream of the reservoir were collected, and soil samples were taken to determine the type and the characteristics of the soils. Based on the river basin and Subak irrigation schemes model, a scenario analysis based on the Subak irrigation systems and the Tri Hita Karana philosophy and Subak regulation was done. The results can be applied as a recommendation for the farmers. Although the Subak farmers are reluctant to change to new irrigation practices, such practices can in principle be useful for them as shown in two recent studies. One of these studies concerned the application of the System of Rice Intensification (SRI) combined with intermittent irrigation (ngenyatin). In the farmer's perspective the SRI method is not easy applicable in practice. Nevertheless, the Subak farmers agreed that 15 days before harvesting they will dry their fields, which is one element of the SRI method. The reservoir operation rule as applied in the fifth scenario gives the best result. The reservoir has especially an important role to increase water supply for the downstream schemes: Meliling, Gadungan and Sungsang. It also has a direct impact to sustain water conservation at the river basin scale

PENGARUH PERUBAHAN TATA GUNA LAHAN TERHADAP DEBIT BANJIR

Bali as tourist destination has great impact to the change of land use. This is related to the development of tourism supporting infrastructures such as hotel, villa, restaurant and other facilities which are developed at strategic area with beautiful landscape. Generally in the area has mountainous area that is from upper course area to downstream and beach area. The impact of this development activity is the need of the area which is originally on open are and function as water absorption area, then changed into impermeable residential area. This condition has resulted toward the increase of surface run off which directly influence the flood discharge in the river. The discharge of flood due to the change of land use is calculated by using Rational Method. The Rational Method has three components i.e. coefficient of run off, C, rainfall intensity, I, and catchment area, A. The value of coefficient run off (C) is determined based on the condition of land uses. The result of flood discharge due to the change of land use from period of 1992 to 2000, at one of Sub Basin Tampus in Ayung Basin has resulted the trend of decrease of flood discharge 30,36 %. This concern is true as according to condition existing DAS Tampus. Explainable theoretically if with the same of rainfall value (analysis from year data 1992 - 2000) but with variation of land opening change therefore time from rain from farthest point to the observation point (tc) related also will change. In the consequence of increase of tc value thus with the same rainfall will causes the intensity of rainfall is decrease. Value of tc in DAS Tampus is increase which in the year 1992 = 116 minute become 121 minute in the year 2000, because of the process of land closing by vegetation that is the continuation of new cultivated area in location, so that the rain process to become the surface run off is more slowly. Keywords: discharge of flood, intensity of rainfall, coefficient of run off, and land us