Analisis Persentase Penghematan Air Irigasi dengan Metode Pergiliran (Magilihan) pada Subak di DAS Ho

Abstract

ABSTRAK

Berkurangnya ketersediaan air irigasi dapat disebabkan oleh debit air sungai yang turun pada musim kemarau, hilangnya air pada saluran irigasi, dan evaporasi. Dengan demikian, upaya-upaya penghematan perlu dilakukan seperti sistem pergiliran dalam pemberian air irigasi dan proposi dalam ditribusi air irigasi pada setiap subak. Penelitian dilakukan untuk mengetahui persentase pengehematan air irigasi yang ada pada suatu subak dan proposi pemberian air irigasi pada saat kurangnya ketersediaan air. Perolehan data primer dilakukan dengan metode wawancara, pengamatan, dan pengukuran sedangkan data sekunder diperoleh dari BMKG Wilayah III Denpasar. Data yang dikumpulkan selanjutnya akann dianalisis untuk mencari persentase pengehematan yang terjadi pada saat kekurangan air dan proposi distribusi air irigasi. Hasil penelitian menunjukan metode pergiliran dilakukan pada saat debit air tersedia tidak bisa memenuhi kebutuhan air irigasi. Metode pergiliran dilakukan pada subak bagian tengah dan subak bagian hulu pada bulan April sampai Mei. Metode pergiliran dilakukan dengan menurunkan jumlah kebutuhan air irigasi dan memberikan air irigasi sesuai dengan debit tersedia dengan rentang waktu setiap dua hari. Subak bagian hulu tidak terjadi penghematan karena proses pergiliran tidak berjalan, penghematan air irigasi pada subak bagian tengah rata-rata sebesar 28,3 persen dan subak bagian hilir sebesar 24 persen. Dengan penerapan metode pergiliran pada saat kekurangan air irigasi kebutuhan air irigasi bisa terpenuhi oleh debit air yang tersedia. Untuk mencapai proposional penghemtan air irigasi pada bulan April sampai Mei, pada subak bagian hulu air irigasi diturunkan sebesar 17,46 persen, subak tengah dinaikan 13,37 persen, dan subak hilir dinaikan 9,84 persen.

ABSTRACT

Availability of irrigation water can be influenced by the discharge of river water that drops in the dry season, loss of water in irrigation channels and evaporation. Thus, austerity measures need to be made such as a system of turns in irrigation water and balanced in the attribution of irrigation water on each subak. Research was conducted to determine the percentage of irrigation water storage present in a subak and the proportion of irrigation water at a time of lack of water availability. The acquisition of primary data is done by interviewing, observation, and measurement methods while secondary data is obtained from BMKG Region III Denpasar. The data collected will then be analyzed to look for the percentage of storage that occurs during water shortages and the balanced of irrigation water distribution. The results showed the method of turns was carried out when the discharge of available water could not meet the needs of irrigation water. The turns method occurs in the middle and upper subak from April to May. The method of turns is carried out by lowering the amount of irrigation water needs and providing irrigation water according to the discharge available with a time span every two days. The upstream subak does not have any savings because the rotating process is not running, irrigation water savings in the central subak averaged 28,3 percent and downstream subak by 24 percent. Water rotational method can be used when there is a shortage of irrigation water, therefor water needs can be met by the discharge of available water. To achieve the proportional irrigation water supply in April to May, the upper subak of irrigation water was lowered by 17,46 percent, the central subak was increased by 13,37 percent, and the downstream subak was increased by 9,84.