ANALISIS NERACA AIR IRIGASI UNTUK TANAMAN PADI PADA SUBAK JAKA SEBAGAI SUBAK NATAK TIYIS - I Putu Riadi Handika; I Made Anom S. Wijaya; Sumiyati Sumiyati (Program Studi Teknik Pertanian dan Biosistem, Fakultas Teknologi Pertanian, Universitas Udayana, Badung, Bali, Indonesia, 2015)
Sumber air sistem irigasi Subak Natak Tiyis berasal dari hulu air drainase subak. Kondisi tersebut menyebabkan neraca air irigasi tidak menentu di Subak Natak Tiyis, sehingga perlu penelitian lebih lanjut untuk menentukan keseimbangan air irigasi yang sesuai dengan ketersediaan dan kebutuhan air irigasi di Subak Natak Tiyis. Tujuan dari penelitian ini adalah untuk menganalisis ketersediaan dan kebutuhan air irigasi Subak Jaka sebagai Subak Natak Tiyis dan menentukan keseimbangan air irigasi di Subak Jaka sebagai Subak Natak Tiyis. Analisis ketersediaan debit dilakukan dengan mengukur debit di inlet Subak Jaka. Kebutuhan air irigasi dianalisis menggunakan perangkat lunak CROPWAT 8.0. Neraca air irigasi diperoleh dengan membandingkan debit air irigasi dengan availabilitis dan kebutuhan air irigasi sehingga didapatkan defisit air irigasi pada Subak Jaka. Analisis ketersediaan debit menunjukkan debit tinggi terjadi pada musim hujan yaitu 115,72 liter / detik dalam setahun. Debit terkecil terjadi pada musim kemarau yaitu 19,01 liter / detik dalam setahun. Kebutuhan air irigasi di MT I dan MT II rata-rata debit yang dibutuhkan berkisar antara 11,0 hingga 98,5 liter / detik selama 15 hari. Hasil neraca air irigasi Subak Jaka terjadi defisit air irigasi tiga periode yaitu 35,2 liter / detik pada periode Juni I yang tertinggi selama 15 hari, 16,8 liter / detik pada periode Juni II dan 30,7 liter / detik pada Januari saya yang tertinggi 15 hari. Water source of Subak Natak Tiyis irrigation system comes from the upstream of subak drainage water. Those condition was causing uncertainly irrigation water balance in Subak Natak Tiyis, thus it requires further research to determine appropriate irrigation water balance according to the availabilitiy and requirement of irrigation water in Subak Natak Tiyis. The purposes of this research were to analyze the availabilities and requirement of irrigation water of Subak Jaka as Subak Natak Tiyis and determine the water balance irrigation in the Subak Jaka as Subak Natak Tiyis. The analysis of discharge availabilities was carried out by measuring discharge at inlet Subak Jaka. Irrigation water requirement was analyzed using CROPWAT 8.0 software. irrigation water balance was obtained by comparing the discharge of irrigation water was availabilitis and irrigation water requirement so get irrigation water deficit on Subak Jaka. The analysis of discharge availabilities showed high discharge occur at rainy season that was 115.72 liter/second within a year. The smallest discharge occurs in dry season that was 19.01 liter/second within a year. Irrigation water requirement in MT I and MT II average required discharge ranged from 11.0 to 98.5 liter/second for 15 days. The result of irrigation water balance the Subak Jaka occurrence irrigation water deficit three period that was 35.2 liter/second on period June I that highest for 15 days, 16.8 liter/second on period June II and 30.7 liter/second on January I that highest for 15 days.