EVALUASI JARINGAN IRIGASI TERHADAP KEBUTUHAN AIR DENGAN METODE PENMAN MODIFIKASI PADA JARINGAN IRIGASI NAMU SIRA-SIRA KANAN

Abstract

The Namu Sira-Sira Irrigation Area is an irrigation area located in Sei Bingei District, Langkat Regency, North Sumatera Province to irrigate 6.500 ha. There is a lot of damage to the irrigation structures, the canal walls were overgrown with grass, sedimentation along the canal and the lack of channel dimensions causes flooding in the rice fields during the rainy season. The purpose of this study is to determine the need for irrigation water and to analyze existing discharge for the channel to re-dimensionalize the channel if the existing discharge for the channel is less than the discharge for the planned channel. Calculation of irrigation water needs using Modified Penman method based on KP-01. The results obtained from this study include the maximum water requirement calculated by the Modified Penman method is 5,207 l/sec/ha. Water demand is used to calculate the planned discharge in planning irrigation channels. The SNT1, SNT2, SNT3, SNT4, SNT6, SSG2, SSG3, SSG4, SSG5 and SSG6 channels were unable to accommodate and carry the water discharge to have flowed, so a re-planning was needed. With trapezoidal channel dimensions planning, for SNT1 channel with channel width (b) = 0.55 m, water level (h) = 0.55 m, slope m = 1.0 and channel base slope = 0.000429. By evaluating the dimensions of the canal, the canal can carry water discharge that will flow to agricultural land.