Analysis of water availability of the Singkoyo River for the irrigation needs in the Banggai Regency, Indonesian

Abstract

Indonesia relies on its food security by expanding the area and productivity of agricultural land. This condition requires water to irrigate existing rice fields, such as in the Singkoyo area. This study aims to determine the study area’s surface water availability (Q80), irrigation needs, and water balance. Some methods are applied, such as Penman-Monteith for the evapotranspiration calculation, and the FJ Mock method for the dependable flow and water need based on the annual cropping plan. The result shows that the Singkoyo River, with a catchment area of 408.55 km2, has an average flow rate for Q80 is 6.24 m3sec-1, whereas the most significant discharge occurs in July 15.48 m3sec-1 and the smallest occurs in November at 2.86 m3sec-1. On the other hand, applying the worst scenario with three times of planting per year with rice, the need for three irrigation areas vary according to the NFR during the plantation phase from 7.20 m3sec-1 at the 3rd planting season in October, and the lowest is 2.0 m3sec-1 at the 2nd planting season in February. The water balance is mostly surplus from December to August, but then deficit during September to November by -1.34 m3 sec-1 on average.