Analisis Keseimbangan Ketersediaan dan Kebutuhan Air Pada Daerah Irigasi Tinalun

Abstract

The balance between water availability and irrigation water demand is a critical factor in maintaining irrigation system sustainability and agricultural production stability. The Tinalun Irrigation Area in Semarang Regency plays a strategic role in supporting paddy field agriculture, yet it is highly influenced by seasonal hydrological fluctuations that may lead to water imbalance. This study aims to comprehensively analyze the balance between water availability and irrigation water demand in the Tinalun Irrigation Area using hydrological, climatological, and existing cropping pattern data. A quantitative descriptive approach was applied. Irrigation water demand was calculated based on effective rainfall, reference evapotranspiration using the FAO Penman–Monteith method, and crop water requirements in accordance with national irrigation planning standards. Water availability was analyzed using dependable discharge calculated by the F.J. Mock method with an 80% reliability level. The data used were secondary data and analysis results from Chapter IV of the undergraduate thesis, including rainfall, climatological data, river discharge, and irrigation area characteristics. The results indicate that the highest dependable discharge occurs in early December I at 32,01 m³/s, while the lowest occurs in October I at 0.15 m³/s. The highest irrigation water demand occurs in November I at 4.28 m³/s, whereas the lowest demand occurs in July II at 0.84 m³/s. Water balance analysis shows surplus conditions during most periods; however, water deficits occur from August II to October II, with deficit values ranging from –0.56 to –1.38 m³/s. These results indicate the need for more adaptive irrigation management, particularly during the dry season, to ensure the sustainability of the Tinalun irrigation system