ANALISIS DISTRIBUSI CURAH HUJAN KAWASAN MENGGUNAKAN METODE ISOHYET DAN PERHITUNGAN KEBUTUHAN AIR IRIGASI DENGAN APLIKASI CROPWAT 8.0

This study focuses on the Dermen irrigation area in the districts of Wlingi, Kesamben, and Selopuro,
Blitar Regency. The objectives of this research are to classify topographic slopes, analyze hydrological
data to determine the spatial extent of rainfall distribution using the Isohyet method, and assess the water
requirement for rice crops using the Cropwat method. Based on the research findings, it is concluded that
the predominant land slope in the area is flat and gently sloping, accounting for 82.53% of the total area.
The analysis of rainfall distribution using the Isohyet method indicates the lowest rainfall in August at
19.8 mm and the highest rainfall in February at 295.8 mm. The irrigation water availability measured by
the Automatic Water Level Recorder (AWLR) at Dermen Dam is 3.10 m3/second. The highest irrigation
water requirement occurs in July III during land preparation and early growth phases of rice, totaling
3015 liters per hectare per day (3.015 m3/second), demonstrating that the available water discharge in
the Dermen irrigation area meets the irrigation water needs for the rice planting schedule throughout the
season.
Key Word: ArcGIS, Cropwat, Topography, Hydrological Analysis, Irrigation Water Requirement.