Studi Potensi Ketersediaan Air Pada Bendung Rejoso Untuk Memenuhi Pemanfaatan Air Secara Optimal Pada Daerah Irigasi Rejoso Kabupaten Pasuruan

The potential irrigation area in the Rejoso Irrigation District (D.I. Rejoso) covers 153 hectares, located in Pandaan Subdistrict, Pasuruan Regency, and is supplied by the Kadalpang River. Farmers in the study area implement a rice–rice–rice cropping pattern. The first planting season is conducted from October to the end of March, while the second season begins in early April and continues until the end of September. Water shortages frequently occur during the dry season, posing a significant challenge to irrigation management. Therefore, adequate water availability is required to sustain agricultural activities within the irrigation area.
This study refers to KP-01 and KP-02 guidelines on Watershed (DAS) management, hydrological theory, and the concept of water resource carrying capacity to analyze irrigation water availability and demand. Water availability was assessed using intake discharge data from the hydrological gauging station and dependable discharge analysis. Cropping pattern and planting schedule engineering were performed to determine the optimal cropping intensity under existing field conditions. A water balance model was applied to evaluate the adequacy of water supply and its impact on the irrigation service area.
The analysis results indicate that the average minimum discharge at the intake weir is 206.90 liters/second, occurring in early November (first period), while the maximum discharge of 468.78 liters/second occurs in early February (first period). The recap of cultivated land area shows variations in cropping intensity for each alternative cropping pattern. The best cropping intensity is achieved under Alternative Cropping Patterns II and III, which cover the entire irrigation service area, with planting schedules starting in the second period of December and the first period of January, respectively. These patterns are considered the most suitable based on the actual water availability conditions at Rejoso Weir, Pasuruan Regency.