Optimasi Pemanfaatan Air Menggunakan Program Solver di Bendungan Jragung Semarang

Abstract

The construction of the Jragung Dam aims to address the imbalance of water availability in Demak and Grobogan Regencies, where droughts occur during the dry season and flooding during the rainy season. With a planned storage capacity of 90 million m³, the dam is expected to fulfill irrigation water demands in the Jragung Irrigation Area (D.I. Jragung), which is still experiencing shortages, as well as providing raw water for the surrounding communities. The existing cropping intensity in D.I. Jragung is 225%. Due to this suboptimal intensity, an optimization analysis of water demand was carried out as a result of the Jragung Dam development, in order to meet raw water needs, increase irrigation cropping intensity, and generate hydropower.The optimization for irrigation was conducted using the linear programming method with the Microsoft Office Solver Add-ins, where the decision variable was the planting time, and the constraints included raw water demand based on population growth projections up to 2030 as well as water availability. The optimization results indicate that the Jragung Dam development can increase cropping intensity to 300%, with the planting season starting in October of the second period. In addition, raw water demand can be met at 0.89 m³/s, while hydropower production is estimated at 3,880 MWh in wet years, 3,859 MWh in normal years, and 3,792 MWh in dry years.