OPTIMIZATION OF IRIGATION WATER ALLOCATION WITH DYNAMIC PROGRAMING(CASE STUDY: DAERAH IRIGASI CANDILIMO KABUPATEN MOJOKERTO PROVINSI JAWA TIMUR)

• Main Author: Sheba Dyolaksti, Forcelita
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/71278
• Institution: Institut Teknologi Bandung

The Candilimo Irrigation Area has an area of 1911 ha, but currently has changed to 1888 ha. The problem that occurs in this irrigation area is that cropping area are not fully serviced, even though it has a large potential area. Fluctuating water flow in each season causing available cropping area are unable to be fully served especialy in the dry season. The aim of this study is to get the most efficient and optimal water distribution in each planting season so the maximum financial benefit in one year of the planting period can be achieved. The optimization method is a method to optimize the distribution of existing water. The optimization model used to solve the problem in this study is a dynamic program using probabilistic approach. To get optimal results, several scenarios for planting patterns and alternative planting schedules are arranged. First Scenario with cropping patterns according to RTTG 2017, Second Scenario with cropping patterns according to 2017 planting realization and Third Scenario using cropping patterns without uncultivated area and 400ha planting area of rice in MT II. In this study, dependable flow are calculated in three conditions which are low water flow (Q75.3%), normal water flow (Q50.7%) and sufficient water flow (Q26.0%). Calculation of water requirements for each alternative in each scenario using LPR FPR method. The selection of alternatives in this study is based on the largest rice cropping index of the three alternatives for each scenario. Then the probability of the available and required flow’s gap for the chosen alternative for each scenario are calculated. Based on these probability distributions, expected value that will be used in optimization with dynamic programs are calculated. In this study there are five stages of dynamic programs which are irrigations channels, i.e. Primary Channel of Candilimo, Secondary Channel of Pengilon, Secondary Channel of Candi Tikus, Secondary Channel of Beloh dan Secondary Channel of Semanding. Dynamic program calculations for every planting season are performed by moving forward calculations towards the end of the stage (forward recursive). Whereas the maximum profit is the amount of profit for each planting season in one planting period. iv The results of the water balance analysis for alternative selection based on the largest rice cropping index are the third alternative for each scenario. For the 3rd Scenario with sufficient air discharge (Q 26%), in MT III optimization are not carried out, because the sufficient percentage is already 100%. After the optimization with a dynamic program, irrigated crop area in a year planting period for all scenarios are increased with average increasing cropping area of 24.45 ha and the highest increase was 72.01 ha. However, there are a number of planting seasons that have decreased cropping area. The area difference before and after optimization is an average of 15.70 ha, while the smallest difference was 0.12 ha. Even though in some planting seasons the cropping area are decreased, but when viewed within a whloe year planting period the overall cropping area increased and the financial returns were increased also. The biggest increased profits for low water flow conditions (Q 75.3%) was the 1st Scenario with total profit in a year planting period of Rp.42,016,501,766.46 or increased by Rp.1,754,149,248.86, while for normal water flow (Q 50.7%) and sufficient water flow (Q 26.0%) occurred in 3rd Scenario with total profit in a year planting period of Rp 51.603.697.273,00 and Rp 67.333.133.339,70 each.