SEDIMENTATION PROBLEM IN WEST TARUM CANAL WEST JAWA, INDONESIA Endah Kurniyaningrum and Trihono Kadri
INTRODUCTION There are several purposes which take water from WTC and they are: agriculture, domestis, municipal and industrial water, flushing, maintannce flow and aquaculture, etc. In 1960, the target user of original WTC is for agriculture and still most imptant until now. Secondly, water user in the area is domestik, municipal and industrial (DMI). DMI watter demand will incresing in the future due to population growth etc. The suburban of Jakarta are on the way of espansion and it leaches to the Bekasi area. This problem not only increase DMI water demand but also deprive lan for irrigation are. According to the phenomena, WTC become important to supply raw water to jakarta and other area. In the other side, due to sedimentation problems the flow capacity of WTC is decreasing not like initial planning. It s may affect to supply raw water to Jakarta. Jakarta is urban area with rapid population development and high population growth that clean water is scarce and expensive goods. Due to population increasing, water need will supply from out of region, that why raw water problem that will be extrimly problem in the next few years.
General Condition West Tarum Canal, which starts at the Curug weir on Citarum River and ends at a junction with Ciliwung River in Jakarta, was contructed as part of the Jatiluhur project in 1960s. Since commencement of comersial operation in 1968, WTC has been conveying raw water of Citarum River for irrigation and Jakata DMI purpose in western region of the Citarum river. The raw water in pumped up at Curug weir located in middle reach of Citarum River by 17 hydraulic pump units, each of which design at 5.5 m 3 /s under a 1.5 lift head Schematic of West Tarum Canal. METHODOLOGY
General Condition The methodology of this research comprise of 4 phases, namely; 1) preparation, 2) fieldwork and data acquisition, 3) hydraulic simulation, and 4) validation, evaluation. Preparation phase comprises of literatures study correlate with the study, ancillary data collection, and fieldwork preparation. Fieldwork and data acquisition phase comprise hydraulic data acquisition, topographic map, canal characteristic, and assessment also to describe the physical canal characteristics on the study area. Canal simulation model has been generated using hec-ras software for hydraulic analysis. Hec-ras program was used to determine the influence of sedimentation on the wtc and to modify the cross section to perform of sediment transport. METHODOLOGY
RESULTS AND ANALYSIS West Tarum Canal is transmission channel which supply of raw water from the Jatiluhur. Now the condition of the canal has undergone degradation which marked by fluctuation of debits in the rainy season and dry season, decreasing of flow the capacity and declining quality of raw water. The decreasing of flow capacity caused by accumulation sedimentation inherent erosion from upstream Citarum river and confluence with Cibeet, Cikarang and Bekasi River. So, that problems make dimension of WTC is smaller. The design discharge is about 82.5 m 3 /s, but now WTC only can accommodate around 35 m 3 /s water discharges. The analysis, : a) Prediction of Water demand b) Sedimentation Transport c) Hydraulic Modelling
Bank over flow in existing canal capacity to supply 2025 water demand prediction. Bank over Flow Prediction of Water demand In 2025, there are 10,853,519.9 people (regresion results) and based on International Water Association Standard (IWA) water need 190 l/day each people daily, therefore the total DMI is about 57.28 m 3 /s. Assume that industry needs 30 % (17.18 m 3 /s) and for safety factor needs 20%. Total calculation of projected water demand in 2025 is around 85.92 m 3 /s, that s why WTC need modification because the water demand in 2025 is more than design discharge (82 m 3 /s).
Dregging Volume Hydraulic Modelling Water demand prediction (85.92 m 3 /s ) is analyzed into simulation program and showed that canal flow capacity is not enough to flow water demand prediction to carrie out the prediction discharge the canal must be modified. The results of the analysis with HEC-RAS program showed WTC needs to redesign and must be removed the sediment deposition. Based on simulation results, the sediment volume to be handle by removal works or dregging volume is estimated at 2.2 million m 3 in total 54.2 km long section betwen Curug pump station and Bekasi Weir.
Sedimentation problem in West Tarum Canal
CONCLUSION In the conclusion it can be stated that HEC-RAS output result of the canal extent closely resembles with the base map of the study area taking into consideration of all the limitations mentioned earlier. The advantage of HEC- RAS aplication program is use to simulate conveyance capacity of the canal. WTC had design capacities in 1985 is about 82.5 m 3 /s, but now the capacity is only around 35 m 3 /s. The reduction was caused by sedimentation processes occur at the base of the channel during in 20 years. Based on simulation results, it is hoped that there is a plan to increase conveyance discharge by dregging that would be able to accommodate the design flow at year of 2025 prediction.