Page - 283 - in Book of Full Papers - Symposium Hydro Engineering

sediment balance in a river. Flushing carried out at Wlingi Dam during the last 10 years is as in the following table: Table 3 Flushing at Wlingi Dam Year Wlingi Reservoir M3) Remaks 2008 395,480 2009 145,514 2010 561,192 2011 351,625 2012 426,481 2013 2014 2015 2016 2017 269,514 No flushing No flushing 1,026,500 787,330 Limited inflow Limited inflow Source: Jasa Tirta I Public Corporation Flushing implementation is done by gradually lowering the water level of the reservoir by operating the gate so that water can flow in free flow condition. After a while, the water level is raised again. In order for optimal results, if the discharge is sufficient, this process can be repeated until obtained the planned reservoir profile. Duration for flushing implementation is about 16 - 20 hours with a potential power loss is approx. 969,000 Kwh. After the completion of flushing, measure of the reservoir profile to calculate the amount of sediment that was flushed and examined the condition of water resources infrastructure in the upstream and downstream of the dam. Technical evaluation conducted to see whether there is damage to water resources infrastructure or not. In the event of damage, calculated how much the damage lost. From the results of several times flushing activities, apparently, no damage to water resources infrastructure. DREDGING RESERVOIR In addition to flushing, to increase lifetime of the reservoir is also dredging. Implementation of flushing have to consider inflow while dredging is less concerned inflow. The main obstacle of dredging is limited spoil bank land. Especially recently where high cost of land acquisition of new spoil. If the land acquisition of spoil bank encounters of constraints, then dredging with riverine disposal to channel below is carried out. The dredging of sediments in the Wlingi reservoir over the last 5 years is as shown in the following table. 283