Seite - 507 - in Book of Full Papers - Symposium Hydro Engineering

The sedimentation problem is made worse by the fact that the mouth of Keduang River enters the Wonogiri reservior is less than 0.5 km from the intake for power plant / irrigation releases. This results in heavy siltation in front of the the intake which needs nearly continuous dredging to keep the reservior operational, especially in the dry seasons. Figure 3. Heavy Siltation requires continues dredging, Source: Nippon Koei staff photo 1.3. The Solution In order to reduce the amount of siltation that will need to be dredge from in front of the intake, a proposed solution is to divide the reservoir into two parts; a Sediment Reservoir to capture and manage sediment from the Keduang River and a Clear Water Reservoir leading to the intake. The division of the reservoir into two parts is to be accomplished with construction of series of closure dikes between partially submerging islands within the reservoir. A total of three closure dike and an overflow dike (broadcrested overflow spillway) are to be constructed as shown below. In addition, a new spillway gates shall be constructed at the east bank of Wonogiri Dam closed to the confluence of Keduang River. Sediment trapped in the sediment reservoir will be flushed down through the new spillway gates into the upper solo river during the rainy (flood) seasons. 507