The Development of Closure Dike as Countermeasure of Sedimentation in the Wonogiri Reservoir, Indonesia

Abstract

The problem of reservoir sedimentation occurs worldwide, including in the Wonogiri reservoir, Indonesia. The reservoir was built from 1977 to 1980, but the dam faces a severe problem of sedimentation. Sediment inflow in the Wonogiri Reservoir comes from several sources, especially from Keduang River, a tributary from Mount Lawu. The sediment management problems are generally complicated and different in every place. In some conditions, it will be possible to prevent sediment from entering the reservoir by adding an internal barrier as applied in the Wonogiri Reservoir. The reservoir is divided into two reservoirs by a closure dike equipped with an overflow dike and a new spillway. This paper will describe the development of closure dike based on field observation and data obtained from the Ministry of Public Works and Housing. Moreover, this paper will also describe the sedimentation status of the Wonogiri reservoir based on the recent bathymetric data. The development of closure dike already completed, which consists of Closure Dike A (700 m), B (700 m), C (302 m), and Overflow Dike (298 m). The recent bathymetric survey revealed that the capacity of effective storage of the main reservoir is 322.84 MCM.