ANALISIS LAJU SEDIMENTASI WADUK GAJAH MUNGKUR WONOGIRI UNTUK PERKIRAAN USIA GUNA WADUK

Sedimentation is one of the issues found in the operational of reservoir. Sedimentation can reduce the working life and the function of the reservoir. Gajah Mungkur reservoir also cannot avoid the sedimentation effect in its operation despite the expectation for the reservoir to function at its optimum capacity. Therefore, the issue needs to be properly addressed. This issue can be overcome by finding the sedimentation distribution in the reservoir. This study analyzed sedimentation rate for operation time of 28 years and 34 years by applying Empirical Area-Reduction Method and Area-Increment Method. After conducting the analysis, it was proven that the most suitable method to apply in Gajah Mungkur reservoir was Empirical Area-Reduction Method due to its smaller deviation compared to Area-Increment Method both for operation time of 28 years and 34 years (2014). The sediment volume for operation time of 28 years reached 40,685 million m3, and for 34 years reached 52,767 million m3. The reservoir working life was found from the analysis which showed the total sediment in the dam upon reaching 100 years of operation time was 138,13.106 m3. While by using sedimentation rate it was found that the total sediment was 2.093. 106 m3/year. Therefore the dead storage that was planned to reach 120 million m3 (1980) would be full before the reservoir’s operation time was 100 years in the 91st year by 2071