Page - 280 - in Book of Full Papers - Symposium Hydro Engineering

3. PROBLEM OF WLINGI DAM AND BRANTAS RIVER MANAGEMENT SEDIMENTATION The main problem in managing the reservoir is sedimentation. This problem is a fundamental problem that is almost experienced by all reservoirs in the world. Illegal logging, volcanic activity and land degradation (due to excessive land use exchange) are the main causes of sedimentation. The Wlingi Reservoir, which was completed in 1979, has a sedimentation rate of 0.81 million m3 per year or 3.34% of reservoir per year, which the Sutami Reservoir, the largest reservoir in the same basin, has a sedimentation rate of 5.07 million m3 per year or 1, 47% of reservoir per year. From the data it appears that the sedimentation rate at Wlingi reservoir is 2.3 times the largest reservoir in the same river basin. The Wlingi Reservoir, built with an initial total storage capacity of approximately 24 million m3, now has only 4.42 million m3 or 18% of its initial storage capacity. This indicates that the sedimentation rate in Wlingi Reservoir is very large. The main cause is the influence of the eruption of Mount Kelud which is still active and is 40 km from Wlingi Reservoir. During the past century, Mount Kelud eruptions occurred in 1901, 1919, 1951, 1966, 1990 and 2014. Table 1 Wlingi Reservoir Capacity Years Gross Storage Effective Storage Dead Storage Volume (million m3) Percen t (%) Volume (million m3) Percent (%) Volume (million m3) Percent (%) 1977 24.00 100.0 5.20 100.0 18.80 100.0 1982 18.32 76.3 NA NA NA NA 1985 14.44 60.2 NA NA NA NA 1988 9.50 39.6 NA NA NA NA Januari 1990 4.60 19.2 2,20 42.3 2.40 12.8 The eruption of Gn Kelud in February 1990 Maret 1990 1.60 6.7 NA NA NA NA 1991 4.77 19.9 2.34 45.0 2.43 12.9 1992 2.51 10.5 1.09 21.0 1.42 7.5 1993 1.98 8.3 1.21 23.3 0.77 4.1 1995 4.63 19.3 1.33 25.7 3.29 17.5 1995 4.94 20.6 1.59 30.6 3.35 17.8 1996 5.75 24.0 1.83 35.2 3.92 20.9 2001 3.97 16.6 2.11 40.7 1.86 9.9 2004 4.41 18.4 2.01 38.6 2.41 12.8 2006 4.00 16.7 2.02 38.9 1.98 10.5 2011 4.42 18.4 2.00 38.5 2.42 12.9 280