ASSESSMENT OF SEDIMENTATION IN RESERVOIR USING SATELLITE REMOTE SENSING TECHNIQUE

Abstract

The life span of the reservoir is determined by the rate of sedimentation which gradually reduces useful storage capacity due to sedimentation. This loss in useful capacity affects the purpose for which it is created. Therefore to optimize the benefits from the project, it is necessary to have the knowledge of likely progressive reduction in storage during planning /operation stage. Methods such as stream flow analysis, hydrographic surveys, Satellite Remote Sensing (SRS) techniques, empirical methods and mathematical models are presently in use for estimation/prediction of sediment deposition in reservoirs. Owing to advantages like cost effectiveness, time saving, less manpower requirement, accuracy in estimation and capability of carrying out past surveys the Satellite Remote Sensing Technique is gaining more importance now a days. From the historical records available, Panshet dam was constructed in the year 1961 but due to heavy floods, it was breached in the same year. After breach, the dam was reconstructed in the year 1973 and the capacity survey was carried out in the year 1977, which is taken as base for the present study. The gross storage of Panshet reservoir for the year 1977 was 303.93 Mm3. The dead and live storage of for the same were 9.00 Mm3 at RL 597.41 m and 294.93 Mm3 at FRI, 635.81 m respectively. As per this SRS survey for the year 2001-02 the gross, dead and live storages were estimated as 284.44 Mm3, 8.703 Mm3 and 275.737 Mm3 respectively. It was found that there was loss of gross storage of 19.49 Mm3 in 25 years. The sediment index worked out considering total period since 1977 upto 2002 (25 years) and catchment area of 120.30 km2 was around 6380 m3/km2/year, which is equivalent to 7656 T/ km2/year. The deposition pattern of Panshet reservoir was compared with the standard types of deposition pattern suggested by Borland and Miller. The comparison indicated that the deposition pattern for the reservoir has remained in Type I during 1977 to 2001-02.