Abstract:
In this paper, an attempt has been made to compare the revised capacities of Rajaval
and Kharo reservoirs of southern Gujarat (India). The image analysis technique of
remote sensing data was used to estimate the revised capacity of these reservoirs.
Seven Linear Image Self Scanning (LISS III) digital data of IRS 1D/P6 were used in
the analysis. The Normalized Difference Water Index (NDWI), band ratio and
slicing were used to classify the water and non-water pixels from the images using
Integrated Land and Water Information System 3.0 (ILWIS 3.0), a GIS software. From
the analysis, it was observed that 5.043 million cu m of gross storage of Rajaval reservoir
has been lost in 25 years (1982-2007) and the average rate of siltation in this reservoir
is 0.202 million cu m/year. In the case of Kharo reservoir, 4.332 million cu m of gross
storage has been lost in 22 years (1982-2007) and the average rate of siltation is 0.197
million cu m/year. The data of silt surveys in the year 2000 was also used and the
pattern of siltation in both reservoirs was analyzed for evaluation periods, namely,
impoundment to 2000 (Evaluation Period-I) and 2000-07 (Evaluation Period-II). From
the analysis, it was observed that the sedimentation rate increased significantly during
2000-07 in both the reservoirs but Rajaval reservoir needs immediate attention for
soil conservation measures because rate of siltation in this reservoir has doubled
during this period. The spatial distribution of sediment in both reservoirs indicated
more deposition in upper part due to flat topography in that region.
