Capacity survey of Nagarjuna Sagar reservoir, India using Linear Mixture Model (LMM) approach

Satellite data has long been in use to estimate the water-spread area at different water levels of a reservoir. Traditional approaches such as maximum likelihood classification and band threshold method involve the per-pixel approach to delineate the water-spread area of a reservoir. One of the limitations of the per-pixel approach is that the pixels representing reservoir border, containing water with soil and vegetation, are also classified as water pixels, thereby giving inaccurate estimate of the water-spread area. To compute the water-spread area accurately, the sub-pixel or linear mixture model (LMM) approach has been adopted in this study. IRS-1C and 1D satellite image data (24m) of eight optimal dates ranging from minimum draw down level (MDDL) to full reservoir level (FRL) were used to estimate the water-spread area of the reservoir. The extracted water-spread areas using sub-pixel approach was in turn used to quantify the capacity of the Nagarjuna Sagar reservoir for the water year 2002. The estimated capacity of the reservoir using sub-pixel approach was 8014.49 Mm³.