Monitoring waterlogging and surface salinity using satellite remote sensing data

Both Landsat MSS and TM and SPOT data, available in SUPARCO archives, have been analysed using both visual interpretation and digital processing techniques to map and monitor the extent and severity of waterlogging and surface salinity in selected parts of the Indus Basin. While historical. Landsat MSS used in the study were acquired from foreign stations, the Landsat TM and SPOT data used have been acquired by SUPARCO´s Satellite Ground Station (SGS) at Islamabad. For selection of suitable data, it was observed that cropping season data, due to contrast, are most suitable for the identification of saline patches. During the summer cropping season, some of the salts are dissolved in the monsoon rain water and percolate into the soil. Therefore, winter cropping season data of February and March is considered to be the best for demarcation of saline patches. The saline areas due to their higher reflectance relative to their surroundings are easily detectable on satellite images. The salinity has been classified on the images according to its severity and has been classed as severely, moderately and slightly saline. Similarly, waterlogged areas, which have lower spectral reflectance values with respect to surrounding areas, have been located and mapped accordingly. It was found that there was reasonably good correspondence between the satellite based results and the waterlogging and salinity maps available with concerned agencies and field verification data