Comparative assessment of multisensor data for suitability in study of the soil salinity using remote sensing and GIS in the Fordwah irrigation division, Pakistan

Assessment of soil salinity and its various factors in time and cost effective manner to reclaim the saline area is one of the prime requirements in the progress and development of an agriculturally dependent country. remote sensing (RS) and geographic information system (GIS) technologies are emerging as indispensable tools in the study and mapping of dynamic phenomenon having spatial and temporal characteristics. This study presents practical application of RS data in integration of GIS in assessment of soil salinity and some of its physical factors. Approximately 788 sq km of salt-affected area in an irrigated regime of southern Punjab, Pakistan was selected for the study. The Landsat Thematic Mapper (TM) and SPOT Multispectral (XS) data have been compared qualitatively and quantitatively using Digital Image Processing and statistical techniques to study their usefulness in soil salinity mapping. The locations of variables in two dimensional feature space were also assessed to achieve higher degree of accuracy in classification. The SPOT XS data have been found more helpful than Landsat TM in study of the salinity at semi-detailed level as it provided finer details of various thematic variables. The extent and intensity of the salinity were corroborated through a 6-day detailed ground survey of the area. The highly saline areas (mostly in crust form) were mapped using satellite RS Data. However, it was found difficult to have an accurate qualitative differentiation between moderately saline and other highly reflective eroded material due to their close correlation in reflectance behaviour. A global decrease in all salinity classes since 1960 has been observed due to various measures of reclamation. Only 1.68% new area is found affected by the salinity during last two decade.