SOIL SALINITY ASSESSMENT IN TOBA TEK SINGH USING TEMPORAL IMAGERY

Abstract

Soil Salinity is the major land degradation process in arid and semi-arid regions, and it has affected about one billion hectares of lands around the world, which represents about 7% of the earth’s continental area. Globally, soil salinity is spreading at a rate of two million hectare per year. Pakistan has a total area of 79.6 million hectares (mha), with 22.0 mha cultivated and 6.28 mha affected by salinity within the irrigated regions. There is a need to develop some methods and techniques that should be time and cost effective for the detection and monitoring of this problem. The use of remote sensing data and GIS can play an important role for the detection and mapping of saline areas in a very short time. The objective of this study was to develop a methodology for detection and mapping of saline areas with the help of remote sensing data in Tehsil Toba Tek Singh. Soil samples were collected to the depth of six inches from field and analysed in laboratory to check the salinity status. Results were interpolated and salinity map of 2011 was developed. Satellite image of Landsat 5 TM of this area was classified and a land cover map was developed containing different classes including saline areas. Saline areas mapped from remote sensing and field data were compared which showed 65% similarity between these two methods. The same methodology was applied on Landsat Images of 1992 and 2000 to check the change in the saline area over this time. Water table map of this area was also generated from water table data and correlation between salinity and water table depth was calculated. The temporal data analysis showed an increasing trend in saline area. It was observed from analysis of results that remote sensing data is mainly helpful for mapping highly saline areas (having salts on surface) and hard to detect where there are even slight vegetation cover.