Study of soil salinity and sodisity variation trend in Marvast of Yazd.

Such as drought, salinity is one of the most serious and oldest problems in the environment. Many civilizations had annihilated due to soil salinization. Top soil salinity always changes and we need to determine this change. Satellite images have information over different times and they have good potentials for monitoring land surface. For study the change of land, specially for soil salinity TM Lansat from 1984 and ETM+ Lansat from 2002 were two satellite images that we used. The study area with 88982 ha. of area locates at Marvast in the Yazd province. At first images were georeferenced and for making False Color Composite (FCC), Optimum Index Factors (OIF) were calculated. 107 ground points were sampled by classified randomization method and analyzed in laboratory. Geology, underground water and other information in the study area were collected. The relationship between variables were measured and correlation coefficient matrix were calculated. Then variables were analyzed by linear and multiple regression. Using these equation and also salinity indices and supervisor classification surface soil salinity map, were produced. By checking results with ground data we found that, for making a specific time salinity map the supervised classification is suitable but when there aren&rsquot any ground information regression equation with DN bands 1,2,3 and 4 is better. The average of soil salinity map that themselves have made by DN bands, had made final map. For 1984 and 2002 raster and classified salinity map were produced, by using SPSS, Surfer and ILWIS softwares. Two different time maps were compared and alterations salinity map and alterations classes salinity map were produced. On the average the surface salinity in study area have increased about 0.98 dS/m among 18 years. At this period 66.59% of the study area were had no changes, 17.65% has decreased and 15.76% of the study area has increased its salinity. The no change area were mainly ranges, the increase area were marginal of playa and agriculture and the decrease area mainly belonged to increased agriculture area. By using satellite information, RS and GIS we can produce accurate maps of soil salinity and these maps can help the managers. The planning managers must consider more to salt budget even for playa.