long term evaluation of temporal and spatial changes in soil salinity (garmsar irrigation and drainage network)

salinity is a phenomenon that does not satisfy the crop water requirement and leads reduction vegetation. to control of this phenomenon requires appropriate management and monitoring of spatial and temporal salinity variations from the past to the present in this study the spatial and temporal changes of soil salinity of irrigation and drainage network located in garmsar, iran, is investigated from 1986 to 2013. for this purpose, using satellite images and ground data, temporal changes of field area ratio are studied in three salinity levels of low, medium and high at the end of fall and spring planting period during these years by and five satellite indexes. finally trend of changes is determined using mann-kendal test. also determined the trend of changes the value of each salinity index’s pixel by mann-kendall test and zoning changes the salinity was extracted results show that with a probability of 95%, at the end of fall planting period the trends of area ratio of fields with low, medium and high soil salinity are decreasing, increasing and increasing, respectively. at the end of spring planting period, trends are similar to fall planting period for fields with low and high levels and medium level shows no significant trend. also zone classification of soil salinity show that north, south and west regions of garmsar plain are at the risk of increasing salinity during the time and the north-east and central regions that have secondary irrigation network presents a decreasing trend in soil salinity. during considered years, of the total 16 thousand ha areas, fields with low soil salinity decrease around 6.5 thousand ha and the areas of fields with medium and high salinity increase around 4.5 thousand ha and 2 thousand ha, respectively, in this region.