Evaluation and validation of salinity monitoring indices in the Qazvin plain

Soil salinity is the predominant soil degradation process in arid and semi-arid regions. There are several methods for monitoring salinity, which are mainly measured as points, which will be difficult to generalize to the whole region. In recent years, remote sensing-based methods for measuring salinity have been widely considered. Soil salinity has led to the limitation of agricultural land use patterns. This is a serious environmental hazard that affects the growth of many crops.

After selecting the study area on satellite images and ground visits, a cluster-cinematic sampling network was designed and implemented for surface soil sampling. In this study, pH, EC, SAR and TDS were measured. In this study, in order to use the remote sensing technique to study the temporal and spatial changes of vegetation density in the region, ground data and ETM+ images of Landsat 7 satellite and MODIS images have been used. Pre-processing operations including geometric, radiometric and co-ordination corrections were performed on each of the satellite images. In the next step, the desired vegetation indices, after calculation, are applied to the satellite images and thus the vegetation density pattern map is obtained based on each of these indices. Then 8 different salinity and vegetation indices were studied during the years 2005 to 2021.

The The results of this study showed that LANDSAT-7-ETM + sensor has been able to produce better results due to better spatial resolution than MODIS sensor. Also, among the salinity indices studied, SI3 index in both ETM + and MODIS sensors with RMSE (1.01 and 1.1) and correlation coefficient R (0.98 and 0.86) was able to have the best performance in Have an area. In the study between EC and SAR, both sensors had a high correlation between red and infrared bands.

In a general summary, by examining the information of the synoptic station of the plain, parameters such as temperature and amount of precipitation in the studied period show that by increasing the average temperature and decreasing the amount of precipitation in the region, the surface temperature increases during the year. Recent causes of drought and significant effects of climate change on the prevailing environmental conditions, which in turn will increase the breadth of salinity in the verse.