Evaluation of Soil Salinity, Actual Evapotranspiration and Soil Moisture Using Remote Sensing (Case Study: Herat Dry Region)

Many factors are involved in agricultural development such as climatic conditions, soil moisture, evapotranspiration and etc. For their effectiveness, it is necessary to examine the key parameters. Timely and accurate monitoring of these committees with the help of satellite imagery is a necessity in this regard. Herat plain is one of the plains where soil salinity and lack of moisture has led to a critical situation of gardens and agricultural lands.

In this research, we have tried to study soil salinity, soil moisture and actual evapotranspiration using the MODIS sensor data for the four months of February, May, August and November 2017.

The first stage of vegetation survey shows 0.4 in May (growing season). While the maximum land surface temperature was recorded in August (54 ° C) and May (45.15 ° C). Then, in the next step, using the results of two indicators of vegetation and land surface temperature, the humidity of the area is investigated by TVDI. The humidity of the region was divided into five classes from zero to 0.5, which indicates the low soil moisture and dryness in the Herat plain. Finally, due to the dryness of the area and to verify the TVDI method, field soil samples were taken from different parts of Herat and especially its agricultural lands to estimate the soil salinity (EC, PH and soil moisture). The results showed that the soil moisture content of the samples at a depth of 5 cm above the ground varies between 0 and 0.3. Also, out of 12 soil samples, 6 samples have saline soils and one sample has saline-acid soils. Of course, it is also important to note that some of the agricultural lands whose soils are in the saline group are dry and left to their own devices.
Finally, the study of actual evapotranspiration with the SEBAL algorithm showed that in this region, despite the lack of moisture, actual evapotranspiration is very high, especially in the hot month of August.