Land use Changes in the Mansouriyeh Wetland and its Relation with the Occurrence of Drought and Dust Formation in the Ahwaz Metropolis

Wetlands are an integral part of the semi-arid and arid ecosystems, which are inundated during major floodings and are transformed into sources of particulate matter during drought. This phase of their life cycle is very disturbing as they affect breathing in downwind areas and result in many pulmonary diseases. Thus their management is very challenging. As the Mansuriyeh Wetland (MW) is transformed into a dust source when dry, and threatens the City of Ahvaz with dust storms in the lean years, and this is mainly caused by an eradication of the vegetative corer, it was decided to survey the area when the MW was brimmed with floodwater. This was achieved benefiting from the images collected by the Landsat TM, ETM+ and DLI during the June of 1988 through the same month in 2017, and the rainfall data provided by the National Meteorological Organization. Analysis of the information was carried out in three steps: preprocessing, preprocessing and post preprocessing using the support vector machine (SVM) along with the ENVIs software. Likewise the image were classificed into the inundated areas the land covered with vegetation, water and the bare land. Truthfulness of the image was validated through Google Earth employing the total accuracy and the kappa procedures. The percentage of the area covered by each class was determined through the GIS zooning. The area contributing water to the MW was determined as its watershed, the rain-gauging network was plotted on the maps, and the mean annual precipitation of the entire watershed was calculated and drought occurrence and its intensity were determined using the standard precipitation index (SPI): the R2 for this item was 0.6. Therefore, variation of the MW as a dependent variable is related to the drought as an independent variable. Thus drought is 60% responsible for dust formation. Other variables, namely numerous small earth banks, oil well drilling installation and agricultural activities may also contribute to dust formation. Variations in the extent of the bare area and its relationship with the dust formation indicated that 80% of the MW had dried during the previous10 years. Moreover, up to 100% of the area had been entirely without a vegetative cover in some of those years. Salinity of a fine- grained soil, also made it a potential source of dust storms that invaded the Ahvaz Metropolis.