Assessment the effects of vegetation degradation on runoff changes and water pollution potential in the sub-watersheds of the Eastern Azerbaijan province

Vegetation is an important factor affecting runoff, quantity and quality of water in a watershed. This study investigates the effects of vegetation reduction in the eastern watershed of Lake Urmia on two parameters of runoff and the potential for water pollution .The WWPSS model was used to simultaneously assess the three parameters. Vegetation shows a fraction of the types of grass, tree and land without vegetation that were obtained from MODIS VCF satellite images. Runoff was calculated as accumulated water budget downstream. This model also provides an indicator to determine the potential level of water pollution. The results showed that rangeland cover decreased by an average of about 32%. Also, the average runoff production increased by 2.6, 3.16, 2.9 and 3.25 percent, respectively, in the existing conditions in 4 sub-basins of Aji Chai, Qaleh Chai, Marduq Chai and Sufi Chai compared to the situation before the reduction of vegetation coverage. According to the results, the difference in water pollution potential between the baseline and existing conditions in different parts of the watershed has fluctuated in the range between -9 to15% and an average of 0.6%. This change has increased the pollution load in some places and decreased it in others; but in general, it has led to incremental changes in water pollution potential with an average of about 2.5% in the total watershed. The method used can be used to quantify and map ecosystem water changes and its application in environmental assessment and management.