The Vegetative Cover Deterioration Due to the Droughts on the Mulla Sadra Watershed and Application of Remote Sensing Techniques in Its Monitoring

Drought is a complex natural phenomenon caused by the breakdown of the water balance and its affection on the environmental field is obvious. In this regard, the application of remote sensing technologies in monitoring drought becomes mandatory where a satisfactory number of climatological stations is lacking. The present study employed NDVI, RVI, VCI, DSI, VSWI, SAVI, TCI and EVI vegetation indices derived from the TM sensor of the LANDSAT satellite in 13.06.2010 and 05.16.2000 for drought monitoring. Furthermore, the amount of precipitation in a span of 14 years (1998-2012) comprising 15 grade points were extracted from the TRMM satellite-assisted collected data with a special resolution of 0.25×0.25. The wet and dry years were identified using the Standard Index of Annual Precipitation (AIAP). The results show a five-year of drought (2011-2006) period, four years with normal and five years with adequate precipitation. The application of the NDVI and SAVI indices reveal that an increase in the minimum and maximum values is expected in the wet years. In addition, as the ambient temperature greatly affects the vegetative covers conditions, the difference between the values in the wet and drought years were obtained through combining the DSI and VSWI temperature and vegetation indices.