Investigation of meteorological, hydrological and agricultural drought using drought indices (Case study: Gharehsou watershed)

Drought as a natural hazard has always affected some parts of the country. Nowadays, it is possible to study drought using remote sensing techniques through its effects on the plants and achieve more accurate and efficient results for drought modelling. This study aims to investigate the relationship between meteorological, hydrological and agricultural drought using drought indices and remote sensing method in Gharehsou watershed. For this purpose, MODIS images (satellite Terra, product MODO9Q1) and rainfall and discharge data of five meteorological and hydrometric stations for 2000 to 2015 time period were used. The results of the comparison of meteorological, hydrological and agricultural drought represent conformity of the three types of drought in the years 2000, 2001, 2004, 2005, 2007, 2009, 2010, 2011, 2012, 2013, 2014 and 2015. Although the SPI and NDVI values were positive in the years 2002, 2003 and 2008, SDI index showed the occurrence of hydrological drought (negative values). In the year 2006 despite the rainfall increase, but this year has been facing the agricultural and hydrological drought. So the results simultaneity of drought there does not exist in all the years. The results of Pearson correlation showed there is a high correlation between mean NDVI and SPI and SDI indices equal to 0.706 and 0.788 respectively at the significance level of 0.01. Generally, the results of SDI and SPI indices largely confirm the results of the NDVI index.