Identification of drought extent using NVSWI and VHI in Iaşi county area, Romania

Drought is a stochastic natural phenomenon that appears from considerable lacking in precipitation. Among natural hazards, drought is known to provoke extensive damage and affects a important number of people. Techniques for observing agricultural drought from R.S. are indirect. These depend on using images based parameters to exemplifed soil moisture condition when the soil is often obscured by a vegetation cover. The procedure are mainly based on determing vegetation health or greenness using VI , often in combination with canopy temperature anomalies using thermal infrared wavebands. In this study were used remote sensing images from the Landsat 8 OLI, taken in may and june 2017. The study area was the county of Iasi. To evaluate drought in this study, for Iasi county, Normalized Vegetation Supply Water Index (NVSWI) and Vegetation Health Index (VHI), were used. VSWI is derived from The Vegetation Supply Water Index (VSWI). This index was developed to combine the NDVI and the land surface temperature (LST) to detect the moisture condition. VHI was developed through a combination of Vegetation Condition Index (VCI), one of the important vegetation indicators when monitoring weather-related variations, such as droughts, and Temperature Condition Index (TCI), which reflects the stress of temperature, that both indicies can be successfully used to determine the spatiotemporal extent of agricultural drought. After applying NVSWI to determine the degree of drought we noticed that for the satellite image of May prevailed “slight drought” and for june “normal”. Second index, VHI indicate that in both months, may and june, is “no drought”. It can be concluded that VHI is a very good indicator for studing extreme drought and NVSWI offer information about areas “normal” and “wet”