Comparasion of Crop Water Stress Index (CWSI) and Water Deficit Index (WDI) by using Remote Sensing (RS)

Drought, water scarcity and climate changes are very important threats for agriculture on a global basis. Remote Sensing (RS) is accepted as a technique to collect data and determine water stress indices. Water Stress Indices (WSI) are useful tools to prevent drought and determine irrigation scheduling. The water stress indices are primarily identified as the Crop Water Stress Index (CWSI) and the Water Deficit Index (WDI). The effect of soil background is major problem to establish CWSI especially during early growth stage measurements of canopy temperature (Ts). Hence, WDI is a better index when it comprised with CWSI because of Ts. CWSI and WDI can be determined by two different techniques. These are determined by using measured by using traditional components to collect data and estimated methods by applying RS components to collect necessary data. Estimated method has many advantages when this method compared with measured method. However, estimated method needs some RS components which are infrared gun (IR), sling psychrometer, Spectro radiometer. With the help of these tools, the necessary data are obtained and WDI is determined. By using Spectro radiometer vegetation indices are defined. Among the many vegetation indices, the Normalized Difference Vegetation Index (NDVI) is mostly used one. By using NDVI determination of vegetation cover is easy and accurate technique to establish WDI. Establishing these both stress indices with less fieldwork and by saving money, time and labor conveys the necessary information for agriculturists using remotely sensed data especially for large agricultural fields.