Understanding TVDI as an index that expresses soil moisture

Abstract

Given the need to search for robust indicators capable of representing the surface water condition in the various agricultural production regions in the state of Rio Grande do Sul, the objective of this study was to analyze the influence of different types of vegetation cover on the definition of Temperature Vegetation Dryness Index (TVDI) as an indicator of soil moisture in agricultural areas on a local scale. A Landsat 8 - OLI image of February 7, 2015 and its Normalized Difference Vegetation Index (NDVI) product were used. The image was classified by the maximum likelihood method, after the surface temperature (TS) was obtained by the split-window algorithm, later the normalization of the TVDI model with the triangular characteristic dispersion was performed. With the data of TVDI, the different types of vegetation cover mapped were identified in the dispersion of the index. Histograms of TVDI frequencies were also made for each of the targets and the dispersion between the index and the NDVI and TS. The results showed that it was possible to differentiate the different types of soil use and cover, through the characteristic water condition of each target. With the dispersions of the targets it was possible to locate them with a certain overlap; the strong relation between the index and TS was observed. TVDI has been shown to be efficient for monitoring the variation of the water condition and can be used for monitoring and sustainable management purposes.