Estimation of topsoil moisture and hydraulic conductivity using infrared thermography in the Brazilian semiarid

Abstract

ABSTRACT This study introduces an exploratory technique for soil moisture and unsaturated hydraulic conductivity estimation, using infrared thermography. The technique consists in applying a certain volume of water to the soil surface and registering the temperature with an infrared camera. The applied water should have a lower or higher temperature than the soil surface in order to create a temperature gradient at the soil surface. Experiments were conducted in the Mimoso catchment, which is located in the semiarid region of the Brazilian state of Pernambuco, in two soils: Yellow Argisol and Fluvic Neossol. Experiments were conducted at two distinct periods of the day: in the morning with cooler soil surface and in the afternoon with hooter soil surface. Different volumes of water were applied to the soil surface originating different soil moisture. Water was applied at two distinct temperatures of 10 – 15 and 80 – 85°C, according to the initial soil surface temperature. The technique allowed us to map estimated soil moisture with values obtained with infrared thermography. When compared with soil sampling, a correlation coefficient higher than 0.70 was observed. Based on the data obtained, it was possible to estimate the topsoil unsaturated soil hydraulic conductivity, relevant to the analysis of hydrological processes, such as infiltration.