Mapping soil moisture in the central Ebro river valley (northeast Spain) with Landsat and NOAA satellite imagery: a comparison with meteorological data

Abstract

This paper analyses and maps the spatial distribution of soil moisture using remote sensing: National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) and Landsat-Enhanced Thematic Mapper (ETM+) images. The study was carried out in the central Ebro river valley (northeast Spain), and examines the spatial relationships between the distribution of soil moisture and several meteorological and geographical variables following a long, intense dry period (winter 2000). Soil moisture estimates were obtained using thermal, visible and near-infrared data and by applying the ‘triangle method’, which describes relationships between surface temperature (T_s ) and fractional vegetation cover (F_r ). Low differences were found between the soil moisture estimates obtained using AVHRR and ETM+ sensors. Soil moisture estimated using remote sensing is close to estimations obtained from climate indices. This fact, and the high similarity between estimations of both sensors, suggests the reasonable reliability of soil moisture remote sensing estimations. Moreover, in estimations from both sensors the spatial distribution of soil moisture was largely accounted for by meteorological variables, mainly precipitation in the dry period. The results indicate the high reliability of remote sensing for determining areas affected by water deficits and for quantifying drought intensity.

Acknowledgments

This work has been supported by the projects: ‘Caracterización espacio-temporal de las sequías en el valle medio del Ebro e identificación de sus impactos' (BSO2002-02743), ‘Variabilidad climática y dinámica forestal en ecosistemas de ecotono’ (REN2003-07453) financed by the Spanish Comission of Science and Technology (CICYT) and FEDER, and ‘Programa de grupos de investigación consolidados' (grupo Clima, Cambio Global y Sistemas Naturales, BOA 147 of 18 December 2002), financed by the Aragón Government. We want to thank the National Institute of Meteorology (INM) for the readiness of the data used in this work. Thanks to Alfredo Romo and Juan de la Riva for the NOAA and Landsat images.