Estimation of Soil Moisture by Remote Sensing and Field Methods: a Review

Understanding the spatial and temporal variations of soil moisture is crucial for the land surface processes and their management. Accurate estimation of spatial and temporal variations of soil moisture is important for various hydrological studies also. Recently, remote sensing techniques have been used to estimate soil moisture. Estimation of soil moisture by remote sensing techniques provides only surface layer information and is unable to observe the entire soil column. On the other hand field measurement provide valuable information regarding both surface and subsurface soil moisture, but are insufficient to characterize the spatial and temporal variability of soil moisture at larger scale. Therefore, remote sensing methods have an edge over field methods in terms of spatial and temporal scale. Soil moisture variations in time and space are controlled by many factors, such as soil texture, vegetation, topography and groundwater table depth. Groundwater table depth, play an important role in determine of soil moisture. It acts as a source of soil water having substantial effect on soil moisture in areas, where water table is within soil column. This paper presents a comprehensive review of the progress in remote sensing as well as field methods for soil moisture studies.