Abstract
The estimation of site water budget is important in Mediterranean areas, where it represents a crucial factor affecting the quantity and quality of traditional crop production. This is particularly the case for spatially fragmented, multi-layer agricultural ecosystems such as olive groves, which are traditional cultivations of the Mediterranean basin. The current paper aims at demonstrating the effectiveness of spatialized meteorological data and remote sensing techniques to estimate the actual evapotranspiration (ETA) and the soil water content (SWC) of an olive orchard in Central Italy. The relatively small size of this orchard (about 0.1 ha) and its two-layer structure (i.e., olive trees and grasses) require the integration of remotely sensed data with different spatial and temporal resolutions (Terra-MODIS, Landsat 8-OLI and Ikonos). These data are used to drive a recently proposed water balance method (NDVI-Cws) and predict ETA and then site SWC, which are assessed through comparison with sap flow and soil wetness measurements taken in 2013. The results obtained indicate the importance of integrating satellite imageries having different spatio-temporal properties in order to properly characterize the examined olive orchard. More generally, the experimental evidences support the possibility of using widely available remotely sensed and ancillary datasets for the operational estimation of ETA and SWC in olive tree cultivation systems.
Highlights
Actual evapotranspiration (ETA ) is a key parameter of the Earth’s hydrological cycle linked to mass and energy exchanges, knowledge of which is fundamental for environmental, economic and social analysis at different spatial and temporal scales [1,2]
Rainfall almost stops from the end of May till the end of September, while the highest ET0 is reached in summer
NDVI is used as an estimate of transpiring green biomass, and is complemented by a meteorological factor, which accounts for short-term water stress
Summary
Actual evapotranspiration (ETA ) is a key parameter of the Earth’s hydrological cycle linked to mass and energy exchanges, knowledge of which is fundamental for environmental, economic and social analysis at different spatial and temporal scales [1,2]. In the last few years, innovative approaches have been developed to improve ETA detection and quantification, using space, air or ground-based instrumentation [9,10] Some of these approaches can potentially improve traditional measurement systems, in particular reducing costs for data acquisition, management and delivery [11], one of the main problems remains the degree of precision of the provided estimation [12,13]. Earth Observation (EO) techniques represent an efficient tool to obtain relatively frequent, low-cost updating of information at different temporal and spatial scales. These techniques provide increasingly satisfactory spatial and temporal coverage, offering good solutions for meeting cross-sectoral needs [14,15]. A comprehensive review of the available EO techniques developed to estimate ETA in different contexts can be found in [16]
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