Speaker: Prof. Vito Telesca, Department of Environmental Engineering and Physics, University of Basilicata

The intensive use of water resources and the increasing climatic variability are sharpening the conflicts for water use also in traditionally water-‐rich areas and accelerate desertification in Mediterranean area, with strong impacts on agriculture and civil and industrial water uses.

In this context, the investigation of evapotranspiration (ET) processes, the more relevant loss in the hydrological cycle, is the main task for the assessment of water availability. Eddy covariance technique is widely used, because it is considered the most reliable approach for in situ measurements of ET, and for its characteristic of estimating latent and sensible heat fluxes of a representative area, and not just at local scale. However, the existing eddy correlation tower networks (FLUXNET, EuroCarbon, AmeriFlux) have been implemented mainly for global carbon cycle assessment purposes and on natural vegetation. In case of hydrological applications to sparse vegetation and crops, these techniques need the definition of specific measurements and data processing protocols in order to achieve reliable ET measurements.

In this framework the debate is open within the scientific community about the level of reliability of ET measurements, the assessment of the representative area and the technical difficulties in the management of eddy covariance stations. Next to the widespread use of eddy covariance systems, techniques for ET assessment from remotely sensed measurements were developed. Specifically, the possibility to retrieve land surface temperature from remote sensors in the thermal infrared band led to the use of methods based on the surface energy balance. Nevertheless, the practical applications of ET monitoring and mapping by means of remote sensing data require the acquisition of high temporal and spatial resolution data, often strongly reduced by the presence of clouds. The combined use of hydrological models and remotely sensed data seems to overcome these problems, leading to reliable continuous evapotranspiration assessment.

The extensive use of energy fluxes measurements by eddy covariance stations is proposed, in combination with remotely sensed data in the reflective and emissive range of the electromagnetic spectrum, in order to develop and validate surface mass and energy balance algorithms. These algorithms are integrated in distributed hydrological models, for the assessment of the impacts of ET processes on available water resources in river basins and irrigated districts.