|Timeline:||July 2016 - 17 July 2020|
Productivity (WP) can generally be defined as the unit of output derived from the unit of input or consumed water. In agricultural water productivity, it is considered the unit of (crop) yield (or biomass) derived from the unit of water evapotranspirated. Evapotranspiration is the focus, as it is considered the component of the water balance that is used by the crop and lost from the system. Recently, with the advance of remote sensing techniques to estimate evapotranspiration and biomass, the ability to estimate WP as large temporal and spatial scales has become within reach. If the reliability and confidence of these estimates can be considered acceptable, it provides water managers, agriculture ministries, farmers and policy makers on both local and global scales to valuable information in decision making for best practice.
Validation is the process of understanding the degree in which the model represents the real world. Despite significant improvements in remote sensing technology over the last decades, there is still significant uncertainty in estimates produced in continental scale attempts to model and determine evapotranspiration and biomass. This is due to the difficulty in fully representing each land class in such a diverse set of environments. Further complexity is added in assessing performance on continents such as Africa and Middle East due to the scarcity of ground data, resulting in under representation of calibration and validation datasets on these continents. Currently, no validation framework or standard currently exists to guide data producers of WP component datasets. The introduction of a framework can ensure datasets are comparable and meet requirements of intended use. Furthermore, there is lack of research in understanding how these datasets perform from a mass and energy balance perspective. The energy balance is applied to understand performance of ground based measurements of flux towers, however, it has not been extrapolated to understand global or continental performance.
The overall objective of this research is to develop a physical approach to validation of remotely sensed WP, focusing on evapotranspiration and biomass components, using fundamental mass and energy balance transfer approaches (and accounting). This can lead to better understanding of the accuracy and performance of the WP datasets. The research will focus on the validation of FRAME datasets, which are being developed as part of the FAO project ‘Remote Sensing of Water Productivity’. The datasets will include evapotranspiration and biomass production for Africa and the Middle East on a dekad scale for the years 2009-2019 at a 250m resolution and 100, and 30m resolution for selected basins.
Figure: Left – FRAME dataset project area. Right – Potato fields, Palestine.