More than four billion people globally live in areas of water stress, with Jordan representing one of the most severe cases worldwide. Situated in an arid region, Jordan is characterised by limited surface water resources, rapidly depleting groundwater aquifers, and escalating demand driven by population growth, economic development and persistent geopolitical pressures. Surface water is largely sourced from transboundary systems controlled by upstream countries, further constraining Jordan’s long-term water security.
In this context, robust water information systems are both essential and largely insufficient. As is common across the Middle East and North Africa (MENA) region, Jordan’s water data landscape is limited by sparse monitoring networks, and planning has historically relied on statistical estimates and long-term averages rather than spatially and temporally resolved assessments. This limits the country’s capacity to implement integrated supply-demand interventions and to plan effectively under growing uncertainty.....

Evapotranspiration (ET) is a major water flux in the terrestrial water balance and a key link between water and surface energy balances. In water sciences and management, the quantification of ET is required but challenging to gauge in situ, leading to the popularity of models based on satellite-derived data. However, uncertainties in satellite-based estimation arise from both methodological and technical factors. This study examines and assesses uncertainties in satellite-based estimation of ET. Part I provides a systematic quantitative literature review, showing the diversity of approaches and constraints arising from the availability and quality of reference data. A meta-analysis of in-situ validations against eddy covariance measurements quantifies the status of uncertainty in terms of reported performance metrics. Part II focuses on the assessment of a satellite-based ET data product for monitoring water productivity from field to global scales. Technical uncertainties through ex-ante and ex-post methods, including error propagation, in-situ validation, and triple collocation analysis are provided. The results highlight spatial variability in uncertainty, limitations of validation data, and challenges in dry and tropical regions providing guidance to users of such products. Finally, this thesis reflects on methodological uncertainties arising from problem framings, model choices, and configurations.