Water crises have been ranked as the top global risk to economies, environments, and people in the 21st century. Nonetheless, the lack of continuous groundwater data availability and inadequate monitoring networks has been a challenge to the development of accurate and representative assessments of groundwater scarcity and risk conditions, especially in developing countries. This characterization is all the more discernible in arid environments and developing localities, such as the Arab Middle East and North Africa (MENA) region. Recent technological advancements, however, have provided the scientific community with hydrologic remote sensing datasets and GIS models, whose integration allows for systematic and detailed assessments of groundwater resources that have been traditionally lacking. Consequently, the following dissertation focuses on the combined use of remote sensing technology and GIS-models to achieve two main objectives: First, the spatio-temporal assessment of groundwater reserves and storage changes between 2003 and 2014, using a distributed ArcGIS model, parameterized with current gridded datasets. Second, the development, construction, and evaluation of a Groundwater Risk Index GRI, as a regional screening tool, to identify cold spots/hot spots of groundwater depletion risk, as a function of hydrological systems and political and socio-economic considerations. The results indicate vast groundwater reserves in the MENA region, averaging 1.28 million km3. Groundwater storage changes between 2003 and 2014, highlighted groundwater declines in areas beneath or in close proximity to urban and demographic concentrations and potential effects of climate change and human impacts. Moreover, results also highlighted the potentiality of recharge occurring in deep sedimentary aquifers within desert areas, albeit at constrained rates. Relative to the large groundwater reserves, groundwater storage changes between 2003 and 2014 are negligibly minimal and do not represent an immediate threat to the region. Similarly, groundwater risk conditions are unevenly distributed, with good governance and high income countries displaying low groundwater risk, and vice versa. GRI results show a strong dependency between groundwater risk, and governance and food security, whereas groundwater reserves were indeterminate of groundwater risk. Sensitivity analysis of the GRI, affirm the indexs insensitivity to alternative methodological choices in relation to subindicator selection, and choice of normalization and aggregation methods.
