In the Mediterranean area water availability is a main economic and social target for most countries since most of them share several features including, for instance, similar water and land resources, agricultural development, demographic pressure coupled with tourism increase, and, last but not least, a climate change evolving toward semiarid to arid conditions. These precious resources, widely exploited, are not distributed at a regional level and within each country, in a homogeneous fashion. The increase in groundwater exploitation poses a severe risk to the availability of the water resources and the resulting resource scarcity is a major concern in most countries of the Mediterranean region. Groundwater paucity often occurs in combination with poor groundwater quality, not only in areas heavily conditioned by human activities or in the often highly saline coastal aquifers, but also in zones not affected by human pressure where geogenic water-rock interaction processes, as those promoting, for instance, Cr(VI) water contamination, may cause pollution with critical effects on the public health.

In more detail, overuse of fertilizers and pesticides in agriculture, overexploitation of groundwater causing salt water intrusion, increases in the discharge of untreated or poorly treated domestic and industrial water, injection of brine and hydrocarbon byproducts from oil production and refinery operation into aquifers, and naturally occurring contaminants are among the principal causes of groundwater pollution. Thus, in the last two decades many Mediterranean countries planned policies devoted to the assessment of the groundwater quality and trends. This special issue aims to deliver contributions facing a range of aspects related to groundwater quality in the Mediterranean countries such as contaminants input and origin, salinization effects, and protection and remediation approaches.

Potential topics include but are not limited to the following:

• Elemental and isotope hydrogeochemistry
• Groundwater modeling
• Groundwater geophysics
• Groundwater contamination and toxicology
• Groundwater protection and remediation
• Groundwater resources management