In semi-arid and arid regions, groundwater tables are generally many meters to hundreds of meters deep and rainfall is infrequent. Increased population density, droughts, and armed conflict have caused hardship to many inhabitants of such areas, who rely on groundwater as the only source of drinking water for humans and cattle when the rivers and wadis are dry. The United Nations (UN) foresee an increased potential for conflicts arising from scarce water resources. The UN anticipates that 40% of countries could experience severe freshwater scarcity by 2020, mostly in low-income countries or regions in sub-Saharan Africa and Asia.

The hydrology of (semi-)arid regions is challenging: the vadose zones are deep and dry. In them, liquid water, water vapor, and heat flows occur simultaneously and interact with one another. Microbial surface crusts affect the albedo of the soil surface as well as infiltration capacity. The hydrology of wadi's is very difficult to capture quantitatively. The climate is often brutal to field workers and equipment alike. Data acquisition is further hampered by inaccessibility of the terrain and political instability. As a consequence, water scarcity and data scarcity often go hand in hand.
Despite these challenges, there is an urgent need to better understand the hydrological cycle in these areas, as it directly affects not only the livelihood but even the chances of survival of the local populations. We invite abstract on all aspects of the hydrology of (semi-)arid regions, its societal implications for local communities, and experimental and modeling strategies dealing with the unique set of challenges posed by such regions.