Sustainable groundwater control system for environmental and geotechnical problems in Sabkha soils in arid regions: case study from Abu Dhabi Metropolitan area

The soil in the coastal areas of the Abu Dhabi emirate is of the Sabkha type and is mainly composed of thin intercalated layers of sand, clay, and evaporites. The water table in these areas is shallow. Subsurface water that accumulates above the "hardpan" near the surface in topographic depressions is often mistakenly identified as a water table rise. The rapid urban expansion during the last twenty years, along with the development of extensive green areas in and around Abu Dhabi City, has exacerbated the waterlogging problem in urban areas. This issue is prevalent in areas with poorly permeable soil under climate change in terms of the change in precipitation magnitude and pattern. The resulting water ponds can range in size from a few square meters to over one square kilometer. Additionally, elevated groundwater levels in these areas can lead to flooding basements, garages, infrastructure, subsurface utilities, and transport routes, and might mobilize pollutants on the ground surface. The novelty of this study lies in identifying the primary source of water, which is primarily the leaching of return flow from irrigation above the shallow hardpan, a situation worsened by the rising water table in Sabkha soil. Previous solutions, such as soil replacement, soil treatment, and pumping water to transport it to the sea, have proven costly, unsustainable, and technically or economically infeasible in certain regions. In contrast, a novel, optimal, effective, and sustainable groundwater control system was simulated using a newly developed, calibrated 3-D groundwater flow model that covers nearly two-thirds of the UAE, encompassing both the surficial and deep carbonate aquifers. This system operates by pumping water from the ponds and injecting it into the deep hypersaline aquifer. The simulation indicated a water table decline of 1.5 m after one year across a large zone of the study area.