Water resources in Lebanon: an overview

This work assesses the current situation of water resources in Lebanon in term of quantity and quality. Hence, 160 water resources studies were gathered from the literature and divided to three categories: water balance (44%), quality (42%) and management (14%). Each category was further divided into sub-topics. The analysis consists of qualitative analysis that discuss the studies topics and their temporal and geographical extent. And a quantitative analysis that compare results of different articles in each topic. Results show that the majority of studies are recent with 60% of the studies published after 2010. Moreover, disparities exist in the studies spatial distribution with only 25% covering the whole country while another 25% concentrated in the inland agricultural Beqaa plain. Moreover, the emphasis is greater on groundwater than surface water for quantity and quality. In term of precipitation, all studies agree on the high spatial variability but still there are difficulties estimating rainfall especially in mountainous and remote areas. Similarly, snow contribution is still poorly estimated and only available for small areas in Mount Lebanon were ground measurement stations exist. In addition, climatic trends show a tendency towards drier conditions, a shrinking snow cover, and an increase of extreme rainfall events frequency. Moreover, although surface hydrology studies are rare, the available ones show some regional pattern which is promising for prediction in ungauged locations. However, global change impact is poorly represented and the studies that exist point towards a decrease in river and spring discharges. On the other hand, groundwater studies show the prevalence of karstic aquifers with some characterized by a high storage capacity making them a pivotal source of water but also a vulnerable one due to their high infiltration rate. For water quality, the dominant hydro-chemical facies is Ca-Mg-HCO₃ due to the prevalence of carbonate rocks. Moreover, the studies show a degradation in surface and groundwater quality. Salt water intrusion, nitrate and pesticides pollution are main challenges in coastal aquifer and agricultural areas respectively. Finally, the steady increase in water resources studies in Lebanon is, unfortunately, accompanied by a decrease in water quantity and a quality degradation.