Integrated water balance and water quality management under future climate change and population growth: a case study of Upper Litani Basin, Lebanon

The impacts of the growing population in Lebanon including Lebanese, Palestinian, and Syrian refugees, together with the changing climate, are putting the Bekaa Valley's water resources in a precarious situation. The water resources are under significant stress limiting the water availability and deteriorating the water quality in the Upper Litani River Basin (ULRB) within the Bekaa Valley. Here, the impacts on water balance and water quality for a 2013 baseline and future scenarios are simulated using the Water Evaluation And Planning model, served by the Watershed Modeling System which provides flows throughout the ungauged zones of the Litani River and its tributaries. The output from a General Circulation Model is used to project the future climate up to 2100 under several emissions' scenarios which shows a critical situation in the high emission scenario where the precipitation will be reduced by about 87 mm from 2013 to 2095. The research highlights the need to reduce the water pollution that limits the availability of usable water, and to minimize the gap between the demand and supply of water within the ULRB to maintain water supply and quality, even after 80 years. This may be achieved by removing encroachments on the river, adding wastewater treatment plants, reducing the amount of lost water in damaged water network, and avoiding the overconsumption of groundwater.