Fracture-controlled groundwater seeps into the Mediterranean Sea along the coast of Lebanon

Abstract

Groundwater has recently become a main resource for domestic water and irrigation in Lebanon. During the last two decades, surface water and shallow groundwater have been severely exhausted to meet water demand. This study seeks to understand the groundwater flow/storage regime and the mechanism of water loss into the sea using a geospatial approach. Landsat thermal satellite images from years 2013–2015 are used to detect freshwater seeps in the coastal waters of Lebanon to analyse their distribution, time of occurrence and origin. The analysis is supplemented with data from the Tropical Rainfall Measuring Mission (TRMM), geological maps, the SRTM Digital Elevation Model (DEM), and springs’ location maps. A groundwater potentiality map is constructed to understand points of surface water entry into the ground, areas of accumulation and water transport pathways. Results show dominant thermal plumes off-shore adjacent to Akkar District and Batroun city. The former relates to direct rainfall and the latter to rainfall and snowmelt on land. No surface drainage is associated with either plume. Both plumes project 8–13 km from inland along fault alignments. These faults act as conduits to channel rainwater and snowmelt from the surrounding mountains before seeping into the sea. It is thus feasible to capture the water lost this way for farming and domestic uses. The study presents an integrative geospatial approach that can be extended and applied throughout the coastal Middle East and North Africa Region to assess freshwater seeps into the sea.