Morphometric changes in the water surface of Lake Al-Malfa, a salt lake in the Jaghbub Depression, eastern Libya

Abstract

Al-Malfa Lake, located in the Jaghbub Depression in eastern Libya, has experienced a significant decline in its water level in recent years due to climatic influences, high evaporation rates, and prolonged drought conditions, leading to a noticeable reduction in its surface area and the degradation of its ecological system.
This study aims to analyze the natural, morphometric, and physicochemical characteristics of Al-Malfa Lake and to assess the impact of climatic and hydrological factors on its surface area and water level changes during the period 2009–2022, in order to determine the causes of the lake’s decline and propose sustainable management approaches. The research adopted a descriptive and analytical methodology, utilizing remote sensing and GIS techniques (ArcGIS 10.3) to analyze Sentinel-2 satellite imagery, along with the Normalized Difference Water Index (NDWI) derived from the EOS LandViewer platform to monitor seasonal variations in the lake’s extent during winter and autumn. Field measurements were also conducted to analyze water samples and estimate the discharge of the northern spring feeding the lake.The results revealed that Al-Malfa Lake has an elliptical shape with irregular shorelines, covering an average area of 0.85 km² and an average depth of about 2 meters. The discharge of the northern spring was estimated at 70 liters per second. The lake’s surface area decreased by about 6% during the study period, with the largest extent (0.88 km²) recorded in February 2009, and the smallest (0.74 km²) in September 2019, accompanied by a water level drop of 45 cm in October 2019. The findings indicate that high temperatures and intense evaporation during summer and early autumn are the main factors causing the lake’s shrinkage, whereas its expansion occurs during the cooler winter months.The study highlights the importance of continuous monitoring of Al-Malfa Lake using remote sensing technologies and emphasizes the need for sustainable water resource management in the Jaghbub Depression to preserve its unique environmental system