<p>Burullus Lake is the second largest coastal natural lake in Egypt. It is in Kafr El Sheikh Governorate and situated in the northernmost part of Nile Delta Egypt and serves as a bridge between the two Nile river branches (Rashid and Damietta), both of which are connected to the Mediterranean Sea. Lake Burullus (LB) has undergone significant water quality degradation due to agricultural drainage, untreated wastewater, and industrial effluents. This study employs remote sensing (RS) and GIS techniques to assess water pollution and to monitor changes in the lake’s surface area and water depth over a 43-year period (1980–2023). Multi-temporal Landsat imagery (Landsat 4, 5, and 8; 30 m resolution) and an official cadastral map were utilized for spatial analysis. Three approaches, unsupervised ISODATA classification, the Normalized Difference Water Index (NDWI), and the Modified Normalized Difference Water Index (MNDWI)—were applied to delineate water bodies and detect spatiotemporal changes. The ISODATA unsupervised classification algorithm was applied to separate water bodies from surrounding land features across all image dates. Variations among NDWI, MNDWI, and unsupervised classification results arise from their differing spectral sensitivities and extraction mechanisms, where NDWI relies on green–NIR contrast, MNDWI enhances water detection using green–MIR reflectance, and classification groups pixels based on spectral similarity rather than fixed thresholds. A physics-based model was employed by this study used to estimate lake water depth, supported by available in-situ depth observations. Additionally, 21 water samples from the lake and surrounding drains were analyzed in accredited laboratories (March and October 2023) to determine heavy metal concentrations and nutrient levels (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\text{NO}}_{{3}}^{ - }\)</EquationSource> </InlineEquation>, <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({\text{NH}}_{4}^{ + }\)</EquationSource> </InlineEquation>). Inverse Distance Weighting (IDW) interpolation was applied to generate continuous pollution surfaces and compare them with satellite-derived indicators. IDW was selected because the sampling points were moderately and evenly distributed, and the method provides stable estimates in shallow lake environments without requiring complex variogram modeling, unlike kriging. Results show that the lake area decreased by approximately 18.15% between 1980 and 2010 and by a further 3.7% from 2010 to 2023. The southern and eastern lake zones exhibited the highest pollution levels due to their proximity to major drainage outlets. By 2023, the average lake depth increased in some regions due to dredging activities along the Burullus inlet. The study demonstrates an 83.5% agreement between satellite-derived pollution indicators and laboratory results, confirming the reliability of integrating RS with field-based measurements. Targeted restoration and strict control of drainage inflows are recommended to protect and rehabilitate this ecologically important lake.</p>

Spatiotemporal assessment of water quality and morphological changes in Lake Burullus, Egypt using remote sensing and GIS techniques

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发表日期：

2026年4月21日

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Ashraf A. A. Beshr,
Emad A. Abd AL-Galil,
Magda H. Farahan

摘要

Burullus Lake is the second largest coastal natural lake in Egypt. It is in Kafr El Sheikh Governorate and situated in the northernmost part of Nile Delta Egypt and serves as a bridge between the two Nile river branches (Rashid and Damietta), both of which are connected to the Mediterranean Sea. Lake Burullus (LB) has undergone significant water quality degradation due to agricultural drainage, untreated wastewater, and industrial effluents. This study employs remote sensing (RS) and GIS techniques to assess water pollution and to monitor changes in the lake’s surface area and water depth over a 43-year period (1980–2023). Multi-temporal Landsat imagery (Landsat 4, 5, and 8; 30 m resolution) and an official cadastral map were utilized for spatial analysis. Three approaches, unsupervised ISODATA classification, the Normalized Difference Water Index (NDWI), and the Modified Normalized Difference Water Index (MNDWI)—were applied to delineate water bodies and detect spatiotemporal changes. The ISODATA unsupervised classification algorithm was applied to separate water bodies from surrounding land features across all image dates. Variations among NDWI, MNDWI, and unsupervised classification results arise from their differing spectral sensitivities and extraction mechanisms, where NDWI relies on green–NIR contrast, MNDWI enhances water detection using green–MIR reflectance, and classification groups pixels based on spectral similarity rather than fixed thresholds. A physics-based model was employed by this study used to estimate lake water depth, supported by available in-situ depth observations. Additionally, 21 water samples from the lake and surrounding drains were analyzed in accredited laboratories (March and October 2023) to determine heavy metal concentrations and nutrient levels ( \({\text{NO}}_{{3}}^{ - }\) , \({\text{NH}}_{4}^{ + }\) ). Inverse Distance Weighting (IDW) interpolation was applied to generate continuous pollution surfaces and compare them with satellite-derived indicators. IDW was selected because the sampling points were moderately and evenly distributed, and the method provides stable estimates in shallow lake environments without requiring complex variogram modeling, unlike kriging. Results show that the lake area decreased by approximately 18.15% between 1980 and 2010 and by a further 3.7% from 2010 to 2023. The southern and eastern lake zones exhibited the highest pollution levels due to their proximity to major drainage outlets. By 2023, the average lake depth increased in some regions due to dredging activities along the Burullus inlet. The study demonstrates an 83.5% agreement between satellite-derived pollution indicators and laboratory results, confirming the reliability of integrating RS with field-based measurements. Targeted restoration and strict control of drainage inflows are recommended to protect and rehabilitate this ecologically important lake.