Temporal Trajectory Analysis of Lake Surface Area: Case study on Lake Tana, Ethiopia

Abstract

Lakes are facing challenges due to climatic and anthropogenic activities with slow changes causing
unnoticed damages over a long time. The long term historic data provides concrete evidence of change.
The earth observation satellites which include both geostationary and polar orbiting satellite provide
different types of environmental data. The main aim of this paper is to evaluate the temporal trajectory
change of the lake surface area of LakeTana from 1985 – 2015 using geospatial technologies. The
study uses seven Landsat TM and ETM+ images to detect the lake surface area change. The change
was examined using modified normalized difference of Water index (MNDWI) method. This was attained
by making use of ERDAS Imagine 2014 and ArcGIS10.1 software. The results of this study
indicate that within the past three decades, the lake area has shown a significant decrease–about
362.74 sq.km. The area calculated from bathymetric surveys and the ccorresponding results from other
alternative methods were gathered and computed with the findings of this study. The results portray
that there is strong relationship between the estimates of lake surface area results of MNDWI with NDVI
alongside the bathymetry results. Hence, lake surface area quantification and characterization using
remote sensing and GIS techniques enables resource managers to project realistic change scenarios
helpful for lake surface area management.