Assessment of morphometric changes in Lake Hawassa by using surface and bathymetric maps

Abstract

Study region: Lake Hawassa, Ethiopian Rift Valley, Southern Region, Ethiopia. Study focus: Lake Hawassa is one of the major Ethiopian Rift Valley Lakes with an endorheic basin system located near Hawassa town. The Lake water is vital to the surrounding communities for irrigation, domestic water supply, recreation, and fish harvesting. The morphological changes due to flood water from the surrounding agricultural areas were noticed and the water quality deteriorates which will be reflecting the agricultural productivity in the region and negatively impacted the socio-economic development. The lake morphometric changes were investigated by using cartographic ArcGIS mapping and bathymetric mapping and during the analysis, the thermal Infrared data of Landsat ™ was used in the digital elevation model (30 × 30 m) and Google Earth Engine (GEE) platform. The morphometric changes for a period of 46 years were considered in this study. The Secchi discs and echo-sounder were used to during the preparation of bathymetric maps and kriging interpolation was used for the water depth assessment of the lake. New hydrological insights for the Lake: The surface area of the Lake increased by 11.28 % from 1973 to 2019. The depth and volume decreased by 33.04 % and 25.32 %, respectively over the same period. The observed Secchi disc depth was 2.06 m. It was found that the increased surface area due to sedimentation and eutrophication in the Lake.

Keywords

• Bathymetric maps
• Eutrophication
• Lake depth
• Lake surface area
• Secchi depth
• Sedimentation