COMPARATIVE ASSESSMENT OF CONVENTIONAL VERSUS REMOTE SENSING BASED APPROACH FOR LAKE EVAPORATION ESTIMATION: THE CASE OF LAKE HAWASSA, ETHIOPIA

Abstract

Evaporation is the major component of the water and energy budget of the water bodies. The Evaporation process needs special attention for a better allocation and management of water resources. The main objective of this study was to compare evaporation estimates based on conventional and Remote Sensing approach. Different methods have been developed and implemented to estimate total evaporation, including meteorological ground-based point data, field measurements and spatially explicit remotely sensed data. Surface Energy Balance System (SEBS) was employed to estimate the Lake Hawassa evaporation and other energy balance components. The SEBS results were compared with meteorological methods results (Debruine Keigeman, BREB method, and Penman), using Pan Evaporation as a reference. Nash-Sutcliffe, efficiency coefficient (E), Wilmott‟s index (dr) for evaporation estimates, and Root Mean Square Deviation (RMSD) were used as a statistical performance measures for energy balance component estimates. The SEBS results indicate that the Lake Hawassa average evaporation estimate is 1.16 mm/day in September and 5.2 mm/day in February. Using Pan Evaporation measurements as a tool; evaporation estimates of SEBS perform better than any other metrological method, with Nash-Sutcliffe, efficiency coefficient (E) = 0.48 and Wilmott‟s index (dr) = 0.48 as well. Penman and BREB methods perform poor in evaporation estimation from Lake Hawassa. SEBS heat fluxes RMSD from the meteorological based estimation were 15.01W/m2 for Net Radiation (Rn), 13.7 W/m2 for Stored Heat Flux (G0), and 11.54 W/m2 for Sensible Heat Flux (H). Generally it was concluded that the SEBS remote sensing algorithm is applicable for evaporation and other energy balance components estimation on Lake Hawassa.