Lake Evaporation from Space: Current Developments that could improve Hydrological Models in Semi-arid Regions
Annor, Frank Ohene; van de Giesen, Nick; Eilander, Dirk; Bogaard, Thom; Menenti, Massimo
Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, NETHERLANDS

Generally, African basins have a very limited number of stream-gauges installed. The Volta basin is no exception to this. In order to overcome this problem, remote sensing data is a good way forward. To determine the different components of the water and energy balance is important in every hydrological model. In the Volta basin of West Africa, large number of small reservoirs have been constructed with donor support. They are used primarily for irrigation and livestock watering but also for domestic water supply and fishing. The problem here is that they are ungauged and often dry out in the dry season when they are most needed. This occurrence has been attributed to low rainfall and high evaporation, with the latter being purported to be the significant factor for the ''losses''. Due to this, there have been questions as to whether medium and large reservoirs should be constructed instead of these small reservoirs or not. To help answer this question, the authors have developed a framework to quantify the losses from small reservoirs by looking at their water and energy balance which at the moment are lumped in most hydrological models due to lack of information on them. In this work, we evaluate the use of different satellite imagery (SPOT- 4, SPOT-5, Landsat-7, Landsat-8, Sentinel-2, MERIS, AATSR, Envisat-ASAR, ALOS and Radarsat-2) for mapping small reservoirs extent and also for estimating evaporation losses from these reservoirs in the Upper East Region of Ghana. We consider the complementarities and appropriateness of these satellites for basin scale analysis. Automated delineation is seen as an important step towards the operational use of remote sensing data for water management within the Volta Basin.