Lake Izabal Water Level Fluctuations from ENVISAT RA-2. Relationships with Water Inputs from a Numerical Runoff Model
Medina, C; Gomez-Enri, J; Alonso, J; Villares, P; Arias, M; Catalan, M
University of Cadiz

Water level fluctuations in a lake reflect water storage variations, since water volume fluctuations are the main responsible of the lakes level changes. In addition, water storage variations in a lake are driven by rainfall/evaporation rates over the lakes surface, the catchment hydrologic conditions and grown water dynamics. The amount of water feeding a lake could be monitored and predicted using numerical models, because this water depends on weather conditions over the basin, its geomorphology and anthropogenic factors, such as deforestation and irrigation systems. This study is focussed on Lake Izabal, which is the largest lake of Guatemala. The Polochic River is the lakes main tributary contributing around 70% of its water. Therefore, climatologic conditions over the Polochic River and the other tributaries watersheds have close relationships with the lake level dynamics. The ENVISAT RA-2 Geophysical Data Records over the lake coupled with level in-situ measurements are used to determine the lake’s surface height variations. The analysis period includes the last three years. A runoff model was used in order to found how much the observed level variations are driven by the water feeding the lakes bed from the tributaries. The climate driven runoff model provides the water discharged to the lake which is then normalized with the lake surface to obtain level variations from the water entering the lake. Comparisons between the RA-2 derived and in-situ measured levels evidenced a high accurate performance of the altimeter. Preliminary results show direct relationships between the lake level fluctuations and the climate driven water discharge model.


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