Satellite remote sensing of water turbidity in Alqueva reservoir and implications on lake modelling

Abstract

The quality control and monitoring of surface freshwaters is crucial, since some of these water masses constitute essential renewable water resources for a variety of purposes. In addition, changes in the surface water composition may affect physical properties of the lake water, such as temperature, which in turn may impact exchanges with the lower troposphere. The use of satellite remote sensing to estimate water turbidity of Alqueva reservoir, located in the south of Portugal, is explored. A validation study of the satellite derived water leaving spectral reflectance is firstly presented, using data taken during three field campaigns carried out during 2010 and early 2011. Secondly an empirical algorithm to estimate lake water surface turbidity from the combination of in situ and satellite measurements is proposed. The importance of water turbidity on the surface energy balance is tested in the form of a lake model sensitivity study to the water extinction coefficient (estimated from turbidity), showing that this is an important parameters tuning the lake surface temperature.