Remote sensing of volumetric storage changes in lakes

Three-dimensional remote sensing promises a giant leap forward for surface-water hydrology in much the same way that radar altimetry transformed physical oceanography. However, the complex geometries of small terrestrial water bodies introduce difficulties, particularly with respect to trade-offs between changing water depth and inundation area. We use in situ measurements of water-surface stage (Delta H/dt) and remotely-sensed area (A) to compute time varying storage changes (Delta S) in nine lakes of the Peace-Athabasca Delta, Canada. Despite their identical geomorphic setting, regression slopes between Delta H and A vary significantly between lakes, primarily from a predictable 'area-effect' but also small bathymetric variations between basins. On average, lateral contraction/expansion (versus stage adjustment) contributes as little as 7% (versus 93%) to as much as 76% (versus 24%) of overall storage change Delta S. We conclude that both surface-area and Delta H/dt, rather than just either alone, must be measured to confidently estimate Delta S from space. Copyright (C) 2009 John Wiley & Sons, Ltd.