Water level changes in a large Amazon lake measured with spaceborne radar interferometry and altimetry

We demonstrate that interferometric processing of JERS-1 SAR data over an A mazon lake containing similar to 1500 islands yields centimeter-scale chang es in the height of the water surface from February 14 to March 30, 1997. F or the method to work, we qualitatively find that inundation of about one o r two leafless trees per 25 m(2) multi-look SAR pixel is sufficient to retu rn the radar pulse to the side-looking antenna. Validation is provided by m ulti-temporal TOPEX-POSEIDON altimetry profiles, which directly measure sur face heights relative to a fixed datum. Because SAR provides an image, the water height changes (similar to 12 cm) can be converted to a net volume me asurement (280 million m(3)) over the 44 days separating the JERS-1 acquisi tions. Compared to historical gauge records, removal of this volume from th e lake required a similar to 50% greater flow.