RIVER FLOW WETLAND MONITORING WITH ENVISAT ASAR GLOBAL MODE IN THE OKAVANGO BASIN AND DELTA

摘要

Wetlands in semiarid regions such as the Okavango Delta depend not only on local rainfall but also on external inflow. Flooding patterns can be estimated if the precipitation and other hydrological parameters of the contributing area are known. The water is intermediately stored in the soil and either evaporates, is taken up by plants or contributes to surface or subsurface runoff. While spatially continuous high resolution rainfall data are difficult to obtain, soil moisture can be derived from microwave satellite data. An approach for derivation of relative soil moisture on 1km resolution in semiarid regions has been realized within the ESA Tiger Innovator project SHARE (Soil moisture for Hydromete-orological Applications over SADC). Active microwave data which are acquired with ENVISAT ASAR operating in Global Mode have been used for the now operational processing chain. With this work we demonstrate that the relative soil moisture derived from the ENVISAT ASAR GM data can be clearly related to river discharge measurements. Additionally, we show the ability of ENVISAT ASAR Global Mode to monitor dynamics of wet or inundated areas as a response to precipitation and soil moisture variation respectively in the upper Okavango basin.