Funding: DAAD - German Academic Exchange Service and Other
The German-Brazilian cooperation between GFZ Potsdam, University of Potsdam and the Federal University of Ceará in Fortaleza is jointly supported by DAAD and CAPES. The cooperation aims at monitoring water resources and improving the understanding of its complex dynamics based on remote sensing technologies in dryland areas and specifically in the North East of Brazil, a region referred to as the drought polygon.
The North East of Brazil is characterized by a high spatial, seasonal and inter-annual variability of rainfall. The climate is semi-arid with pronounced wet and dry seasons. For the dry season, water supply is ensured by the construction of reservoirs of various sizes. The stored water is essential for the local population in terms of drinking and irrigation usage. However, the region regularly experiences drought spells when low rainfall rates during the wet season result in insufficient refill of reservoirs, inducing a need for effective and integrated water resource management. In recent years, an increasing growth of macrophytes has been observed indicating an increase in eutrophication of the reservoirs that in turn is related to changes in land use. Particularly direct access of cattle to the reservoirs and the degradation of the natural Caatinga vegetation are supposed to be major causes of increased nutrient inflow. Given the large number of reservoirs, the complex dynamics of water storage and quality and the size and remoteness of the area, multi-sensor satellite remote sensing is believed to be an ideal source to assist monitoring of water resources as a basis for a sustainable water resources management.
Specific objectives of the joint project are to (1) derive bathymetric information of the reservoirs using InSAR technology to estimate height-area-volume curves, (2) monitor the effective water storage dynamics from water surface delineation by SAR and optical image time-series and the previously derived storage curves, (3) monitor water quality by use of hyperspectral and multispectral imagery, (4) identify macrophyte types and monitor their spatial and temporal dynamics, (5) characterise reservoir sediments using spectroscopy, (6) detect land use changes and relate it to the observed eutrophication dynamics and macrophyte growth and (7) use the information derived from satellite data for improving flood and drought forecasting in the region. The multi-sensor remote sensing approach is supported by an extensive ground-truthing programme to calibrate and validate image analysis as well as to identify processes on site.