Sarah Schönbrodt-Stitt

Assessment of geo-hazards in a rapidly changing landscape: the three Gorges Reservoir Region in China

Large dam projects attract worldwide scientific attention due to their environmental impacts and socioeconomic consequences. One prominent example is the Three Gorges Dam (TGD) at the Yangtze River in China. Due to considerable resettlements, large-scale expansion of infrastructure and shifts in land use and management, the TGD project has irreversible impacts on the Upper Yangtze River Basin and strongly challenges the environmental conditions of this fast-developing region. Soil erosion and landslides are major geo-hazards. Knowing the extent and consequences of those geo-hazards for the landscape is essential to predict and evaluate their risk potential and allows for the development of strategies for a sustainable future land use in the Three Gorges Region (TGR). In this context, our research objectives are (1) to better understand the mechanisms of soil erosion, landslides, and diffuse matter fluxes in the TGR and their anthropogenic and environmental control factors, (2) to predict their hazard potential by combining spatial and temporal, scenario-driven high-resolution modeling in combination with multi-scale earth observation data, and (3) to develop a multi-component approach for the assessment and monitoring of geogene structures and processes. The paper describes the workflow of the project and introduces case studies, representing the current state of our research. It is shown that land-use changes as well as the water-level fluctuations of the reservoir are the crucial drivers for the soil erosion and landslide hazard. Furthermore, we present a framework aiming at the establishment of a monitoring and measuring network as well as an early warning system.

Cropping Intensity in the Aral Sea Basin and Its Dependency from the Runoff Formation 2000-2012

This study is aimed at a better understanding of how upstream runoff formation affected the cropping intensity (CI: number of harvests) in the Aral Sea Basin (ASB) between 2000 and 2012. MODIS 250 m NDVI time series and knowledge-based pixel masking that included settlement layers and topography features enabled to map the irrigated cropland extent (iCE). Random forest models supported the classification of cropland vegetation phenology (CVP: winter/summer crops, double cropping, etc.). CI and the percentage of fallow cropland (PF) were derived from CVP. Spearman’s rho was selected for assessing the statistical relation of CI and PF to runoff formation in the Amu Darya and Syr Darya catchments per hydrological year. Validation in 12 reference sites using multi-annual Landsat-7 ETM+ images revealed an average overall accuracy of 0.85 for the iCE maps. MODIS maps overestimated that based on Landsat by an average factor of ~1.15 (MODIS iCE/Landsat iCE). Exceptional overestimations occurred in case of inaccurate settlement layers. The CVP and CI maps achieved overall accuracies of 0.91 and 0.96, respectively. The Amu Darya catchment disclosed significant positive (negative) relations between upstream runoff with CI (PF) and a high pressure on the river water resources in 2000–2012. Along the Syr Darya, reduced dependencies could be observed, which is potentially linked to the high number of water constructions in that catchment. Intensified double cropping after drought years occurred in Uzbekistan. However, a 10 km × 10 km grid of Spearman’s rho (CI and PF vs. upstream runoff) emphasized locations at different CI levels that are directly affected by runoff fluctuations in both river systems. The resulting maps may thus be supportive on the way to achieve long-term sustainability of crop production and to simultaneously protect the severely threatened environment in the ASB. The gained knowledge can be further used for investigating climatic impacts of irrigation in the region.

The German-Chinese research collaboration YANGTZE-GEO : Assessing the geo-risks in the Three Gorges Reservoir area; [EGU General Assembly 2012; 22-27 April 2012, Vienna, Austria]

(1) University of Tuebingen, Department of Geosciences, Chair of Physical Geography and Soil Science, Germany, (2) University of Kiel, Department of Hydrology and Water Resources Management, Germany, (3) University of Erlangen-Nuremberg, Department of Applied Geology, Erlangen, Germany, (4) University of Potsdam, Department of Geosciences, Potsdam, Germany, (5) University of Giessen, Center for International Development and Environmental Research (ZEU), Germany, (6) Research Centre Juelich, Institute of Chemistry and Dynamics of the Geosphere, Jülich, Germany, (7) University of Geosciences, Department of Geotechnical Engineering and Engineering Geology, Wuhan, P.R. China