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C3: ID.10697 Dongting Lake Flood Dynamics
Flow-sediment Exchange, Flood and Drought in Dongting Lake Basin in Recent 60 Years
1Hunan Normal University, China, People's Republic of; 2Beijing Normal University,China, People's Republic of;
Dongting Lake basin is one of the important agricultural production areas in China. However, floods & droughts occurr frequently, and which restricts the sustainable development of agriculture. Based on time series hazards and hydrological data obtained from 1950 to 2010, the evolution characteristics of floods and droughts, flow-sediment exchange between the Dongting Lake and the Yangtze River basin, regional differentiation, factors and development trends of hazards have been analyzd, and the influence of the Three Gorges Dam (TGD) also have been fully discussed.The results are shown as follows.
(1) Flow-sediment exchange between the Dongting Lake and the Yangtze River has an obvious seasonal variation. From July to September, the compensation ability of the Three Outlets into the Dongting Lake is stronger than that from lake into the Yangtze River, and from January to March, the compensation ability of the Dongting Lake into the Yangtze River tends to be stronger than the former. (2) Flow-sediment exchange has a significant interannual variability. During the periods of 1951-1958 and 1959-1968, the compensation ability of the Three Outlets into the Dongting Lake tends to be stronger, but in 2003-2010, the compensation ability of the Dongting Lake into the Yangtze River are strengthened. (3) The mutual effects and an interacting & interdependent relationship between the flow-sediment process and the characteristics of lake morphology have been confirmed. (4) Flood in different levels occurs almost every year, drought in different levels intermittently taken place from 1950 to 1999, but with a highest frequence of 80% between 2000 and 2009. (5) The loss of flood tends to decrease while the loss of drought increase slightly. (6) The dyke broken of the Dongting Lake has been effectively under control since the operation of the Three Gorges Dam, but waterlogging still occurred frequently, and long-time droughts, which lasted from summer to autumn taken place alomost every year.
Multi-Sensor Earth Observation Data for the Detection of Surface Water Dynamics at Dongting Lake
1German Aerospace Center (DLR), Germany; 2Hunan Normal University (HNNU), China; 3Beijing Normal Univeristy (BNU), China;
The Dongting Lake – one of the largest Yangtze River flood plain lakes – is home to one of the biggest and most dynamic wetlands in China. Dongting Lake as a natural environment formerly provided buffer for natural disasters such as floods and droughts. Anthropogenic processes such as lake regulation, urbanization, and agricultural intensification nowadays impact on the well–being of Dongting Lakes wetlands.
In the presented project current advances in multi–scale and multi–sensor wetland inundation monitoring and analyses of surface water dynamics are presented for the years 2000–2016. New European Sentinel–1 data available since 2014 were analysed to provide up–to–date and high–resolution information on surface water coverage and change. These data extend the time series for surface water detection formerly conducted with Envisat–ASAR data. Furthermore, TerraSAR–X data were used for very–high resolution focus analyses. In general, SAR is selected as the preferred technology to provide information with high spatial resolution independent from persistent cloud coverage. High temporal resolution can be achieved by using optical data with medium spatial resolution such as MODIS, and future Sentinel–3.
The variation of surface water area in Dongting Lake region was furthermore explored with time series dataset which was built from 8–day surface reflectance data (250m) and 16–day vegetation indices (250m) of MODIS-Terra sensor. By means of remote sensing information extraction 169 scenes of surface water area were derived for 2000–2015 to analyse the submerged frequency and variation regulation.
The results show that: multi–sensor remote sensing time series information can be used to derive surface water area in Dongting Lake region, and to present the observed intra-annual and inter-annual change processes. The analyses revealed that the lake area is relatively large from June to September and smaller from December to April. In the last 15 years Dongting Lake has shown a shrinking trend. Moreover, in the observed period the flood duration ended earlier every year and water resources of low water period significantly decreased.
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Conference: 2016 Dragon 3 Final Results Symposium
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