The Potential of Earth Observation Time Series for the Assessment of Wetland and Water Shed Dynamics
1German Aerospace Center (DLR), Oberpfaffenhofen, Germany; 2Jiangxi Normal University, Nanchang, China; 3Max Planck Institute for Ornithology, Radolfzell, Germany; 4ICube, University of Strasbourg, France
The Poyang Lake and Dongting Lake are Chinas two largest freshwater lakes. Located in the middle reaches of the Yangtze River catchment these large floodplain lakes are home to four Ramsar sites initiated by the UNESCO, to foster wetland conservation. The wetlands in and around the lakes provide numerous important ecosystem services for human well-being, e.g. freshwater resources, retention area for Yangtze River floods, buffer for drought events, natural habitats for millions of endemic and migratory birds, etc. However, anthropogenic influences and related degradation of the lakes wetlands have dramatically increased.
In the project presentation current advances and first results of EO data analyses will be exhibited. EO data, especially from the new European Sentinel-family available since 2014, provide high-resolution information about the Earth surface. Multi-sensor satellite data are used to generate time series for the assessment of water surface and wetland dynamics. Qualitative and quantitative analyses will provide insights into the changes on the Earth’s surface in and around the Yangtze flood plain lakes that have taken place due to anthropogenic influence during the last 10 to 15 years. The results show that: Both lakes have shown a shrinking trend in water surface extent. Wetlands are increasingly used for natural resources exploitation, e.g. sand mining on lake ground and the cultivation of economically important plants at lake shores.
Within the project duration the potential of newly available Sentinel-data in combination with historic satellite data (Landsat, Envisat, etc.) and Chinese satellite data will be demonstrated for the generation of longer and preferably consistent Earth observation time series.
Analysis of the Relationship between Water level and Natural Water Surface in Poyang Lake
Key Laboratory of Poyang Lake Wetland and Watershed Research, Ministry of Education, Jiangxi Normal University, Nanchang, China
The spatial and temporal variation characteristics of the inundation extent for a lake have a great influnce on landscape structure and function of wetland ecosystem. Poyang Lake is the largest freshwater lake in
China. Poyang Lake wetland is a very important wetland in the world for biodiversity conservation. It is very important to measure accurately the water surface dynamics of the Poyang Lake. In this paper, the scatterplot between lake level and MODIS-derived inundation area of the Poyang Lake was used as a starting point, and the uncertainty of inundation areas with lake water levels was discussed. The results showed that: (1) though a significant linear relationship was found for the water level and inundation area for the Poyang Lake, the water surface area shows uncertainty; (2) Water level in Poyang Lake is higher in the south and lower in the north when lake water level is low, and the spatial heterogeneity of water level was decreasing with lake level increasing; (3) Water level slope in Poyang Lake in the time period of water withdrawal was greater than that in flood period; (4) Affected by fishery practice by levees of dish-shaped sublakes, the water surface area of the sublakes in water withdrawal period is greater than that in flood period. Sand mining also changed the water extent around the sandpits when in low lake level. Therefore the inundation extent for Poyang Lake was affected by topography of lake basin, water discharge from the tributaries in Poyang Lake watershed, and the backwater effect of the Yangtze River, as well as with human activities such as sand mining and fishing practice with levees.