Study On Ecological Risk Of Nansi Lake Based On RS And

Uncertainty and spatiality are the two most important features of the task of regionalecological risk assessment (ERA). It is a type of development of general ecological riskassessment. Both the receptors and sources of risk in ERA should be in regional scale，and thefinal assessment must take account of their uncertainty and spatial heterogeneity.With the development of the RS and GIS，the ERA is becoming more efficient andpractical. RS data contains vast geographic information and usually covers broad areas，accordingly，it could instead once the necessary field investigation which might cost lots oftime and money. What’s more，Landsat continuous observation also makes the ERA possible torealize the dynamic change monitoring. Spatial analysis module is a core function in GIS，which integrates some of the newest technology in many disciplines，such as interpolation，gridand so on，and it makes the complex advanced spatial analysis task simple，thus lowering thethreshold of the ERA to achieve.A very important step of ERA is the analysis of the eco-risk sources. The eco-risk sourcesnot only have different effects on different receptors，but also that he himself shows differentstrength for space changes. The former in the existing related research has been given sufficientattention，but the later has often been overlooked. And this article has established anempowerment approach which had been fully considered on the risk sources spatiality based onGIS.Urban construction and expansion is an inevitable process during the social-economicdevelopment，but urban development has some nonegligible impacts on regional ecosystems，particularly in fragile and sensitive wetland areas.Taking the NanSi lake as a study case，and following the general process of theERA—analysis of the risk receptor，analysis of the risk sources，exposure and hazard analysis，and integrated regional ecological risk assessment，we have firstly divided the whole area into1178square grids and each one as an evaluation unit，then defined the main eco-risk source inthis region，including drought，flood and water pollution，and regarding the area proportion ofthe eco-risk source distributed in the evaluation unit after interpolation as the weight of thedifferent eco-risk sources，here we obtain the eco-risk source index; And according to theeco-risk value calculative model，the status and vulnerabilities of ecosystems were assessed bythe landscape index，and here we obtain the losing degree of the ecosystem; Then，in processingthe final stage of the ERA—integrated regional ecological risk assessment，the eco-risk valuewas integrated from the eco-risk source index and the losing degree of the ecosystem. What’s more，we expand the study area as NanSi Lake and the surrounding three counties，apart from analyzing the land use and land cover change and the changes of theeco-vulnerability in study area from1987to2010，and exploring the relationships between theurbanization and regional ecological fragility.Results include1178eco-risk values derived from every cell of the grid， ranging from theminimum0.1934to the maximum9.6719，and its standard deviation is1.662，these numbersindicated that there are great eco-risk differences in the1178square kilometers study area.When Interpolated the eco-risk values into a raster image，which showed two main spatialdiversities--North and South differentiation and lakeside zonal differentiation，which obviouslyembodies the NanSi lake spatial heterogeneity of regional ecological risk. The eco-riskdisplayed more vivid in the north area of the dam，where including NanYang lake，DuShan lakeand the north part of the ZhaoYang lake than in the south of the dam，where including WeiShanlake and the south part of the ZhaoYang lake，all these lakes composed the NanSi lake; Beyondthat，all lakes showed one thread that the eco-risk in lakeside were higher than that in openwater area.And from1987to2010，the growth in urban areas has accounted for effective regionallandscape changes more than60%，but the largest regional eco-loss are water body and greenfields，and the most obvious changes of the ecological vulnerability is happened in the shores ofthe NanSi Lake.