Ecological Evolution And Impact Assessment Of A Small Plain Watershed Driven By Coal Mining

A watershed is the land area that drains into a stream system. Within the watershed, the ecological system is relatively integrated. In the watershed with rich coal resources, mining subsidence makes great damage to land resources; coal mine industrial site construction occupies a lot of eco-land, which have significantly changed the land use, vegetation cover and landscape pattern. Studying the ecological evolution rules of watershed driven by coal mining systematically and intensively and evaluating the eco-impact of coal mining have an important significance to protect watershed ecological system and realize sustainable utilization of water resource and green mining.This thesis presents a case study in Nihe watershed of Huainan, which focuses on the evolution rules of surface water bodies, land use and landscape pattern and the comprehensive ecological impact assessment of coal mining on small watershed scale, using Remote Sensing (RS) and Geographic Information System (GIS) techniques with multi-source data. This thesis is jointly supported by National Environmental Protection Specialized Fund for Commonweal Industry (200809128) and the National High Technology Research and Development Program of China ("863 Program") (2007AA12Z162). Main contents of the thesis are listed as follows:(1) Water body and land use information was extracted from Landsat MSS and TM image data. A hierarchical classification strategy based on SVM was built. The result shows that the strategy has higher accuracy.(2) According to the features of coal mining impact on water bodies, three kinds of water bodies in a watershed are classified which are water bodies formed by subsidence (WBS), water bodies affected by coal mining (WBCM) and other water bodies (OWB). One kind of water body type identification technique was proposed, which is supported by mining field information.(3)Based on the water body extraction and land use classified results, a method for detecting water body change was proposed. Dynamic degree index, water body change detecting and spatial distribution center were used for systematically analyzing temporal-spatial evolution features. Using water body density and location entropy, the spatial clustering features within and without mining area were analyzed. A simple and effective water body change driving index of coal mining (CMWDI) was constructed.(4) The land use change characteristics of Nihe watershed were analyzed using land use dynamic degree and area change value. The single land use class and comprehensive land use change driving index of coal mining (CMLDI) were built and applied in Nihe watershed at different scales. The CMLDI of Nihe watershed shows the driving strength of water body change is the biggest of all land use classes. The single and comprehensive CMLDI at mining area scale are larger than that at watershed scale.(5) Using RUSLE model, a method for calculating LS factors of subsidence basin based on DEM was proposed and applied in Panbei coal mine. The result indicates that the maximum soil erosion modulus of subsidence basin increases. The significant increasing area is located on the edge of subsidence basin. Comparing with normal landscape, the total erosion value increases by 23 percent after subsidence without water logging. Under the condition of subsidence with water logging, the total erosion amount only increased by 0.4 percent compared with normal landscape.(6)The characteristics of landscape pattern change of Nihe watershed were analyzed based on landscape metrics. The landscape pattern became more fragmented, heterogeneous and lower connective from 1987 to 2006. However, it became more continuous, homogeneous and higher connective from 2006 to 2009. Farm land is the matrix of Nihe watershed, while its dominance declined from 1987 to 2009 and the dominance of SWB ascended from 1987 to 2009. The patch number and edge density of SWB increased from 1987 to 2009. The connectivity of the patch classes formed by coal mining is the highest of all classes.(7)The key factors of coal mining impact on plain small watershed ecosystem were selected and an eco-response index (ERIcum) was constructed. The technique process of assessment was proposed and applied in Nihe watershed. The result shows the ERIcum increases from 2009 to 2030. But more attention should be paid on the biodiversity destroy, vegetation cover decreasing and other adverse effects induced by coal mining in the future.