An Assessment Of Watershed Ecosystem Health In Dongting Lake Based On RS And GIS

Ecosystem health research first appeared in the 1970's. With human activities and ecosystems are getting closer, its impact on ecosystems is also growing. Research of ecosystem health has become a hot spot within the ecological study area. Watershed as a relatively complete basic unit of ecology, Assessments of ecological health based on watershed as a unit are getting more and more attention from ecological experts and professionals. Meanwhile, development of RS and GIS technologies provides strong technical means for the study of watershed ecosystem health. Assessment of watershed ecosystem health based on RS and GIS technologies has become an important research direction for the ecosystem health study and the core of integrated ecosystem management.First the scope of watershed is defined and sub-watershed boundaries are marked in this paper, with Dongting Lake area regarded as the research object, landscape ecology and watershed ecology as the theoretical basis and remote sensing data as the basis combined with other supplementary data. According to the composition of watershed ecosystem and ecological processes of"terrestrial pollution sources-riparian filtration-stream influxion"within the watershed, the watershed is divided into Terrestrial, riparian and aquatic ecosystems, and evaluation index systems are selected respectively based on different ecological features. Terrestrial indicators are selected based on land factors, biological factors and pollution threat features; riparian indicators are selected with reference to structural stability and functional integrity, and aquatic indicators are selected in consideration of water quality and the condition of aquatic habitat. Then index weight is determined according to AHP, combined with expert opinion. Finally, watershed ecological health is evaluated by adopting the integrated index method, revealing the spatial distribution of ecological health of each sub-watershed in Dongting Lake area.The results showed that integrated health indices range from 3 to 8 for each sub-watershed in Dongting Lake area, with health conditions mostly falling within the levels of good or average. Sub-watersheds of Datong Lake located in the central part and Xiangjiang River to the southeast are in poor health, with integrated health indices scoring 3.98 and 4.43 respectively, corresponding to health levels of poor and average. Measures should be taken to strengthen the efforts of returning farmland to the shores, vegetation recovery in riparian zone and water quality monitoring. South Dongting Lake and Xinqiang River sub-watersheds are in good ecological health, with ecological health indices scoring 7.32 and 7.43. Prevention and control on river water pollution and soil erosion should be the main concerns.The study shows that it is feasible to perform ecological health assessment by assorting and selecting indicators through terrestrial-riparian-aquatic ecosystem division, based on RS and GIS technologies. The assessment results reveal in full the spatial distribution of watershed ecological health, providing scientific basis for the protection and management of local ecosystem and providing platform of discussion for the related research of ecological health assessment.