Research On Landcape's Dynamic Evolution For Watershed's Ecological Security

Ecological security is defined as the undamaged or unthreatened conditions of eco-environment for regional sustainable development. The dynamic landscape pattern of land use is the most important driving factor that influences the watershed's ecological security. The Shule River is one of the three most important rivers in Hexi Corridor region of China. It plays an important role in the production of economic crop, and occupies an extremely important position of economic and strategic in China. After the 90's, with the implementation of agricultural development projects, the developments and utilizations of water resources and soil resources (referred to as water-soil resources) has been going in the Shule River Basin, which has changed the ecological environment and landscape pattern of the Basin. The unreasonable and transitive utilization of the resources have caused a series of eco-environmental problems. Particularly in the past ten years after the implementation of the migration and development project which began in 1996. The development of agriculture and the growth of population have greatly increased the demand on water resources. The irrigated areas in Shuangta, Changma and Huahai irrigated districts have been expanded, which requiring the increasing amount of required water used for agricultural irrigation. To meet the requirements of the irrigated water, most of the water flowed into channels for increasing the utilization rate of water. As the result, the amount of groundwater recharge has been declined, and the total volume of flows falling into the lower reaches of Anxi-Dunhuang Basin has been decreasing continuously. On the one hand, the groundwater level has been declining in the basin, while the spring water has disappeared. On the other hand, the construction of artificial facilities in the basin has changed the natural water cycle of the temporal and spatial distribution of water, which resulted in the distribution of original ecosystems' balance, and the negative effects caused by the soil and water resources development rose such as the sharply decline of natural oasis, salinization of soil, desertification of soil, and so on.These negative effects have caused more and more attentions from the entire world. However, most previous studies focused on the composition, evolution and evaluation of water resources, most of the previous researches were carried out by analyzing into point data statistically. The researches on the evolution of landscape pattern and its driving force are few, the researches on the perspective of two-dimensional combination of temporal and spatial are even fewer.Landscape ecology is a new rapidly developing discipline; it has brought a lot of fresh perspectives for traditional ecology and geography. The spatial information technologies including remote sensing technology (RS) and geographic information systems (GIS) provide strong technical support to the analysis of natural, geographic and cultural phenomena with different spatial and temporal scales. With the development of landscape ecology and spatial information technology, the researches focus on landscape pattern and its dynamic evolutions, driving force and its simulation of the future evolution have become more and more popular in the arid and semi-arid districts all over the world. The theories of Landscape ecology and spatial information science have provided strong theoretical support. Especially, the spatial technologies have provided the integrated platform for spatial analysis and spatio-temporal simulation.In order to explore the dynamics of Shule River basin's landscape pattern and the driving mechanism, this thesis focused on the research of the evolution of watershed landscape pattern between 2000～2008 based on the availability of topographic maps, hydro-geological data, remote sensing vegetation indices' images, monitored historical groundwater level's data and the previous researches' results. This thesis focused on the following researches according to the theories of landscape ecology, hydrogeology and spatial statistical principle.(1) This thesis analyzed the landscape pattern and its dynamic evolution using time series MODIS vegetation indices data in Shule River basin.(2) This thesis proposed a new approach for exploring the driving mechanisms by spatial correlated analysis. Firstly, the driving factors were classified into the natural driving factors and man-made driving factors. The natural driving factors include natural river network and terrain; the man-made driving factors include the distribution of artificial canal network, the distribution of irrigated well, the distribution of road traffic conditions, the conditions of the residents and so on. Secondly, we established the coupling models between vegetation indices and driving factors based on spatial distribution models, which were established by spatial interpolation models. Thirdly, the correlation coefficients between various driving factors and vegetation indices were obtained by statistic analysis.(3) The thesis proposed a new approach on calculation ecological groundwater level using spatial correlated analysis into groundwater and vegetation indices. Based on the analysis to the formal model of ecological water, new ecological water calculation model was established. Finally, the ecological water requirement within different three vegetation landscape was calculated based on evaporation models and "3S" technologies, which provides a new way for calculation of watershed scale ecological water requirement.In the end of the thesis, some suggestion was proposed for the further research basedon the analysis into the deficiencies of the thesis.