Based on the land cover types and land use status of Dongting Lake eco-economic zone, this paper revises the regional equivalence of ecosystem services value per unit area proposed by Gaodi Xie et al. And we calculated the equivalent value of ecological service function of supply function, regulation function, support function, cultural function and the total ecological services in the study area. According to the relevant provisions of national eco-county, eco-city and eco-province construction index and per capita resource consumption, the value equivalent of each ecological service demand is obtained by combining the land area and resident population of each district within the region. According to the assessment results of the equivalent value of the supply of ecosystem services, we can obtain the supply-demand profit-loss status of the regional ecosystem services. Research indicates that: (1) The overall supply and demand of various ecological functions and ecological services in the Dongting Lake eco-economic zone are in a good condition with the ratio of supply and demand being more than 1.2; (2) There are differences in the supply and demand of various ecological functions within the region, which is listed as supporting service (1.46) > regulating service (1.44) > supplying service (1.39) > cultural service (1.28); (3) The supply-demand ratio shows a distribution mode of areas with high values around it, but the supply and demand is relatively low in Jingzhou area on the north side of the region; (4) From the perspective of supply and demand of ecological services, the difference between urban and rural areas is significant. In this study, the supply-demand ratio analysis is limited to the boundaries of administrative divisions. The research on the natural boundary of spatial distribution based on supply and demand needs to be further strengthened.
The main causes of urban waterlogging are decrease of urban storage land, the spillway network fragmented by construction land, overlap of stormwater storage and construction land, and so on. This paper, based on the three levels of substrate (source of runoff), corridor (runoff pathway) and patch (confluence land), attempts to set up a low-impact urban development mode to absorb extreme storm water through its inherent storage capacity of natural hydrological system: Suyuyuan, a typical area of Changsha in southern China was taken as an example to build the low-impact development mode by spatial analysis tools ArcGIS and in hydrological analysis module in soil conservation service (SCS) based on geomorphologic and hydrometeorological data. The waterlogging security pattern was built according to the flood submergence scope and runoff path simulation of extreme rainfall. According to the construction target of sponge city with annual runoff control rate of 85%, the source control water volume and corridor control water quantity were determined respectively, and then the patch control water quantity was obtained. It is estimated that the area should preserve 228.2 ha stormwater storage regulation patch and 1.075 million m3 controlled water volume, and 51.5 ha waterlogging corridors and 0.101 million m3 controlled water volume after the development. This method can provide a reference for exploring the new model of sponge city construction based on extreme climate waterlogging prevention and control.
The ecosystem service value, which is an effective tool to measure the ecosystem services, to a certain extent, reflects the relation between land use and social economic system by changing the value of regional ecosystem services. Spatial analysis of West Dongting Lake region based on massive vector and raster data were made with the aid of ArcGIS 10. Eco-economic regulation mechanism was studied by constructing the ecological economic coordination index and analyzing the characters of spatial differentiation of eco-economic harmony degrees between land the ecosystem service and economic development. The results are shown as follows: (1) The ecosystem service value of West Dongting Lake area decreased from 1292.13×106 yuan in 2000 to 953.03×106 yuan in 2011, a reduction of 339.10×106 yuan. (2) In the whole study area except Taoyuan, 6 counties have low intensity conflict in the whole research period, which are Changde, Anxiang, Hanshou, Lixian, Linli and Jinshi. All this shows that there are conflicts and the potential crisis between the economic and social development. (3) In terms of spatial differentiation, the ecological economic coordination of land use from 2000 to 2008 and 2008 to 2011 is basically a state of low intensity conflict, and that from 2008 to 2011 was a potential crisis in space. It is necessary to take measures in ecological service recovery and reconstruction and control the rapid growth of the consumption demand of ecological services.
Lake water quality monitoring is the foundation for the effective implementation of comprehensive management of lake water environment as well as water pollution prevention and control. Moreover, the dynamic monitoring of water quality can provide an important basis for the assessment of the risk of algal bloom in lakes and the ecological safety construction in the lake area. Dongting Lake is the second largest freshwater lake in China, the acceleration industrialization and urbanization had caused the lake water pollution to be more and more serious in recent years. Many studies were focused on the traditional water quality monitoring method that rely on chemical analysis after water sample collection, but paid less attention to the remote sensing technique due to the shortages of aerospace imagery. In this paper, the GF-1 image during the period 2014-2016 were collected based on the high resolution earth observation system Hunan Data and Application Center, and the inversion of water quality parameters of Dongting Lake was carried out including chlorophyll-a concentration, suspended matter concentration and transparency. The water boundary of Dongting Lake was extracted by the normalized water index (NDWI), and water quality parameters were quantitatively retrieved by the remote sensing model. The results show that the chlorophyll-a was mainly concentrated in the Anle Lake, Daxiao West Lake and the western part of East Dongting Lake, where the flow speed is slow, the chlorophyll-a content in other parts of Dongting Lake is relatively low due to water disturbance. The transparency of water quality is relatively high in the tributaries, then decreases from south to north and reaches the peak in the Yangtze River Estuary. There is a negative correlation of spatial distribution between transparency and suspended matter concentration as a whole, which is consistent with the routine monitoring rule. The water quality of the East Dongting Lake is much worse than that of the southern Dongting Lake and the West Dongting Lake. The water pollution of East Dongting Lake is at the highest level of the whole lake, which is closely related to human activities, causing a large amount of pollutants, agriculture and forestry chemical fertilizer being discharged into the East Dongting Lake. The GF-1 PMS imagery can accurately reflect the spatial variation of chlorophyll a concentration, suspended solids concentration and transparency index, and this study is expected to provide an important reference for the study of theory, method and application of inland lake water quality monitoring based on high-resolution remote sensing images.