| Xiaojiang basin is located in the southwest karst area.Because the unique geological structure,rainfall in this area is rich.But the water utilization rate in this area is extremely low.In recent years,with the development of economy,population growth,increased demand for water in the whole basin,and the background of technology and management level,led to serious waste of water resources,requirement excess the ability of this basin,hence,rocky desertification in this area become more and more seriously and the ecological environment degradation.Therefore,it has a great significant of study the ecological water demand of Xiaojiang basin,to achieve the rational allocation of water resources,to restoration the vegetation,to management the rock desertification.This research based on the technology of GIS,according to the GPS data,using the ENVI5.0 software process the remote sensing images,connect the observed data,calculation the vegetation ecological water demand.Using ArcGIS analysis the temporal and spatial distribution of VEWR.The main conclusions are as follows:(1)According to the year distribution of vegetation evapotranspiration mainly shows:the minimum occurs in January and December,the maximum occurs in March to May,it's arranges from 276.00 to 429.96mm,and the to total of three months accounts for 36.53%to 37.72%of the evapotranspiration throughout the year.From all towns of the annual average ET0 values,the towns values descending are Yongning,Wujiepu,Jinma,Yipu station,Baishi,Jiucheng,Xiangyang station,Santang station.The maximum towns appeared in the southwest part of basin,which value is 2945.12mm;The minimum value is 2581.52mm,located in the eastern of the basin.(2)From the remote sensing we know farmland vegetation is the main vegetation types in the Xiaojiang basin,which accounts for 55.67%of whole basin area.Farmland vegetation mainly distributed in the basin downfaulted basin area and flat area.Opening forest area account for 21.41%of the whole basin area,ranked second for the whole area.Mainly distributed in the southeast and southwest part of the mountain.Wet land is the most small area in this six vegetation types,which accounts for only 3.77%of the whole area,mainly distributed in the middle of the Xiaojiang basin,near the luxi county area.(3)There have six vegetation types in the whole basin area,mainly include forest,opening forest,rassland,shrub,farmland,wet land.The different types of ecological water requirement descending are openging forest,farmland,forest,grassland,shrub,wetland.In wet year,suitable ecological water requirement is0.745billion m~3,accounted for 46.71%of the whole basin water demand.Wet land suitable ecological water requirement is 0.014 billion m~3,accounts for only 0.87%of all the basin.And the vegetation ecological water value in three typical years are0.313billion m~3,0.27billion m~3,0.278billion m~3.Each vegetation type of water demand in the distribution of the whole basin's overall from basin southwest to east the value increase.(4)Farmland throughout the growing season is almost not lack of water.Opening forest is still the largest vegetation type to shortage of water,the value range 0.189 billion m~3 to 0.636 billion m~3,accounts for 77.38%to84.43%.Water deficit in Yongning station is the largest station,the minimum station is Santang station.The whole river basin water deficit showed from the east to southwest water increased gradually,in the northeast of river basin water quantity changed few.In the five geomorphic units of the Xiaojiang Basin,the ecological health monitoring and management area is focused on the Xiaojiang karst valley area and the surrounding karst mountains in the basin. |
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