Remote Sensing Of The Water Dynamic Changing In North America And The Driving Forces Analysis Of Lake Changes In Typical Area Region

Under the global climate change condition,land surface water body which distributed in different geographical environment had responses to different degrees.So for North America which is complex land surface types and configuration,the distribution land-surface water is timely refreshed,the dynamic changing process is investigated,and then the driving factors is explored.It has a very important significance to properly utilize and protect water resources and to stabilize ecological environment.Taking 976 Landsat satellite remote sensing images as basic data in this thesis Land surface water body distribution data of North America was obtained in 2012 after bands combination,fault data repair,overlap area clip,water body extract and classification,splicing and re-projection,In method,the Modified Normalized Difference Water Index(MNDWI)was used to extract water body information,and Normalized Difference Snow Index(NDSI)and single band threshold was assisted to remove noise information like snow-ice and hill shade.Then the 147 sample points has selection to analysis the change trend of water body in 1980~2000,hope to reflect the dynamic change process.Order to analysis the driving factors of water area changes,take the Great Basin of America as a typical area,and then through comparing the tendency of the lake topography,climate factors and other recharges with the primary lake area change.The results showed that:(1)The total land water body area was 1.404×106km2,and the water body percentage was 6.47%.Which has the latest number and the biggest area is lake water body,the average area was 0.24km2 per one,the reservoir water body has a lower number,the average area is 26.23km2 per one.If divide lake and reservoir according the area level,the relation of number and area showed that the scale of lake in 0.01~1km2 was relatively concentrated,which occupies 70.74% of total lake number;the area of reservoir was concentrated in 0.01~1km2 and 1~10km2,the number occupies 72.57% of total.In every level,no matter lake and reservoir,the average often far lower than the median.Contrast the distribution of countries,Canadian water body percentage is the highest in the country of North America with 9.76%,the second highest was Nicaragua with 7.62%,the water body percentage of America is 5.74%,and the value of Honduras and Mexico is relative lower are 0.99% and 0.54% respectively.The land territory and water body percentage not in direct proportion.(2)In 1980~2000,land surface water body of North America has a tendency of increase,the average rate of change being 0.171%.Area trend of lake water body was increase continuously with speed of 0.139%,and reservoir water body was increase first and then to diminish with 0.151%.Take sample points as a turn of longitude,the change range of water body area in polar climate,alpine climate and tropical rain forest climate is the biggest,and the change range in temperate marine climate,Mediterranean climate and tropical desert climate which in the west coastal of North America showed a negative growth.(3)The lake at east or west in Great Basin has inner consistency respectively on area change tendency.But under the influence of surrounding topography,a different degree of change rate in each orientation in each lake.According to compare the relative of the trend of Shoreline Box Dimension(SBD),Shoreline Development Index(SDI)and water level of Utah and Mono lake,the results showed a high relativity,because of the difference of lake topography,in different water level has a different area.There are not in direct proportion between area and reference evapor transpiration.Compare the trend of temperature and precipitation in same period,find a synchronous increase in area and reference evapotranspiration in some lake in 1975~1985,is leaded by the substantial increase of precipitation.And the synchronous decrease in area and reference evapotranspiration in most lake in 2005~2014,is leaded by the substantial increase of temperature and the small decrease of precipitation.Climate factors is the main cause of the variation of lake.Underground water and runoff supply has a certain extent effects on the variation.