Studies On Changes Of Surface Water Storage In Zoige Plateau

Basing upon the data of field investigation and experiments,landsat image and DEM image,a polygon region was selected to study on the changes of land use coverage and surface water storage in Zoige plateau during 1977～2006.In this study,Surface Water Storage included soil water storage,water storage in vegetation and water storage in water region.Data analysis was based on the ArcGIS 9.2 and ERDAS IMAGEN 9.2 platform.The main results were as follows.After taking geometric correction and radiation calibration,supervised classifications for landsat images of three periods were implemented.The classification accuracy in ETM~+ was the best among three images,which's overall accuracy was 90.87%,and classification accuracies of the other two(TM and MSS) were 87.92%and 89.98%.During 1977～2006,the land cover types transferred violently.The degradating trend of study area was lake-pleteau-moist meadow-grass plot-sandy land.In 29a,the area of wetland landscapes decreased gradually.Oppositely,the region of sandy land enlarged rapidly.During 1977～1994,degradation of wetland landscapes mainly liked internal transference.In one of the key regions-wetland area,54.47% of lake degradated mainly toward to seasonal seeper peat bog and perennial seeper peat bog.46.75%of perennial seeper peat bog also trasfered to temporary seeper peat bog and seasonal seeper peat bog.During 1994～2006,peteau landscapes started degradated to un-peteau landscapes.On the ground of supply from the transfer of herbage peat bog and moist meadow,area of grass plot in 2006 was 4.29 times of area in 1994.The area of sandy land increased by 56.72%from 1977 to 2006.but,the area of sandy land in 2006 was 98.27%of area in1994.From the analysis of two key regions,during 1977～2006,area of sandy land in wetland region decreased from 4.90hm~2 to 2.82hm~2.On the other hand, area of sandy land in sandy area increased by 81.71%,which benefited from the degradation of grass plot,shrub-grass plot and temporary seeper peat bog.During 1994～2006,area of sandy land in wetland region increased to 41.42hm~2,and the area of sandy land in sandy area redused to 53.83%.Surface Water Storage in study area was 321829.54×10~4m~3 in 1977.when it came to 1994,this quantity reduced to226328.89×10~4m~3.it was 198847.19×10~4m~3 in 2006.Soil water storage was 167782.84×10~4m~3 in 1977;this quantity reduced to 145393.54×10~4m~3 and 113044.87×10~4m~3 in 1994 and 2006.Water storage in vegetation was 348.42×10~4m~3 in 1977;this quantity reduced to 294.44×10~4m~3 in 1994,and continued to reduce to 196.18×10~4m~3 in 2006.Water storage in water region was153697.40×10~4m~3 in 1977,and decreased to 80639.77×10~4m~3 in 1994.When it came to 2006,the water storage in water region increased slightly to 85605.37×10~4m~3.