Study On Water And Soil Losses Dynamic Monitor In Anxi Country Based On Geomatics

Water and soil losses have affected the survival of human being and social development, and it is one of the research topics of current environmental change.Applying 3S technology to investigate the present situation and dynamic changes of soil and water loss can provide a scientific guarantee for soil and water conservation program and ecological environment construction. In this study, it took Anxi County as Survey Region and used the method of image averaging and comparative analyzing, selected 1995 and 2000 TM remote sensing images,all together with 2004 SPOT Image and 2008 ALOS image, and used multiyear average rainfall datas,digital elevation model dem of the research area,the investigation datas of the plots of the four years ,to dynamic monitoring the current situation of water and soil loss in AnXi with the general equation of water and soil loss called USLE.By analyzing the dynamic changes of the degree and the area of the soil and water loss in the different spacetime and different land supplying types and finding dominant driving force of soil and water loss in Anxi County, and using Markov , it was predicted variation tendency of soil erosion intensity. On this basis, it combined with practical experience of the comprehensive management in Anxi County, proposed countermeasures. The main research conclutions were as followes:(1)In the Anxi County the largest area of soil erosion is the total area of 73874 hm2,accounting for 25.50% of the county's total land area in 2004; then the total area of soil erosion 66837 hm2, accounting for 23.07% of the county's total land area in 2008;followed a total area of soil erosion 64464 hm2 accounting for22.25% of the county's total land area in 2000; the smaller of the total area of soil erosion is 61240 hm2, with a proportion of 21.14%. In these periods of 1995-2000,2000-2004,2004-2008 wastage rate respectively rose by 1.11%, 3.25%, and decreased by 2.43%.(2)In the spacial distribution,the soil and water loss mainly distributed in the northern 5 rural township, Gande,Changkeng,Xianghua,Jiandou,Hushang and in the sounthern 2 rural township,such as Guanqiao,Longmen ,and the loss area is 108256hm2, which accouts to 37.37% of the whole county,but during the four periods,the area of water and soil covers over 53% of all the area that soil had been washed away. In other areas ,the loss has a slight degree.(3)From the area and degree of soil erosion, to analyze the current soil erosion situation of four periods of each land types in the Anxi County, land status, the results showed that soil erosion mainly existed in forest land , cultivated land, garden and non utilize land and industrial and mining land and so on . The erosion degree of forest land and garden land were mainly among mild,miderate,intensity, ect.And in each period ,the loss area above intensity which accounted for the total area of the land types were:forest land was over 18%,cultivated land was 3.1% or so,garden land was all over 34%,non utilize land and industrial and mining land was all over 35%.The highest value of the total loss area of each land use type and the erosion degree was in 2004 . (4)The results of analysing in soil erosion extending and changing characters of pitches show that soil erosion in Anxi Country, mainly in mild, moderate and strength lossing grades.The percentage of total erosion area goes to total pitches in four periods is 98.11%, 97.96 %, 96.10%, 96.20%. Based on the number of patches,during 1995-2004, the number of landscape patches showed an increasing trend;while during 2004-2008, the number were decreased, especially the numbers of intensity and the dramatic intensity patches showed a obvious changes. Based on fragmentation , during 1995-2000, the landscape fragmentation showed an increasing trend; the intensity and dramatic intensity ones during 2000-2004 showed an increasing trend, which tended to be instable and complexable; while during 2004-2008, mild and intensity ones were induced, and the landscape tended to be stably and simple; moderate and dramatic intensity ones showed an increasing trend, the lanscape tended to be unstable and complexable.(5) Based on the results of Markov prediction, results of the comparative analysis between predicted values( NO.1 is the predicted value of changing trend during 1995-2000,NO.2 is the predicted value of changing trend during 1995-2004) and the actual values(USLE measured value): compared with the initial value(1995 USLE measured value), all predicted values in 2004 were less than the actual values; in 2008,among predicted value 1 ,sizes of miderate intensity increased, the sizes of mild ,miderate ,intensity and dramatic intensity reduced, while among predicted value 2,the sizes of miderate intensity,intensity and dramatic intensity increased,with the decrease of mild.According the above data, the soil and water loss of Anxi country increased rapidly during 2000-2004, which is badly than 1995-2000. I n other kind of saying, the fact that soil and water conservation efforts are not enough.