Analysis Of Water & Soil Security In YanQi Oasis Bases On 3S Technologies

This paper takes ecology, landscape ecology, agriculture ecology, soil and water resource as theoretical foundation, covers 5 periodes remote sensing images which are 1964,1973,1990,2000 and 2007 year and integrates the field investigating data on local water and soil data acquired in 2007 and 2008 separately as data resource. With the supports of 3S technologies, statistics theory, Analytical Hierarchy Process, the paper analyzes the water security, soil security and landscape diversity security of YanQi oasis. The main conclusions are as followings:In the past half century nearly, the landscape pattern of YanQi oasis had changed fiercely, the specific manifestations were that:areas of grass land and forestry decreased and the area of farmland increased. The ratio of farmland landscape in the research area grown from 8.96% to 44.69% during the period from 1964 to 2007 and farmland landscape had become the biggest landscape in the research area. In the internal of the landscape factors, the spatial cohesion of farmland patches increased and the fragmentation of farmland patches decreased, while the other factors'spatial connectivity decreased and fragmentation increased. The landscape diversity of the oasis decreased, to 2007 year, the Shannon diversity index had decreased to 43.29% compared with that in 1964 year, the rank of the landscape security is worse.The per capita water share is 4195m3 per year in YanQi oasis, which is twice than the per capita water share in the whole nation. The water supply is abundant and the rank of the water supply is best. In oasis, the high salinity groundwater region mainly distributes around Bositeng lake, and the low salinity groundwater mainly distributes in this region which is far away from Bositeng lake, in contrast. Six ranges were divided about groundwater salinity that were 0-1 g/l,1-2g/l,2-3g/l,3-5g/l,5-10 g/l,and>10 g/l,and the area of each range mentioned above accounts for 10.35%,31.72%,12.71%,12.71%,15.01%and 7.49%in the whole land area of the research area separately. The areas which the wheat grown is normal, inhibiting and extinct account for 49.34%,18.25% and 32.14% in the whole land area because of ground water salinity separately. Compare with the wheat, the areas which the cotton grown is normal, inhibiting and extinct account for 55.87%,12.20% and 31.92% in the whole land area because of groundwater salinity separately. The rank of the groundwater salinity security is better. In YanQi oasis, the low depth of groundwater regions mainly distribute around Bositeng lake, Kaidu river and Huangshui channel. The depth of groundwater which is benefit and not benefit to the grown of natural vegetation accounts for 70.04% and 29.96% in the whole land area separately.1 meter of groundwater depth is the critical level to agricultural production, the areas which is higher than 1 meter and lower than 1 meter accounts for 81.92% and 18.18%. The rank of groundwater depth security is better.In the oasis, the distribution of soil salinity is similar to the distribution of groundwater depth. The high salinity areas mainly around Bositeng lake and the low salinity areas are far away from Bositeng lake regularly. Five ranges were divided about soil salinity that were 0-1g/kg, 1-2g/kg,2-4g/kg,4-5g/kg and >5g/kg and the area of each range accounts for 8.18%,12.20%,23.77%,5.27% and 50.56% separately. The areas which the wheat grown is normal, inhibiting and extinct account for 23.04%,36.81% and 40.15% in the whole land area attribute to soil salinity separately. As similar as the wheat, the areas which the cotton grown is normal, inhibiting and extinct account for 20.38%,23.77% and 55.83% in the whole land area attribute to soil salinity separately. The rank of soil salinity security is normal. At present time, the population density of the oasis is 22 persons per square kilometer and there are still 48 years time to reach its critical level which is 33 persons per square kilometer providing the population increasing ratio is same as the increasing ratio in 2008. The rank of the soil carrying capacity security is best.The result of analysis for water security, soil security and landscape security by analytic hierarchy process shows that the weight of water security, soil security and landscape diversity security is 0.59,0.25 and 0.16. The water & soil security Synthetical score is 7.17, the rank of security is better.