Arid Dynamic Monitoring Study Of Winter Wheat Based On TVDI Index In Xingtai Region

In China,drought has caused the most severe loss among all of the natural disasters.Caused by the interaction of nature,society and eco-environment,agriculture drought is the restricted barrier for agriculture sustainable development. Except the direct consequences of agricultural drought such as decreases of agricultural yield,shortages of food supply, the long-term drought will destroy the land resources degradation, water scarcity seriously,ecological environments destruction, and ultimately restrict agricultural and sustainable development of society and economy. It is an important issue for the relevant departments that how to monitor the drought quickly and timely.With the continuous development of remote sensing technology, the capabilities of acquiring the data which is high spectral and high temporal resolution are increased.Researches on terrain analysis with hyper spectral data, obtained the widespread application in various fields, among which the temporal and spatial dynamic monitoring of crop drought becomes a focus of hyper-spectral remote monitoring research in agricultural research. The use of remote sensing technology for dynamic monitoring of agricultural drought, which reflects the affected area of drought,extent and trends timely and accurately,will provide scientific basis for the government for disaster prevention and mitigation,and all these are of great practical significance.Taking Xingtai as the study area, which is a irrigated agriculture area of frequent droughts and serious water environmental degradation,we combine the normalized difference vegetation index and land surface temperature data to establish temperature vegetation drought index(TVDI) in remote sensing monitoring model. The model is applied to the drought monitoring of winter wheat in Xingtai during main growth period.The dates we selected come from March to May in four years including two normal years 2006 and 2008,one severe drought year 2010 and a partial drought year 2012. Then we monitored the spatial-temporal changes in the overall Xingtai City throughout dividing the different drought grades. At last,we analyzed the factors of drought and provided appropriatedrought prevention countermeasures. The conclusions in this paper are as follows:(1)The surface temperature data,which comes from pretreatment and model calculation from MOD11A2 remote sensing images,is proved to be positively correlated to the true temperature,so the result is more accurate.(2) The calculated surface temperature shows that the low temperature area of Xingtai City is mainly the central plains area,while the temperature of hilly area and eastern low plains is high from March to May. At the same time,normalized difference vegetation index calculation results show that vegetation coverage in the central plain is high, but the vegetation coverage is low in hilly area and the eastern low plains.(3)The analysis of TVDI in this article as well as the data of measured soil moisture of underground 10 cm shows that it is reasonable to monitor the dynamic variation of drought in Xingtai City by using TVDI model,which is constructed with MODIS data. And the model provides both basic data and feasible method for the future monitoring of drought. The correlation analysis shows that higher surface temperature comes along with higher drought grade. The lower vegetation index,the greater the degree of drought is.(4) We monitored the changes in the overall Xingtai City by the TVDI Index and divided the different drought grades. The result shows that the drought distribution curve of Xingtai from March to May in 2006,2008,2010 and 2012 was aggravating gradually from the central plains area to the eastern low plain area and western hilly area. The low plains area was in moderate or mild drought most of the time. The drought of the central plains area was lighter,even not threatened by the drought. Most areas centered in Xingtai were often threatened by the severe drought in the western hilly area. In terms of time,the drought was severe in March,significantly reduced in April and some areas were even unaffected by the drought.Moreover,in May,the drought was further alleviated compared with April.(5) The drought index from March to May about winter wheat was evaluated comprehensively. Then we made a comprehensive rating map. As it can be seen from the zoning map,which indicates levels of drought of winter wheat in Xingtai City,the overall drought of Xingtai City can be divided into three areas: the western hilly area is mainly highdrought zone,the eastern low plains area is less,forming a medium risk zone,the central plains area is a low grade zone due to lightest drought.(6)Two major factors affecting the changes of Xingtai agricultural drought are nature factors and human activities. Nature factors include topography,water and soil texture while human activities include the growth of population, the amount of chemical fertilizers,pesticides,plastic sheeting used in the agricultural production activities,irrigation area and the area of income guaranteed land and so on.(7)In the research of countermeasure against risks,appropriate countermeasures are put forward according to different natural environment of every area. The countermeasures are as following: First,Strengthening construction of water facilities; Second,Saving irrigation water,developing water saving agriculture; The last,Selecting drought-resistant varieties,adjusting the agricultural structure.