| Drought is a climatic phenomenon which presents such features as high frequency, largescale and long duration. Long term drought will affect industrial and agricultural production.Drought has a great influence on our agricultural production, it is important to know the effect ofdrought on crop yield and judge the beginning of drought and its evolution process in order totake reasonable measures to reduce the cost. The study is carried on Jinghuiqu irrigation district,the suitability of precipitation anomaly (Pa), standard precipitation index (SPI) and Z index iscomPared. The proper drought index is chosen to analyze drought evolution in the irrigationdistrict. On the basis of this, the relationship of drought and climatic yield of main crop isanlysised; critical dry period and drought index value and quantitative relation between droughtand climatic yield are achieved. Besides, the study also calculates crop water requirement andirrigation requirement according to drought year which is judged by drought index.The studypresents following main conclusion:(1) The result of linear trend estimation showed Pa, SPI and Z index can reflect yearlychange trends of precipitation; the response extent of Z index to precipitation deficit year wasmore obvious than SPI, Pa was relatively insensitive to the fluctuation of precipitation; SPIresponsed more quickly to the fluctuation of precipitation than Z index; Pa, SPI and Z indexshowed consistency in judgments of drought occurrence; on the aspect of drought degreejudgments, SPI was better than Z index, while Pa tended to underestimate drought degree.Generally speaking, the performance of SPI is the best among three drought indices.(2) Precipitation, temperature and solar duration distributed unevenly in irrigation district:precipitation was rich during June to October and annual fluctuation was evident in this period,while in January, February and December, precipitation was relatively less and remained stable;high temperature often occurred in June to August, low temperature occurred in January andOctober, the annual change of temperature was stable; the analysis of solar duration showed thatthe solar duration of February and October were shorter than other months, while that of May toAugust were longer than others.(3) The analysis of multiscalar SPI showed that the drought trend of Jinghuiqu irrigation district was obvious, especially in spring, summer and autumn; yearly drought had decadalvariation period of16years, inter-annual variation period of4to5years; there was a trend tobecoming drought during the decadal variation period of drought; seasonal drought hadinter-annual variation period of2to3years; the drought condition became severe after1990s,and slight drought was the most frequent type of yearly drought in irrigation district; mostseasonal drought occurred in summer and winter, and slight drought was the main type of thedrought season.(4) Analyzing the effect of drought on winter wheat, summer corn and cotton based on SPI,and the results showed that: there was a critical period for a specific crop that the influence ofdrought was severe, for winter wheat was July to September, for summer corn was April to June,for cotton was April to June; there was a key point of SPI when yield of winter wheat, summercorn and cotton changed from positive to negative, they were SPI3-9=0.5, SPI6-6=0, SPI1-9=0respectively; the influence of SPI3-9on winter wheat was increasing with the increasing ofdrought, while the negative effect was decreasing at the same time; though the climate tend tobecome drought, the ability to resist drought of summer corn was enhanced.(5) The ETcof winter wheat, summer corn and cotton were366~481mm,395~570mm,583~805mm respectively; precipitation during growth stage can’t fulfill the need of crop, waterdeficit ratio of winter wheat, summer corn and cotton were50.6%,36.5%,35.3%respectively;the irrigation requirement increased with the rise in drought degree, this was evident in heavydrought year. |
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