| Irrigation water monitoring is an important part of agricultural water management.The accurate acquisition of irrigation area and it's spatial distribution information can provide scientific support for agriculture water management and help improve the efficiency of agriculture water use.The traditional irrigation area monitoring is based on manual observation and reporting statistics.It's about point observation information.The obtained date can not accurately reflect the spatial distribution of irrigation area in large area,and timeliness is poor.It seriously restricts the refined level of agriculture water management.Remote sensing is a regionalized wide range monitoring technology.It has been gradually introduced into the modern agricultural management of irrigation districts.In recent years,some attempts have been made to obtain irrigation area based on the variation characteristics of soil water content.These method avoid the shortcomings of traditional ground observation methods,such as poor timeliness and poor spatial description.However,the accuracy of remote sensing soil moisture is easy to be affected by vegetation coverage,and soil moisture will also be disturbed by precipitation factors.Therefore,the recognition accuracy of the irrigation area is been affected.In this paper,evapotranspiration is introduced to eliminate the shortcomings of the above methods.At the same time,the low resolution MODIS data is used to meet the convenience of data acquisition.Based on the principle of water balance,the irrigation area was obtained by remote sensing of soil moisture and evapotranspiration.This paper takes Yichang irrigation area in Hetao Irrigation District of Inner Mongolia as an example.Based on the meteorological data from May 13,2014 to May 31 st and MODIS 1km product data,we use the land surface energy balance model(SEBAL)to calculate the evapotranspiration of Yichang irrigation area.The modified perpendicular drought index model(MPDI)is used to get the soil moisture at the beginning and the end of the study period.The amount of irrigation is calculated by the water balance principle.Because agriculture irrigation occurs in the filed,1km scale information can not be directly used to explain changes in filed.In order to improve the research of irrigation area in filed scale,we introduce the pixel abundance to convert the 1km scale irrigation area to the filed scale.The formula for calculating actual irrigation area at 1km scale is put forward.The irrigated area of Yichang irrigation area is obtained by this formula.The results show that the soil moisture content,evapotranspiration,irrigation water and irrigation area are generally higher in the northern part of the study area than the South.And the results are the same as the irrigation order from north to south.The irrigation area calculated by the irrigation area formula is 82.29 million mu.Compared with statistical data,the consistency of irrigated area identification is 81.13 %.Therefore,the introduction of remote sensing evapotranspiration to obtain irrigation area can not only avoid the influence of rainfall and vegetation cover with soil moisture means,but also improve the effectiveness of the irrigation area.The application of this method is more extensive.And it can provide effective data and method support for fine irrigation management and scientific irrigation in irrigation area. |
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