Study On Estimation Method Of Irrigation Water Effective Utilization Coefficient Based On Remote Sensing Evapotranspiration

The effective utilization coefficient of irrigation water is the main indicator of the red line of agricultural water use efficiency.It is one of the most important indicators for the most stringent water resources management assessment.It is also a manifestation of the implementation of the most stringent water resources management effects.It is of great significance to build a water-saving society.However,the current overall rate of agricultural water use is insufficient.The direct measurement method and observation analysis method are more dependent on the water metering rate in irrigation areas.In the assessment period,it is difficult to determine the effective utilization coefficient of irrigation water,which results in the lack of an effective grasp of the assessment.Therefore,exploring new technological means,to study a fast and accurate method for estimating irrigation water use efficiency.To better implement the strictest water resources management system,strengthen the rational and efficient allocation of water resources to provide technical support.With the continuous development of remote sensing technology,it has provided new technical means for the accurate distribution and regulation of agricultural water resources and has played an increasingly important role.The purpose of this study is to try to use remote sensing evapotranspiration techniques to construct a method for estimating the effective utilization coefficient of irrigation water in southern China based on remote sensing.To achieve this goal,the study focused on the scientific issue of how to use the remote sensing evapotranspiration method to calculate the effective utilization coefficient of irrigation water.The key technologies of cropland structure extraction,evapotranspiration calculation method regional adaptation and optimization,and time scale development were studied in depth.The main research contents and conclusions are as follows:(1)Research has proposed a human-computer interaction and object-oriented method for remote sensing spatial interpretation of planting structures in irrigation areas.Through the coupling analysis of the spectrum,texture,shape,and vegetation index of the characteristic crops,built a set of extraction rules for different types of crops,solved the spectral peaks and spectral shapes of different types of objects are basically consistent,and there is more foreign matter in the spectrum between crops.Remote sensing image segmentation methods with different scales at different levels are proposed for different planting types,which solves the problem of different scales of segmentation in remote sensing images.In the study,field data from 116 survey sites were used to evaluate the accuracy of the interpretation of planting structures.The results show that the Kappa coefficient obtained by this method is 0.82,and the interpretation accuracy is very high.(2)Based on the traditional SEBAL remote sensing evapotranspiration model,combined with the characteristics of southern China,an optimization method using polynomial functions to fit the wet and dry edges was proposed.Improved sensible heat flux calculation method in SEBAL model.The analysis results show that the method is more stable than the traditional wet and dry edge fitting method,and the model calculation result is more accurate.It is of great significance to expand the regional applicability of the SEBAL model.(3)For the "transient" problem of remote sensing satellite imagery,comprehensive analysis of the commonly used method of time scale expansion combined with the basic data conditions of the observation irrigation area.A sinusoidal function method is proposed for time scale expansion.Comparing the remote sensing inversion results with the measured data of the lysimeter.The results show that the RMSE of daily evapotranspiration from remote sensing inversion is smaller and the precision of time scale expansion is higher.(4)The research formed a set of irrigation water use efficiency estimation method based on remote sensing technology adapted to southern China.Comparing its calculation results with traditional monitoring methods,the results are credible.This method has a wide application prospect,especially for large-scale irrigation areas with poor monitoring conditions and inadequate measurement facilities.