Study On Rice Water Requirement And Irrigation Forecast Model In Huailian Irrigation District

Large-scale irrigation districts play an important role in my country's agricultural production.How to scientifically allocate regional irrigation water resources has always been a concern of irrigation district managers.Traditional irrigation management often differs from actual crop water requirements according to the representative year method.The basis of scientific irrigation management decision-making lies in the accurate prediction of the crop water demand in the irrigation area.Therefore,it is of great practical significance to study the crop water demand and irrigation forecast models applicable to large irrigation areas for modern water management.In this study,rice was used as the test material,and the experiment was conducted during the main growth period.The daily water requirement of the rice was obtained by weighing,and the canopy temperature of rice and related crops,meteorology,and soil elements were collected simultaneously to construct an estimation model of the daily water requirement of rice.Based on this,an irrigation forecast was made for rice within the bucket canal of the Huailian irrigation area,and the following research results were obtained:(1)Using the daily meteorological data of Dingji Meteorological Station in irrigation area for analysis from June to October 2018,the calculation results of the P-M method ET0 and the Priestley-Taylor method,FAO-24 Radiation method,and Hargreaves have coefficients of determination greater than 0.9.Among them,the determination coefficient of Priestley-Taylor method is 0.97 at the highest and the average absolute error is 1.01mm/d;the determination coefficient of the FAO-24 Radiation method is next,but the average absolute error is the smallest at 0.77mm/d;the Hargreaves method has slightly worse accuracy.The average absolute error is 1.21 mm/d;the Mc cloud formula has the largest deviation among the four calculation methods,and the average absolute error reaches 3.66mm/d.(2)Analysis of the canopy temperature change rule from August 9 to September 22,the absolute value of the canopy temperature difference decreases as the growth period continues,and the canopy temperature difference at the jointing and booting stage is-3?0.5?;Crown temperature difference during heading and flowering period is-2?1.?;crown temperature difference during mature period is-1.5?1.5?.The correlation between ET and Rn and Tc-Ta was high,reaching 0.918 and-0.884,respectively,and the correlation with TC was second,0.706.(3)A daily water demand estimation model for rice was constructed with the parameters of net solar radiation and canopy temperature difference.Logistic equation was used to simulate LAI,and the LAI value obtained by model fitting was used to modify the original model.Verification from 15 days from September 23 to October 7:The determination coefficients of the two models are above 0.85,and the root mean square error and relative error of the revised models are 0.183 mm/d and 5.07%;The relative error is 0.299mm/d,8.26%.The statistical parameters of the modified model are better than the original model,and the model accuracy is better.(4)Using the rice water demand estimation model,an irrigation forecast method based on water balance was established based on the characteristics of the rice field.Through simulation and empirical studies,the irrigation system within the forecast unit was well predicted.