Research On Optimization Method Of Irrigation Schedule For Paddy Field In Southern Large-scale Irrigation Districts Based On Short-term Weather Forecast

The construction and reconstruction of large and medium irrigation districts play an important role in agricultural production.The projects can ensure the supply of food and major agricultural products,promote the increase of agricultural production,farmer's income and rural development.They encourage comprehensive,harmonious and sustainable development of economic social and accelerate the process of agricultural modernization Based on short-term precipitation forecast,water requirement prediction and water balance equation,a research on optimization of irrigation schedule for paddy in southern large-scale irrigation districts is conducted in this paper.The method was applied to Hongjin irrigation district in Huai'an,Jiangsu.It has great significance to improve efficiency of agricultural irrigation,develop precision irrigation and optimize regional water resources distributionThis paper summarized research progress on real-time optimization of irrigation schedule,prediction of crop water requirements and development of irrigation decision-support system in irrigation districts.Specific research is carried out in combination with actual situation of irrigation in southern large irrigation districts.The traditional method determines irrigation schedule during the rice growth period by precipitation and evapotranspiration of the design representative year.But the actual precipitation in the year is rarely considered in traditional method.Based on short-term weather forecast and the BP neural network of rice water requirement prediction,the optimization of irrigation schedule is carried out in this paper.Making full use of short-term precipitation by the meteorological department,the optimized method adjusts the daily irrigation water of each irrigation group during the irrigation duration.It improves the situation that once the traditional irrigation schedule is formulated,the daily irrigation quotas of different irrigation groups or the same rotation irrigation group will not be adjusted in the irrigation duration of the implementation process.And it also provides a new way for real-time optimization of rice in southern large irrigation districts.Taking a 7-days irrigation time in mid-July in 2018 as an example,the net irrigation water derived from the optimized method was 1.54 million cubic meters less than that derived from the traditional method in Hongjin irrigation district,accounting for 15.8%of the total.It can improve rainwater utilization,facilitate rational allocation of irrigation water and optimize regional water resources.A 4-13-1 BP neural network model is established by MATLAB software to predict the daily water requirement of rice.The average temperature,relative humidity,sunshine time,and net solar radiation are used as input factors,and the daily reference crop water requirement is used as the output factor in this model.The network was trained and adjusted with meteorological input factors and reference crop water requirement calculated by Penman-Monteith from 2010-2016.It finally reached the accuracy to form a BP neural network model for predicting crop water requirement.According to the weather forecast information,it was applied to predict the daily rice water requirement every 7 days during rice growth period in Hongjin irrigation district in 2018 by using 7 days as the forecast time series.The establishment of this model can simplify the complicated process that should be used to calculate by Penman-Monteith,and provide support for real-time optimization of irrigation schedule.With Visual Basic6.0 as the programming platform,a real-time optimization module for rice irrigation schedule in Hongjin irrigation district was developed.It mainly includes three major sections:field water layer(moisture)regulation indicators,short-term weather forecast and crop water requirement predicting,real-time optimized calculation of irrigation schedule.By importing data of the meteorological forecast and the rice water requirement for 7days,the program can use the prepared water balance equation to calculate the daily water surface depth and irrigation water,and generate an irrigation plan schedule.The module development can enrich the existing irrigation decision-support system in Hongjin irrigation district,and provide a reference for the scientific management for irrigation district operation.