| Hongjin irrigation district of Huaian city,Jiangsu Province which founded in 1958 is a national large-scale plain gravity irrigation area.It is located in east of Hongze Lake,west of Baima Lake and Baoying Lake,south of Caoze River,north of Huaihe-Changjiang waterway.Hongjin irrigation district is between east trail 118°28’ to 119°22’ and north latitude 32°02’ to 33° 13’.It’s across Hongze and Jinhu counties(districts),with 491.6 km2 of national land area,420 thousand mu of arable land,340 thousand mu of designed irrigation and 314 thousand mu of effective irrigation area.As a result of continuous rebuilding and water-saving transformation for many years,the basic water conservancy condition is complete.However,irrigation management and services of Hongjin irrigation district are still in the traditional way,and the scientific management capacity of irrigation and water distribution needs to be further strengthened.Based on the rice water-saving irrigation technology(shallow-wet irrigation),this paper conducted a research on the real-time optimization of irrigation methods in Hongjin irrigation district.Paddies were divided into two types:water layer and water-free layer.Simulating and predicting water or soil moisture daily.Based on the principle of water balance,a real-time irrigation forecast model for paddy fields in Hongjin irrigation district was established and real-time correction was made during the irrigation forecast process.This article took the rice growth period from July 2 to July 7(tillering stage),July 21 to July 29(jointing,booting stage)as an example.According to the short-term meteorological forecast,the principle of water balance was used to predict and calculate the depth of surface water layer or the daily change of soil moisture and forecasted each irrigation dates and corresponding irrigation volume.Using real-time irrigation forecast model to guide irrigation can enable crops to receive irrigation in appropriate time and degree.This will be beneficial to the sustainable use of agricultural water resources in Hongjin irrigation district.According to the constraints of irrigation and water distribution in irrigation areas,under the irrigation water limit plan,a water distribution plan of simulation model based on irrigation forecast was constructed.According to three irrigation models of rotational irrigation by the number of principal canals,rotational irrigaiton by the segmented principal canal and continuous irrigation,the irrigation water distribution plan was simulated.The goal is to maximize the area of gravity irrigation,determining the water diversion flow of Hongjin Canal Head in each irrigation,gate opening height,water level of trunk and branch or straight lateral canals.A constant non-uniform irrigation simulation model of main canals was established under different irrigation operation modes.Calculating the water level along the main channel,opening height of the first gate of each branch or straight lateral canal and water level under the gates,the area of gravity irrigation was achieved as a result.On this basis,through the comparison of alternatives,the optimal channel irrigation system and the corresponding water distribution plan was found,which could provide auxiliary decision-making support for irrigation water distribution in Hongjin irrigation district and optimize the allocation of water resources. |
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