A dynamic control method for farmland-irrigation area-watershed drainage system in black soil area

Abstract

The present invention relates to the field of agricultural water conservancy technology, and discloses a method for dynamically regulating the water conservation and drainage system of a farmland-irrigation area-watershed in a black soil region. The method comprises the following steps: S1: collecting basic data, including meteorological and hydrological data, irrigation data, environmental data, and soil monitoring data; S2: using the naive Bayesian method to analyze the water conservation thresholds and soil fitting parameters of four types of soil; S3: calculating the functional relationship between water demand and yield; the soil water conservation thresholds are used as input into the management file of a DSSAT model, and the DSSAT model is used at the farmland scale to simulate the growth of the four types of soil under the conditions of planting multiple crops; S4: constructing a dynamic regulation framework for the soil-farmland-irrigation area-watershed water conservation and drainage system. The method quantifies the minimum water conservation thresholds and effective water thresholds of different soil types in black soil regions, estimates the crop water consumption based on the crop growth process, and obtains a response relationship function between soil water, crop water demand, and irrigation water.

Description

Technical Field

[0001] The present invention relates to the field of agricultural water conservancy technology, and in particular to a dynamic control method for a farmland-irrigation area-watershed drainage system in a black soil region. Background Art

[0002] With global climate change and the growing demand for agricultural production, the efficient use and management of water resources has become a key challenge for the sustainable development of modern agriculture. This is particularly true in black soil regions, where soil fertility is high and cultivation has a long history. However, due to inappropriate agricultural practices and frequent extreme weather events, the region faces water shortages, soil degradation, and ecological deterioration. Therefore, achieving efficient use and management of agricultural water resources in black soil regions to ensure green and sustainable agricultural development has become a focus of both academia and industry.

[0003] Traditional agricultural water management methods usually rely on static water resource allocation strategies, lack consideration of multi-scale dynamic systems, cannot accurately quantify the water retention and drainage thresholds of different soil types in black soil areas, do not combine management with the water demand during crop growth, and cannot adapt to changes in complex environments such as farmland, irrigation areas, and watersheds. Summary of the Invention

[0004] In order to overcome or alleviate one or more of the above technical problems, the purpose of the present invention is to provide a method for dynamic regulation of farmland-irrigation area-watershed water conservation and drainage system in black soil areas. Through quantitative analysis and simulation technology, the minimum water conservation threshold and effective water threshold of different soil types are accurately quantified, combined with the water demand assessment of the crop growth process; the impact of floods, droughts and waterlogging on the system is studied, and water resource management strategies under these natural disaster conditions are revealed. By introducing the DSSAT model, the model can simulate and evaluate the growth and yield performance of rice, corn and soybeans in various irrigation scenarios under different soil types, thereby providing data support and theoretical basis for optimizing irrigation strategies. While exploring green and efficient agricultural water resource efficient utilization and management technologies, a green and sustainable agricultural development ecological model is realized.

[0005] The present invention provides the following technical solutions:

[0006] A method for dynamically controlling a farmland-irrigation area-watershed drainage system in a black soil region comprises the following steps:

[0007] S1: Basic data collection, including meteorological and hydrological data, irrigation data, environmental data, and soil monitoring data. The soil monitoring data is based on the main soil types in the study area, which are divided into four types: meadow soil, white soil, black soil, and dark brown soil. Each black soil type is monitored at a fixed point, and the soil moisture content and porosity-related soil properties of the four soil types are monitored over a long period of time.

[0008] S2: Naive Bayes method was used to analyze the water retention threshold and soil fitting parameters of four soils;

[0009] S3: Based on the soil water retention threshold and soil fitting parameters obtained in step S2, the functional relationship between water requirement and yield is calculated; the soil water retention threshold is used as input and entered into the management file of the DSSAT model. The DSSAT model is used at the farmland scale to simulate the growth of four soils under the condition of planting multiple crops; different irrigation scenarios are set for the DSSAT model; the yield of multiple different crops planted in the four soils under different irrigation scenarios is obtained; the naive Bayes method is used to fit the functional relationship between water requirement and yield. The yield per unit area of ​​each crop is calculated as follows:

[0010]

[0011] Where i is the soil type index, i=1...4; c is the crop type, c=1...3; YA ic is the yield per unit area of ​​crop c in soil type i, kg / hm 2 IQ ic is the irrigation water quantity for crop c of soil type i, i.e., the decision variable, m 3 / hm 2 ;a ic 、b ic and d ic is the fitting parameter of soil type i and crop c;

[0012] S4: Construct a dynamic control framework for the water conservation and drainage system of soil-farmland-irrigation area-watershed. The dynamic control framework synergistically considers the water transmission time, water transmission and distribution energy consumption, and water transmission loss process, establishes a drainage feedback system that considers soil water retention thresholds, farmland water demand feedback, and watershed water supply information, and constructs a drainage dynamic control system that automatically adjusts according to the drainage feedback system.

[0013] According to some embodiments, step S3: Based on the soil water retention threshold and soil fitting parameters obtained in step S2, the functional relationship between total water demand and total yield can also be calculated, and the specific steps are as follows:

[0014] S31: Prepare the data required for the water demand and yield function, including: the 12 sets of yield-water correlation coefficients output in step S2; data related to the irrigation area's water supply and drainage canal system, including canal length, width, depth, design flow, and loss coefficient; sluice gate data, including sluice gate power consumption, flow rate, and gate parameters; soil and crop properties of the farmland in the irrigation area; and meteorological data related to rainfall, floods, droughts, and waterlogging.

[0015] S32: Irrigation area scale calculation: First, select the appropriate yield-water correlation coefficient based on the soil and crop properties of the input irrigation area farmland, and calculate the maximum total yield of each crop:

[0016]

[0017] Where A ic is the area of ​​soil type i and crop c, hm 2 ;

[0018] S33: Construct water delivery objective function:

[0019] minWP=WT·CP (3)

[0020] WT=Σq ur t ur +∑IQ ic ·A ic (4)

[0021] Where WP is the total electrical energy loss of the canal water distribution system, kWh; WT is the total water loss of the canal water distribution system, m 3 CP is the electrical energy consumed by the canal system to transport water per cubic meter, kWh / m 3 ; u is the number of channel sections; r is the water distribution period; q ur is the water distribution loss flow rate of channel section u during period r, m 3 / s;t ur is the water distribution time for channel section u during period r, in s;

[0022]

[0023] Where, β u is the reduction coefficient of channel bed leakage after anti-seepage measures are taken in channel section u; u is the groundwater support correction coefficient for channel section u; X u is the soil permeability coefficient of channel section u; m u is the soil permeability index of channel section u; l u is the length of channel segment u;

[0024] minTI=(st j +t j ) (6)

[0025] Where j is the field index; TI is the total time of water distribution in the canal system, s; st j is the time when water distribution starts in field j, s; t j is the duration of water distribution to field j, s;

[0026] S34: Water transmission and distribution constraints, including:

[0027] Constraints on channel water delivery capacity: The water delivery flow of channels at all levels shall not exceed the design flow;

[0028]

[0029] Where DQ is the design flow rate of the channel, m 3 / s;

[0030] Irrigation time constraints: water distribution start and end times should be within the maximum allowable canal water distribution cycle;

[0031] 0≤st j ≤st j +t j ≤3600T (8)

[0032] Where T is the maximum allowable canal water distribution cycle, h;

[0033] Channel water balance constraints:

[0034]

[0035] Where, X ur is a 0-1 variable, X ur =1 means water distribution starts; X ur =0 means no water distribution;

[0036] S35: Construct drainage targets:

[0037] WD=(δ·R+H+G-∑p ur t ur -∑IQ ic ·A ic )·Z (10)

[0038] Where WD is the total displacement, m 3 ; δ is the rainfall runoff coefficient; R is the total rainfall, m 3 ; H is the flood water volume, m 3 ; G is the total water supply, m 3 ; Z is a drainage 0-1 variable, Z = 1 means drainage starts; Z = 0 means no drainage; p ur is the drainage flow rate m 3 / s;

[0039] S36: Drainage constraints, including:

[0040] When rainfall is greater than crop water demand, and flood damage and water allocation are greater than the sum of crop water demand and loss water consumption, the drainage system begins to drain water;

[0041]

[0042] During irrigation, when the drainage is turned on, the water distribution system is automatically closed, and when the water distribution starts, the drainage is automatically closed; when not irrigating, both the water distribution and drainage are closed;

[0043]

[0044] S37: Output: irrigation water plan for each canal system and field, total amount of irrigation water required, optimal crop yield and water ratio.

[0045] According to some embodiments, step S4 comprises the following steps:

[0046] S41: Prepare the data required for the dynamic control framework of the soil-farmland-irrigation area-watershed water conservation and drainage system, including: the total amount of irrigation water required according to the output of step S3; meteorological data related to rainfall, floods, droughts, and waterlogging; the total agricultural runoff supplied to the irrigation area; and the amount of surface water and groundwater.

[0047] S42: Basin-scale calculation: The input surface water and groundwater are used as the available water volume of the basin, and the overall division is made according to the total amount of irrigation water required output by S3 and the water allocation plan of each irrigation area:

[0048] When the available water volume in the basin is greater than the total water demand in the irrigation area, the operation mode of the constructed dynamic control framework platform for water conservation and drainage system is S1→S2→S3→S4;

[0049] When the available water volume in the basin is less than the total water demand in the irrigation area, the operation mode of the constructed dynamic control framework platform for water conservation and drainage system is S4→S3→S2→S1;

[0050] When the amount of water from floods, droughts, and waterlogging is greater than the threshold set by the dynamic control framework of the soil-farmland-irrigation area-watershed water conservation and drainage system, the dynamic control framework will adjust the available water volume in the watershed based on the feedback of flood, drought, and waterlogging information, and then return to the S3 module.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The present invention quantifies the minimum water retention threshold and effective water threshold of different soil types in black soil areas, estimates the crop water consumption based on the crop growth process, and obtains the response relationship function between soil water-crop water demand-irrigation water; it helps to improve the water resource utilization efficiency of agricultural production, provide flexible response plans in the face of climate change and extreme weather events, and promote the green and sustainable development of agriculture.

[0053] (2) By constructing a multi-scale irrigation and drainage system, coordinating the water delivery time, water delivery and distribution energy consumption, and water delivery loss process, a drainage feedback system that takes into account the soil water retention threshold, farmland water demand feedback, and basin water supply information is established, and a drainage dynamic control system that automatically adjusts according to the drainage feedback information is designed.

[0054] (3) Reveal the impact mechanism of floods, droughts and waterlogging on dynamic systems, and characterize the water conservation and drainage potential of dynamic regulation systems. DETAILED DESCRIPTION

[0055] The present invention is described in detail below with reference to the embodiments. However, it should be understood that the embodiments are merely illustrative of the present invention and do not limit the scope of protection of the present invention. All reasonable variations and combinations within the scope of the present invention fall within the scope of protection of the present invention.

[0056] The present invention provides a method for dynamically controlling a farmland-irrigation area-watershed drainage system in a black soil region, comprising the following steps:

[0057] S1: Basic data collection, including meteorological and hydrological data, including effective rainfall, irrigation water utilization coefficient, and crop water requirement; irrigation data, including irrigated area and fertilizer, pesticide, and plastic film usage per unit area, and head loss along the irrigation system; environmental data, including surface water availability, groundwater availability, runoff, aquifer permeability, and evapotranspiration; and soil monitoring data, including 0.1-1m soil temperature, soil moisture content, and collected snowmelt water data. Based on the main soil types in the study area, the black soil is divided into four types: meadow soil, white slurry soil, black soil, and dark brown soil. Fixed-point monitoring is conducted for each black soil type, monitoring soil moisture content and porosity-related soil properties over a long period of time for each of the four soil types.

[0058] S2: The Naive Bayes method is used to analyze the water retention thresholds of the four soil types, so that the water retention thresholds of the soils can be output to the farmland scale.

[0059] S3: Soil water retention threshold is used as input to the DSSAT model management file. For example, the DSSAT model is used at the farmland scale to simulate the growth of four soil types under the conditions of planting rice, corn, and soybeans. The DSSAT model is set to different irrigation scenarios. The irrigation scenario for rice is 0-4500m 3 / hm 2 , each scenario increases by 50m 3 / hm 2 There are 90 scenarios for irrigation water volume; the irrigation scenarios for corn and soybeans are 0-2500m 3 / hm 2 , each scenario increases by 25m3 / hm 2 The irrigation water volume was calculated for 100 scenarios. The yields of three different crops, rice, corn, and soybeans, grown on four different soil types under different irrigation scenarios were obtained. The Naive Bayes method was used to fit the functional relationship between water volume and yield. The yield per unit area of ​​each crop was calculated as follows:

[0060]

[0061] Where i is the soil type index, i=1...4; c is the crop type, c=1...3; YA ic is the yield per unit area of ​​crop c in soil type i, kg / hm 2 IQ ic is the irrigation water quantity for crop c of soil type i, i.e., the decision variable, m 3 / hm 2 ;a ic 、b ic and d ic are the fitting parameters for soil type i and crop c.

[0062] S4: Construct a dynamic control framework for the water conservation and drainage system of soil-farmland-irrigation area-watershed. This dynamic control framework synergistically considers the water transmission time, water transmission and distribution energy consumption, and water transmission loss process, establishes a drainage feedback system that considers soil water retention thresholds, farmland water demand feedback, and watershed water supply information, and constructs a drainage dynamic control system that automatically adjusts according to the drainage feedback system.

[0063] The present invention will be further described below in the form of examples.

[0064] Example 1

[0065] S1, collect basic data. The basic data are as follows:

[0066] Soil types: meadow soil, white soil, black soil and dark brown soil;

[0067] Crops grown: rice, corn, soybeans;

[0068] Fixed-point monitoring equipment: Meadow soil-rice, meadow soil-corn, meadow soil-soybean; white soil-rice, white soil-corn, white soil-soybean; black soil-rice, black soil-corn, black soil-soybean; dark brown soil-rice, dark brown soil-corn, dark brown soil-soybean. A total of 12 fixed-point collection equipment monitors soil moisture content and porosity.

[0069] S2: Based on the collected basic data, calculate the corresponding soil water retention threshold under different scenarios.

[0070] Calculation and output: The long-term series data monitored by S1 are used for soil-scale calculation to obtain soil water retention thresholds for different scenarios monitored by 12 fixed-point equipment.

[0071] The details are as follows:

[0072] Data preparation: Based on the output of 12 scenarios’ water retention thresholds, meteorological remote sensing data, soil type data, and crop management data, the lowest soil moisture content is set as the water retention threshold for the medium scenario.

[0073] Scenario settings: 90 irrigation schemes for meadow soil-rice, 100 irrigation schemes for meadow soil-corn, and 100 irrigation schemes for meadow soil-soybean; 90 irrigation schemes for white soil-rice, 100 irrigation schemes for white soil-corn, and 100 irrigation schemes for white soil-soybean; 90 irrigation schemes for black soil-rice, 100 irrigation schemes for black soil-corn, and 100 irrigation schemes for black soil-soybean; 90 irrigation schemes for dark brown soil-rice, 100 irrigation schemes for dark brown soil-corn, and 100 irrigation schemes for dark brown soil-soybean. A total of 1,160 scenarios.

[0074] The Farm-Scale Smart Platform Calculation Module calculates input data through the platform, generating 1,160 meteorological, soil, and management files. The DSSAT program is called to generate yield and water data for 1,160 scenarios. This data is then fed into a Naive Bayesian program to fit yield and water function coefficients for 12 scenarios generated using four soil types and three crops.

[0075] Output: a ic 、b ic and d ic are the fitting parameters of soil type i and crop c, with a total of 12 groups.

[0076] S3: Calculating the functional relationship between total water demand and total yield based on the soil water retention threshold and soil fitting parameters obtained in step S2;

[0077] S31: Prepare the data required for the water demand and yield function, including: 12 sets of yield and water volume correlation coefficients output in step S2; canal system-related data for water supply and drainage in the irrigation area, including channel length, channel width, channel depth, design flow, and loss coefficient; sluice-related data, including sluice power consumption, flow through the sluice, and gate parameters; soil and crop properties of the farmland where the irrigation area is located; and meteorological data related to rainfall, floods, droughts, and waterlogging.

[0078] S32: Irrigation area scale calculation: First, select the appropriate yield-water correlation coefficient based on the soil and crop properties of the input irrigation area farmland, and calculate the maximum total yield of each crop:

[0079]

[0080] Where A ic is the area of ​​soil type i and crop c, hm 2 .

[0081] S33: Construct water delivery objective function:

[0082] minWP=WT·CP (3)

[0083] WT=∑q ur t ur +∑IQ ic ·A ic (4)

[0084] Where WP is the total electrical energy loss of the canal water distribution system, kWh; WT is the total water loss of the canal water distribution system, m 3 CP is the electrical energy consumed by the canal system to transport water per cubic meter, kWh / m 3 ; u is the number of channel sections; r is the water distribution period; q ur is the water distribution loss flow rate of channel section u during period r, m 3 / s;t ur is the water distribution time for channel section u during period r, in s.

[0085]

[0086] Where, β u is the reduction coefficient of channel bed leakage after anti-seepage measures are taken in channel section u; u is the groundwater support correction coefficient for channel section u; X u is the soil permeability coefficient of channel section u; m u is the soil permeability index of channel section u; l u is the length of channel segment u.

[0087] minTI=(st j +t j ) (6)

[0088] Where j is the field index; TI is the total time of water distribution in the canal system, s; st j is the time when water distribution starts in field j, s; t j is the duration of water distribution to field j, s.

[0089] S34: Water distribution constraints:

[0090] (1) Channel water delivery capacity constraints: The water delivery flow of channels at all levels shall not exceed the design flow.

[0091]

[0092] Where DQ is the design flow rate of the channel, m 3 / s.

[0093] (2) Irrigation time constraints: The start and end times of water distribution should be within the maximum allowable canal water distribution cycle.

[0094] 0≤st j ≤st j +t j ≤3600T (8) Where T is the maximum allowable canal water distribution cycle, h.

[0095] (3) Channel water balance constraints

[0096]

[0097] Where, X ur is a 0-1 variable, X ur =1 means water distribution starts; X ur =0 means no water is provided.

[0098] S35: Construct drainage targets:

[0099] WD=(δ·R+H+G-∑p ur t ur -ΣIQ ic ·A ic )·Z (10)

[0100] Where WD is the total displacement, m 3 ; δ is the rainfall runoff coefficient; R is the total rainfall, m 3 ; H is the flood water volume, m 3 ; G is the total water supply, m 3 ; Z is a drainage 0-1 variable, Z = 1 means drainage starts; Z = 0 means no drainage; p ur is the drainage flow rate m 3 / s.

[0101] S36: Drainage constraints:

[0102] (1) When rainfall is greater than crop water demand, and flood damage and water allocation are greater than the sum of crop water demand and loss water consumption, the drainage system begins to drain water.

[0103]

[0104] (2) During irrigation, when the drainage is turned on, the water distribution system is automatically closed, and when the water distribution starts, the drainage is automatically closed; when not irrigating, both the water distribution and drainage are closed.

[0105]

[0106] S37: Output: irrigation water plan for each canal system and field, total amount of irrigation water required, optimal crop yield and water ratio.

[0107] S4: Construct a dynamic control framework for the soil-farmland-irrigation area-watershed water conservation and drainage system, including the following steps:

[0108] S41: Prepare the data required for the dynamic control framework of the water conservation and drainage system of soil-farmland-irrigation area-watershed, including: the total amount of irrigation water required according to the output of step S3; meteorological data related to rainfall, floods, droughts, and waterlogging; the total agricultural runoff supplied to the irrigation area; and the amount of surface water and groundwater.

[0109] S42: Basin-scale calculation: The input surface water and groundwater are used as the available water volume of the basin, and the overall division is made according to the total amount of irrigation water required output by S3 and the water allocation plan of each irrigation area:

[0110] When the available water volume in the basin is greater than the total water demand in the irrigation area, the operation mode of the constructed dynamic control framework platform for water conservation and drainage system is S1→S2→S3→S4;

[0111] When the available water supply in the basin is less than the total water demand in the irrigation area, the operation mode of the constructed dynamic control framework platform for water conservation and drainage systems is S4→S3→S2→S1.

[0112] When the amount of water from floods, droughts, and waterlogging is greater than the threshold set by the dynamic control framework of the soil-farmland-irrigation area-watershed water conservation and drainage system, the dynamic control framework will adjust the available water volume in the watershed based on the feedback of flood, drought, and waterlogging information, and then return to the S3 module.

[0113] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of protection of the present invention are within the scope of protection of the present invention. It should be noted that improvements and modifications that can be made by a person skilled in the art without departing from the principles of the present invention are also considered to be within the scope of protection of the present invention.

Claims

1. A method for dynamically controlling the drainage system of farmland, irrigation area and watershed in black soil region, characterized in that: The following steps are included: S1: Basic data collection, including meteorological and hydrological data, irrigation data, environmental data, and soil monitoring data. The soil monitoring data is based on the main soil types in the study area, which are divided into four types: meadow soil, white soil, black soil, and dark brown soil. Each black soil type is monitored at a fixed point, and the soil moisture content and porosity-related soil properties of the four soil types are monitored over a long period of time. S2: Based on the collected basic data, the soil water retention thresholds corresponding to different scenarios were calculated; the naive Bayesian method was used to analyze the fitting parameters of the four soils. The soil water retention thresholds were used as input into the management file of the DSSAT model. The DSSAT model was used to simulate the growth of the four soils under the conditions of planting multiple crops at the farmland scale; different irrigation scenarios were set for the DSSAT model; the yields of multiple different crops planted in the four soils under different irrigation scenarios were obtained; the naive Bayesian method was used to fit the functional relationship between water volume and yield. The yield per unit area of ​​each crop was calculated as follows: （1） Where, is the soil type index, ; It is a type of crop, ; Is the soil type crop Yield per unit area, kg / hm 2 ; Is the soil type crop The irrigation water volume is the decision variable, m 3 / hm 2 ; 、 and Is the soil type crop The fitting parameters of S3: Calculate the functional relationship between water demand and yield based on the soil water retention threshold and soil fitting parameters obtained in step S2; S4: Construct a dynamic control framework for the water conservation and drainage system of soil-farmland-irrigation area-watershed. The dynamic control framework synergistically considers the water transmission time, water transmission and distribution energy consumption, and water transmission loss process, establishes a drainage feedback system that considers soil water retention thresholds, farmland water demand feedback, and watershed water supply information, and constructs a drainage dynamic control system that automatically adjusts according to the drainage feedback system.

2. The method for dynamically controlling the drainage system of farmland-irrigation area-watershed in black soil region according to claim 1, characterized in that: Step S3: Calculate the functional relationship between total water demand and total yield based on the soil water retention threshold and soil fitting parameters obtained in step S2. The specific steps are as follows: S31: Prepare the data required for the water demand and yield function, including: the 12 sets of yield-water correlation coefficients output in step S2; data related to the irrigation area's water supply and drainage canal system, including canal length, width, depth, design flow, and loss coefficient; sluice gate data, including sluice gate power consumption, flow rate, and gate parameters; soil and crop properties of the farmland in the irrigation area; and meteorological data related to rainfall, floods, droughts, and waterlogging. S32: Irrigation area scale calculation: First, select the appropriate yield-water correlation coefficient based on the soil and crop properties of the input irrigation area farmland, and calculate the maximum total yield of each crop: （2） Where, Is the soil type crop Planting area, hm 2 ; S33: Construct water delivery objective function: （3） （4） Where, is the total electrical energy lost in canal water distribution, kWh; is the total water loss of the canal system, m 3 ; is the electrical energy consumed by the canal system to transport a single cubic meter of water, kWh / m 3 ; is the number of channel sections; It is the water supply and distribution period; It is a channel section Time Water distribution loss flow, m 3 / s; It is a channel section Time Water distribution time, s; （5） Where, It is a channel section Reduction coefficient of water leakage from the channel bed after anti-seepage measures are taken; It is a channel section Groundwater support correction factor; It is a channel section Channel bed soil permeability coefficient; It is a channel section Channel bed soil permeability index; It is a channel section length; （6） Where, It is the field index; is the total water delivery and distribution time of the canal system, s; It's a field Water distribution start time, s; It's a field water distribution duration, s; S34: Water transmission and distribution constraints, including: Constraints on channel water delivery capacity: The water delivery flow of channels at all levels shall not exceed the design flow; （7） Where, is the design flow rate of the channel, m 3 / s; Irrigation time constraints: water distribution start and end times should be within the maximum allowable canal water distribution cycle; （8） Where, is the maximum permissible canal system water distribution cycle, h; Channel water balance constraints: （9） Where, is a 0-1 variable, =1 means water distribution starts; =0 means no water distribution; S35: Construct drainage targets: （10） Where, is the total displacement, m 3 ; is the rainfall runoff coefficient; is the total rainfall, m 3 ; is the flood water volume, m 3 ; is the total water supply, m 3 ; is a drainage 0-1 variable, =1 means start drainage; =0 means no drainage; is the drainage flow rate m 3 / s; S36: Drainage constraints, including: When rainfall is greater than crop water demand, and flood damage and water allocation are greater than the sum of crop water demand and loss water consumption, the drainage system begins to drain water; （11） During irrigation, when the drainage is turned on, the water distribution system is automatically closed, and when the water distribution starts, the drainage is automatically closed; when not irrigating, both the water distribution and drainage are closed; （12） S37: Output: irrigation water plan for each canal system and field, total amount of irrigation water required, optimal crop yield and water ratio.

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