CN118395867A - A method for field-scale irrigation and drainage simulation in rice fields - Google Patents

Abstract

The invention discloses a method suitable for rice field scale irrigation and drainage simulation, and belongs to the technical field of agricultural irrigation model application. The method of the invention comprises the following steps: establishing a relation formula of the water content of the soil of the cultivated layer and the water level of the soil of the cultivated layer through field actual measurement; acquiring field irrigation test actual measurement data and corresponding irrigation mode index data, taking the actual measurement data as model input data, aiming at the input data, carrying out analog calculation according to the index data, acquiring daily-scale field water quantity change data, training the model according to the actual measurement field water level change data by the water quantity change data, and generating a rice field irrigation and drainage model; and obtaining target data, inputting the target data into a rice field irrigation and drainage model for operation, obtaining simulation data of the rice field scale irrigation and drainage, and simulating irrigation and drainage according to the simulation data. The invention solves the problem of difficult simulation of the paddy field irrigation and drainage process caused by frequent change of water layers and water-free layers in the field in the dry-wet alternate irrigation of paddy rice in the river network area of the south plain.

Description

A method for simulating irrigation and drainage at inter-field scale in rice fields

Technical Field

The present invention relates to the technical field of agricultural irrigation model application, and more specifically, to a method suitable for rice field scale irrigation and drainage simulation.

Background technique

The main sources of water in rice fields are rainfall, irrigation and groundwater recharge, and the main field consumption is evaporation, field seepage, drainage, etc. Some water elements can be obtained through field experiments, but field experiments are time-consuming and expensive. Using models to simulate the process of field water changes can simulate the changes of various water elements in rice fields under different climatic conditions and different irrigation modes in a short time. It can not only guide the design of field experiments, but also provide references for various field water management issues such as the selection of regional irrigation modes, the formulation of irrigation systems, and the assessment of agricultural water use. However, for the simulation of rice field water balance, there are two main problems. First, the field water level frequently exchanges between the water layer and the water-free layer, which will have a great impact on evaporation and transpiration, seepage, etc. Second, when there is no water layer in the field, the soil moisture content needs to be measured. The calculation of soil moisture content is relatively complex and has a high randomness. It is not convenient and accurate without water level observation; third, the water volume of rice fields changes frequently, the change range is large, and there are many water elements involved. The conversion relationship between the elements is complex and difficult to simulate.

Summary of the invention

In view of the above problems, the present invention proposes a method suitable for rice field scale irrigation and drainage simulation, comprising:

The relationship formula between the soil moisture content of the rice cultivation layer and the soil water level of the cultivation layer was established through field measurements.

Obtain the measured data of the field irrigation test and the corresponding irrigation mode index data, use the measured data as the model input data, simulate and calculate the input data according to the index data, obtain the field water volume change data on a daily scale, train the model according to the measured field water level change data, and generate a rice field irrigation and drainage model;

Obtain target data, input it into the rice field irrigation and drainage model for calculation, obtain simulation data of rice field-scale irrigation and drainage, and simulate irrigation and drainage based on the simulation data.

Optionally, the experimental measured data include: meteorological data, rainfall data, irrigation data and drainage data.

Optional, meteorological data, rainfall data, irrigation data and drainage data;

The rainfall data and meteorological data are obtained through meteorological stations near the fields;

The irrigation data and drainage data are obtained through field test measurements.

Optional, target data, including: weather, rainfall, and irrigation pattern data.

Optional simulation data, including: daily-scale field water level change data and daily-scale data of water volume elements.

Optional, daily-scale data for water quantity elements, including:

Evapotranspiration of field water, deep infiltration and groundwater recharge.

Optional irrigation modes include: conventional irrigation and water-saving irrigation, and their indicators mainly include: irrigation upper limit, irrigation lower limit and rainwater storage upper limit.

Optionally, evapotranspiration, deep seepage and groundwater recharge can be obtained as follows:

When there is a layer of water on the surface of the field and evaporation is not limited:

The calculation method of evapotranspiration ET _c is as follows:

ET _c =K _cmax ×ET ₀

Where ET ₀ is the reference crop evapotranspiration, K _cmax is the maximum crop coefficient;

The deep seepage volume DP is selected according to the preset data according to the field soil type and field crop type;

The groundwater recharge CR is taken as 0;

When there is no water layer on the surface of the field, evaporation is limited:

The calculation method of evapotranspiration ET _c is as follows:

ET _c =(K _cb +K _e )×ET ₀

Among them, _ETc is the evapotranspiration of rice, _ET0 is the evapotranspiration of the reference crop under standard conditions, _Kcb is the basic crop coefficient, and _Ke is the soil evaporation coefficient.

The calculation method of deep leakage DP is as follows:

Among them, WT is the soil water level in the root layer, H is the soil water level corresponding to the field when the soil moisture content is 1.5, and m is the infiltration constant;

The groundwater recharge CR is taken as 0;

When water stress occurs:

When there is no water layer on the field:

The calculation method of evapotranspiration ET _c is as follows:

ET _c =K _c *K _s *ET ₀

Among them, ET _c is the actual rice evapotranspiration during the period, K _c is the crop coefficient during the period, and K _s is the soil moisture stress coefficient during the period;

The calculation method of deep leakage DP is as follows:

The calculation method of groundwater recharge CR is as follows:

CR=min{(b×(-WT)+n), CR _max }

Where b and n are fitting coefficients, CR _max is the maximum groundwater recharge, and WT is the soil water level in the root layer.

The present invention solves the problem that the field water level frequently exchanges between the aquifer and the water-free layer, which has a great impact on evaporation and transpiration, leakage, etc., and also solves the problem that the groundwater is shallow and the hydraulic connection between soil water and groundwater is close.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a method for simulating irrigation and drainage at inter-field scale in a rice field according to the present invention.

Detailed ways

Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units/elements are marked with the same reference numerals.

Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

In view of the above problems, the present invention proposes a method suitable for simulating irrigation and drainage in rice fields, as shown in FIG1 , comprising:

A method suitable for field-scale irrigation and drainage simulation of rice, comprising:

The relationship formula between the soil moisture content of the rice cultivation layer and the soil water level of the cultivation layer was established through field measurements.

Obtain the measured data of the field irrigation test and the corresponding irrigation mode index data, use the measured data as the model input data, simulate and calculate the input data according to the index data, obtain the field water volume change data on a daily scale, train the model according to the measured field water level change data, and generate a rice field irrigation and drainage model;

Obtain target data, input it into the rice field irrigation and drainage model for calculation, obtain simulation data of rice field-scale irrigation and drainage, and simulate irrigation and drainage based on the simulation data.

The measured data of the experiment include: meteorological data, rainfall data, irrigation data and drainage data.

Meteorological data, rainfall data, irrigation data and drainage data;

The rainfall data and meteorological data are obtained through meteorological stations near the fields;

The irrigation data and drainage data are obtained through field test measurements.

Target data, including: weather, rainfall, and irrigation pattern data.

Simulation data include: daily-scale field water level change data and daily-scale data of water volume elements.

Daily-scale data on water quantity elements, including:

Evapotranspiration of field water, deep infiltration and groundwater recharge.

Optional irrigation modes include: conventional irrigation and water-saving irrigation, and their indicators mainly include: irrigation upper limit, irrigation lower limit and rainwater storage upper limit.

The evapotranspiration, deep seepage and groundwater recharge are obtained as follows:

When there is a layer of water on the surface of the field and evaporation is not limited:

The calculation method of evapotranspiration ET _c is as follows:

ET _c =K _cmax ×ET ₀

Where ET ₀ is the reference crop evapotranspiration, K _cmax is the maximum crop coefficient;

The deep seepage volume DP is selected according to the preset data according to the field soil type and field crop type;

The groundwater recharge CR is taken as 0;

When there is no water layer on the surface of the field, evaporation is limited:

The calculation method of evapotranspiration ET _c is as follows:

ET _c =(K _cb +K _e )×ET ₀

Among them, _ETc is the evapotranspiration of rice, _ET0 is the evapotranspiration of the reference crop under standard conditions, _Kcb is the basic crop coefficient, and _Ke is the soil evaporation coefficient.

The calculation method of deep leakage DP is as follows:

Among them, WT is the soil water level in the root layer, H is the soil water level corresponding to the field when the soil moisture content is 1.5, and m is the infiltration constant;

The groundwater recharge CR is taken as 0;

When water stress occurs:

When there is no water layer on the field:

The calculation method of evapotranspiration ET _c is as follows:

ET _c =K _c *K _s *ET ₀

Among them, ET _c is the actual rice evapotranspiration during the period, K _c is the crop coefficient during the period, and K _s is the soil moisture stress coefficient during the period;

The calculation method of deep leakage DP is as follows:

The calculation method of groundwater recharge CR is as follows:

CR=min{(b×(-WT)+n),CR _max }

Where b and n are fitting coefficients, CR _max is the maximum groundwater recharge, and WT is the soil water level in the root layer.

The relationship formula of position;

The present invention will be further described below in conjunction with embodiments:

Obtain the measured data of field irrigation experiments and the corresponding irrigation mode index data, use the measured meteorological data, rainfall data, irrigation data, drainage data, etc. as the input data of the model, simulate and calculate the field water volume changes on a daily scale based on the water balance principle, train the model based on the measured field water level change data, obtain the best parameter combination, and generate a rice field irrigation and drainage model;

After the model is built, the meteorological, rainfall and irrigation pattern data that need to be simulated are input, and the water level changes in the field on a daily scale are output. If needed, the daily scale data of water elements such as irrigation water volume, drainage volume, evaporation and transpiration, and leakage during the simulation period can also be further calculated.

The relationship formula between the soil moisture content of the rice tillage layer (about 0-20cm) and the soil water level of the tillage layer needs to be obtained through field measurement. The measurement requires the installation of a 30cm water gauge in the field, and the height of the field water level is recorded using the water gauge; a cylindrical PVC pipe is selected with a diameter of about 6cm and a length of 40cm. A cylindrical area 15cm below the field surface is drilled with 5mm diameter seepage holes every 2cm to keep it connected in the soil tillage layer to observe changes in the soil water level; another PVC pipe of the same diameter is selected with a length of 60cm. A cylindrical area 15cm below the pipe wall is drilled with 5mm diameter seepage holes every two centimeters to observe changes in the groundwater level. The field is irrigated from the waterless layer (only the groundwater level reading), and then gradually recedes downward after being irrigated above the field surface. A fitting curve between the soil moisture content of the tillage layer (0-20cm) and the soil water level of the tillage layer is established. The soil moisture content is measured by the drying method.

The measured data include: field rainfall data, irrigation data, drainage data, meteorological data and water quantity element data;

Water quantity element data, including:

Evapotranspiration of field water, deep infiltration and groundwater recharge.

Irrigation modes include: conventional irrigation and water-saving irrigation. Their indicators mainly include: upper limit of irrigation, lower limit of irrigation and upper limit of rainwater storage.

The evapotranspiration, deep seepage and groundwater recharge are obtained as follows:

(1) When there is a water layer on the field surface and evaporation is not limited:

The calculation method of evapotranspiration ET _c is as follows:

ET _c =K _cmax ×ET ₀

Among them, ET ₀ is the reference crop evapotranspiration, which is calculated using the Penman-Monteith formula recommended in FAO-56 (Allen et al., 1998). The calculation of ET ₀ is based on the reference surface defined by FAO, which is a grassland with uniform height, vigorous growth, complete soil coverage, and sufficient water supply, with a height of 0.12m, a surface resistance of 70sm- ¹ , and a reflectivity of 0.23ET _0. The calculation of ET ₀ has nothing to do with the amount of water in the field. It is only related to the meteorological data of the day at the same location and time. The calculation formula is as follows:

Where _Rn is the net radiation of the canopy surface (mm/d), G is the soil heat flux (MJ/m2d), T is the daily average temperature (℃), _μ2 is the wind speed at a height of 2m (m/s), _ea is the saturated water vapor pressure (kPa), e _s is the actual water vapor pressure (kPa), Δ is the slope of the water vapor pressure curve (kPa/℃), and γ is the hygrometer constant (kPa/℃). These parameters can be calculated from meteorological observation data and geographic information. The data that need to be observed include the daily maximum temperature, daily minimum temperature, wind speed, relative humidity, sunshine duration, latitude and altitude of the test area, etc.

Parameter calculation:

(1) Atmospheric pressure (P)

Atmospheric pressure P is the pressure exerted by the weight of the earth's atmosphere. It is related to the altitude, but the effect is relatively small. In the calculation program, the average value of one place is generally used to fully meet the accuracy requirements. For the standard atmosphere, assuming the temperature is 20℃, P can be calculated using the simplified ideal air law:

(2) Latent heat of vaporization (λ)

The latent heat of vaporization A represents the energy required to convert a unit mass of water from liquid to water vapor under constant pressure and temperature conditions. As a function of temperature, the value of the latent heat of vaporization changes with temperature, and high temperatures require less energy than low temperatures. Since λ changes slightly with temperature within the normal temperature range, only a single value is used in the simplification of the Penman-Monteith formula, namely λ＝2.45MJ/kg, which is equivalent to the latent heat when the air temperature is about 20℃.

(3) Hygrometer constant (γ)

The hygrometer constant γ is expressed by the formula:

Where: γ is the hygrometer constant (kPa/℃); P is the atmospheric pressure (kPa); ε is the ratio of the molecular weight of water vapor to dry air = 0.622; λ is the latent heat of vaporization. 2.45 (MJ/kg); _cp is the specific heat at constant pressure (MJ/kg·℃).

(4) Average temperature during the period

For the normalized case, the mean temperature over a 24-hour period is defined as the average of the daily maximum temperature (Tmax) and the daily minimum temperature (Tmin), rather than as the average of the hourly temperature observations.

(5) Average saturated vapor pressure (es)

When the saturated water vapor pressure is correlated with the air temperature, the saturated water vapor pressure can be calculated using the air temperature. The relationship expression is:

Where: e ⁰ (T) is the saturated water vapor pressure at air temperature T (kPa); T is the air temperature (℃).

Due to the nonlinearity of the above equation, the average saturated water vapor pressure per decade or month is calculated by the average of the water vapor pressures at the corresponding daily average maximum and minimum temperatures during that period:

(6) Slope of the curve of saturated water vapor pressure and temperature (Δ)

When calculating the water demand, the slope Δ of the saturated water vapor pressure versus temperature curve is required. The slope of the curve at different temperatures is given by the following formula:

(7) Actual water vapor pressure (ea):

Where: RH _mean is the average relative humidity during the period.

(8) Net radiation (Rn)

Net radiation (Rn) is the difference between the net shortwave radiation received (Rns) and the net longwave radiation lost (Rnl):

_Rn ＝ _Rns - _Rnl

in:

_Rns ＝(1-α) _RS

R _so =( _as + _bs ) _Ra

Where: _Ra is the total solar radiation of the blue sky (MJ/m2·d); _Gsc is the solar constant, which is 0.0820min-1; _dr is the reciprocal of the relative distance between the sun and the earth; is the geographic latitude, δ is the magnetic declination of the sun; _RS is the solar or shortwave radiation (MJ/m2·d); _ωs is the solar hour angle; n is the actual sunshine hours; N is the maximum astronomical sunshine hours; _as is the regression constant, which represents the part of the outer space radiation that reaches the earth's surface on a cloudy day; _as + _bs represents the part of the outer space radiation that reaches the earth's surface on a clear and cloudless day; _Rso is the clear sky solar radiation; α is the reflectivity or canopy reflectance.

(9) Soil heat flux (G)

Since the soil heat flux is smaller compared to Rn, especially when the surface is covered by vegetation, when the calculation time step is 24 hours or longer, the soil temperature follows the idea of venting temperature conduction:

Where: G is the soil heat flux, _cs is the soil heat capacity, _Ti is the air-space graph at time i, _Ti-1 is the air-space graph at time i-1; Δt is the time interval length; Δz is the effective soil depth.

(10) Wind speed

Wind speeds measured at different heights above the soil surface are different. Surface friction tends to slow down the wind passing over the surface. Wind speeds are lowest at the surface and increase with height. For this reason, anemometers are placed at a standard height, such as 10m in meteorology and 2m or 3m in agrometeorology. For water demand calculations, wind speeds are required to be measured at a height of 2m above the surface. In order to adjust wind speed values measured by instruments at heights other than the standard height, measurements on mowed grass surfaces can be recalculated using logarithmic wind speed profiles.

In the formula: _u2 is the wind speed at 2m above the ground, _uz is the wind speed measured at zm above the ground, and z is the measurement height above the ground.

For the maximum crop coefficient, _Kcmax can be calculated using the following formula:

Wherein μ2 is the wind speed at a height of 2m (m/s), _RHmin is the minimum relative humidity (%), h is the crop plant height (mm), and _Kcb is the basic crop coefficient, which varies with the growth period of the crop. FAO gives the basic crop coefficient values under standard conditions for the initial growth period, middle growth period and late growth period of rice as follows: _{Kcbini (recommended)} = 1.0, _{Kcbmid (recommended)} = 1.15, and _{Kcbend (recommended)} = 0.7.

The deep seepage volume DP is selected according to the preset data according to the field soil type and field crop type;

The groundwater recharge CR is taken as 0;

(2) When there is no water layer on the field surface, evaporation is limited:

The calculation method of evapotranspiration ET _c is as follows:

ET _c =(K _cb +K _e )×ET ₀

Where _ETc is the evapotranspiration of rice, _ET0 is the evapotranspiration of the reference crop under standard conditions, _Kcb is the basic crop coefficient, and _Ke is the soil evaporation coefficient.

Under non-standard conditions (i.e. the minimum relative humidity is not 45%, the wind speed is not 2m/s), _Kcb needs to be corrected:

Where _μ2 is the wind speed at a height of 2 m (m/s), _RHmin is the daily minimum relative humidity (%), and h is the height of the rice plant (m).

Ke is used to describe soil evaporation, and the calculation formula is as follows:

Where De,i-1 is the accumulated soil evaporation from rainfall or irrigation day i to the previous calculation day (mm); REW is the soil evaporation during the atmospheric evaporation control stage (mm); TEW is the total evaporation after rainfall or irrigation (mm). FAO has given corresponding reference values for different soil texture types.

The calculation method of deep leakage DP is as follows:

Where WT is the soil water level in the root layer, H is the soil water content corresponding to the field, and m is the leakage constant.

The groundwater recharge CR is taken as 0;

(3) When water stress occurs:

When there is no water layer on the field:

The calculation method of evapotranspiration ETc is as follows:

ET _c =K _c *K _s *ET ₀

Where ETc is the actual rice evapotranspiration during the period, _Kc is the crop coefficient during the period, and _Ks is the soil moisture stress coefficient during the period.

The calculation formula of Ks is as follows:

Where TAW is the total available water in the root layer (mm2); Dr is the water consumption in the root layer (mm2); and p is the ratio of the available water absorbed by the crop from the root layer to the total available water TAW when it is not subjected to water stress.

The calculation method of deep leakage DP is as follows:

The calculation method of groundwater recharge CR is as follows:

CR=min{(b×(-WT)+n),CR _max }

Where b and n are fitting coefficients, CRmax is the maximum groundwater recharge, and WT is the soil water level in the root layer.

rainfall data, irrigation data, drainage data, and meteorological data;

The rainfall data and meteorological data are obtained through meteorological stations near the fields;

Irrigation and drainage data are obtained through field test measurements.

The present invention solves the problem that the field water level frequently exchanges between the aquifer and the water-free layer, which has a great impact on evaporation and transpiration, leakage, etc., and also solves the problem that the groundwater is shallow and the hydraulic connection between soil water and groundwater is close.

Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of complete hardware embodiments, complete software embodiments, or embodiments in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The scheme in the embodiments of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal translation scripting language JavaScript, etc.

The present application is described with reference to the flowchart and/or block diagram of the method, device (system) and computer program product according to the embodiment of the present application. It should be understood that each process and/or box in the flowchart and/or block diagram, and the combination of the process and/or box in the flowchart and/or block diagram can be realized by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for realizing the function specified in one process or multiple processes in the flowchart and/or one box or multiple boxes in the block diagram.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device that implements the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and/or one or more boxes in the block diagram.

Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims (8)

1. A method for simulating irrigation and drainage in rice fields, the method comprising: The relationship formula between the soil moisture content of the rice cultivation layer and the soil water level of the cultivation layer was established through field measurements. Obtain the measured data of the field irrigation test and the corresponding irrigation mode index data, use the measured data as the model input data, simulate and calculate the input data according to the index data, obtain the field water volume change data on a daily scale, train the model according to the measured field water level change data, and generate a rice field irrigation and drainage model; Obtain target data, input it into the rice field irrigation and drainage model for calculation, obtain simulation data of rice field-scale irrigation and drainage, and simulate irrigation and drainage based on the simulation data. 2. According to the method of claim 1, the experimental measured data includes: meteorological data, rainfall data, irrigation data and drainage data. 3. The method according to claim 2, wherein the meteorological data, rainfall data, irrigation data and drainage data; The rainfall data and meteorological data are obtained through meteorological stations near the fields; The irrigation data and drainage data are obtained through field test measurements. 4. The method according to claim 1, wherein the target data comprises: weather, rainfall, and irrigation pattern data. 5. According to the method of claim 1, the simulation data includes: daily-scale water level change data in the field and daily-scale data of water quantity elements. 6. The method according to claim 5, wherein the daily scale data of the water quantity element comprises: Evapotranspiration of field water, deep infiltration and groundwater recharge. 7. The method according to claim 1, wherein the irrigation modes include conventional irrigation and water-saving irrigation, and their indicators mainly include an irrigation upper limit, an irrigation lower limit, and a rain storage upper limit. 8. The method according to claim 6, wherein the evapotranspiration, deep seepage and groundwater recharge are obtained as follows: When there is a layer of water on the surface of the field and evaporation is not limited: The calculation method of evapotranspiration ET _c is as follows: ET _c =K _cmax ×ET ₀ Where ET ₀ is the reference crop evapotranspiration, K _cmax is the maximum crop coefficient; The deep seepage volume DP is selected according to the preset data according to the field soil type and field crop type; The groundwater recharge CR is taken as 0; When there is no water layer on the surface of the field, evaporation is limited: The calculation method of evapotranspiration ET _c is as follows: ET _c =(K _cb +K _e )×ET ₀ Among them, _ETc is the evapotranspiration of rice, _ET0 is the evapotranspiration of the reference crop under standard conditions, _Kcb is the basic crop coefficient, and _Ke is the soil evaporation coefficient. The calculation method of deep leakage DP is as follows: Among them, WT is the soil water level in the root layer, H is the soil water level corresponding to the field when the soil moisture content is 1.5, and m is the infiltration constant; The groundwater recharge CR is taken as 0; When water stress occurs: When there is no water layer on the field: The calculation method of evapotranspiration ET _c is as follows: ET _c =K _c *K _s *ET ₀ Among them, ET _c is the actual rice evapotranspiration during the period, K _c is the crop coefficient during the period, and K _s is the soil moisture stress coefficient during the period; The calculation method of deep leakage DP is as follows: The calculation method of groundwater recharge CR is as follows: CR=min{(b×(-WT)+n), CR _max } Where b and n are fitting coefficients, CR _max is the maximum groundwater recharge, and WT is the soil water level in the root layer.