Dynamic coupling simulation method, system, equipment and medium suitable for tetrahydrate conversion and vegetation growth in arid underground water shallow buried irrigation area

Abstract

The invention relates to the technical field of hydrological models, and discloses a dynamic coupling simulation method, a dynamic coupling simulation system, dynamic coupling simulation equipment and a dynamic coupling simulation medium suitable for four-water conversion and vegetation growth in an arid underground water shallow buried irrigation area, and the dynamic coupling simulation method, the dynamic coupling simulation system and the dynamic coupling simulation equipment are characterized in that a physics-based soil water-underground water-surface water equation and an improved crop growth model are tightly coupled on the spatio-temporal scale; the influence of various agricultural and land management measures (such as land cover, earth embankments, channels and ditches) in the irrigation area on water conversion and the influence of soil salinization caused by shallow burying of underground water on water absorption and growth of plant roots are reasonably considered; the four-water conversion process and the coupling process of vegetation growth in the arid groundwater shallow buried irrigation area are accurately and efficiently simulated, the precision and stability of simulating soil water-groundwater-surface water space-time dynamic and interaction and associated process (salt migration) thereof and crop growth conditions are effectively guaranteed, the simulation efficiency is high, and the method is easy to implement. The operability and the practicability are high.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrological models, and in particular to a dynamic coupling simulation method, system, equipment and medium suitable for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas. Background Art

[0002] Distributed hydrological simulation is an effective method to clarify the hydrological processes in a watershed and quantitatively analyze the complex dynamics of eco-hydrological systems. It is widely used in evaluating water use efficiency, water resources management, and hydrological forecasting.

[0003] In arid irrigation areas, artificially transformed farmland, scattered natural land, and crisscrossing multi-level canal networks have profoundly changed the underlying surface conditions; at the same time, irrigation and drainage activities have caused closer hydraulic connections and frequent water transformation and associated processes in the region (such as soil water-groundwater exchange, lateral movement of groundwater and water exchange with drainage ditches, step-by-step drainage of drainage ditches, and salt migration with water movement, etc.). Therefore, agricultural hydrological processes are very complex and difficult to simulate accurately. Research on agricultural hydrological processes also pays more attention to the accuracy of farmland soil water (salt)-crop simulation, which is the core of agricultural water management. And with the implementation of agricultural water-saving measures (expanding the degree of channel lining, water-saving irrigation) and the joint management of groundwater and surface water, the simulation of modern agricultural irrigation areas needs to consider more spatiotemporal details than the simulation of irrigation areas using traditional irrigation methods, and the requirements for simulation accuracy are also higher. For shallow groundwater irrigation areas, efficient and accurate simulation of the four agricultural water transformation processes is not only helpful to improve the water use efficiency of the irrigation area itself, but also of great significance to the rational allocation and utilization of water resources in the basin.

[0004] However, the existing simulation methods still have shortcomings when applied to arid irrigation areas with shallow groundwater and greater human influence: (1) Some widely used conceptual models have low accuracy in simulating the spatiotemporal dynamics of soil water, groundwater, and surface water; (2) Most models do not adequately describe the flow generation-confluence process of arid agricultural watersheds, and lack practical methods for simulating the flow confluence process of drainage ditches at different levels in irrigation areas; (3) When using the model with full surface-underground coupling method to model agricultural watersheds with shallow groundwater, the strong nonlinearity of the three-dimensional vertical soil hydrodynamic equation will make it impossible to ensure the solution accuracy and efficiency. It can be seen that the existing simulation methods lack the ability to uniformly describe the coupling relationship between soil water (salt)-groundwater-surface water migration and vegetation growth in arid irrigation areas with shallow groundwater from a mechanistic perspective, and are difficult to be well applied in practice.

[0005] Therefore, there is an urgent need for a new dynamic coupling simulation method, system, equipment and medium suitable for the transformation of four waters and vegetation growth in arid groundwater shallow irrigation areas, so as to more accurately simulate the spatiotemporal dynamics of soil water-groundwater-surface water and their interactions, as well as the associated processes (salt migration) and crop growth, to meet the needs of quantitative research on the dynamics of hydrological cycle in arid irrigation areas. Summary of the invention

[0006] The present invention provides a dynamic coupling simulation method, system, equipment and medium suitable for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas, so as to solve the defect that the existing simulation methods lack the ability to uniformly characterize the coupling relationship between soil water (salt)-groundwater-surface water migration and vegetation growth in groundwater shallow arid irrigation areas from a mechanism perspective, and are difficult to be well applied in practice.

[0007] The present invention provides a dynamic coupling simulation method for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas, comprising:

[0008] S0. Obtain channel drainage data, soil water data, groundwater data, surface water data, and planting structure data of the irrigation area to be simulated;

[0009] S1. According to the channel drainage data and planting structure data of the irrigation area to be simulated, the irrigation area to be simulated is divided into several sub-basins, and each of the several sub-basins is divided into several hydrological response units according to the land type and planting structure, and the water and salt migration process of the unsaturated zone soil of each hydrological response unit is simulated;

[0010] S2. Based on the groundwater data of the irrigation area to be simulated, combined with the influence of channel leakage, ditch drainage and soil water on groundwater, the groundwater dynamics of the irrigation area to be simulated are simulated using an improved groundwater flow model;

[0011] S3. Based on the surface water data of the irrigation area to be simulated, combined with the surface runoff in the sub-basin, the drainage volume of the low-level drainage ditch and the influence of groundwater on the surface water flow of the irrigation area to be simulated, the confluence evolution process of the surface water flow of the irrigation area to be simulated is simulated;

[0012] S4. Use the improved crop growth model to simulate the crop growth in the simulated irrigation area, and closely couple it with the soil water and salt simulation process to obtain a dynamic coupling simulation model of the four water transformations and vegetation growth in the simulated irrigation area;

[0013] S5. Based on the simulation results of S1-S4, the interaction between soil water, groundwater and surface water in the irrigation area to be simulated is coupled and simulated using the space-time coupling method.

[0014] According to a dynamic coupling simulation method for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas provided by the present invention, S1 includes:

[0015] The vertical one-dimensional water flow movement of each hydrological response unit in several hydrological response units is simulated by using the vertical soil hydrodynamic equation;

[0016] The solute transport equation is used to simulate the solute transport process in the soil of each hydrological response unit in several hydrological response units;

[0017] The vertical soil hydrodynamic equation is:

[0018]

[0019] In the vertical soil hydrodynamic equation, θ represents the soil volume moisture content (cm 3 cm -3 ); t is time (day); z is depth below the ground (cm, upwards means positive); S a represents soil water source sink (cm 3 cm -3 d -1 , i.e. water absorption by roots); h s represents soil pressure head (cm); K (h S ) represents soil hydraulic conductivity (cm d -1 );

[0020] The solute transport equation is:

[0021]

[0022] In the solute transport equation, θ represents the soil volumetric moisture content (cm 3 cm -3 );ρ b It indicates the dry bulk density of soil (g cm -3 );q represents the soil water flux between nodes (cm d -1 ); c represents soil salt concentration (g L -1 ); z represents the depth below the ground (cm, upwards represents positive); D dif represents the solute diffusion coefficient (cm 2 d -1 );D dis represents the hydrodynamic diffusion length (cm); Q represents the amount of solute adsorbed by the soil (gg -1 );S s represents the solute source and sink term (g cm -3 d -1 ).

[0023] According to a dynamic coupling simulation method for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas provided by the present invention, S2 includes:

[0024] Use the variable water supply formula to update the water supply degree of the irrigation area to be simulated;

[0025] The channel leakage formula is used to obtain the channel leakage of the low-level channel in the irrigation area to be simulated;

[0026] Combined with the updated water supply degree, the channel leakage of the low-level channels in the simulated irrigation area, and the exchange amount between soil water and groundwater obtained by S1, the improved groundwater flow model is used to simulate the groundwater dynamics of the simulated irrigation area through the three-dimensional groundwater flow motion equation;

[0027] Among them, the formula for changing water supply degree is:

[0028]

[0029] In the formula for changing water supply degree, S y Represents the updated water supply degree; θ s ,θ r Represents saturated moisture content and residual moisture content (cm 3 cm -3 );d represents the groundwater depth (m); α (cm -1 ) and n(-) represent the empirical shape parameters; d0 represents the critical value of groundwater depth, S ycons It indicates that above d0 the water supply degree is assumed to be a conventional constant (m);

[0030] The formula for channel leakage is:

[0031]

[0032] In the channel leakage formula, CS k represents the channel leakage in the kth hydrological response unit (mm d -1 );K c,sat Indicates the effective saturated hydraulic conductivity of the channel bottom (mm d -1 ); X represents the wetted perimeter (m), estimated based on the irrigation water volume given in each hydrological response unit; L c,k represents the channel length in the kth hydrological response unit (m); A k represents the area of ​​the kth hydrological response unit (m 2 );

[0033] The three-dimensional groundwater flow equation is:

[0034]

[0035] In the three-dimensional groundwater flow equation, K xx , K yy and K zz represents the hydraulic conductivity along the x, y and z axes respectively (md -1 ), h is the groundwater head (m), t is the time (day), W is the source-sink term (m), which indicates the amount of water flowing into or out of the aquifer per unit volume per unit time, and S y and S s Respectively represent the water supply and storage coefficient of porous media (m -1 ).

[0036] According to a dynamic coupling simulation method for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas provided by the present invention, S3 includes:

[0037] The Hooghoudt equation is used to obtain the surface runoff and low-level drainage ditch discharge in the sub-basin;

[0038] Combining the influence of surface runoff in the sub-basin, drainage of low-level drainage ditches and aquifer-river exchange obtained by S2 on the surface water flow in the simulated irrigation area, the one-dimensional diffusion wave equation is used to simulate the confluence evolution process of the surface water flow in the simulated irrigation area.

[0039] The Hooghoudt equation is:

[0040]

[0041] m m =d d -GWD j-1 ,

[0042]

[0043] In the Hooghoudt equation, Q g Indicates the displacement (md -1 ), where Q g,hru and Q g,sub represent the discharge of the hydrological response unit and sub-basin respectively; GWD is the groundwater depth (m); j is the simulation date (-); K e Indicates lateral hydraulic conductivity (md -1 );m m Indicates the drainage elevation of the groundwater surface (m); d e Indicates equivalent depth (m); d d Indicates the depth of the impermeable layer (m); L d represents the drainage ditch spacing (m); nHRU represents the number of hydrological response units in the sub-basin; A HRU Represents the area of ​​the hydrological response unit (m 2);

[0044] The one-dimensional diffusion wave equation is:

[0045]

[0046] In the one-dimensional diffusion wave equation, V represents the volume of any control volume (m 3 ); t is time (days); nconn is the number of connections of the control volume; A is the cross-sectional area (m 2 ); H represents the surface water level above the reference plane (m); x represents the spatial coordinate (m); Q LAT represents the source and sink items (i.e., surface runoff and low-level drainage drainage in the sub-basin, m 3 d -1 ) volume flow rate; Q PR Indicates rainfall (m 3 d -1 );Q EV Indicates evaporation (m 3 d -1 );Q AQ represents the aquifer-river exchange volume (m 3 d -1 );D Mi represents a nonlinear diffusion term (md -1 ).

[0047] According to a dynamic coupling simulation method for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas provided by the present invention, S4 includes:

[0048] Using the improved crop growth model, the potential root water absorption, actual root water absorption, actual transpiration rate and plant growth regulation factor of crops in the simulated irrigation area are obtained through the potential root water absorption expression, actual root water absorption expression, actual transpiration rate and plant growth regulation factor expression;

[0049] According to the potential root water absorption, actual root water absorption, actual transpiration rate and plant growth regulation factor of the crops in the simulated irrigation area, the growth of crops in the simulated irrigation area is simulated, and it is coupled with the soil water and salt simulation to obtain the dynamic coupling simulation model of the simulated irrigation area;

[0050] Among them, the expression of potential root water absorption is:

[0051]

[0052] In the expression of potential root water absorption, S p represents the potential root water uptake at a specific node z (cm d -1 );D rootIndicates the maximum root depth of the day (cm); T p represents the potential transpiration of plants without water and salt stress (cm d -1 ), which uses the leaf area index (LAI) to convert potential evapotranspiration (ET p , cm d -1 ) represents the potential soil evaporation (E p , cm d -1 ) and plant transpiration (T p , cm d -1 ) root represents the root length density at a specific node z depth (cm cm -3 );

[0053] The actual root water absorption expression is:

[0054] S a (z) = α rw α rs ·S p (z),

[0055] In the expression of actual root water absorption, S a represents the actual root water uptake at a specific node z (cm d -1 ); α rw (-) and α rs (-) indicates the reduction coefficients of water stress and salt stress, respectively;

[0056] The actual transpiration rate expression is:

[0057]

[0058] In the actual transpiration rate expression, T a represents the actual transpiration rate (cm d -1 );S a represents the actual root water uptake at a specific node z (cm d -1 );D root Indicates the deepest root depth on that day (cm);

[0059] The expression of plant growth regulator is:

[0060] γ reg =1-max(α rw α rs ,strs t ),

[0061] In the expression of plant growth regulators, γ reg represents the plant growth regulator, i.e. the fraction of potential growth achieved in a given day; α rw (-) and αrs (-) represent the water stress and salt stress reduction coefficients respectively; strst represents the temperature stress coefficient (-).

[0062] According to a dynamic coupling simulation method for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas provided by the present invention, S5 includes:

[0063] Based on the simulation results of S1-S4, in the dimension of time, sequential coupling and iterative coupling are combined to conduct coupling simulation on the interaction between soil water, groundwater and surface water in the simulated irrigation area;

[0064] In the spatial dimension, mapping expressions are used to couple the interaction between soil water, groundwater and surface water in the simulated irrigation area.

[0065] The mapping expression is:

[0066]

[0067] In the mapping expression, RECH grid represents the daily cumulative vertical net recharge (m) of each groundwater grid in the groundwater simulation; nDHRU represents the number of DHRUs overlapping with the groundwater grid, and DHRU represents an independent sub-hydrological response unit decomposed by HRU; CS DHRU,p and are the soil bottom flux, channel leakage and drainage of the decomposed independent sub-hydrological response units (mm); A overlap Indicates the overlapping area (m 2 );A grid Indicates the area of ​​the groundwater grid (m 2 ), GWD grid represents the groundwater depth (m) of each groundwater grid; nGRID represents the number of DHRUs overlapping with the groundwater grid; A DHRU and A HRU Represent the areas of DHRU and HRU respectively (m 2 );GWD DHRU and GWD HRU Represent the groundwater depth (m) of DHRU and HRU respectively.

[0068] According to the present invention, a dynamic coupling simulation method for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas is provided. In the dimension of time, sequential coupling and iterative coupling are combined to couple the interaction between soil water, groundwater and surface water in the simulated irrigation area, including:

[0069] The water-salt transport process and groundwater dynamics of the unsaturated zone soil in the simulated irrigation area are solved by sequential coupling.

[0070] The iterative coupling method is used to solve the groundwater dynamics and surface water flow evolution process of the irrigation area to be simulated until the preset convergence criteria are met;

[0071] Using mapping expressions, the interaction between soil water, groundwater and surface water in the simulated irrigation area is spatially coupled and simulated.

[0072] The expression of the preset convergence standard is:

[0073]

[0074] In the expression of the preset convergence criterion, Q AQii represents the aquifer-reach exchange for reach ii by the current external iteration of the surface water simulation (m 3 d -1 );Q MFii represents the aquifer-reach exchange for reach ii by the current external iteration of the groundwater simulation (m 3 d -1 );f AQmax represents the maximum relative difference allowed in any reach for the given aquifer-reach exchange; nr represents the number of reaches in the surface water dataset.

[0075] The present invention also provides a dynamic coupling simulation system suitable for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas, comprising:

[0076] A data acquisition module is used to execute S0: acquiring channel drainage ditch data, soil water data, groundwater data, surface water data, and planting structure data of the irrigation area to be simulated;

[0077] The soil water simulation module is used to execute S1: according to the channel drainage ditch data and planting structure data of the irrigation area to be simulated, the irrigation area to be simulated is divided into several sub-basins, and each of the several sub-basins is divided into several hydrological response units according to the land type and planting structure, and the water and salt migration process of the unsaturated zone soil of each hydrological response unit is simulated;

[0078] A groundwater simulation module is used to execute S2: based on the groundwater data of the irrigation area to be simulated, combined with the influence of channel leakage, ditch drainage and soil water on groundwater, using an improved groundwater flow model to simulate the groundwater dynamics of the irrigation area to be simulated;

[0079] The surface water simulation module is used to execute S3: based on the surface water data of the irrigation area to be simulated, combined with the surface runoff in the sub-basin, the drainage volume of the low-level drainage ditch and the influence of groundwater on the surface water flow of the irrigation area to be simulated, simulate the confluence evolution process of the surface water flow of the irrigation area to be simulated;

[0080] The crop growth simulation module is used to execute S4: using the improved crop growth model to simulate the crop growth in the simulated irrigation area, and closely coupling it with the soil water and salt simulation process to obtain a dynamic coupling simulation model of the four water transformations and vegetation growth in the simulated irrigation area;

[0081] The coupled simulation module is used to execute S5: based on the simulation results of S1-S4, the interaction between soil water, groundwater and surface water in the irrigation area to be simulated is coupled and simulated using the spatiotemporal coupling method.

[0082] The present invention also provides an electronic device, comprising a processor and a memory storing a computer program, wherein when the processor executes the computer program, the processor implements any of the above-mentioned dynamic coupling simulation methods for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas.

[0083] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the computer program implements any of the above-mentioned dynamic coupling simulation methods applicable to the four-water transformation and vegetation growth in arid groundwater shallow irrigation areas.

[0084] The present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute any of the above-mentioned dynamic coupling simulation methods applicable to the four-water transformation and vegetation growth in arid groundwater shallow irrigation areas.

[0085] The present invention provides a dynamic coupling simulation method, system, equipment and medium suitable for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas. The method uses dynamic equations to accurately simulate the dynamics of soil water (salt)-groundwater-surface water and an improved crop growth model to simulate the vegetation growth process. It relies on efficient spatiotemporal coupling methods to reasonably describe the complex interactions of various water systems in time and space, and accurately simulates the four-water transformation and vegetation growth process in arid groundwater shallow irrigation areas. The present invention reasonably considers the effects of various agronomic and land management measures (such as surface cover, earth embankments, channels, drainage ditches, etc.) in arid irrigation areas on water transformation, and considers the effects of soil salinization caused by shallow groundwater on plant root water absorption and growth. The present invention has significant advantages in simulation accuracy and calculation efficiency, is simple and convenient to operate, and can provide clear result output, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0087] Figure 1 One of the flow diagrams of a method for dynamic coupling simulation of four-water transformation and vegetation growth in arid groundwater shallow irrigation areas provided by the present invention;

[0088] Figure 2 The second flow diagram of a method for dynamic coupling simulation of four-water transformation and vegetation growth in arid groundwater shallow irrigation areas provided by the present invention;

[0089] Figure 3 It is a schematic diagram of the "mapping" method between different spatial divisions (hydrological response units, groundwater grid units and surface water river sections) of the present invention;

[0090] Figure 4 This is a schematic diagram of the geographical location of Example 1 of the present invention;

[0091] Figure 5 The simulation results of soil moisture content and soil salinity of a corn field in Example 1 of the present invention and the comparison chart with the measured values;

[0092] Figure 6 The simulation results of groundwater in four observation wells in Example 1 of the present invention and the comparison chart with the measured values;

[0093] Figure 7 A diagram showing the dynamic changes in groundwater space before and after irrigation during the simulation period of Example 1 of the present invention;

[0094] Figure 8 The simulation result of the crop leaf area index in Example 1 of the present invention and the comparison chart with the measured value;

[0095] Fig. 9 The simulation results of soil moisture content and soil salinity at 22 observation points in Example 2 of the present invention and the comparison chart with the measured values;

[0096] Fig.10 The simulation results of the groundwater levels of 12 wells in Example 2 of the present invention and the comparison chart with the measured values;

[0097] Fig.11 The flow simulation results of 6 drainage ditch sections in Example 2 of the present invention and the comparison chart with the measured values;

[0098] Fig.12 A schematic diagram of the structure of a dynamic coupling simulation system for four-water conversion and vegetation growth in arid groundwater shallow irrigation areas provided by the present invention;

[0099] Fig.13 This is a schematic structural diagram of an electronic device provided by the present invention. DETAILED DESCRIPTION

[0100] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments, and they should not be understood as limitations on the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In the description of the present invention, it should be understood that the terms used are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0101] Figure 1 A flowchart of a method for kinetic coupling simulation of four-water transformation and vegetation growth in arid shallow groundwater irrigation areas provided by the present invention. The execution subject of the method for kinetic coupling simulation of four-water transformation and vegetation growth in arid shallow groundwater irrigation areas provided by the present invention can be any applicable terminal-side device or network-side device, such as a kinetic coupling simulation device for four-water transformation and vegetation growth in arid shallow groundwater irrigation areas.

[0102] See also Figure 1 The present invention provides a dynamic coupling simulation method for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas, which may include:

[0103] S0. Obtain channel and ditch data of the irrigation area to be simulated; soil water data; planting structure data; groundwater level data; and surface water flow (or water level) data.

[0104] The irrigation area to be simulated in this embodiment is an arid groundwater shallow buried irrigation area. The channel drainage ditch data may include channel drainage ditch cross-sectional dimensions, roughness, geographical location and other data. The soil water data may include soil classification, soil water content and salt content and other data.

[0105] S1. According to the channel and ditch data of the irrigation area to be simulated (the geographical location data of the channel and ditch in this embodiment), the irrigation area to be simulated is divided into several sub-basins (i.e., irrigation units), and the areas with the same land use, soil type and slope in each of the several sub-basins are divided into different hydrological response units (HRUs), the soil profile of each HRU is discretized into soil layers of the same or different thicknesses in the vertical direction (i.e., one-dimensional finite difference grids), and the vertical soil hydrodynamic equation and solute-transport equation are used to simulate the water and salt migration process in the unsaturated zone of each of the several hydrological response units.

[0106] In one embodiment, S1 includes:

[0107] S101, using a vertical soil hydrodynamic equation (Richards equation in this embodiment) to simulate the vertical one-dimensional water flow movement of each hydrological response unit in a plurality of hydrological response units;

[0108] Among them, the vertical Richards equation is:

[0109]

[0110] In the vertical Richards equation, θ represents the soil volume moisture content (cm 3 cm -3 ); t is time (day); z is depth below the ground (cm, upwards means positive); S a represents soil water source sink (cm 3 cm -3 d -1 , i.e. water absorption by roots); h s represents soil pressure head (cm); K (h S ) represents soil hydraulic conductivity (cm d -1 );

[0111] In this embodiment, for soil water flow movement, the upper boundary is controlled according to the actual soil evaporation rate and the flux calculated by irrigation and precipitation, and water accumulation in the field is allowed. The soil evaporation rate is adjusted by multiplying the potential soil evapotranspiration by the film covering reduction factor to reasonably estimate the impact of surface film on soil evaporation. In order to make full use of the incoming water, earth embankments are usually built around the farmland, so that field water accumulation will occur when rainfall or irrigation fails to infiltrate. Only when the depth of water accumulation exceeds the maximum water accumulation height (z sill , cm), surface runoff will occur. In this embodiment, the surface runoff generated in each HRU is calculated according to the following formula:

[0112]

[0113] In the formula, q runoff Expresses surface runoff (cm d -1 ); γ sill represents runoff resistance (d); β sill Indicates an exponential parameter (-); h pond Indicates the depth of water accumulation (cm); z sill Indicates the maximum height of accumulated water (cm).

[0114] In shallow groundwater basins, the lower soil boundary usually adopts a variable head boundary determined by the groundwater depth:

[0115]

[0116] In the formula, h bot represents the pressure head at the bottom node of the soil (cm); bot represents the depth of the soil bottom node (cm, upward is positive); GWD represents the groundwater depth (m); j represents the calculation date (-).

[0117] S102, using a solute transport equation (the advection-dispersion equation, ADE, in this embodiment) to simulate the solute transport process in the soil of each hydrological response unit in a plurality of hydrological response units;

[0118] The convection-dispersion equation is:

[0119]

[0120] In the convection-diffusion equation, θ represents the soil volume moisture content (cm 3 cm -3 );ρ b It indicates the dry bulk density of soil (g cm -3 );q represents the soil water flux between nodes (cm d -1 ); c represents soil salt concentration (g L -1 ); z represents the depth below the ground (cm, upwards represents positive); D dif represents the solute diffusion coefficient (cm 2 d -1 );D dis represents the hydrodynamic diffusion length (cm); Q represents the amount of solute adsorbed by the soil (gg -1 );S s represents the solute source and sink term (g cm -3 d -1 ). For solute transport simulation, the upper and lower boundary conditions of this embodiment are set as concentration flux boundaries. A fully implicit finite difference format can be used for numerical solution, and the GridPeclet number and Courant number are used to ensure the accuracy and stability of the solution.

[0121] S2. Based on the groundwater data of the irrigation area to be simulated, combined with the influence of channel leakage and the exchange volume between soil water and groundwater obtained by S1 on groundwater, the groundwater dynamics of the irrigation area to be simulated are simulated using an improved groundwater flow model (improved MODFLOW-NWT model).

[0122] In one embodiment, S2 includes:

[0123] Use the variable water supply formula to update the water supply degree of the irrigation area to be simulated;

[0124] The channel leakage formula is used to obtain the channel leakage of low-level channels (i.e., agricultural channels and ditches that mainly carry water in the fields) in the irrigation area to be simulated;

[0125] Combined with the updated water supply degree, the channel leakage of the low-level channels in the simulated irrigation area and the exchange amount between soil water and groundwater obtained by S1, the improved groundwater flow model is used to simulate the groundwater dynamics of the simulated irrigation area through the groundwater dynamic simulation equation;

[0126] Among them, the exchange amount of soil water and groundwater obtained by S1 is:

[0127] Q bot =Q top -SW end +SW ini

[0128] In the formula, θ bot is the exchange amount between soil water and groundwater; θ bot is the soil upper boundary flux; SW end SW is the water content at the end of soil hydrodynamic equation calculation; ini Calculate the initial water content for the soil hydrodynamic equation;

[0129] The formula for changing water supply degree is:

[0130]

[0131] In the formula for changing water supply degree, S y Represents the updated water supply degree; θ s ,θ r Represents saturated moisture content and residual moisture content (cm 3 cm -3 );d represents the groundwater depth (m); α (cm -1 ) and n(-) represent the empirical shape parameters; d0 represents the critical value of groundwater depth, S ycons It indicates that above d0 the water supply degree is assumed to be a conventional constant (m);

[0132] The formula for channel leakage is:

[0133]

[0134] In the channel leakage formula, CS k represents the channel leakage in the kth hydrological response unit (mm d -1 );K c,sat Indicates the effective saturated hydraulic conductivity of the channel bottom (mm d -1 ); X represents the wetted perimeter (m), estimated based on the irrigation water volume given in each hydrological response unit; L c,k represents the channel length in the kth hydrological response unit (m); A k represents the area of ​​the kth hydrological response unit (m 2 ); For higher-level channels (such as main channels and branch channels) in the irrigation area, due to their greater burial depth and better connectivity with groundwater, the channel leakage is directly set as the flux boundary of the corresponding groundwater grid in the first layer of groundwater simulation. The leakage is usually determined by the water flow and water use efficiency of the higher-level channels;

[0135] The groundwater dynamic simulation equation (three-dimensional groundwater flow equation) is:

[0136]

[0137] In the three-dimensional groundwater flow equation, K xx , K yy and K zz represents the hydraulic conductivity along the x, y and z axes respectively (md -1 ), h is the groundwater head (m), t is the time (day), W is the source-sink term (m), which indicates the amount of water flowing into or out of the aquifer per unit volume per unit time, and S y and S s Respectively represent the water supply and storage coefficient of porous media (m -1 ).

[0138] Among the aquifer properties that control groundwater flow, water supply is affected by various factors such as soil water retention characteristics, groundwater depth and its rate of change, especially when the groundwater depth is shallow. Therefore, a variable water supply formula is introduced to update the water supply of each grid according to the variable water supply formula before the simulation starts every day, thereby improving the simulation accuracy of this embodiment when the groundwater is shallow. At the same time, the water supply can still be directly specified by the user as a constant value in the input file.

[0139] S3. Based on the surface water data of the irrigation area to be simulated, combined with the surface runoff in the sub-basin, the drainage volume of the low-level drainage ditch and the influence of the aquifer-river section exchange volume obtained by S2 on the surface water flow of the irrigation area to be simulated, the confluence evolution process of the surface water flow in the irrigation area to be simulated is simulated.

[0140] In one embodiment, S3 includes:

[0141] The Hooghoudt equation was used to obtain the surface runoff and the drainage volume of low-level drainage ditches (i.e., agricultural ditches) in the sub-basin;

[0142] Combined with the influence of surface runoff in the sub-basin, drainage of low-level drainage ditches and aquifer-river exchange obtained by S2 on the surface water flow of the simulated irrigation area, the one-dimensional diffusion wave equation is used to simulate the confluence evolution process of the surface water flow of the simulated irrigation area (i.e., receiving drainage from low-level drainage ditches and transporting it to high-level drainage ditches outside the irrigation area, such as main, branch, and ditch)

[0143] Among them, the aquifer-river exchange volume obtained through S2 is:

[0144] Q AQ =C ii (H j,i -h ii )

[0145] In the formula, C ii represents the hydraulic conductivity of the aquifer in section ii; h ji , represents the groundwater level of the groundwater unit (jth column, ith row) containing the river segment ii; H ji represents the surface water level of river section ii;

[0146] The Hooghoudt equation is:

[0147]

[0148] m m =d d -GWD j-1 ,

[0149]

[0150] In the Hooghoudt equation, Q g Indicates the displacement (md -1 ), where Q g,hru and Q g,sub represent the discharge of the hydrological response unit and sub-basin respectively; GWD is the groundwater depth (m); j is the simulation date (-); K e Indicates lateral hydraulic conductivity (md -1 );m mIndicates the drainage elevation of the groundwater surface (m); d e Indicates equivalent depth (m); d d Indicates the depth of the impermeable layer (m); L d represents the drainage ditch spacing (m); nHRU represents the number of hydrological response units in the sub-basin; A HRU Represents the area of ​​the hydrological response unit (m 2 );

[0151] The one-dimensional diffusion wave equation is:

[0152]

[0153] In the one-dimensional diffusion wave equation, V represents the volume of any control volume (m 3 ); t is time (days); nconn is the number of connections of the control volume; A is the cross-sectional area (m 2 ); H represents the surface water level above the reference plane (m); x represents the spatial coordinate (m); Q LAT represents the source and sink items (i.e., surface runoff and low-level drainage drainage in the sub-basin, m 3 d -1 ) volume flow rate; Q PR Indicates rainfall (m 3 d -1 );Q EV Indicates evaporation (m 3 d -1 );Q AQ represents the aquifer-river exchange volume (m 3 d -1 );D Mi represents a nonlinear diffusion term (md -1 ), which can be defined using the Manning formula. In arid agricultural watersheds, the drainage ditches of channels and ditches are usually much smaller than the finite difference grid, and the effects of rainfall and evaporation have been considered in the unsaturated zone. Therefore, this embodiment defaults to Q for each river section PR and Q EV In addition, to solve the one-dimensional diffusion wave equation, the user needs to specify the initial water level, upstream boundary conditions (i.e., Q inlet = Q(t)) and downstream boundary conditions (e.g., h outlet =h(t),Q outlet =Q(t) and Q outlet =Q(t)). The water level-flow relationship of the downstream boundary condition can be specified by the user or inferred from the information of the hydraulic structures specified downstream (such as weirs, pumps, gates). For example, the improved form of the general weir equation used in this embodiment can describe the free outflow and submerged outflow processes affected by the weir:

[0154] Qs =C D C F W S d max (2gd max ) 1 / 2 ,

[0155] d max =max(0,h max -h STR ) 1 / 2 ,

[0156] In the formula, Q s Indicates free outflow or flooded outflow (m 3 d -1 );C D Indicates the weir discharge coefficient (-); C F Indicates flooding coefficient (-); W S Indicates the length of the weir perpendicular to the direction of water flow (m); h STR Indicates the elevation of the weir bottom (m); h max represents the maximum elevation of the dam bottom (m); g represents the acceleration due to gravity (ms -2 ).

[0157] S4. Use the improved crop growth model to simulate the crop growth conditions (such as leaf area index, crop height, root depth, biomass and yield, etc.) in the simulated irrigation area, and couple it with the soil water and salt simulation (i.e. the simulation result of S1) to obtain the dynamic coupling simulation model of the four water transformations and vegetation growth in the simulated irrigation area.

[0158] The actual water absorption of plant roots is the main source and sink item for calculating soil water movement. Soil water content and salt concentration will also affect the actual water absorption of crops. This embodiment quantifies the stress of unsuitable environment (i.e., water, salt and temperature) on root water absorption, evapotranspiration and crop growth by calculating soil water-salt, temperature stress coefficient and plant growth regulating factor. Crop growth conditions (LAI, root depth) affect the actual root water absorption by affecting potential plant transpiration and root length density.

[0159] In one embodiment, S4 includes:

[0160] Using an improved crop growth model (the improved EPIC_CG model in this embodiment), the potential root water absorption, actual root water absorption, actual transpiration rate and plant growth regulating factor of crops in the irrigation area to be simulated are obtained through the potential root water absorption expression, the actual root water absorption expression, the actual transpiration rate expression and the plant growth regulating factor expression;

[0161] According to the potential root water absorption, actual root water absorption, actual transpiration rate and plant growth regulation factor of the crops in the simulated irrigation area, the growth of crops in the simulated irrigation area is simulated, and it is coupled with the soil water and salt simulation to obtain the dynamic coupling simulation model of the simulated irrigation area;

[0162] In this embodiment, the potential soil root water absorption of plant roots at a certain soil node (soil layer) is calculated by allocating the potential plant evapotranspiration to each soil layer of the soil profile. It is a function of the specified root length density, that is, the potential root water absorption expression is:

[0163]

[0164] In the expression of potential root water absorption, S p represents the potential root water uptake at a specific node z (cm d -1 );D root Indicates the maximum root depth of the day (cm); T p represents the potential transpiration of plants without water and salt stress (cm d -1 ), which uses the leaf area index (LAI) to convert potential evapotranspiration (ET p , cm d -1 ) represents the potential soil evaporation (E p , cm d -1 ) and plant transpiration (T p , cm d -1 ) root represents the root length density at a specific node z depth (cm cm -3 ), which can be specified by the user and is determined by the ratio of the node depth to the node depth of the maximum root length on that day.

[0165] The actual root water absorption expression is:

[0166] S a (z) = α rw α rs ·S p (z),

[0167] In the expression of actual root water absorption, S a represents the actual root water uptake at a specific node z (cm d -1 ); α rw (-) and α rs (-) indicates the reduction coefficients of water stress and salt stress, respectively;

[0168] The actual transpiration rate expression is:

[0169]

[0170] In the actual transpiration rate expression, T a represents the actual transpiration rate (cm d -1 );S a represents the actual root water uptake at a specific node z (cm d -1 );D root Indicates the deepest root depth on that day (cm);

[0171] The effect of environmental stress on plant growth is quantified by plant growth regulators, which are expressed as:

[0172] γ reg =1-max(α rw α rs ,strs t ),

[0173] In the expression of plant growth regulators, γ reg represents the plant growth regulator, i.e. the fraction of potential growth achieved in a given day; α rw (-) and α rs (-) represent the water stress and salt stress reduction coefficients respectively; strst represents the temperature stress coefficient (-).

[0174] Two specific embodiments are used below to describe a dynamic coupling simulation method for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas provided by the present invention.

[0175] S5. Based on the simulation results of S1-S4, the interaction between soil water, groundwater and surface water in the irrigation area to be simulated is coupled and simulated using the space-time coupling method.

[0176] In one embodiment, S5 includes:

[0177] S501, using a sequential coupling method to solve the soil water and salt migration process and groundwater dynamics in the unsaturated zone of the irrigation area to be simulated;

[0178] S502, using an iterative coupling method to solve the groundwater dynamics and surface water flow evolution process of the irrigation area to be simulated until the preset convergence standard is met, wherein the expression of the preset convergence standard is:

[0179]

[0180] In the expression of the preset convergence criterion, Q AQii represents the aquifer-reach exchange for reach ii by the current external iteration of the surface water simulation (m 3 d -1 );Q MFiirepresents the aquifer-reach exchange for reach ii by the current external iteration of the groundwater simulation (m 3 d -1 );f AQmax represents the maximum relative difference allowed in any reach for the given aquifer-reach exchange; nr represents the number of reaches in the surface water dataset.

[0181] The time step required to solve the unsaturated zone soil water and salt migration process and the confluence evolution process of surface water flow is often much shorter than that required to solve the groundwater dynamics. Therefore, this embodiment uses different time steps to solve soil water flow, groundwater flow, and surface water flow. Figure 2 As shown, groundwater is simulated with a time step of day, and the calculation day is subdivided into multiple time steps when solving the Richards equation and the one-dimensional diffusion wave equation.

[0182] This embodiment adopts the sequential coupling method to solve soil water flow and groundwater flow: when calculating soil water dynamics, it is assumed that the pressure head of the lower boundary of the soil remains unchanged on the day. After the unsaturated zone process calculation is completed, the daily cumulative vertical net recharge of each HRU will be "mapped" to the RCH subroutine package in the groundwater calculation as the source and sink item of its grid (positive or negative values ​​can be regarded as recharge or phreatic evaporation, respectively). The surface runoff and low-level drainage ditch drainage in each sub-basin will be "mapped" to the inlet of its upper drainage ditch as the source and sink item.

[0183] This embodiment uses an iterative coupling method to solve groundwater flow and surface water flow: the solution of surface water flow starts with the boundary conditions formed by the groundwater head on the previous day, and after the last time step when solving the diffusion wave equation converges, the groundwater system is solved using the new boundary conditions formed by the surface water level. The iterations of the groundwater level and the surface water level always lag each other by one day. Therefore, in order to further ensure the degree of convergence between the surface water and groundwater systems, even if the solutions of the groundwater equation and the diffusion wave equation have met their respective convergence criteria, the above process will be repeated until the user-defined aquifer-reach convergence criteria (preset convergence criteria) are reached.

[0184] When modeling arid irrigation areas with shallow groundwater, it is necessary to set a sufficiently deep soil profile so that its bottom is always below the groundwater level. The groundwater depth updated every day is used to determine the soil lower boundary condition for the next simulation day. After the groundwater depth is updated, since the matrix potential of the soil profile needs to match the updated groundwater depth, the above coupling method will cause a sudden inflow or outflow flux (pseudo-flux) at the bottom of the soil profile, resulting in oscillation of the simulation results. Therefore, in this embodiment, the pressure head of the soil profile on the simulated day is adjusted by simultaneously considering the daily net vertical recharge of the unsaturated zone and the updated groundwater depth, thereby eliminating the pseudo-flux.

[0185] S503, in the spatial dimension, using mapping expressions, coupling simulation is performed on the interaction between soil water, groundwater, and surface water in the simulated irrigation area;

[0186] The mapping expression is:

[0187]

[0188] In the mapping expression, RECH grid represents the daily cumulative vertical net recharge (m) of each groundwater grid in the groundwater simulation; nDHRU represents the number of DHRUs overlapping with the groundwater grid, and DHRU represents an independent sub-hydrological response unit decomposed by HRU; and are the soil bottom flux, channel leakage and drainage of the decomposed independent sub-hydrological response units (mm); A overlap Indicates the overlapping area (m 2 );A grid Indicates the area of ​​the groundwater grid (m 2 ), GWD grid represents the groundwater depth (m) of each groundwater grid; nGRID represents the number of DHRUs overlapping with the groundwater grid; A DHRU and A HRU Represent the areas of DHRU and HRU respectively (m 2 );GWD DHRU and GWD HRU Represent the groundwater depth (m) of DHRU and HRU respectively.

[0189] See also Figure 3 In this embodiment, the spatial discretization of surface water flow is consistent with that of groundwater flow, but the spatial discretization scheme of the unsaturated zone (i.e., HRU) is different from that of groundwater and surface water (i.e., grid and river section / river section group). Therefore, the interaction between different water systems needs to be "mapped" through the positional relationship between HRU and groundwater grid, sub-basin and river section / river section group. When HRUs are not geographically adjacent, they are first decomposed into independent DHRUs. The area overlap rate of DHRU and groundwater grid can be calculated in ArcGIS, and then a file is generated for model input. The vertical net flux at the bottom of the soil of each DHRU is the same as that of the HRU in which it is located. The flux is then "mapped" to the overlapping groundwater grid based on the percentage of area occupied by the DHRU in the groundwater grid (see Formula 1 in the mapping expression).

[0190] A two-dimensional array (ASCII code) matching the rows and columns of the groundwater grid is used as a spatial location to establish the connection between the sub-basin and the river section / river section group. In this array, the value at the river inlet grid position is assigned to the corresponding sub-basin number, so that the surface water source and sink items (surface runoff and agricultural ditch drainage) generated in each sub-basin can be "mapped" to the corresponding river section / river section group inlet. After the groundwater and surface water simulation is completed every day, the updated groundwater depth in the grid is "mapped" to the DHRU according to the percentage of the groundwater grid area to the DHRU area where it is located (see equation 2 in the mapping expression). Then, according to the percentage of the DHRU area to the HRU area where it is located, it is "mapped" to the HRU (see equation 3 in the mapping expression).

[0191] Example 1

[0192] Using the experimental area of ​​Yangchang Canal in Hetao Irrigation District in 2012 and 2013 ( Figure 4 The present invention was tested using soil moisture and salt concentration, crop leaf area index and groundwater depth data of different soil layers (0-10, 10-20, 20-40, 40-60 and 60-80 cm) observed at four observation points (corn, sunflower, watermelon and natural land) in the Yangtze River Delta.

[0193] The Yangchangqu test area was considered as an independent sub-basin based on the location of the canal system and drainage ditches, and was divided into 68 HRUs based on land use, soil type and slope. The profile for simulating soil water and salt migration was set to 0-300 cm below the surface, and the profile was evenly divided into 300 nodes with a node spacing of 1 cm. The simulation period was from early May to late September each year, covering the entire growth period of corn, sunflower and watermelon. The upper boundary condition of water flow movement is determined by actual evaporation, irrigation, precipitation or field waterlogging, while the lower boundary condition is determined by the pressure head obtained from the daily calculated and updated groundwater depth. The upper and lower boundary conditions of solute migration are the measured salt concentrations of irrigation water and groundwater (0.5 and 2.0 g L -1 ). The initial hydraulic head of the soil profile was determined by the hydrostatic balance of the initial groundwater level, and the initial salt concentration was obtained by Kriging interpolation of the observed values. The maximum root depths of corn, sunflower, wheat, watermelon, and tamarisk were set to 90, 80, 100, 150, and 90 cm, respectively.

[0194] The groundwater system is divided into a layer with a thickness of 30 m vertically and a uniform 10 m × 10 m grid horizontally, divided into 33 columns and 66 rows. The surface elevation is obtained by interpolation of observed data. The aquifer is assumed to be horizontally isotropic and the permeability is set to 10 m d -1 , the vertical permeability coefficient is one tenth of the horizontal value, and the water storage coefficient is 1×10 -6 m-1 The water supply degree of the simulation layer at the beginning of a new day is calculated using Equation 6. The initial groundwater head of each grid cell is obtained by interpolating the observed data on the first day of simulation. The agricultural ditch on the southeast side of the study area is calculated using the diffusion wave equation, and the other boundaries are defined as zero flux boundaries.

[0195] Based on the groundwater grid, the agricultural ditch in the southeast of the study area was divided into 94 river sections, which were further divided into 9 river section groups according to the land use type near the agricultural ditch. The cross-sectional shape of these river sections was defined as trapezoidal, with a bottom width of 1m, a bottom elevation of 1037.3m, a side slope of 1:1, and a Manning roughness coefficient of 0.045sm. -1 / 3 , the hydraulic conductivity of the riverbed is 2m 2 d -1 Since the inflow from the upstream of the study area is not considered, the boundary condition of the upstream of the agricultural ditch is Q inlet =Q(t)=0, the downstream boundary condition is Q outlet =Q(h), outflow(Q outlet The relationship between the water level (h) and the river section water level (h) is calculated using the Manning formula. Since the agricultural ditch is dry at the beginning of the growing season, the initial water level is the elevation of the river section bottom. In addition, the Mao ditch in the study area is not considered.

[0196] The simulation results show that the present invention can accurately capture the dynamic changes of soil water and salt in the stratified soil and its response to environmental changes during the simulation process ( Figure 5 ). For example, after irrigation, the soil moisture content increases rapidly, the salt concentration in the upper layer decreases significantly, while the salt concentration in the deep layer does not change significantly. After irrigation or rainfall, the soil moisture content gradually decreases due to water consumption and redistribution, and salt accumulates again in the soil surface. In the case of shallow groundwater during the growth period, due to the capillary rise effect, the soil moisture content in the field that is not irrigated at a certain time also remains at a relatively high level ( Figure 5 ). The present invention can accurately capture the spatiotemporal dynamic changes of groundwater, and the simulated values ​​are well consistent with the measured values ​​( Figure 6 , Figure 7 ). Although the shallow groundwater system in the study area is complex and the soil planting structure is fragmented, the present invention can still accurately describe the interaction between groundwater and the unsaturated zone in time and space. The simulation results of groundwater can prove the ability of the present invention to simulate the movement of surface water flow and its interaction with groundwater. The simulation of the leaf area index of corn and sunflower in the study area by the present invention is also highly consistent with the measured values ​​( Figure 8 ), proving that the present invention can reasonably simulate crop growth.

[0197] In Example 1, the present invention exhibits satisfactory simulation performance and accuracy, has high numerical stability and can better characterize the spatiotemporal dynamics of soil water and salt, shallow groundwater, surface water and crop growth and the interactions between them in shallow groundwater arid agricultural basins.

[0198] Example 2

[0199] Taking advantage of the opportunity in the Hetao Irrigation District in 2021, the research area ( Figure 4 ) and 12 observation wells within the region and six water-passing sections along the central and southern tributaries to verify and apply the model at a regional scale by measuring soil moisture content, salinity (0-10, 10-20, 20-40, 40-60 and 60-80 cm), groundwater depth and drainage flow.

[0200] The Jiyuan study area was divided into 42 sub-basins according to the layout of the canal and ditch network, and further subdivided into 2307 HRUs according to land use, soil type and slope. The soil profile of each HRU is discretized into 60 layers, with a spacing of 5 cm between each layer. The upper and lower boundary conditions, initial conditions and plant growth parameters of soil water and salt migration in the Jiyuan study area are similar to those in the Yangchang Canal Experimental Area (see Example 1). A uniform grid of 100m×100m is used in the horizontal direction to divide the groundwater system into 109 columns and 133 rows. The groundwater system is discretized into three layers vertically, each with a thickness of 10m. A zero flux boundary was established on the southwest side of the Jiyuan study area, and a flux boundary condition was set on the southeast side. The one-dimensional diffusion wave equation was used to model the drainage ditches in the central and eastern parts of the study area, which were divided into 819 river sections and further grouped into 49 river section groups according to geographical location. The upstream boundary condition of the drainage ditch is Q inlet =Q(t)=0, the downstream boundary condition at the outlet of the study area (Q outlet =Q(h)) was estimated using the Manning formula, and the drainage volume of the agricultural ditches in the study area was calculated using the Hooghoudt equation.

[0201] The simulation results show that the present invention has a high accuracy in simulating soil moisture and salt concentrations at soil observation points (including typical farmland and natural land) in a larger scale area ( Fig. 9 ) and efficiency. The simulated groundwater levels agree well with the observed values ​​( Fig.10 ), although the simulated values ​​of some wells (such as well 2 and well 11) are lower than the observed values, the simulated fluctuation trend is well consistent with the observed data, and the results are acceptable. For the simulation of surface water flow, the present invention also performs well in simulating the drainage volume and water level of the two main drainage ditches in the Jiyuan study area, accurately capturing the change process of drainage ditch flow caused by groundwater fluctuations during each irrigation period ( Fig.11). Especially for the observation section B1-B4 located in the middle drainage ditch (which only receives drainage from the internal part of the Jiyuan study area), the simulation results are highly consistent with the observed flow.

[0202] Example 2 further verifies the high accuracy of the present invention in simulating soil water and salt migration, groundwater fluctuations, crop growth and their interactions on a larger regional scale, and conducts a detailed evaluation of the accuracy and applicability of the surface water flow module in a complex multi-level drainage system. In addition, the example only takes about 18 minutes to run on a computer configured with a 16-core 2.90GHz CPU, indicating that the present invention has high computational efficiency.

[0203] The present invention provides a dynamic coupling simulation method, system, equipment and medium suitable for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas. The method uses dynamic equations to accurately simulate the dynamics of soil water (salt)-groundwater-surface water and an improved crop growth model to simulate the vegetation growth process. It relies on efficient spatiotemporal coupling methods to reasonably describe the complex interactions of various water systems in time and space, and accurately simulates the four-water transformation and vegetation growth process in arid groundwater shallow irrigation areas. The present invention reasonably considers the effects of various agronomic and land management measures (such as surface cover, earth embankments, channels, drainage ditches, etc.) in arid irrigation areas on water transformation, and considers the effects of soil salinization caused by shallow groundwater on plant root water absorption and growth. The present invention has significant advantages in simulation accuracy and calculation efficiency, is simple and convenient to operate, and can provide clear result output, and has strong practicality.

[0204] The following is a description of the dynamic coupling simulation system for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas provided by the present invention. The dynamic coupling simulation system for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas described below and the dynamic coupling simulation method for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas described above can be referenced to each other.

[0205] See also Fig.12 The present invention provides a dynamic coupling simulation system for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas, comprising:

[0206] The data acquisition module is used to execute S0: obtain the channel and ditch cross-sectional dimensions, roughness, and geographic location data of the irrigation area to be simulated; soil classification, soil moisture content, and salt content data; planting structure data; groundwater level data; and surface water flow (or water level) data;

[0207] The soil water simulation module is used to execute S1: divide the irrigation area to be simulated into several sub-basins according to the geographical location of the canals and ditches of the irrigation area to be simulated, and divide the several sub-basins into several hydrological response units (HRUs) according to the land type and planting structure data, and simulate the soil water and salt migration process in the unsaturated zone of each of the several hydrological response units;

[0208] A groundwater simulation module is used to execute S2: based on the initial water level data of the irrigation area to be simulated, combined with the influence of channel leakage, ditch drainage and soil water on groundwater, the groundwater dynamics of the irrigation area to be simulated are simulated using an improved groundwater flow model;

[0209] The surface water simulation module is used to execute S3: based on the surface water section size, roughness and other data of the irrigation area to be simulated, combined with the surface runoff in the sub-basin, the drainage volume of the low-level drainage ditch and the influence of groundwater on the surface water flow of the irrigation area to be simulated, the confluence evolution process of the surface water flow in the irrigation area to be simulated is simulated;

[0210] The crop growth simulation module is used to execute S4: using the improved crop growth model to simulate the crop growth in the simulated irrigation area, and coupling it with the soil water and salt simulation to obtain a dynamic coupling simulation model of the four water transformations and vegetation growth in the simulated irrigation area;

[0211] The coupled simulation module is used to execute S5: based on the simulation results of S1-S4, an efficient spatiotemporal coupling method is proposed and used to couple the interaction between soil water, groundwater and surface water in the irrigation area to be simulated.

[0212] Fig.13 An example of a physical structure diagram of an electronic device is shown in FIG. Fig.13 As shown, the electronic device may include: a processor 810, a communication interface 820, a memory 830 and a communication bus 840, wherein the processor 810, the communication interface 820 and the memory 830 communicate with each other through the communication bus 840. The processor 810 may call the logic instructions in the memory 830 to execute any of the above-mentioned dynamic coupling simulation methods for four water conversion and vegetation growth in arid groundwater shallow irrigation areas.

[0213] In addition, the logic instructions in the above-mentioned memory 830 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0214] On the other hand, the present invention also provides a computer program product, which includes a computer program, and the computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute any of the above-mentioned dynamic coupling simulation methods applicable to the four water transformations and vegetation growth in arid groundwater shallow irrigation areas.

[0215] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute any of the above-mentioned dynamic coupling simulation methods for four water transformations and vegetation growth in arid groundwater shallow irrigation areas.

[0216] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0217] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0218] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dynamic coupling simulation method for water conversion and vegetation growth in arid shallow groundwater irrigation areas, characterized in that: include: S0. Obtain channel drainage data, soil water data, groundwater data, surface water data, and planting structure data of the irrigation area to be simulated; S1. According to the channel drainage data and planting structure data of the irrigation area to be simulated, the irrigation area to be simulated is divided into several sub-basins, and each of the several sub-basins is divided into several hydrological response units according to the land type and planting structure, and the water and salt migration process of the unsaturated zone soil of each hydrological response unit is simulated; S2. Based on the groundwater data of the irrigation area to be simulated, combined with the influence of channel leakage, ditch drainage and soil water on groundwater, the groundwater dynamics of the irrigation area to be simulated are simulated using an improved groundwater flow model; S3. Based on the surface water data of the irrigation area to be simulated, combined with the surface runoff in the sub-basin, the drainage volume of the low-level drainage ditch and the influence of groundwater on the surface water flow of the irrigation area to be simulated, the confluence evolution process of the surface water flow of the irrigation area to be simulated is simulated; S4. Use the improved crop growth model to simulate the crop growth in the simulated irrigation area, and closely couple it with the soil water and salt simulation process to obtain a dynamic coupling simulation model of the four water transformations and vegetation growth in the simulated irrigation area; S5. Based on the simulation results of S1-S4, the interaction between soil water, groundwater and surface water in the irrigation area to be simulated is coupled and simulated using the space-time coupling method.

2. The method for dynamic coupling simulation of water conversion and vegetation growth in shallow groundwater irrigation areas in arid areas according to claim 1 is characterized in that: S1 includes: The vertical one-dimensional water flow movement of each hydrological response unit in several hydrological response units is simulated by using the vertical soil hydrodynamic equation; The solute transport equation is used to simulate the solute transport process in the soil of each hydrological response unit in several hydrological response units; The vertical soil hydrodynamic equation is: In the vertical soil hydrodynamic equation, θ represents the soil volume moisture content; t represents time; z represents the depth below the ground; S a represents the soil water source sink; h S represents soil pressure head; K(h S ) represents soil hydraulic conductivity; The solute transport equation is: In the solute transport equation, θ represents the soil volume moisture content; ρ b represents soil dry bulk density; q represents soil water flux between nodes; c represents soil salt concentration; z represents depth below ground level; D dif represents the solute diffusion coefficient; D dis represents the hydrodynamic diffusion length; Q represents the amount of solute adsorbed by the soil; S s Represents solute source and sink terms.

3. The method for dynamic coupling simulation of water conversion and vegetation growth in shallow groundwater irrigation areas in arid areas according to claim 2, characterized in that S2 include: Use the variable water supply formula to update the water supply degree of the irrigation area to be simulated; The channel leakage formula is used to obtain the channel leakage of the low-level channel in the irrigation area to be simulated; Combined with the updated water supply degree, the channel leakage of the low-level channels in the simulated irrigation area and the exchange amount between soil water and groundwater obtained by S1, the improved groundwater flow model is used to simulate the groundwater dynamics of the simulated irrigation area through the three-dimensional groundwater flow motion equation; Among them, the formula for changing water supply degree is: In the formula for changing water supply degree, S y Represents the updated water supply degree; θ s ,θ r denote saturated water content and residual water content respectively; d denotes groundwater depth; α and n denote shape empirical parameters; d0 denotes the critical value of groundwater depth, S ycons It indicates that above d0 the water supply degree is assumed to represent a conventional constant; The formula for channel leakage is: In the channel leakage formula, CS k represents the channel leakage in the kth hydrological response unit; K c,sat represents the effective saturated hydraulic conductivity of the canal bottom; X represents the wetted perimeter, which is estimated based on the irrigation water volume given in each hydrological response unit; L c,k represents the channel length within the kth hydrological response unit; A k represents the area of ​​the kth hydrological response unit; The three-dimensional groundwater flow equation is: In the three-dimensional groundwater flow equation, K xx , K yy and K zz represents the hydraulic conductivity along the x, y and z axes respectively; h represents the hydraulic head; t represents time; W represents the source-sink term, which represents the amount of water flowing into or out of the aquifer per unit volume per unit time; S y and S s They represent the water supply degree and water storage coefficient of porous media respectively.

4. The method for dynamic coupling simulation of water conversion and vegetation growth in shallow groundwater irrigation areas in arid areas according to claim 3, characterized in that: include: The Hooghoudt equation is used to obtain the discharge of low-level drainage ditches in the sub-basin; Combining the influence of surface runoff in the sub-basin, drainage of low-level drainage ditches and aquifer-river exchange obtained by S2 on the surface water flow in the simulated irrigation area, the one-dimensional diffusion wave equation is used to simulate the confluence evolution process of the surface water flow in the simulated irrigation area. The Hooghoudt equation is: m m =d d -GWD j-1 , In the Hooghoudt equation, Q g represents the displacement, where Q g,hru and Q g,sub represent the discharge of the hydrological response unit and sub-basin respectively; GWD represents the groundwater depth; j represents the simulation date; K e Indicates lateral hydraulic conductivity; m m Indicates the drainage elevation of the groundwater surface; d e Indicates equivalent depth; d d Indicates the depth of the impermeable layer; L d represents the drainage ditch spacing; nHRU represents the number of hydrological response units in the sub-basin; A HRU represents the area of ​​the hydrological response unit; The one-dimensional diffusion wave equation is: In the one-dimensional diffusion wave equation, V represents the volume of any control volume; t represents time; nconn represents the number of connections of the control volume; A represents the cross-sectional area; H represents the surface water level above the reference plane; x represents the spatial coordinate; Q LAT represents the source-sink term, i.e., the volume flow of surface runoff and low-level drainage in the sub-basin; Q PR Indicates rainfall; Q EV Indicates evaporation; Q AQ represents the aquifer-river exchange volume; D Mi represents a nonlinear diffusion term.

5. The method for dynamic coupling simulation of water conversion and vegetation growth in shallow groundwater irrigation areas in arid areas according to claim 4, characterized in that S4 include: Using the improved crop growth model, the actual root water absorption and plant growth regulation factor of crops in the simulated irrigation area are obtained through the potential root water absorption expression, the actual root water absorption expression, the actual transpiration rate expression, and the plant growth regulation factor expression; According to the actual root water absorption and plant growth regulatory factors of the crops in the simulated irrigation area, the growth of crops in the simulated irrigation area is simulated and coupled with the soil water and salt simulation; Among them, the expression of potential root water absorption is: In the expression of potential root water absorption, S p represents the potential root water absorption at a specific node z; D root Indicates the deepest root depth of the day; T p Represents the potential evapotranspiration of plants not under water and salt stress; I root Represents the root length density at a specific node z depth; The actual root water absorption expression is: S a (z)=α rw ·α rs ·S p (z), In the expression of actual root water absorption, S a Indicates the actual root water absorption at a specific node z; α rw and α rs represent the reduction factors of water stress and salt stress, respectively; The actual transpiration rate expression is: In the actual transpiration rate expression, T a Indicates the actual transpiration rate; S a Indicates the actual root water absorption at a specific node z; D root Indicates the deepest root depth on that day; The expression of plant growth regulator is: γ reg =1-max(α rw α rs ,strs t ), In the expression of plant growth regulators, γ reg represents the plant growth regulator, i.e. the fraction of potential growth achieved in a given day; α rw and α rs represent the reduction coefficients of water stress and salt stress respectively; strst represents the temperature stress coefficient.

6. The method for dynamic coupling simulation of water conversion and vegetation growth in shallow groundwater irrigation areas in arid areas according to claim 5, characterized in that: include: In the dimension of time, sequential coupling and iterative coupling are combined to couple the interaction between soil water, groundwater and surface water in the simulated irrigation area. In the spatial dimension, mapping expressions are used to couple the interaction between soil water, groundwater and surface water in the simulated irrigation area. The mapping expression is: In the mapping expression, RECH grid represents the daily cumulative vertical net recharge of each groundwater grid in the groundwater simulation; nDHRU represents the number of DHRUs overlapping with the groundwater grid, and DHRU represents the independent sub-hydrological response unit decomposed by HRU; and A represents the soil bottom flux, channel leakage and drainage of the decomposed independent sub-hydrological response unit respectively; overlap Represents the overlapping area; A grid Represents the area of ​​the groundwater grid, GWD grid represents the groundwater depth of each groundwater grid; nGRID represents the number of DHRUs overlapping with the groundwater grid; A DHRU and A HRU Represent the areas of DHRU and HRU respectively; GWD DHRU and GWD HRU Represent the groundwater depths of DHRU and HRU respectively.

7. The method for dynamic coupling simulation of water conversion and vegetation growth in arid groundwater shallow irrigation areas according to claim 6 is characterized in that: In the time dimension, sequential coupling and iterative coupling are combined to couple the interaction between soil water, groundwater and surface water in the simulated irrigation area, including: The sequential coupling method is used to solve the soil water and salt migration process and groundwater dynamics in the unsaturated zone of the irrigation area to be simulated; The iterative coupling method is used to solve the groundwater dynamics and surface water flow evolution process of the irrigation area to be simulated until the preset convergence criteria are met; The expression of the preset convergence standard is: In the expression of the preset convergence criterion, Q AQii represents the aquifer-reach exchange for reach ii by the current external iteration of the surface water simulation; Q MFii represents the aquifer-reach exchange for reach ii by the current external iteration of the groundwater simulation; f AQmax represents the maximum relative difference allowed in any reach for the given aquifer-reach exchange; nr represents the number of reaches in the surface water dataset.

8. A dynamic coupling simulation system suitable for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas, characterized in that: include: A data acquisition module is used to execute S0: acquiring channel drainage ditch data, soil water data, groundwater data, surface water data, and planting structure data of the irrigation area to be simulated; The soil water simulation module is used to execute S1: according to the channel drainage ditch data and planting structure data of the irrigation area to be simulated, the irrigation area to be simulated is divided into several sub-basins, and each of the several sub-basins is divided into several hydrological response units according to the land type and planting structure, and the water and salt migration process of the unsaturated zone soil of each hydrological response unit is simulated; A groundwater simulation module is used to execute S2: based on the groundwater data of the irrigation area to be simulated, combined with the influence of channel leakage, ditch drainage and soil water on groundwater, using an improved groundwater flow model to simulate the groundwater dynamics of the irrigation area to be simulated; The surface water simulation module is used to execute S3: based on the surface water data of the irrigation area to be simulated, combined with the surface runoff in the sub-basin, the drainage volume of the low-level drainage ditch and the influence of groundwater on the surface water flow of the irrigation area to be simulated, simulate the confluence evolution process of the surface water flow of the irrigation area to be simulated; The crop growth simulation module is used to execute S4: using the improved crop growth model to simulate the crop growth in the simulated irrigation area, and closely coupling it with the soil water and salt simulation process to obtain a dynamic coupling simulation model of the four water transformations and vegetation growth in the simulated irrigation area; The coupled simulation module is used to execute S5: based on the simulation results of S1-S4, the interaction between soil water, groundwater and surface water in the irrigation area to be simulated is coupled and simulated using the spatiotemporal coupling method.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the dynamic coupling simulation method for four-water transformation and vegetation growth in arid groundwater shallow irrigation areas as described in any one of claims 1 to 7 is implemented.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, it implements the dynamic coupling simulation method for four water transformations and vegetation growth in arid groundwater shallow irrigation areas as described in any one of claims 1 to 7.

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