Distributed hydrological hydrodynamic model construction method and system based on physical mechanism

Abstract

The invention relates to a method and a system for constructing a distributed hydrological hydrodynamic model based on a physical mechanism. The method comprises the following steps of: dividing a drainage basin into grids on a horizontal plane, performing digital terrain analysis based on a DEM (Digital Elevation Model), establishing a water flow dependency relationship between two-dimensional grids, and dividing each grid into different horizontal layers in the vertical direction; on each grid and different horizontal layers, two-dimensional hydrodynamic models used for describing rainfall, evaporation, soil moisture movement, slope runoff production and slope confluence are constructed on the basis of a physical mechanism; a distributed hydrological model and a two-dimensional hydrodynamic model are coupled, the distributed hydrological model is established in a mountainous area to realize fine simulation of a hydrological process, and a two-dimensional hydrodynamic model of flood routing of a river channel-flood storage and detention area is established on the basis of real-time subdivision of a terrain irregular grid in a plain flood storage and detention area. Submerged water depth and a time-space change process of a submerged area are simulated, and tight coupling of runoff production in a mountainous area, one-dimensional river channel confluence and a two-dimensional flood submerging process in a plain area is realized.

Description

Technical Field

[0001] The present invention relates to the field of hydrology, water resources and computer technology, and in particular to a method and system for constructing a distributed hydrology and hydrodynamic model based on a physical mechanism. Background Art

[0002] Affected by climate change and human activities, the frequent occurrence of extreme precipitation events around the world has led to increasingly serious flood disasters, directly threatening people's lives and property safety. Flood forecasting provides a scientific basis for flood control and dispatching decisions by making scientific predictions of future hydrological conditions, and plays an important supporting role in improving disaster prevention and mitigation capabilities.

[0003] The basin hydrological model is an important tool for flood forecasting and water resources management. By making scientific predictions and scenario analysis of future hydrological conditions, it provides a scientific basis for flood control dispatching and command decision-making, which helps to improve disaster prevention and mitigation capabilities. Although the flood forecasting and warning business has developed rapidly in recent years and the level of flood forecasting and warning has been significantly improved, there are still many problems and shortcomings in the face of new requirements for flood forecasting and warning in the new situation. The main methods used in flood forecasting include statistical methods and hydrological models. Statistical forecasting methods, such as the rainfall-runoff method, establish mathematical relationships based on historical observation data of precipitation and runoff, and thus predict floods. This type of method does not consider the physical process of water cycle, and can only make flood warnings and forecasts for hydrological stations with historical measured data. It cannot make flood forecasts for areas with lack of data, and it is difficult to adapt to the requirements of flood forecasting in the new era. The models used for flood forecasting based on hydrological models include lumped conceptual models and distributed models. At present, most flood forecasts use lumped conceptual models. This type of model conceptualizes the runoff generation and confluence process and simplifies the spatial distribution process into a centralized one. Therefore, the forecast accuracy is often relatively low. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to provide a method and system for constructing a distributed hydrological and hydrodynamic model based on physical mechanisms, which can overcome the problem that most statistical models or conceptual lumped models are currently used in flood forecasting.

[0005] To achieve the above-mentioned purpose, in the first aspect, the technical solution adopted by the present invention is: a method for constructing a distributed hydrological and hydrodynamic model based on a physical mechanism, which includes: constructing a distributed hydrological model, dividing the watershed into grids on the horizontal plane, establishing a water flow dependency relationship between two-dimensional grids based on digital terrain analysis of DEM, and dividing each grid into different horizontal layers in the vertical direction; on each grid and different horizontal layers, constructing a two-dimensional hydrodynamic model for describing precipitation, evaporation, soil moisture movement, slope runoff and slope confluence based on physical mechanisms; using the runoff of each grid unit simulated by the distributed hydrological model as the input flow of the two-dimensional hydrodynamic model to couple the distributed hydrological model with the two-dimensional hydrodynamic model, establishing a distributed hydrological model in mountainous areas to achieve a fine simulation of the hydrological process, and establishing a two-dimensional hydrodynamic model of flood evolution in a river-flood storage and detention area based on real-time segmentation of irregular terrain grids in plain flood storage and detention areas, simulating the spatiotemporal variation process of the flood depth and the flooded area, so as to achieve a close coupling of the runoff generation in mountainous areas, the one-dimensional river confluence and the two-dimensional flood inundation process in plain areas.

[0006] Furthermore, the distributed hydrological model includes: planar structural features and vertical structural features; Divide the watershed into grids or sub-basins on the plane, and each grid is used as a basic calculation unit; On the vertical plane, each basic calculation unit is divided into different horizontal layers, including the canopy layer, surface layer, soil layer and groundwater layer.

[0007] Furthermore, the two-dimensional hydrodynamic model includes: The snowmelt process module uses the degree-day model to calculate the amount of snowmelt based on the empirical relationship between temperature and snowmelt rate; Runoff module, which calculates evapotranspiration, soil water and groundwater interaction, surface runoff and infiltration; Slope confluence module uses unit lines to simulate the slope confluence process; The river confluence module uses Muskingum method to simplify the Saint-Venant equation and converts the inflow process of the upstream section of the river into the outflow process of the downstream section. The 2D inundation module is used to simulate flooded areas using shallow water equations.

[0008] Furthermore, the runoff generation module includes an evapotranspiration process simulation module, a soil moisture movement process simulation module, and an infiltration process simulation module; The evapotranspiration process simulation module includes three types of evaporation: canopy interception evaporation process simulation module, vegetation transpiration process simulation module and bare soil evaporation process simulation module. The sum of the three is the total actual evapotranspiration of each grid. The soil moisture movement simulation module is described by the Richards equation, which is calculated using the mixed one-, two-, and three-dimensional Richards equations in a rectangular coordinate system; The infiltration process simulation module adopts the Green-Ampt layered infiltration calculation mode. When net rain infiltrates into the first layer until it is saturated, the actual hydraulic conductivity of water infiltrating from the first layer to the second layer is calculated by the average value of the soil moisture content of the first layer and the soil moisture content of the second layer until the second layer reaches saturation; the actual hydraulic conductivity from the second layer to the third layer is calculated by the same method, and so on, until the infiltration process stops.

[0009] Furthermore, the slope confluence module uses unit lines to simulate the slope confluence process, including: calculating the confluence response of the grid and the confluence response of the flow path; Calculate the grid confluence response, assuming that the slope confluence process of the grid unit is a one-dimensional unstable flow, and use the diffusion wave equation for calculation; The confluence response of the flow path is calculated by the first pass time density function of the Brownian motion.

[0010] Furthermore, the river confluence module uses the Muskingum method to simplify the Saint-Venant equation and convert the inflow process of the upstream section of the river into the outflow process of the downstream section, which is: In the formula, , , yes , , The function of , They refer to the inflow and outflow at the previous moment respectively. , They refer to the inflow and outflow at this moment respectively; is the storage constant, is the dimensionless flow weighting factor, is the calculation time step.

[0011] Furthermore, the 2D inundation module is used to simulate the flooded area, using shallow water equations to solve, including: The shallow water equation is the integral form of the Reynolds equation along the water depth direction under basic assumptions; The basic assumptions include: ignoring the vertical velocity and vertical velocity gradient, assuming that the pressure is hydrostatic along the water depth, the flow form is a gradual flow, the amplitude of water surface fluctuation is small compared with the water depth and / or the local head loss is negligible.

[0012] In the second aspect, the technical solution adopted by the present invention is: a distributed hydrological and hydrodynamic model construction system based on physical mechanisms, which includes: a distributed hydrological model construction module, which is used to construct a distributed hydrological model, divide the basin into grids on the horizontal plane, establish the water flow dependency relationship between the two-dimensional grids based on the digital terrain analysis of DEM, and divide each grid into different horizontal layers in the vertical direction; a two-dimensional hydrodynamic model construction module, which constructs a distributed hydrological model based on physical mechanisms on each grid and different horizontal layers to describe precipitation, evaporation, soil moisture movement, slope runoff and slope A two-dimensional hydrodynamic model of surface confluence; a coupling module that uses the flow production of each grid unit simulated by the distributed hydrological model as the input flow of the two-dimensional hydrodynamic model to couple the distributed hydrological model with the two-dimensional hydrodynamic model, establishes a distributed hydrological model in mountainous areas, and realizes a detailed simulation of the hydrological process. In plain flood storage and detention areas, a two-dimensional hydrodynamic model of flood evolution in the river channel-flood storage and detention area is established on the basis of real-time subdivision of irregular terrain grids to simulate the spatiotemporal changes of the flood depth and the flooded area, so as to realize the close coupling of runoff production in mountainous areas, one-dimensional river confluence, and two-dimensional flood inundation processes in plain areas.

[0013] In a third aspect, the technical solution adopted by the present invention is: a computer-readable storage medium storing one or more programs, wherein the one or more programs include instructions, and when the instructions are executed by a computing device, the computing device executes any one of the above methods.

[0014] In a fourth aspect, the technical solution adopted by the present invention is: a computing device, comprising: one or more processors, a memory and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include instructions for executing any of the above methods.

[0015] The present invention adopts the above technical solution, which has the following advantages: 1. The present invention constructs a distributed hydrological and hydrodynamic model with physical mechanism for ensemble forecasting. Compared with the traditional lumped hydrological model, the model of the present invention can describe in detail the physical processes of water cycle such as precipitation, evaporation, soil moisture movement, slope runoff, slope confluence, etc., simulate the rainfall-runoff process more reasonably, and provide multi-dimensional flood forecast results of points, lines and surfaces.

[0016] 2. The present invention couples the distributed hydrological model with the two-dimensional hydrodynamic model, establishes a distributed hydrological model in mountainous areas, realizes the fine simulation of hydrological processes, and establishes a two-dimensional hydrodynamic model of flood evolution in river channels and flood storage areas in plain flood storage areas to simulate the spatiotemporal changes of flood depth and flooded areas, providing scientific decision-making support for disaster prevention and mitigation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of a method for constructing a distributed hydrological and hydrodynamic model based on a physical mechanism in an embodiment of the present invention; Figure 2 is a schematic diagram of a distributed hydrological and hydrodynamic model based on a physical mechanism in an embodiment of the present invention, wherein: For precipitation, As a stream in the soil, is surface runoff, It is underground runoff; Figure 3 is a schematic diagram of the hydrological process in cold regions according to an embodiment of the present invention; Figure 4 Schematic diagram of degree-day factor model in an embodiment of the present invention; Figure 5 It is a schematic diagram of slope confluence simulation based on IUH in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] With the rapid development of remote sensing and GIS technology, distributed hydrological models based on physical mechanisms have made great progress. Distributed hydrological models start from the physical mechanism of the water cycle process, fully consider the spatial variability of meteorological, hydrological and surface information, improve the mechanism of the model, and accurately describe the spatiotemporal variation characteristics of the basin hydrological process. This type of model includes Topmodel, MIKE SHE, SWAT, GBHM, HHmodel, etc. However, so far, the application of distributed hydrological models in flood forecasting is relatively small, resulting in insufficient accuracy of flood forecasting, and there is a large gap with the current flood control decision-making needs. In addition, most distributed hydrological models only consider the runoff and confluence process, and do not consider the two-dimensional flooding process in the plain area. Flood forecasts cannot provide flood inundation processes in the plain area, which is difficult to meet the needs of flood control dispatching and command decisions.

[0019] In order to solve the problems of insufficient accuracy guarantee of existing flood forecasts and a large gap with the current flood prevention decision-making needs, the present invention provides a distributed hydrological and hydrodynamic model construction method and system based on physical mechanisms. The model divides the basin into grids in space, and establishes water flow dependencies between two-dimensional grids based on digital terrain analysis of DEM. Each grid is divided into different horizontal layers in the vertical direction, including canopy, surface layer, soil layer, and groundwater layer. Based on physical mechanisms, the physical processes of water cycle such as precipitation, evaporation, soil moisture movement, slope runoff, slope convergence and two-dimensional hydrodynamic processes are described in detail. Therefore, the present invention solves the problem that most statistical models or conceptual lumped models are used in current flood forecasts.

[0020] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0021] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0022] In one embodiment of the present invention, a method for constructing a distributed hydrological and hydrodynamic model based on a physical mechanism is provided. In this embodiment, Figure 1 , Figure 2 As shown, the method comprises the following steps: 1) Construct a distributed hydrological model, divide the watershed into grids on the horizontal plane, establish the water flow dependency between two-dimensional grids based on digital terrain analysis of DEM, and divide each grid into different horizontal layers in the vertical direction; the horizontal layers include canopy layer, surface layer, soil layer and groundwater layer.

[0023] 2) On each grid and at different horizontal layers, a two-dimensional hydrodynamic model is constructed based on physical mechanisms to describe precipitation, evaporation, soil moisture movement, slope runoff generation and slope runoff. 3) The flow rate of each grid unit simulated by the distributed hydrological model is used as the input flow of the two-dimensional hydrodynamic model to couple the distributed hydrological model with the two-dimensional hydrodynamic model, and a distributed hydrological model is established in the mountainous area to realize the fine simulation of the hydrological process; in the plain flood storage area, a two-dimensional hydrodynamic model of the flood evolution of the river channel-flood storage area is established on the basis of real-time subdivision of irregular terrain grids to simulate the spatiotemporal variation of the flood depth and the flooded area, so as to realize the close coupling of the flow rate in the mountainous area, the one-dimensional river confluence and the two-dimensional flood inundation process in the plain area, and provide multi-dimensional flood forecast results of points, lines and surfaces.

[0024] In the above step 1), the distributed hydrological model includes planar structural features and vertical structural features. On the plane, the watershed is divided into grids or sub-basins, and each grid is used as a basic calculation unit; on the vertical plane, each basic calculation unit is divided into different horizontal layers, including the canopy layer, surface layer, soil layer, and groundwater layer.

[0025] In this embodiment, the simulation time step of the distributed hydrological model is variable. For example, when the net rainfall is relatively large, the time step is refined to make the simulation process more detailed; when the net rainfall is small, the step is increased to speed up the simulation.

[0026] In the above step 2), the two-dimensional hydrodynamic model includes a snowmelt process module, a runoff generation module, a slope confluence module, a river confluence module and a two-dimensional flooding module. Among them: The snowmelt process module adopts the degree-day model which is widely used in snowmelt research. This degree-day model calculates the amount of snowmelt based on the empirical relationship between temperature and snowmelt rate.

[0027] Flow generation module, calculates evapotranspiration process (including canopy interception evaporation , vegetation transpiration and bare soil evaporation ), the interaction process between soil water and groundwater, and the surface runoff and infiltration process.

[0028] The slope confluence module uses unit lines to simulate the slope confluence process. In this embodiment, it is assumed that the slope confluence is an approximate linear motion (diffusion) wave and is calculated using the diffusion equation.

[0029] The river confluence module adopts the Muskingum method, which is a river flow calculation algorithm based on water balance and channel storage equations. It is based on the simplified Saint-Venant equation and converts the inflow process of the upstream section of the river into the outflow process of the downstream section. It is an approximate simplified solution method for the calculation of non-steady flow in rivers.

[0030] The two-dimensional flooding module is used to simulate the flooded area and solve the shallow water equation. The shallow water equation is a mathematical model that describes the flow of shallow water bodies. It explains the general laws of shallow water flow during the flow process and is a basis for reflecting shallow water flow.

[0031] When used, compared with the traditional lumped hydrological model, the model used in the present invention can describe in detail the physical processes of water cycle such as precipitation, evaporation, soil moisture movement, slope runoff, slope confluence, etc., and more reasonably simulate the rainfall-runoff process.

[0032] In this embodiment, optionally, Figure 3 , Figure 4 As shown in the figure, the snowmelt process module uses the degree-day factor model (also called the degree-day model) to calculate the snow and ice melt. The degree-day model is a glacier snow melt method based on a single climate factor. Specifically, (1) Where, MELT is the snowmelt depth, in mm / day; CMELT is the hourly meltwater factor, in mm / ℃×hour; TT is the critical temperature of solid precipitation, in ℃; is the air temperature in °C.

[0033] The degree-day model has a simple structure, and its parameters have clear physical meanings and are easy to determine. It is conducive to seeking the relationship between parameters and geographical characteristics, reflecting the main influencing factors of the basin's hydrological process, and greatly improving the accuracy of snowmelt runoff simulation.

[0034] In this embodiment, optionally, the runoff generation module includes an evapotranspiration process simulation module, a soil moisture movement process simulation module and an infiltration process simulation module.

[0035] The evapotranspiration process simulation module includes three types of evaporation: canopy interception evaporation process simulation module, vegetation transpiration process simulation module and bare soil evaporation process simulation module, and the sum of the three is the total actual evapotranspiration of each grid. In this embodiment, only one vegetation cover type is considered in each grid.

[0036] Among them, the canopy interception evaporation process simulation module needs to determine the stress coefficient of soil root distribution and soil water on vegetation transpiration: (1) Soil root distribution: Determining the distribution ratio of vegetation in each soil layer (i.e., root density) is the key prerequisite for estimating plant transpiration in each soil layer. Based on the logist formula, the distribution of roots in each layer is deduced. The reference formula is as follows, and the corresponding parameters are set for each land use. During the calculation process, the active soil root distribution can be dynamically adjusted according to the calculated soil depth (roots below the groundwater surface do not participate in evapotranspiration).

[0037] (2) In the formula, is the cumulative distribution of root biomass in a layer, is the biomass of the root system at a certain layer, The soil depth at which biomass accumulates to 50%, c is the shape coefficient, and d is the soil depth.

[0038] (2) Stress coefficient of soil water on vegetation transpiration: Based on the FAO formula, the model uses the relationship between the soil water in this layer and the field water holding capacity and residual water to calculate the stress coefficient of each layer of soil water on evapotranspiration: When the soil water content in this layer reaches or exceeds the field water holding capacity, the stress coefficient is 1; when the soil water content in this layer is lower than the residual water content, the stress coefficient is 0; when it is between the two, the stress coefficient is calculated based on ( soilwater - soilwaterres ) / ( soilwaterfield - soilwaterres ) is calculated. Among them, soilwater is the soil moisture content, soilwaterfield is the field water holding capacity, soilwaterres is the residual water content.

[0039] Among them, the parameter method for vegetation transpiration calculation is as follows: (1) If there is no vegetation in the grid or the remaining evaporation capacity after interception is close to zero, the evaporation of each layer of soil is zero, and the total evaporation of plants and the total evaporation capacity after evaporation are also zero; (2) For each layer of soil with roots, the model first estimates the potential evaporation capacity of the soil layer based on the root distribution and the stress coefficient of soil water on evaporation: (3) Here, i represents the number of soil layers with roots. is the evaporation of the i-th layer of soil, is the root distribution of the i-th soil layer, petainter To intercept the remaining evaporation capacity after evaporation, is the slope coefficient.

[0040] In addition, the model further estimates the amount of water available for evaporation in this layer of soil according to equation (3), namely: (4) in, is the amount of water available for evaporation in the i-th layer of soil, is the soil moisture of the i-th layer, is the residual moisture of the i-th layer of soil, is the thickness of the i-th soil layer (cm).

[0041] For each layer of soil, the actual evaporation cropet Calculate according to formula (4): (5) in, petatrans To intercept the remaining evaporation capacity after evaporation, i, petcrop, cropwater As shown in formula (2) and formula (3) respectively.

[0042] Bare soil evaporation only considers evaporation from the soil surface with a depth of 10 cm. The current model setting mainly considers the following two conditions: (1) When the residual evaporation capacity after transpiration is close to zero, the model does not consider the evaporation of the surface soil, that is, the evaporation of bare soil is zero; (2) When residual evaporation capacity after transpiration still exists, the model estimates the potential evaporation capacity of bare soil based on the product of the soil water stress coefficient on evapotranspiration and the residual evaporation capacity after transpiration; the model compares the potential evaporation capacity of bare soil with the actual amount of water used for bare soil evaporation, and the minimum value between the two is the actual evaporation of bare soil.

[0043] In this embodiment, canopy interception evaporation only occurs in grids covered by vegetation. If the LAI value in a grid is close to zero, the canopy interception evaporation in the grid is also zero. When canopy evaporation occurs, the evapotranspiration process simulation module in this embodiment considers two situations: whether there is precipitation or not: (1) No precipitation: If the previous residual interception is zero, the canopy interception evaporation is also zero; if the previous residual interception is greater than zero, the interception evaporation is the minimum between the previous residual interception and the potential evapotranspiration. In particular, when the previous residual interception exceeds the potential evapotranspiration, the difference between the two is the remaining interception after the end of the step. It should be noted that there is no net rain in this case.

[0044] (2) When there is precipitation: If the sum of rainfall and the previous interception residual is lower than the potential evapotranspiration, canopy evaporation is equal to the sum of the two, and the interception residual and net rain after the step are both zero; if the sum of the two is higher than the potential evapotranspiration, the model considers two situations: (2.1) When the excess is lower than the maximum interception on the leaf surface, the current step does not produce net rain, the remaining interception after the step is equal to the excess, and the canopy evaporation is equal to the potential evaporation; (2.2) When the excess is higher than the maximum interception on the leaf surface, the interception surplus and canopy evaporation are the same as in the first case, and the net rainfall is the difference between the excess and the maximum interception on the leaf surface. The maximum water interception on the leaf surface is calculated as follows: (6) In the formula, is the maximum water retention capacity, is the leaf area index, is the coefficient.

[0045] In this embodiment, optionally, the soil moisture movement satisfies Darcy's law and the law of conservation of mass, and the soil moisture movement process simulation module is described by the Richards equation, which is calculated using a mixed one-, two-, and three-dimensional Richards equation in a rectangular coordinate system. For example, a two-dimensional form is used as an example for explanation: (7) in, is the soil volume moisture content , For time, Soil water potential , Hydraulic conductivity , is the soil moisture content The function of , are the horizontal and vertical coordinates respectively. Using the finite difference method, the above equation is discretized in time and space as follows: (8) The relationship between soil water matrix potential and soil moisture content can be described by the soil water characteristic curve. Since the soil water characteristic curve is affected by many factors such as soil texture, structure, bulk density, temperature, etc., a unified theoretical formula has not yet been established. Therefore, the van Genuchten model empirical formula is used in this embodiment. This formula describes the soil moisture absorption process and can fit most soil water characteristic curves well. : (9) in, Residual moisture content of soil , Soil saturation moisture content , Soil suction , is a parameter related to intake suction force, , is the shape factor, and The unsaturated hydraulic conductivity of soil is a function of soil moisture content (or soil water matrix potential). In this embodiment, the unsaturated hydraulic conductivity is used. The expression is: (10) (11) in, is the pore tortuosity, taken under the van Genuchten model .

[0046] The surface of the slope is set as the flux boundary, where the flux is the infiltration amount; the bottom is set as the free outflow boundary considering the bedrock leakage; the left boundary of the top of the slope is set as the zero flux boundary; and the right boundary of the foot of the slope is the seepage boundary.

[0047] The expression of the outflow of each grid at the free outflow boundary is shown in the following formula. When the soil moisture content is less than the residual moisture content, the outflow is 0. When it is greater than the residual moisture content, the outflow is calculated under the condition that the hydraulic gradient is always 1.

[0048] (12) in, For outflow , is the horizontal coordinate , is the hydraulic conductivity.

[0049] The outflow rate of each grid at the seepage boundary is as follows: (usually set to 0), outflow occurs in the grid.

[0050] (13) in, is the boundary gradient reduction factor, which is to prevent This is set because an unreasonable value causes traffic abnormality.

[0051] In this embodiment, it is optional that since the rainfall infiltration model mainly adopts the Green-Ampt layered infiltration calculation mode. Therefore, the infiltration process simulation module adopts the Green-Ampt layered infiltration calculation mode. When the net rain infiltrates into the first layer until saturation, the actual hydraulic conductivity of water infiltrating from the first layer to the second layer is calculated by the average value of the first layer soil moisture content and the second layer soil moisture content until the second layer reaches saturation; then the actual hydraulic conductivity from the second layer to the third layer is calculated by the same method, and so on, until the infiltration process stops. Specifically, the following steps are included: (3.1) In a time step ( ), calculate the total infiltration water content within this step according to the net rain and the actual surface infiltration rate ( ), if the infiltration water is equal to 0, the infiltration ends; if there is infiltration, go to the next step; (3.2) When water infiltrates into the first layer, calculate the maximum capacity of the first layer (Formula 9) determines whether the layer can accommodate all the infiltrated water. If not, the cumulative infiltration volume of the layer is the maximum capacity of the layer. , then calculate the time to reach saturation , Residual infiltration water ( ) and the remaining infiltration time ( ),when and When , it enters the next layer; otherwise, the infiltration ends; (3.3) After the first layer reaches saturation, the effective hydraulic conductivity of water from the first layer to the second layer is calculated by the average of the soil moisture content of the first layer and the soil moisture content of the second layer (Equation 10), and the maximum capacity of the second layer is calculated , determine whether the layer can accommodate all the remaining infiltration water, if not, calculate the time to reach saturation , Residual infiltration water ( ) and the remaining infiltration time ( ),when and When , it enters the next layer; otherwise, the infiltration ends; (3.4) After the second layer reaches saturation, the effective hydraulic conductivity of water entering the third layer from the second layer is calculated by the average of the soil moisture content of the second layer and the soil moisture content of the third layer, and the maximum capacity of the third layer is calculated... and so on, until the last layer is saturated; (3.5) When the last layer reaches saturation, if and , the remaining water is discharged into the groundwater through free outflow, and the infiltration ends.

[0052] (3.6) After the infiltration is completed, the soil moisture content of each layer in the previous time step is added to the cumulative infiltration of each layer to obtain the soil moisture content of each layer in the current time step, which is used for the next calculation.

[0053] In the calculation of each layer, in addition to the remaining infiltration water and the remaining time, if the groundwater level is higher than the lower interface of the current soil layer, the infiltration ends and the remaining infiltration water is freely discharged into the groundwater.

[0054] The dimensionless formula for stratified infiltration can be written as: (14) In the formula, represents the cumulative infiltration time, Indicates the depth of the soil layer, Represents the cumulative infiltration volume.

[0055] In the above embodiment, Figure 5 As shown, the slope confluence module uses the unit line (IUH) to simulate the slope confluence process, including: calculating the grid confluence response and the confluence response of the flow path.

[0056] Calculate the grid confluence response, assuming that the slope confluence process of the grid unit is a one-dimensional unstable flow, and use the diffusion wave equation to calculate: (15) in, express time Slope flow at location, For the The speed of the grid motion wave, For the The diffusion coefficient of the grid.

[0057] At the exit of the grid, the velocity and diffusion coefficient of the moving wave are considered to be constants, and the following equation is solved based on the first pass time density function of the Brownian motion: (16) in, For the The impulse response of a grid cell, For the The size of the grid cell, For the The speed of the grid motion wave, For the The diffusion coefficient of the grid. and It can be calculated according to the following formula: (17) (18) For Grid The average water conservancy radius, For Grid The slope For Grid Flow rate. It can be calculated based on the upstream control area of ​​the grid: (19) in, For Grid The upstream cumulative confluence area, and are the network coefficient and geometric expansion index respectively.

[0058] It can be calculated based on the Manning coefficient: (20) in, For Grid Manning coefficient, For Grid The average water conservancy radius, For Grid The slope of the

[0059] The confluence response of the calculated flow path is obtained by the first pass time density function of the Brownian motion. Specifically, the confluence response of a flow path is also the first pass time density function of the Brownian motion. , defined as follows: (twenty one) is the average confluence time from the starting grid to the outlet grid on the flow path, is the variance of the confluence time.

[0060] Calculated based on flow rate and expansion factor: (twenty two) In the formula, For the The size of the grid cell, For the The speed of the wave moving through each grid, N is the number of grids.

[0061] Variance of confluence time : (twenty three) In the formula, For the The diffusion coefficient of the grid.

[0062] In the above embodiment, the river confluence module adopts Muskingum method, which calculates the inflow process of the upstream section of the river into the outflow process of the downstream section based on the simplification of Saint-Venant equation.

[0063] In this embodiment, the water balance equation is: (twenty four) In the formula, , They refer to the inflow and outflow at the previous moment respectively. , They refer to the inflow and outflow at this moment respectively. and is the water storage capacity of the river section at the previous moment and this moment, is the calculation time step.

[0064] Tank storage equation: (25) in, is the water storage capacity of the river section, is the storage constant with time dimension, Dimensionless flow weighting factor.

[0065] Solving equation (24) and equation (25) together, we can obtain the flow rate of the river: In the formula, , , yes , , The function of , They refer to the inflow and outflow at the previous moment respectively. , They refer to the inflow and outflow at this moment respectively; is the storage constant with time dimension, is the dimensionless flow weighting factor, is the calculation time step.

[0066] In the above embodiment, shallow water flow is composed of flowing water with a water depth far less than that of horizontal flow, which is generally seen in the flow of natural rivers. Studying shallow water flow is an important part of flood control and other projects. The shallow water equation is an integral form of the Reynolds Equation (RE) along the water depth direction under certain basic assumptions.

[0067] The movement of water flow follows several basic physical laws, such as the law of conservation of mass, Newton's second law, and the law of conservation of energy. After the above physical laws are applied to the fluid motion process, the continuity equation, momentum equation, energy equation and other equations applicable to fluid motion are derived. Most of these equations exist in the form of nonlinear hyperbolic conservation law equations, and the shallow water equation is one of them. The shallow water equation is a mathematical model that describes the flow of shallow water bodies. It explains the general laws of shallow water flow during the flow process and is a basis for reflecting shallow water flow.

[0068] Therefore, the 2D inundation module is used to simulate the flood inundation area, using shallow water equations to solve, including: The shallow water equation is the integral form of the Reynolds equation along the water depth direction under basic assumptions; The basic assumptions include: ignoring the vertical velocity and vertical velocity gradient, assuming that the pressure is hydrostatic along the water depth, the flow form is a gradual flow, the amplitude of water surface fluctuation is small compared with the water depth and / or the local head loss is negligible.

[0069] In this embodiment, the complete shallow water equation is in the form of: (26) In the above formula, l is a dummy indicator ( l = 1,2), i is a free indicator; S i The first item in is the gravity term, which is determined by the terrain characteristics; S i The second item in is the surface wind stress term and the bottom resistance source term; S i The third item in is the viscosity term, including the molecular viscosity term and the turbulent viscosity term. In general, the molecular viscosity term is much smaller than the turbulent viscosity term and can be ignored. S i The last item is the Coriolis force term, f cor is the Coriolis parameter. When only the evolution of floods is considered, the convection effect is dominant over the diffusion effect. Therefore, in most existing models, the viscosity term is generally ignored. When the spatial scale of the model application is much smaller than the global scale, or when the model is applied to low-latitude areas, the influence of the Coriolis force is generally ignored. The present invention selects the shallow water equation that ignores the wind stress term, the viscosity term and the Coriolis force term as the control equation.

[0071] In summary, the present invention uses a distributed hydrological and hydrodynamic model with a physical mechanism to make an ensemble forecast. Compared with the traditional lumped hydrological model, the model used in the present invention describes in detail the physical processes of water cycle such as precipitation, evaporation, soil moisture movement, slope runoff, and slope confluence, and simulates the rainfall-runoff process more reasonably, and can provide multi-dimensional flood forecast results of points, lines, and surfaces. In addition, the present invention couples the distributed hydrological model with the two-dimensional hydrodynamic model, establishes a distributed hydrological model in mountainous areas, realizes a fine simulation of the hydrological process, and establishes a two-dimensional hydrodynamic model of the evolution of river-flood storage and detention areas in plain flood storage and detention areas, simulating the spatiotemporal changes of the flood depth and flooded area, and providing scientific support for flood control dispatching and command decision-making.

[0072] In one embodiment of the present invention, a distributed hydrological and hydrodynamic model construction system based on physical mechanism is provided, which includes: Distributed hydrological model building module, used to build a distributed hydrological model, divide the watershed into grids on the horizontal plane, establish the water flow dependency between two-dimensional grids based on digital terrain analysis of DEM, and divide each grid into different horizontal layers in the vertical direction; The two-dimensional hydrodynamic model building module builds two-dimensional hydrodynamic models for describing precipitation, evaporation, soil moisture movement, slope runoff and slope confluence based on physical mechanisms on each grid and different horizontal layers. The coupling module couples the distributed hydrological model with the two-dimensional hydrodynamic model, establishes a distributed hydrological model in mountainous areas, realizes the fine simulation of hydrological processes, and establishes a two-dimensional hydrodynamic model of flood evolution in river-flood storage areas based on the real-time subdivision of irregular terrain grids in plain flood storage areas. The model simulates the spatiotemporal changes of flood depth and flooded area, so as to realize the close coupling of runoff generation in mountainous areas, one-dimensional river confluence and two-dimensional flood inundation processes in plain areas.

[0073] In the above embodiment, the distributed hydrological model includes: planar structural features and vertical structural features; Divide the watershed into grids or sub-basins on the plane, and each grid is used as a basic calculation unit; On the vertical plane, each basic calculation unit is divided into different horizontal layers, including the canopy layer, surface layer, soil layer and groundwater layer.

[0074] In the above embodiment, the two-dimensional hydrodynamic model includes: The snowmelt process module uses the degree-day model to calculate the amount of snowmelt based on the empirical relationship between temperature and snowmelt rate; Runoff module, which calculates evapotranspiration, soil water and groundwater interaction, surface runoff and infiltration; Slope confluence module uses unit lines to simulate the slope confluence process; The river confluence module uses Muskingum method to simplify the Saint-Venant equation and converts the inflow process of the upstream section of the river into the outflow process of the downstream section. The 2D inundation module is used to simulate flooded areas using shallow water equations.

[0075] In this embodiment, the runoff generation module includes an evapotranspiration process simulation module, a soil moisture movement process simulation module, and an infiltration process simulation module; The evapotranspiration process simulation module includes three types of evaporation: canopy interception evaporation process simulation module, vegetation transpiration process simulation module and bare soil evaporation process simulation module. The sum of the three is the total actual evapotranspiration of each grid. The soil moisture movement simulation module is described by the Richards equation, which is calculated using the mixed one-, two-, and three-dimensional Richards equations in a rectangular coordinate system; The infiltration process simulation module adopts the Green-Ampt layered infiltration calculation mode. When net rain infiltrates into the first layer until it is saturated, the actual hydraulic conductivity of water infiltrating from the first layer to the second layer is calculated by the average value of the soil moisture content of the first layer and the soil moisture content of the second layer until the second layer reaches saturation; the actual hydraulic conductivity from the second layer to the third layer is calculated by the same method, and so on, until the infiltration process stops.

[0076] In this embodiment, the slope confluence module uses unit lines to simulate the slope confluence process, including: calculating the confluence response of the grid and the confluence response of the flow path; Calculate the grid confluence response, assuming that the slope confluence process of the grid unit is a one-dimensional unstable flow, and use the diffusion wave equation for calculation; The confluence response of the flow path is calculated based on the first pass time density function of the Brownian motion.

[0077] In this embodiment, the river confluence module adopts Muskingum method, which simplifies the Saint-Venant equation and converts the inflow process of the upstream section of the river into the outflow process of the downstream section, which is: In the formula, , , yes , , The function of , They refer to the inflow and outflow at the previous moment respectively. , They refer to the inflow and outflow at this moment respectively; is the storage constant, is the dimensionless flow weighting factor, is the calculation time step.

[0078] In this embodiment, the two-dimensional flooding module is used to simulate the flooding area, and the shallow water equation is used to solve it, including: The shallow water equation is the integral form of the Reynolds equation along the water depth direction under basic assumptions; The basic assumptions include: ignoring the vertical velocity and vertical velocity gradient, assuming that the pressure is hydrostatic along the water depth, the flow form is a gradual flow, the amplitude of water surface fluctuation is small compared with the water depth and / or the local head loss is negligible.

[0079] The system provided in this embodiment is used to execute the above-mentioned method embodiments. Please refer to the above-mentioned embodiments for specific processes and detailed contents, which will not be repeated here.

[0080] In one embodiment of the present invention, a computing device is provided, which may be a terminal, and may include: a processor, a communication interface, a memory, a display screen, and an input device. Among them, the processor, the communication interface, and the memory communicate with each other through a communication bus. The processor is used to provide computing and control capabilities. The memory includes a non-volatile storage medium and an internal memory, and the non-volatile storage medium stores an operating system and a computer program. When the computer program is executed by the processor, the method in each of the above embodiments is implemented; the internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be implemented through WIFI, a management network, NFC (near field communication) or other technologies. The display screen may be a liquid crystal display screen or an electronic ink display screen, and the input device may be a touch layer covered on the display screen, or a key, trackball or touchpad provided on the housing of the computing device, or an external keyboard, touchpad or mouse, etc. The processor may call the logic instructions in the memory.

[0081] In addition, the logic instructions in the above-mentioned memory can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when 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, which is stored in a storage medium and includes several 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, etc., which can store program code.

[0082] In one embodiment of the present invention, a computer program product is provided, wherein the computer program product includes a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program includes program instructions. When the program instructions are executed by a computer, the computer can execute the methods provided by the above-mentioned method embodiments.

[0083] In one embodiment of the present invention, a non-transitory computer-readable storage medium is provided, wherein the non-transitory computer-readable storage medium stores server instructions, and the computer instructions enable a computer to execute the methods provided in the above embodiments.

[0084] The above embodiment provides a computer-readable storage medium, whose implementation principle and technical effect are similar to those of the above method embodiment, and will not be repeated here.

[0085] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented 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 generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0086] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0087] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0088] 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 method for constructing a distributed hydrological and hydrodynamic model based on physical mechanisms, characterized in that: include: Construct a distributed hydrological model, divide the watershed into grids on the horizontal plane, establish the water flow dependency between two-dimensional grids based on digital terrain analysis of DEM, and divide each grid into different horizontal layers in the vertical direction; On each grid and at different horizontal layers, a two-dimensional hydrodynamic model is constructed based on physical mechanisms to describe precipitation, evaporation, soil moisture movement, slope runoff and slope confluence. The flow production of each grid unit simulated by the distributed hydrological model is used as the input flow of the two-dimensional hydrodynamic model to couple the distributed hydrological model with the two-dimensional hydrodynamic model. A distributed hydrological model is established in the mountainous area to realize the fine simulation of the hydrological process. In the plain flood storage and detention area, a two-dimensional hydrodynamic model of flood evolution in the river channel and flood storage and detention area is established on the basis of real-time subdivision of irregular terrain grids to simulate the spatiotemporal changes of the flooded water depth and the flooded area, so as to realize the close coupling of the flow production in the mountainous area, the one-dimensional river confluence and the two-dimensional flood inundation process in the plain area.

2. The method for constructing a distributed hydrological and hydrodynamic model based on physical mechanism according to claim 1, characterized in that: The distributed hydrological model includes: planar structural characteristics and vertical structural characteristics; Divide the watershed into grids or sub-basins on the plane, and each grid is used as a basic calculation unit; On the vertical plane, each basic calculation unit is divided into different horizontal layers, including the canopy layer, surface layer, soil layer and groundwater layer.

3. The method for constructing a distributed hydrological and hydrodynamic model based on physical mechanism according to claim 1, characterized in that: The 2D hydrodynamic model includes: The snowmelt process module uses the degree-day model to calculate the amount of snowmelt based on the empirical relationship between temperature and snowmelt rate; Runoff module, which calculates evapotranspiration, soil water and groundwater interaction, surface runoff and infiltration; Slope confluence module uses unit lines to simulate the slope confluence process; The river confluence module uses Muskingum method to simplify the Saint-Venant equation and converts the inflow process of the upstream section of the river into the outflow process of the downstream section. The 2D inundation module is used to simulate flooded areas using shallow water equations.

4. The method for constructing a distributed hydrological and hydrodynamic model based on physical mechanism as claimed in claim 3, characterized in that: The runoff generation module includes the evapotranspiration process simulation module, the soil moisture movement process simulation module and the infiltration process simulation module; The evapotranspiration process simulation module includes three types of evaporation: canopy interception evaporation process simulation module, vegetation transpiration process simulation module and bare soil evaporation process simulation module. The sum of the three is the total actual evapotranspiration of each grid. The soil moisture movement simulation module is described by the Richards equation, which is calculated using the mixed one-, two-, and three-dimensional Richards equations in a rectangular coordinate system; The infiltration process simulation module adopts the Green-Ampt layered infiltration calculation mode. When net rain infiltrates into the first layer until it is saturated, the actual hydraulic conductivity of water infiltrating from the first layer to the second layer is calculated by the average value of the soil moisture content of the first layer and the soil moisture content of the second layer until the second layer reaches saturation; the actual hydraulic conductivity from the second layer to the third layer is calculated by the same method, and so on, until the infiltration process stops.

5. The method for constructing a distributed hydrological and hydrodynamic model based on physical mechanism as claimed in claim 3, characterized in that: The slope confluence module uses unit lines to simulate the slope confluence process, including: calculating the confluence response of the grid and the confluence response of the flow path; Calculate the grid confluence response, assuming that the slope confluence process of the grid unit is a one-dimensional unstable flow, and use the diffusion wave equation for calculation; The confluence response of the flow path is calculated by the first pass time density function of the Brownian motion.

6. The method for constructing a distributed hydrological and hydrodynamic model based on physical mechanism as claimed in claim 3, characterized in that: The river confluence module uses the Muskingum method. Based on the simplified Saint-Venant equation, the inflow process of the upstream section of the river section is calculated into the outflow process of the downstream section, which is: In the formula, , , yes , , The function of , They refer to the inflow and outflow at the previous moment respectively. , They refer to the inflow and outflow at this moment respectively; is the storage constant, is the dimensionless flow weighting factor, is the calculation time step.

7. The method for constructing a distributed hydrological and hydrodynamic model based on physical mechanism as claimed in claim 3, characterized in that: The 2D Inundation Module is used to simulate flooded areas using shallow water equations, including: The shallow water equation is the integral form of the Reynolds equation along the water depth direction under basic assumptions; The basic assumptions include: ignoring the vertical velocity and vertical velocity gradient, assuming that the pressure is hydrostatic along the water depth, the flow form is a gradual flow, the amplitude of water surface fluctuation is small compared with the water depth and / or the local head loss is negligible.

8. A distributed hydrological and hydrodynamic model construction system based on physical mechanism, characterized in that: include: Distributed hydrological model building module, used to build a distributed hydrological model, divide the watershed into grids on the horizontal plane, establish the water flow dependency between two-dimensional grids based on digital terrain analysis of DEM, and divide each grid into different horizontal layers in the vertical direction; The two-dimensional hydrodynamic model building module builds two-dimensional hydrodynamic models for describing precipitation, evaporation, soil moisture movement, slope runoff and slope confluence based on physical mechanisms on each grid and different horizontal layers. The coupling module uses the flow production of each grid unit simulated by the distributed hydrological model as the input flow of the two-dimensional hydrodynamic model to couple the distributed hydrological model with the two-dimensional hydrodynamic model, establishes a distributed hydrological model in the mountainous area, and realizes the fine simulation of the hydrological process. In the plain flood storage area, based on the real-time subdivision of the irregular terrain grid, a two-dimensional hydrodynamic model of the flood evolution of the river channel-flood storage area is established to simulate the spatiotemporal variation of the flood depth and the flooded area, so as to realize the close coupling of the flow production in the mountainous area, the one-dimensional river confluence and the two-dimensional flood inundation process in the plain area.

9. A computer-readable storage medium storing one or more programs, characterized in that: The one or more programs include instructions, which, when executed by a computing device, cause the computing device to perform any one of the methods of claims 1 to 7.

10. A computing device, characterized in that include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include instructions for executing any one of the methods described in claims 1 to 7.

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