A method for calculating spatial heterogeneity time-varying mixed runoff based on dynamic evolution of infiltration capacity

Abstract

The application discloses a kind of based on the spatial heterogeneity time-varying mixed runoff calculation method of dynamic evolution of infiltration capacity, the method includes the following steps: step 1, target basin spatial heterogeneity partitioning;Step 2, small watershed unit runoff characteristic curve construction;Step 3, runoff parameter functionization representation based on underlying surface characteristics;Step 4, spatial heterogeneity time-varying mixed runoff calculation.The method described in the application systematically solves the problems of the existing runoff method, such as insufficient representation of time variation and spatial heterogeneity of key parameters, and weak coupling of different runoff mechanisms, significantly improves the physical mechanism rationality of basin runoff calculation under complex hydro-meteorological and underlying surface conditions, and provides more reliable technical support for basin hydrological simulation.

Description

Technical Field

[0001] This invention belongs to the field of hydrological simulation and flood forecasting technology, and in particular relates to a spatially heterogeneous time-varying mixed runoff calculation method based on the dynamic evolution of infiltration capacity. Background Technology

[0002] Runoff generation calculation is a core issue in hydrological simulation and is of great significance for flood forecasting and water resource assessment. Although existing runoff generation calculation methods have developed technical systems with different focuses for different application scenarios, such as infiltration runoff that focuses on the comparison between rainfall intensity and soil infiltration capacity, and storage runoff that relies on soil moisture saturation to initiate the runoff process, their mechanistic characterization still needs to be deepened.

[0003] First, existing runoff calculation methods mostly rely on the assumption of watershed homogenization and employ lumped parameterization schemes. Even with spatial discretization, they fail to fully consider the physical control of underlying surface characteristics such as soil type, topography, and vegetation on the spatial differentiation of parameters, making it difficult for algorithms to accurately analyze the spatial distribution patterns of runoff. Second, existing calculation methods are insufficient in handling time-varying physical processes such as soil infiltration. They often set soil infiltration capacity as a constant or use simple empirical decay functions, failing to effectively describe the dynamic feedback of soil moisture and structure during rainfall, resulting in fundamental deviations in the description of the time-varying characteristics of infiltration. Furthermore, in actual watersheds, over-infiltration and storage mechanisms commonly coexist and dynamically switch with hydrological conditions. Existing models mostly rely on a single mechanism, unable to adapt to the dynamic switching of runoff generation mechanisms under different rainfall intensities and soil conditions, and thus failing to meet the accuracy requirements of flood simulation and forecasting under complex hydrological and meteorological conditions.

[0004] Therefore, there is an urgent need in this field for a runoff generation calculation method that can comprehensively reflect the spatial heterogeneity of the watershed, the dynamic evolution characteristics of parameters, and the scientific coupling relationship between the over-infiltration and storage mechanisms. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating spatially heterogeneous time-varying mixed runoff based on the dynamic evolution of infiltration capacity, so as to solve the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention discloses a method for calculating spatially heterogeneous time-varying mixed runoff based on the dynamic evolution of infiltration capacity. The method includes the following steps:

[0008] Step 1: Spatial Heterogeneity Zoning of the Target Watershed: Based on multi-source geographic information data of the target watershed, which is obtained through public data platforms or surveying and mapping departments, and taking into account factors such as topography, water system, and administrative boundaries, the watershed is divided into a series of smaller watershed units according to a certain catchment area threshold based on hydrological runoff relationships and hydrological analysis tools; then, the smaller watershed units are classified according to infiltration characteristics and water storage characteristics.

[0009] Step 2: Construction of runoff generation characteristic curves for small watershed units: Based on the continuous variation characteristics of runoff generation indicators within small watershed units, spatial distribution curves are constructed for quantitative description, including spatial distribution curves of infiltration capacity and spatial distribution curves of free water storage capacity.

[0010] (1) Constructing the spatial distribution curve of infiltration capacity: describing the relationship between the infiltration capacity threshold f and the area ratio α f The functional relationship for the proportion of area with infiltration capacity less than or equal to f is:

[0011] (1)

[0012] In the formula: G is α f The functional relationship between f and f; For the set of function parameters;

[0013] The G-function relationship has the following characteristics: ① When α f When f increases from 0, f increases monotonically from 0; ② The growth rate of f increases with α. f Increases and gradually decreases; ③ When α f As f approaches 1, f approaches its maximum value. m ;

[0014] (2) Constructing the spatial distribution curve of free water storage capacity: describing the free water storage capacity threshold S and the area ratio α S The functional relationship for the area proportion of regions with free water storage capacity less than or equal to S is as follows:

[0015] (2)

[0016] In the formula: H is α S The functional relationship between S and S; For the set of function parameters;

[0017] The H-function relationship has the following characteristics: ① When α S When S increases from 0, it monotonically increases from 0; ② The growth rate of S increases with α. S Increases and gradually decreases; ③ When α S As S approaches 1, S approaches its maximum value. m ;

[0018] Step 3: Functional characterization of runoff generation parameters based on underlying surface characteristics: This involves setting the set of function parameters for the spatial distribution curve of infiltration capacity. And the set of function parameters for the spatial distribution curve of free water storage capacity A physical mechanism for deriving parameters is established by characterizing the underlying surface features as a function.

[0019] (1) To address the time-varying dynamic characteristics of the spatial distribution curve of soil infiltration capacity caused by the dynamic attenuation characteristics of soil infiltration capacity during rainfall events, the following measures will be taken: Characterized as a time-varying dynamic function:

[0020] (3)

[0021] In the formula: The values ​​of the parameters of the spatial distribution curve of infiltration capacity at time t are determined by the time-varying characteristic function α and the time-invariant characteristic function β. V1(t), V2(t), ..., V5(t) represent soil moisture content, surface temperature, surface water depth, surface soil crust state, and ground rainfall intensity, respectively. R1, R2, ..., R5 represent land use, soil texture, soil layer thickness, impermeable layer depth, and average slope, respectively. For small watershed units with different infiltration characteristics, different functional relationships α and β are used to reflect the spatial heterogeneity of the parameters.

[0022] (2) The free water storage capacity does not change significantly within a single rainfall event. Characterized as a time-invariant static function:

[0023] (4)

[0024] In the formula: The time-invariant characteristic function is used; for small watershed units with different watershed characteristics, different functional relationships φ are used to reflect the spatial heterogeneity of parameters.

[0025] Step 4, Calculation of spatially heterogeneous time-varying mixed runoff: The processes of infiltration excess runoff and saturation runoff are vertically coupled in series. The runoff calculation for each small watershed unit in each time period is performed as follows:

[0026] (1) Calculation of upper layer over-permeability flow:

[0027] ① Based on the soil condition at time t, determine the spatial distribution curve of the current infiltration capacity according to formulas (1) and (3), and denote the maximum infiltration capacity at the watershed point as . Further integration of the curve yields the average infiltration capacity of the current small watershed unit. ;

[0028] ② Compare the average rainfall intensity of small watershed units during time period t. and The size relationship is used to calculate the actual average infiltration rate of a small watershed unit. and average infiltration rate F(t);

[0029] if The entire small watershed unit infiltrates using its infiltration capacity. = Conversely, surface runoff occurs only in localized areas where the infiltration capacity is less than or equal to i(t); in other areas, infiltration occurs at a rate of i(t). for:

[0030] (5)

[0031] Calculation of small watershed units Subsequently, the average infiltration rate F(t) of the small watershed unit during this period is:

[0032] (6)

[0033] ③ Based on the calculated average infiltration volume F(t), calculate the surface runoff RS generated by excessive infiltration. 超渗 for:

[0034] (7)

[0035] (2) Calculation of flow generation when the lower layer is fully filled:

[0036] ① Determine the spatial distribution curve of free water storage capacity according to formulas (2) and (4), and denote the maximum point and average free water storage capacity of the small watershed unit as S. m and Based on the average free water storage of the small watershed at the beginning of the period The maximum free water storage capacity at the saturated point within the corresponding small watershed can be obtained by inverse calculation using curve integral. ;

[0037] ② Using the average infiltration flow F(t) obtained from the super-infiltration flow calculation as input, calculate the change in free water storage in the small watershed after infiltration replenishment;

[0038] if After infiltration replenishment, the free water at all points in the small watershed is fully stored, resulting in an increased average free water storage. = Simultaneously, the entire small watershed generates excess water storage, replenishing surface runoff RS. 蓄满 for:

[0039] (8)

[0040] Conversely, only in certain areas where the water storage capacity can be met after supplementing F(t) will the free water be filled, while simultaneously generating supplementary surface runoff RS. 蓄满 With excess water storage, in this case, RS 蓄满 for:

[0041] (9)

[0042] Correspondingly, for:

[0043] (10)

[0044] ③ Calculate the free water storage after infiltration replenishment. The interflow RI and groundwater runoff RG are obtained by proportionally discharging free water:

[0045] (11)

[0046] In the formula, KI and KG are the outflow coefficients;

[0047] ④Calculate the average free water storage of the small watershed unit at the end of the calculation period. As the initial value for the next period, This enables continuous simulation of flow generation calculation across time periods;

[0048] (12)

[0049] (3) Calculation of total output flow:

[0050] The total runoff R of each small watershed unit during time period t 总 (t) represents the sum of all runoff components, including surface runoff, interflow, and groundwater runoff, i.e.:

[0051] (13)

[0052] After the runoff generation calculations for all small watershed units are completed, the distributed runoff generation results for the entire target watershed are obtained.

[0053] Furthermore, the multi-source geographic information data mentioned in step 1 includes digital elevation model (DEM) and remote sensing imagery; the catchment area threshold is set based on experience.

[0054] Furthermore, the classification of small watershed units according to infiltration characteristics and storage characteristics in step 1 is specifically as follows:

[0055] Infiltration characteristics classification: Based on the attributes that affect infiltration capacity, cluster analysis is used to divide small watershed units into several infiltration characteristic types. Small watershed units within the same type have similar infiltration physical characteristics. Among them, the attributes that affect infiltration capacity include soil texture, organic matter content, and bulk density.

[0056] Water storage capacity classification: Based on the attributes that affect water storage capacity, cluster analysis is used to divide small watershed units into several water storage capacity types. Small watershed units within the same type have similar water storage capacity characteristics. Among them, the attributes that affect water storage capacity include slope, soil thickness, vegetation cover, and land use type.

[0057] Furthermore, in step 2, the function G takes the form of an S-curve, an exponentially saturated curve, or a polynomial fitting curve; the function H takes the form of an S-curve, an exponentially saturated curve, or a polynomial fitting curve.

[0058] The beneficial effects of the present invention are: the method described in the present invention systematically solves the problems of insufficient characterization of the time-varying and spatial heterogeneity of key parameters and weak coupling of different runoff generation mechanisms in existing runoff generation methods, significantly improves the rationality of the physical mechanism of watershed runoff generation calculation under complex hydrological and meteorological conditions and underlying surface conditions, and provides more reliable technical support for watershed hydrological simulation.

[0059] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0060] Figure 1 This is a schematic diagram of the method flow described in this invention;

[0061] Figure 2 This is a schematic diagram of the spatial distribution curve of infiltration capacity;

[0062] Figure 3 This is a schematic diagram of the spatial distribution curve of free water storage capacity;

[0063] Figure 4 This is a schematic diagram of localized over-permeability flow.

[0064] Figure 5 This is a schematic diagram of a localized area filled with runoff. Detailed Implementation

[0065] This invention discloses a spatially heterogeneous time-varying mixed runoff calculation method based on the dynamic evolution of infiltration capacity, such as... Figure 1 As shown, the method includes the following steps:

[0066] Step 1: Spatial heterogeneity partitioning of the target watershed.

[0067] Based on multi-source geographic information data of the target watershed (multi-source geographic information data includes digital elevation models (DEM), remote sensing images, etc., which are generally obtained through public data platforms or surveying and mapping departments), taking into account factors such as topography, water system, and administrative boundaries, and according to hydrological confluence relationships (such as the D8 algorithm) and combined with hydrological analysis tools, sub-watersheds are automatically divided according to a certain catchment area threshold (set based on experience), thus dividing the target watershed into a series of small watershed units.

[0068] Then, the dual attributes of the small watershed units are classified:

[0069] (1) Classification of infiltration characteristics: Based on soil texture, organic matter content, bulk density and other attributes that affect infiltration capacity, cluster analysis is used to divide small watershed units into several infiltration characteristic types. Small watershed units within the same type have similar infiltration physical characteristics.

[0070] (2) Classification of water storage capacity characteristics: Based on the attributes that affect water storage capacity, such as slope, soil thickness, vegetation coverage, and land use type, cluster analysis is used to divide small watershed units into several water storage capacity characteristics. Small watershed units within the same type have similar water storage capacity characteristics.

[0071] By classifying the watershed into small watershed units, different infiltration and storage characteristics were distinguished in the target watershed.

[0072] Step 2: Constructing the runoff characteristic curve of a small watershed unit.

[0073] To quantitatively describe the continuous variation characteristics of runoff generation indicators (infiltration capacity and free water storage capacity) within small watershed units caused by micro-topography, local variations in soil structure, and uneven vegetation distribution, spatial distribution curves (including spatial distribution curves of infiltration capacity and free water storage capacity) are constructed.

[0074] (1) Construct a spatial distribution curve of infiltration capacity, the shape of which is shown in the figure. Figure 2 As shown. Describes the infiltration capacity threshold f in relation to the area ratio α. f The functional relationship between (the proportion of area with infiltration capacity less than or equal to f) and (the percentage of area with infiltration capacity less than or equal to f) is as follows:

[0075] (1)

[0076] In the formula, G is α f The functional relationship between f and f; This is the set of function parameters.

[0077] The G-function relationship has the following characteristics: ① When α f When f increases from 0, f increases monotonically from 0; ② The growth rate of f increases with α. f Increases and gradually decreases; ③ When α fAs f approaches 1, f approaches its maximum value. m .

[0078] The curve shape described above reflects the spatial heterogeneity of permeability distribution: low-permeability areas account for a large proportion while high-permeability areas account for a small proportion, which conforms to the statistical characteristics of natural watersheds. G can be a continuous smooth function form such as an S-curve, an exponential saturation curve, or a multi-order polynomial.

[0079] (2) Construct a spatial distribution curve of free water storage capacity, the shape of which is shown in the figure. Figure 3 As shown. Describes the relationship between the free water storage capacity threshold S and the area ratio α. S The functional relationship between (the area percentage of regions with free water storage capacity less than or equal to S) and (the area percentage of regions with free water storage capacity less than or equal to S) is as follows:

[0080] (2)

[0081] In the formula, H is α S The functional relationship between S and S; This is the set of function parameters.

[0082] The H-function relationship has the following characteristics: ① When α S When S increases from 0, it monotonically increases from 0; ② The growth rate of S increases with α. S Increases and gradually decreases; ③ When α S As S approaches 1, S approaches its maximum value. m .

[0083] The curve shape described above reflects the spatial heterogeneity of free water storage capacity: low-capacity areas account for a large proportion while high-capacity areas account for a small proportion, which conforms to the statistical characteristics of natural watersheds. H can be a continuous smooth function form such as an S-curve, an exponential saturation curve, or a multi-order polynomial.

[0084] Step 3: Functional characterization of runoff generation parameters based on underlying surface characteristics.

[0085] Set of function parameters for the spatial distribution curve of infiltration capacity And the set of function parameters for the spatial distribution curve of free water storage capacity A physical mechanism for deriving parameters is established by characterizing the underlying surface features as a function.

[0086] (1) The time-varying dynamic function: This addresses the time-varying dynamic characteristics of the spatial distribution curve of soil infiltration capacity during rainfall events, stemming from the dynamic decay of unsaturated hydraulic conductivity with varying water content due to surface crust formation and the evolution of water content. Characterized as a time-varying dynamic function:

[0087] (3)

[0088] In the formula: The values ​​of the parameters of the spatial distribution curve of infiltration capacity at time t are determined by the time-varying characteristic function α and the time-invariant characteristic function β. V1(t), V2(t), ..., V5(t) represent soil moisture content, surface temperature, surface water depth, surface soil crust state, and ground rainfall intensity, respectively. These parameters change with time during a rainfall event, affecting the dynamic changes of the parameters. R1, R2, ..., R5 represent land use, soil texture, soil layer thickness, impermeable layer depth, and average slope, respectively. These parameters do not change with time during a rainfall event, reflecting the influence of the inherent properties of the underlying surface.

[0089] For small watershed units with different infiltration characteristics, different functional relationships α and β are used to reflect the spatial heterogeneity of parameters.

[0090] (2) The time-invariant static function: the free water storage capacity does not change significantly within a single rainfall event. Characterized as a time-invariant static function:

[0091] (4)

[0092] In the formula: It is a time-invariant characteristic function; it is different from the β function type in formula (3).

[0093] For small watershed units with different watershed characteristics, different functional relationships φ are used to reflect the spatial heterogeneity of parameters.

[0094] Step 4: Calculation of spatially heterogeneous time-varying mixed flow generation:

[0095] The processes of excessive permeability runoff and saturation runoff are vertically coupled in series, and the runoff calculations for each small watershed unit at each time period are performed in the following order:

[0096] (1) Calculation of upper layer over-permeability flow:

[0097] ① Based on the soil condition at time t, determine the spatial distribution curve of the current infiltration capacity according to formulas (1) and (3), and denote the maximum infiltration capacity at the watershed point as . Furthermore, the average infiltration capacity of the current small watershed unit is obtained by integrating the curve. .

[0098] ② Compare the average rainfall intensity of small watershed units during time period t. (Calculated using the Thiessen polygon method, based on the spatial distribution of rain gauges) and The size relationship is used to calculate the actual average infiltration rate of a small watershed unit. And the average infiltration rate F(t).

[0099] if The entire small watershed unit infiltrates using its infiltration capacity. = Conversely, infiltration occurs only in localized areas where the infiltration capacity is less than or equal to i(t), resulting in surface runoff; in other areas, infiltration occurs at a rate of i(t), without generating surface runoff. For example... Figure 4 As shown, in this case, for:

[0100] (5)

[0101] Calculation of small watershed units Subsequently, the average infiltration rate F(t) of the small watershed unit during this period is:

[0102] (6)

[0103] ③ Based on the calculated average infiltration volume F(t), calculate the surface runoff RS generated by excessive infiltration. 超渗 :

[0104] (7)

[0105] (2) Calculation of flow generation when the lower layer is fully filled:

[0106] ① Determine the spatial distribution curve of free water storage capacity according to formulas (2) and (4), and denote the maximum point and average free water storage capacity of the small watershed unit as S. m and Based on the average free water storage of the small watershed at the beginning of the time period. The maximum free water storage capacity at the saturated point within the corresponding small watershed can be obtained by inverse calculation using curve integral. ,like Figure 5 As shown.

[0107] ②Use the average infiltration volume F(t) obtained from the super-infiltration flow calculation as input to calculate the change in free water storage in the small watershed after infiltration replenishment.

[0108] if After infiltration replenishment, the free water at all points in the small watershed is fully stored, resulting in an increased average free water storage. = At the same time, the entire small watershed generates excess water storage, replenishing surface runoff RS. 蓄满 :

[0109] (8)

[0110] Conversely, only in certain areas where the water storage capacity can be met after supplementing F(t) will the free water be filled, while simultaneously generating supplementary surface runoff RS. 蓄满The excess water storage capacity, such as Figure 5 As shown, in this case, RS 蓄满 for:

[0111] (9)

[0112] Correspondingly, for:

[0113] (10)

[0114] ③ Calculate the free water storage after infiltration replenishment. The interflow RI and groundwater runoff RG are obtained by proportionally discharging free water:

[0115] (11)

[0116] In the formula, KI and KG are the outflow coefficients.

[0117] ④Calculate the average free water storage of the small watershed unit at the end of the calculation period. As the initial value for the next period, This enables continuous simulation of flow generation calculation across time periods.

[0118] (12)

[0119] (3) Calculation of total output flow:

[0120] The total runoff R of each small watershed unit during time period t 总 (t) represents the sum of all runoff components, including surface runoff, interflow, and groundwater runoff, i.e.:

[0121] (13)

[0122] After the runoff generation calculations for all small watershed units are completed, the distributed runoff generation results for the entire target watershed are obtained.

[0123] The core of the method described in this invention lies in constructing a vertically coupled over-infiltration-saturation runoff analysis and calculation framework: First, over-infiltration runoff is calculated using soil infiltration capacity as the core indicator to determine surface runoff and infiltration volume; then, using infiltration volume as input and free water storage capacity as the core indicator, saturation runoff is calculated to delineate groundwater runoff components. During the framework construction process, considering the shortcomings of existing runoff algorithms in three aspects—insufficient spatial heterogeneity representation, neglect of time-varying key parameters, and weak coupling of the over-infiltration-saturation mechanism—a systematic design was implemented, aiming to significantly improve hydrological simulation, especially the accuracy and physical mechanism rationality of runoff calculations under complex underlying surface watersheds and rainfall conditions.

[0124] Finally, it should be noted that the above description is only used to illustrate the technical solution of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred arrangement, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for calculating spatially heterogeneous time-varying mixed runoff based on the dynamic evolution of infiltration capacity, characterized in that, The method includes the following steps: Step 1: Spatial Heterogeneity Zoning of the Target Watershed: Based on multi-source geographic information data of the target watershed, which is obtained through public data platforms or surveying and mapping departments, and taking into account factors such as topography, water system, and administrative boundaries, the watershed is divided into a series of smaller watershed units according to a certain catchment area threshold based on hydrological runoff relationships and hydrological analysis tools; then, the smaller watershed units are classified according to infiltration characteristics and water storage characteristics. Step 2: Construction of runoff generation characteristic curves for small watershed units: Based on the continuous variation characteristics of runoff generation indicators within small watershed units, spatial distribution curves are constructed for quantitative description, including spatial distribution curves of infiltration capacity and spatial distribution curves of free water storage capacity. (1) Constructing the spatial distribution curve of infiltration capacity: describing the relationship between the infiltration capacity threshold f and the area ratio α f The functional relationship for the proportion of area with infiltration capacity less than or equal to f is: (1) In the formula: G is α f The functional relationship between f and f; For the set of function parameters; The G-function relationship has the following characteristics: ① When α f When f increases from 0, f increases monotonically from 0; ② The growth rate of f increases with α. f Increases and gradually decreases; ③ When α f As f approaches 1, f approaches its maximum value f. m ; (2) Constructing the spatial distribution curve of free water storage capacity: describing the free water storage capacity threshold S and the area ratio α S The functional relationship for the area proportion of regions with free water storage capacity less than or equal to S is as follows: (2) In the formula: H is α S The functional relationship between S and S; For the set of function parameters; The H-function relationship has the following characteristics: ① When α S When S increases from 0, it monotonically increases from 0; ② The growth rate of S increases with α. S Increases and gradually decreases; ③ When α S As S approaches 1, S approaches its maximum value. m ; Step 3: Functional characterization of runoff generation parameters based on underlying surface characteristics: This involves setting the set of function parameters for the spatial distribution curve of infiltration capacity. And the set of function parameters for the spatial distribution curve of free water storage capacity A physical mechanism for deriving parameters is established by characterizing the underlying surface features as a function. (1) To address the time-varying dynamic characteristics of the spatial distribution curve of soil infiltration capacity caused by the dynamic attenuation characteristics of soil infiltration capacity during rainfall events, the following measures will be taken: Characterized as a time-varying dynamic function: (3) In the formula: The values ​​of the parameters of the spatial distribution curve of infiltration capacity at time t are determined by the time-varying characteristic function α and the time-invariant characteristic function β. V1(t), V2(t), ..., V5(t) represent soil moisture content, surface temperature, surface water depth, surface soil crust state, and ground rainfall intensity, respectively. R1, R2, ..., R5 represent land use, soil texture, soil layer thickness, impermeable layer depth, and average slope, respectively. For small watershed units with different infiltration characteristics, different functional relationships α and β are used to reflect the spatial heterogeneity of the parameters. (2) The free water storage capacity does not change significantly within a single rainfall event. Characterized as a time-invariant static function: (4) In the formula: The time-invariant characteristic function is used; for small watershed units with different watershed characteristics, different functional relationships φ are used to reflect the spatial heterogeneity of parameters. Step 4, Calculation of spatially heterogeneous time-varying mixed runoff: The processes of infiltration excess runoff and saturation runoff are vertically coupled in series. The runoff calculation for each small watershed unit in each time period is performed as follows: (1) Calculation of upper layer over-permeability flow: ① Based on the soil condition at time t, determine the spatial distribution curve of the current infiltration capacity according to formulas (1) and (3), and denote the maximum infiltration capacity at the watershed point as . Further integration of the curve yields the average infiltration capacity of the current small watershed unit. ; ② Compare the average rainfall intensity of small watershed units during time period t. and The size relationship is used to calculate the actual average infiltration rate of a small watershed unit. and average infiltration rate F(t); if The entire small watershed unit infiltrates using its infiltration capacity. = Conversely, surface runoff occurs only in localized areas where the infiltration capacity is less than or equal to i(t); in other areas, infiltration occurs at a rate of i(t). for: (5) Calculation of small watershed units Subsequently, the average infiltration rate F(t) of the small watershed unit during this period is: (6) ③ Based on the calculated average infiltration volume F(t), calculate the surface runoff RS generated by excessive infiltration. 超渗 for: (7) (2) Calculation of flow generation when the lower layer is fully filled: ① Determine the spatial distribution curve of free water storage capacity according to formulas (2) and (4), and denote the maximum point and average free water storage capacity of the small watershed unit as S. m and Based on the average free water storage of the small watershed at the beginning of the period The maximum free water storage capacity at the saturated point within the corresponding small watershed can be obtained by inverse calculation using curve integral. ; ② Using the average infiltration flow F(t) obtained from the super-infiltration flow calculation as input, calculate the change in free water storage in the small watershed after infiltration replenishment; if After infiltration replenishment, the free water at all points in the small watershed is fully stored, resulting in an increased average free water storage. = Simultaneously, the entire small watershed generates excess water storage, replenishing surface runoff RS. 蓄满 for: (8) Conversely, only in certain areas where the water storage capacity can be met after supplementing F(t) will the free water be filled, while simultaneously generating supplementary surface runoff RS. 蓄满 With excess water storage, in this case, RS 蓄满 for: (9) Correspondingly, for: (10) ③ Calculate the free water storage after infiltration replenishment. The interflow RI and groundwater runoff RG are obtained by proportionally discharging free water: (11) In the formula, KI and KG are the outflow coefficients; ④Calculate the average free water storage of the small watershed unit at the end of the calculation period. As the initial value for the next period, This enables continuous simulation of flow generation calculation across time periods; (12) (3) Calculation of total output flow: The total runoff R of each small watershed unit during time period t 总 (t) represents the sum of all runoff components, including surface runoff, interflow, and groundwater runoff, i.e.: (13) After the runoff generation calculations for all small watershed units are completed, the distributed runoff generation results for the entire target watershed are obtained.

2. The spatial heterogeneous time-varying hybrid runoff calculation method based on the dynamic evolution of infiltration capacity according to claim 1, characterized in that, The multi-source geographic information data mentioned in step 1 includes digital elevation model (DEM) and remote sensing imagery; the catchment area threshold is set based on experience.

3. The spatially heterogeneous time-varying mixed runoff calculation method based on the dynamic evolution of infiltration capacity according to claim 1, characterized in that, The classification of small watershed units according to infiltration characteristics and storage characteristics in step 1 is specifically as follows: Infiltration characteristics classification: Based on the attributes that affect infiltration capacity, cluster analysis is used to divide small watershed units into several infiltration characteristic types. Small watershed units within the same type have similar infiltration physical characteristics. Among them, the attributes that affect infiltration capacity include soil texture, organic matter content, and bulk density. Classification of water storage capacity characteristics: Based on the attributes that affect water storage capacity, cluster analysis is used to divide small watershed units into several water storage capacity characteristic types. Small watershed units within the same type have similar water storage capacity characteristics. The attributes that affect water storage capacity include slope, soil thickness, vegetation cover, and land use type.

4. The spatial heterogeneous time-varying hybrid runoff calculation method based on the dynamic evolution of infiltration capacity according to claim 1, characterized in that, In step 2, the function G takes the form of an S-curve, an exponential saturation curve, or a polynomial fitting curve; the function H takes the form of an S-curve, an exponential saturation curve, or a polynomial fitting curve.

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