A method for calculating vertically and laterally coupled mixed stream production

Abstract

This invention belongs to the technical field of runoff forecasting and discloses a vertically and laterally coupled hybrid runoff calculation method. The method includes: obtaining the excess surface runoff and the current infiltration amount based on the infiltration capacity distribution curve; constructing a watershed water storage capacity distribution curve and a relative impermeable layer infiltration capacity distribution curve; coupling the watershed water storage capacity distribution curve and the relative impermeable layer infiltration capacity distribution curve to the same coordinate system, and obtaining the total groundwater runoff based on the intersection of the two curves and the current infiltration amount; dividing the total groundwater runoff into interflow runoff and groundwater runoff using the watershed average stable infiltration capacity and the watershed stable infiltration distribution non-uniformity coefficient; and summing the excess surface runoff, interflow runoff, and groundwater runoff to obtain the total watershed outlet runoff. This application solves the technical problems of unclear runoff generation and segmentation mechanisms and large flood forecasting errors in existing hybrid runoff methods for flood forecasting.

Description

Technical Field

[0001] This invention belongs to the technical field of runoff forecasting, and more specifically, relates to a method for calculating runoff generation by a combination of vertical and lateral coupling. Background Technology

[0002] High-precision hydrological forecasting provides decision-making support for reservoir operation, flood control and disaster reduction, and optimal water resource allocation, playing a vital role in water resource management, water resource development and utilization, and national economic construction. Runoff generation calculation is a key process in rainfall-runoff modeling. Driven by natural conditions and land surface hydrological processes, watershed runoff exhibits exceptionally complex spatiotemporal variability. Single models of full storage or excessive infiltration runoff generation are no longer sufficient to accurately depict the spatiotemporal variability of runoff generation processes. Therefore, conducting research on watershed flood forecasting based on mixed runoff generation is an important future development direction.

[0003] Currently, commonly used mixed runoff models include vertical mixed runoff, lateral compatible mixed runoff, and VIC-3L mixed runoff. Surface runoff, interflow, and groundwater runoff constitute all runoff components under different runoff mechanisms. Compared with single runoff models, the forecast accuracy of mixed runoff models is significantly improved. However, existing mixed runoff theories are still insufficient to accurately characterize the compositional variation of various runoff components. The main reasons are as follows: Existing mixed runoff theories assume that interflow occurs after soil moisture content reaches field capacity, and then divide the full-saturation runoff generated by the water storage capacity distribution curve into interflow and groundwater runoff, ignoring the possibility of interflow occurring in the unsaturated zone. Secondly, when existing runoff theories divide groundwater runoff based on the watershed stable infiltration rate, they assume that the vadose zone soil and rock structure is spatially uniform in the horizontal direction. This assumption is inconsistent with reality. Theoretically, the watershed stable infiltration rate is spatially unevenly distributed and is related to the underlying surface characteristics such as watershed vegetation cover, topography, and soil. Therefore, existing mixed runoff calculation methods suffer from technical problems such as inaccurate runoff generation mechanisms and unreasonable runoff segmentation mechanisms, resulting in low flood forecast accuracy. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a vertical and lateral coupled mixed runoff calculation method, which aims to solve the technical problems of unclear runoff generation and segmentation mechanisms and large flood forecasting errors in the existing mixed runoff methods for flood forecasting.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for calculating vertically and laterally coupled mixed runoff is provided. The method includes: S1: obtaining the excess surface runoff based on the infiltration capacity distribution curve, and then obtaining the infiltration amount for the current period; S2: constructing a watershed water storage capacity distribution curve using the average watershed storage capacity and the watershed water storage capacity distribution unevenness coefficient as parameters, and constructing a relative impermeable layer infiltration capacity distribution curve using the average infiltration rate of the relative impermeable layer and the relative impermeable layer infiltration capacity distribution unevenness coefficient as parameters; S3: coupling the watershed water storage capacity distribution curve and the relative impermeable layer infiltration capacity distribution curve to the same coordinate system, and obtaining the total groundwater runoff based on the intersection of the two curves and the infiltration amount for the current period; S4: dividing the total groundwater runoff into interflow runoff and groundwater runoff using the watershed average stable infiltration capacity and the watershed stable infiltration distribution unevenness coefficient; S5: summing the excess surface runoff, interflow runoff, and groundwater runoff to obtain the total watershed outlet runoff.

[0006] Preferably, the formulas for calculating the excess surface runoff RS and the current infiltration FA are as follows:

[0007]

[0008] FA = P - RS

[0009] Where P represents rainfall. The area enclosed by the infiltration capacity distribution curve represents the average infiltration rate of the watershed; BF is the coefficient of infiltration capacity unevenness; Δt represents the calculation period.

[0010] Preferably, step S2 further includes obtaining the area proportion α where the watershed water storage capacity is less than a certain fixed value WM′ based on the watershed water storage capacity distribution and the relative impermeable layer infiltration capacity distribution curve, and obtaining the area proportion α where the watershed water storage capacity is less than a certain fixed value f based on the relative impermeable layer infiltration rate. s Area ratio γ:

[0011]

[0012]

[0013] Where WM′ represents the water storage capacity at a point in the basin, WM is the area enclosed by the water storage capacity distribution curves, representing the average water storage capacity of the basin, B is the water storage capacity unevenness coefficient, and f s For the point infiltration capacity of a relatively impermeable layer, The area enclosed by the infiltration capacity distribution curves of the relatively impermeable layer represents the average infiltration rate of the relatively impermeable layer, BF. s It represents the coefficient of uneven distribution of the infiltration capacity of a relatively impermeable layer.

[0014] Preferably, step S3 specifically involves: coupling the watershed water storage capacity distribution curve and the relative impermeable layer infiltration capacity distribution curve to the same coordinate system, using the infiltration volume as input, and calculating the total groundwater runoff RR based on the intersection of the two curves.

[0015] ① When the watershed water storage capacity distribution curve and the relatively impermeable layer infiltration capacity distribution curve intersect and but:

[0016]

[0017] ② When the watershed water storage capacity distribution curve and the relatively impermeable layer infiltration capacity distribution curve intersect and but:

[0018]

[0019] ③When a+FA≤y, then:

[0020]

[0021] ④ When the watershed water storage capacity distribution curve and the relative impermeable layer infiltration capacity distribution curve do not intersect and a+FA>WM(1+B), then:

[0022] RR = FA - WM + W

[0023] Where FA is the infiltration rate in the current period, y is the ordinate of the intersection of the infiltration capacity distribution curve of the relatively impermeable layer and the watershed water storage capacity distribution curve, a is the maximum value of the average soil moisture content of the watershed in the current period, WM′ is the water storage capacity of the watershed point, WM is the area enclosed by the watershed water capacity distribution curve, representing the average water storage capacity of the watershed, W is the soil moisture content in the previous period, α is the proportion of the area where the watershed water storage capacity is less than a certain fixed value WM′, and γ is the infiltration rate of the relatively impermeable layer less than a certain fixed value f. s The area ratio, WM′ is the water storage capacity of the watershed point, f s B represents the point infiltration capacity of the relatively impermeable layer, and B is the coefficient of uneven distribution of water storage capacity in the watershed. The area enclosed by the distribution curves of the infiltration capacity of the relatively impermeable layer represents the average infiltration rate of the relatively impermeable layer.

[0024] Preferably, in step S4, the total groundwater runoff is divided into subsurface runoff RI and groundwater runoff using the average stable infiltration capacity of the watershed and the watershed stable infiltration distribution non-uniformity coefficient. The specific formula is as follows:

[0025]

[0026] RG = RR - RI

[0027] Where RR is the total groundwater runoff. The average stable infiltration capacity of the watershed; BF c Δt represents the coefficient of uneven distribution of steady infiltration in the watershed, and Δt represents the calculation period.

[0028] Preferably, in step S5, the linear reservoir and Muskingen method are used to summarize the super-permeable surface runoff, soil runoff and groundwater runoff to obtain the total runoff at the watershed outlet.

[0029] Preferably, the total runoff at the watershed outlet is obtained by summing the excess surface runoff, interflow runoff, and groundwater runoff using a linear reservoir and the Muskingen method, as follows:

[0030]

[0031]

[0032]

[0033] QT(t) = QS(t) + QI(t) + QI(t)

[0034] Q(t)=C0·QT(t)+C1·QT(t-1)+C2·Q(t-1)

[0035] In the formula, RS(t), RI(t), and RG(t) represent the excess surface runoff, interflow runoff, and groundwater runoff at time t, respectively; QS(t), QI(t), and QG(t) represent the excess surface runoff, interflow runoff, and groundwater runoff at time t, respectively; QS(t-1), QI(t-1), and QG(t-1) represent the excess surface runoff, interflow runoff, and groundwater runoff at time t-1, respectively; CS, CI, and CG represent the excess surface runoff reduction coefficient, interflow reduction coefficient, and groundwater runoff reduction coefficient, respectively; F is the watershed area; QT(t-1) and QT(t) represent the total inflow of the river network per unit area at time t-1 and time t, respectively; Q(t-1) and Q(t) represent the total outflow of the river network per unit area at time t-1 and time t, respectively; C0, C1, and C2 are Muskingen parameters.

[0036] In summary, compared with the prior art, the vertically and laterally coupled hybrid flow generation calculation method provided by this invention has the following beneficial effects:

[0037] 1. To address the incomplete interflow generation mechanism in traditional mixed runoff generation models, this invention introduces a distribution curve of the infiltration capacity of a relatively impermeable layer, which improves the interflow generation mechanism in areas that have not been fully filled, enhances the accuracy of net rainfall calculation, and can provide a more accurate input background field for watershed runoff segmentation.

[0038] 2. In view of the problem that the traditional two-source water separation method does not take into account the unevenness of the horizontal spatial distribution of the vadose zone soil and rock structure, this application uses the average stable infiltration capacity of the watershed and the unevenness coefficient of the stable infiltration distribution of the watershed to divide the total groundwater runoff. The introduction of the unevenness coefficient of the stable infiltration capacity distribution takes into account the heterogeneity of the spatial distribution of the underlying surface, which improves the accuracy of the division of interflow and groundwater runoff.

[0039] 3. This application proposes a distribution curve of the infiltration capacity of a relatively impermeable layer, which more precisely characterizes the non-uniformity of the runoff generation process from the aspects of net rainfall calculation and runoff segmentation. Based on this, a linear reservoir and Muskingen method are used to obtain the total runoff at the watershed outlet by dividing the water source and converging the runoff. This solves the technical problems of inaccurate runoff generation mechanism and unreasonable runoff segmentation mechanism in the application of traditional mixed runoff generation calculation methods, and improves the accuracy of flood prediction. Attached Figure Description

[0040] Figure 1 This is a step diagram of a vertically and laterally coupled hybrid flow generation calculation method according to this application;

[0041] Figure 2 This is a schematic diagram of the Hanjiang River basin upstream of the Xiangjiaping hydrological station;

[0042] Figure 3 This is a schematic diagram of the vertical and lateral coupled mixed runoff generation process in an embodiment of this application, where ① is the intersection point of the watershed water storage capacity distribution curve and the relatively impermeable layer infiltration capacity distribution curve. In case ②, the distribution curve of watershed water storage capacity and the distribution curve of infiltration capacity of relatively impermeable layer intersect and In cases ③(a) and ③(b), a+FA≤y, and in cases ④(a) and ④(b), the watershed water storage capacity distribution curve and the relative impermeable layer infiltration capacity distribution curve do not intersect and a+FA>WM(1+B);

[0043] Figure 4 This is a schematic diagram of the permeability distribution curve of an embodiment of this application;

[0044] Figure 5 (a) is a schematic diagram of the forecast results of the improved vertical mixed runoff and the vertical mixed runoff, (b) is a schematic diagram of the forecast results of the improved lateral mixed runoff and the lateral mixed runoff, and (c) is a schematic diagram of the forecast effect of the vertical-lateral integrated mixed runoff model and the forecast results of the improved vertical mixed runoff model and the improved lateral mixed runoff model. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0046] This application provides a method for calculating hybrid vertical and lateral coupled current generation, such as... Figure 1 As shown, the method includes the following steps S1 to S5, as detailed below.

[0047] S1: Use the infiltration capacity distribution curve as a parameter to obtain the excess surface runoff, and then obtain the infiltration amount for the current period.

[0048] The infiltration capacity distribution curve can be obtained using existing technologies such as the Green-Ampt method, the Philips method, and the Horton method. First, the excess surface runoff RS is obtained, and then the infiltration amount FA for the current period is obtained. Specifically, the calculation formulas for the excess surface runoff RS and the infiltration amount FA for the current period are as follows:

[0049]

[0050] FA = P - RS

[0051] Where P represents rainfall. The area enclosed by the infiltration capacity distribution curve represents the average infiltration rate of the watershed; BF is the coefficient of infiltration capacity unevenness; Δt represents the calculation period.

[0052] S2: Construct a watershed water storage capacity distribution curve using the average water storage capacity and the watershed water storage capacity unevenness coefficient as parameters, and construct a relative impermeable layer infiltration capacity distribution curve using the average infiltration rate of the relative impermeable layer and the relative impermeable layer infiltration capacity unevenness coefficient as parameters.

[0053] Step S2 further includes obtaining the area proportion α where the watershed water storage capacity is less than a certain fixed value WM′ based on the watershed water storage capacity distribution and the relative impermeable layer infiltration capacity distribution curve, and the area proportion α where the watershed water storage capacity is less than a certain fixed value f based on the relative impermeable layer infiltration rate. s Area ratio γ:

[0054]

[0055]

[0056] Where WM′ represents the water storage capacity at a point in the basin, WM is the area enclosed by the water storage capacity distribution curves, representing the average water storage capacity of the basin, B is the water storage capacity unevenness coefficient, and f sFor the point infiltration capacity of a relatively impermeable layer, The area enclosed by the infiltration capacity distribution curves of the relatively impermeable layer represents the average infiltration rate of the relatively impermeable layer, BF. s It represents the coefficient of uneven distribution of the infiltration capacity of a relatively impermeable layer.

[0057] S3: Couple the water storage capacity distribution curve of the basin and the infiltration capacity distribution curve of the relatively impermeable layer to the same coordinate system, and obtain the total groundwater runoff based on the intersection of the two curves and the infiltration amount of the current time period.

[0058] Specifically, the watershed water storage capacity distribution curve and the relative impermeable layer infiltration capacity distribution curve are coupled to the same coordinate system, with the infiltration volume as input, and the total groundwater runoff RR is calculated based on the intersection of the two curves:

[0059] ① When the watershed water storage capacity distribution curve and the relatively impermeable layer infiltration capacity distribution curve intersect and but:

[0060]

[0061] ② When the watershed water storage capacity distribution curve and the relatively impermeable layer infiltration capacity distribution curve intersect and but:

[0062]

[0063] ③When a+FA≤y, then:

[0064]

[0065] ④ When the watershed water storage capacity distribution curve and the relative impermeable layer infiltration capacity distribution curve do not intersect and a+FA>WM(1+B), then:

[0066] RR = FA - WM + W

[0067] Wherein, FA represents the infiltration rate in the current period, y is the ordinate of the intersection of the relative impermeable layer infiltration capacity distribution curve and the watershed water storage capacity distribution curve, a is the maximum value of the average soil moisture content in the watershed in the current period, WM′ is the water storage capacity at a point in the watershed, WM is the area enclosed by the watershed water capacity distribution curve, representing the average water storage capacity of the watershed, W is the soil moisture content in the previous period, α is the proportion of the area where the watershed water storage capacity is less than a certain fixed value WM′, γ is the proportion of the area where the relative impermeable layer infiltration rate is less than a certain fixed value, WM′ is the water storage capacity at a point in the watershed, γ is the infiltration capacity at a point in the relative impermeable layer, and B is the watershed water storage capacity distribution unevenness coefficient. The area enclosed by the distribution curves of the infiltration capacity of the relatively impermeable layer represents the average infiltration rate of the relatively impermeable layer.

[0068] S4: The total groundwater runoff is divided into soil runoff and groundwater runoff using the average stable infiltration capacity of the watershed and the uneven distribution coefficient of stable infiltration in the watershed.

[0069] The average stable infiltration capacity of the watershed and the coefficient of non-uniformity of stable infiltration distribution can both be obtained from the stable infiltration capacity distribution curve. The stable infiltration capacity distribution curve can be obtained using methods similar to those used for infiltration capacity distribution curves, such as the Green-Ampt, Philips, and Houghton methods.

[0070] The total groundwater runoff is divided into interflow runoff RI and groundwater runoff RG using the average stable infiltration capacity of the watershed and the unevenness coefficient of stable infiltration distribution in the watershed. The specific formula is as follows:

[0071]

[0072] RG = RR - RI

[0073] Where RR is the total groundwater runoff. The average stable infiltration capacity of the watershed; BF c Δt represents the coefficient of uneven distribution of steady infiltration in the watershed, and Δt represents the calculation period.

[0074] S5: Sum the excess surface runoff, soil runoff, and groundwater runoff to obtain the total runoff at the watershed outlet.

[0075] In a further preferred embodiment, a linear reservoir and the Muskingen method are used to summarize the excess surface runoff, interflow runoff, and groundwater runoff to obtain the total runoff at the watershed outlet. The specific expression is as follows:

[0076]

[0077]

[0078]

[0079] QT(t) = QS(t) + Q,(t) + Q,(t)

[0080] Q(t)=C0·QT(t)+C1·QT(t-1)+C2·Q(t-1)

[0081] In the formula, RS(t), RI(t), and RG(t) represent the excess surface runoff, interflow runoff, and groundwater runoff at time t, respectively; QS(t), QI(t), and QG(t) represent the excess surface runoff, interflow runoff, and groundwater runoff at time t, respectively; QS(t-1), QI(t-1), and QG(t-1) represent the excess surface runoff, interflow runoff, and groundwater runoff at time t-1, respectively; CS, CI, and CG represent the excess surface runoff reduction coefficient, interflow reduction coefficient, and groundwater runoff reduction coefficient, respectively; F is the watershed area; QT(t-1) and QT(t) represent the total inflow of the river network per unit area at time t-1 and time t, respectively; Q(t-1) and Q(t) represent the total outflow of the river network per unit area at time t-1 and time t, respectively; C0, C1, and C2 are Muskingen parameters.

[0082] Example

[0083] This embodiment focuses on the area upstream of the Xiangjiaping hydrological station in the Hanjiang River basin. A schematic diagram of the basin is shown below. Figure 2 .

[0084] (1) Calculate surface runoff and infiltration rate based on the infiltration capacity distribution curve:

[0085]

[0086] In the formula, P represents the rainfall; The area enclosed by the infiltration capacity distribution curve represents the average infiltration rate of the watershed; BF is the coefficient of infiltration capacity unevenness; Δt represents the calculation period; RS represents the surface runoff. Therefore, the infiltration amount for the current period is:

[0087] FA = P - RS (2)

[0088] In the formula, FA represents the infiltration amount during the current period.

[0089] (2) Couple the infiltration capacity distribution curve of the relatively impermeable layer with the water storage capacity distribution curve to the same coordinate system, using the infiltration rate FA as input, and calculate the total groundwater runoff based on the intersection of the two curves. There are six possible scenarios, such as... Figure 3 As shown, the calculation equations for cases ③(a) and (b) are consistent and can be combined into one case; similarly, the calculation equations for cases ④(a) and (b) are consistent and can be combined into one case. Specifically, the calculation results for groundwater runoff in each case are as follows:

[0090] ① When two curves intersect and but

[0091]

[0092] ② When two curves intersect and but

[0093]

[0094] ③When a+FA≤y, then

[0095]

[0096] ④ When the two curves do not intersect and a+FA>WM(1+B)

[0097] RR = FA - WM + W (6)

[0098] In the formula, RR is the total groundwater runoff; y is the ordinate of the intersection of the distribution curve of the infiltration capacity of the relatively impermeable underground layer and the distribution curve of the watershed water storage capacity; and a is the maximum value of the average soil moisture content of the watershed in the current period.

[0099] (3) Establish a permeability distribution curve, dividing the total groundwater runoff into interflow and groundwater runoff. A schematic diagram of the permeability distribution curve is shown below. Figure 4 As shown, specifically:

[0100]

[0101] RG = RR - RI(8)

[0102] (4) The process of obtaining the watershed outlet flow by combining surface runoff, soil runoff, and groundwater runoff from water sources:

[0103] QS(t)=0.99·QS(t-1)+2.98.RS(t) (9)

[0104] QI(t)=0.54.QI(t-1)+137.32.RI(t) (10)

[0105] QG(t)=0.96·QG(t-1)+11.94·RI(t) (11)

[0106] QT(t)=QS(t)+QI(t)+QG(t) (12)

[0107] Furthermore, the total inflow into the river network is calculated to the basin outlet using the Muskingen method to obtain the total outflow into the basin:

[0108] Q(t)=0.04·QT(t)+0.42·QT(t-1)+0.54·Q(t-1) (13)

[0109] To verify the forecasting accuracy of the proposed method, a flood forecast was conducted using the flood season event from May 31 to October 2, 2011, at the Xiangjiaping hydrological station. The forecast results are as follows: Figure 5As shown, using Nash efficiency coefficient (NSE) and Kling-Gupta coefficient (KGE) as evaluation indicators, the NSE of the vertical mixed runoff model, the laterally compatible mixed runoff model, the improved vertical mixed runoff model, the improved laterally compatible mixed runoff model, and the integrated vertical-lateral mixed runoff model are 0.840, 0.694, 0.866, 0.858, and 0.866, respectively, and the KGE coefficients are 0.719, 0.538, 0.751, 0.696, and 0.758, respectively. To analyze the accuracy of the proposed improved method, the prediction results of mixed runoff, laterally compatible mixed runoff, and improved vertical mixed runoff and improved laterally compatible mixed runoff are first compared to verify the accuracy of the prediction results after the improvement of the groundwater runoff segmentation method. After introducing the coefficient of uneven distribution of seepage stability capacity to improve the water source segmentation mechanism, the NSE of the improved vertical mixed runoff increases from 0.840 to 0.866, and the KGE increases from 0.719 to 0.751. Figure 5 In (a) of the improved horizontally compatible hybrid flow generation model, the NSE increased from 0.694 to 0.858, and the KGE increased from 0.538 to 0.696. Figure 5 In (b) of the model, the forecast accuracy is improved to a certain extent; furthermore, the forecasting effect of the vertical and horizontal integrated mixed runoff model is compared with that of the improved vertical mixed runoff model and the improved horizontal mixed runoff model. Figure 5 (c) shows that, overall, the accuracy of the proposed forecasting method is better than that of the traditional mixed runoff generation model, proving that the proposed improved interflow generation mechanism has a practical physical basis.

[0110] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calculating hybrid vertical and lateral coupled current generation, characterized in that, The method includes: S1: Obtain the excess surface runoff based on the infiltration capacity distribution curve, and then obtain the infiltration amount for the current period; S2: Construct a watershed water storage capacity distribution curve using the average water storage capacity and the water storage capacity unevenness coefficient as parameters, and construct a relative impermeable layer infiltration capacity distribution curve using the average infiltration rate and the relative impermeable layer infiltration capacity unevenness coefficient as parameters. S3: Couple the water storage capacity distribution curve of the basin and the infiltration capacity distribution curve of the relatively impermeable layer to the same coordinate system, and obtain the total groundwater runoff based on the intersection of the two curves and the infiltration amount in the current period. S4: The total groundwater runoff is divided into soil runoff and groundwater runoff by using the average stable infiltration capacity of the watershed and the uneven distribution coefficient of stable infiltration in the watershed. S5: Sum the excess surface runoff, interflow runoff, and groundwater runoff to obtain the total runoff at the watershed outlet; Step S2 further includes obtaining data based on the distribution of water storage capacity in the basin and the distribution curve of infiltration capacity of the relatively impermeable layer, respectively, to determine if the water storage capacity of the basin is less than a certain fixed value. area ratio And based on the fact that the infiltration rate of the relatively impermeable layer is less than a certain fixed value area ratio : in, For the water storage capacity of the basin, The area enclosed by the watershed water capacity distribution curves represents the average water storage capacity of the watershed, and B is the coefficient of uneven distribution of water storage capacity in the watershed. For the point infiltration capacity of a relatively impermeable layer, The area enclosed by the distribution curves of the infiltration capacity of the relatively impermeable layer represents the average infiltration rate of the relatively impermeable layer. The coefficient representing the uneven distribution of the infiltration capacity of a relatively impermeable layer; Step S3 specifically involves: coupling the watershed water storage capacity distribution curve and the relative impermeable layer infiltration capacity distribution curve to the same coordinate system, using the infiltration rate as input, and calculating the total groundwater runoff based on the intersection of the two curves. RR : ① When the watershed water storage capacity distribution curve and the relatively impermeable layer infiltration capacity distribution curve intersect and ,but: ② When the watershed water storage capacity distribution curve and the relatively impermeable layer infiltration capacity distribution curve intersect and ,but: ③When ,but: ④ When the watershed water storage capacity distribution curve and the relatively impermeable layer infiltration capacity distribution curve do not intersect and ,but: in, y represents the current infiltration rate, y is the ordinate of the intersection of the relative impermeability layer infiltration capacity distribution curve and the watershed water storage capacity distribution curve, a is the maximum value of the watershed average soil moisture content in the current period, and W is the soil moisture content in the previous period. If the water storage capacity of the basin is less than a certain fixed value area ratio, For a relatively impermeable layer, the infiltration rate is less than a certain fixed value. The area ratio.

2. The method according to claim 1, characterized in that, The super-permeable surface runoff RS and current infiltration volume FA The calculation formula is: in, P For rainfall, The area enclosed by the infiltration capacity distribution curve represents the average infiltration rate of the watershed; This is the coefficient for uneven distribution of infiltration capacity; This represents the calculation period.

3. The method according to claim 1, characterized in that, In step S4, the total groundwater runoff is divided into interflow runoff using the average stable infiltration capacity of the watershed and the watershed stable infiltration distribution non-uniformity coefficient. and underground runoff The specific formula is as follows: in, RR Total underground runoff, This represents the average stable infiltration capacity of the watershed. The coefficient of uneven distribution of steady infiltration in the watershed. This is the calculation period.

4. The method according to claim 1 or 3, characterized in that, In step S5, the linear reservoir and Muskingen method are used to summarize the super-permeable surface runoff, soil runoff and groundwater runoff to obtain the total runoff at the watershed outlet.

5. The method according to claim 4, characterized in that, The total runoff at the watershed outlet is obtained by summing the excess surface runoff, interflow runoff, and groundwater runoff using the linear reservoir and Muskingen method. The specific expression is as follows: In the formula, , , Represent t Time-varying surface runoff, interflow runoff, and groundwater runoff; , , Represent t Time-varying infiltration of surface runoff, interflow, and groundwater runoff; , , Represent t -1 time period: infiltration of surface runoff, interflow and groundwater runoff; , , These represent the recession coefficients of excess permeability surface runoff, interflow, and groundwater runoff, respectively. F The drainage area; Represent t -1 time period and t Total inflow into the river network within a given time period; Represent t -1 time period and t Total outflow of the river network within a given time period; These are the Muskingu parameters.

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