CN114741865B - Time-varying distributed dynamic convergence calculation method - Google Patents

Time-varying distributed dynamic convergence calculation method Download PDF

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CN114741865B
CN114741865B CN202210351519.9A CN202210351519A CN114741865B CN 114741865 B CN114741865 B CN 114741865B CN 202210351519 A CN202210351519 A CN 202210351519A CN 114741865 B CN114741865 B CN 114741865B
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time
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CN114741865A (en
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陈璐
易彬
冯宝飞
许银山
张寒松
张俊
祝宾皓
刘一卓
郭鹤翔
占挺
张潇
李思明
杨彬林
李洁
宋巧
郑婕
杨雁飞
田逸飞
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Huazhong University of Science and Technology
Bureau of Hydrology Changjiang Water Resources Commission
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Abstract

The invention discloses a time-varying distributed dynamic convergence calculation method, and belongs to the field of runoff forecasting. According to the invention, the terrain indexes are introduced to depict the spatial uneven distribution of the watershed grid water storage capacity, the water storage capacity of each grid can be quantitatively represented, and the watershed full-storage grids and the full-storage grids can be divided from the grid scale by combining with the runoff yield calculation result, so that a higher-precision input field can be provided for the grid flow velocity field calculation; the invention provides a confluence velocity calculation formula considering time-varying rainfall intensity and soil water content, and more accurately describes the spatial distribution rule of a flow velocity field; the method and the device have the advantages that based on the theoretical basis of the runoff yield of the full storage area and the runoff yield of the non-full storage area, the dynamic confluence paths of the watershed at different flooding proportions are calculated, the theoretical basis of unit line calculation is perfected, the accuracy of distributed unit line confluence time calculation is improved, the problem that the flood peak is greatly predicted by the traditional distributed unit line is solved, and the accuracy of flood prediction is improved.

Description

Time-varying distributed dynamic convergence calculation method
Technical Field
The invention belongs to the field of runoff forecasting, and particularly relates to a time-varying distributed dynamic convergence calculation method.
Background
The high-precision hydrological forecast can provide decision basis for reservoir scheduling, flood control and disaster reduction, water resource optimization configuration and the like, and plays an important role in the fields of water resource management, water resource development and utilization, national economic construction and the like. The rainfall runoff modeling mainly comprises two parts of runoff production and confluence, a unit line is a confluence calculation method which is most widely applied, and a common unit line method comprises the following steps: time period unit lines, instantaneous unit lines, integrated unit lines, distributed unit lines, etc.
The application of the traditional confluence method has certain limitation, and the main problems are that the whole basin confluence process is generalized into a linear system, the rainfall time-space distribution characteristics and the spatial heterogeneity of an underlying surface cannot be accurately depicted, and secondly, a runoff forecast result with high precision cannot be obtained depending on detailed hydrological meteorological data. Under the background, the time-varying distributed unit line method considering the basin confluence nonlinear effect is advocated because of less required data, simple deduction process and higher application precision, however, the existing distributed confluence theory has two defects: firstly, only considering the influence of rainfall spatial-temporal distribution nonuniformity and underlying surface spatial distribution heterogeneity on the flow area confluence speed, assuming that the flow area can reach a saturated state before the end of a rainfall pulse, which is not consistent with the actual situation, and neglecting the change of the underlying surface state caused by the time-varying soil water content; secondly, the existing distributed unit line assumes full basin runoff yield, and adopts a static confluence path to estimate the unit line, theoretically, in a southern wet area mainly dominated by full runoff yield, only the full basin runoff yield before the runoff area is not full, therefore, the runoff confluence path should dynamically change along with the change of the full basin, and when the full basin is full, the dynamic confluence path is converted into the static confluence path.
Therefore, when the existing distributed unit line converging method is applied, the converging speed of the slope of the drainage basin is overestimated, and the drainage basin is supposed to have a unique static converging path, so that the technical problem of low flood forecasting precision is caused.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides a time-varying distributed dynamic convergence calculation method, aiming at solving the technical problems of overestimation of convergence speed and large flood forecast error in the conventional time-varying distributed unit line flood forecast.
In order to achieve the above object, the present invention provides a time-varying distributed dynamic convergence calculation method, including:
s1, calculating the flow rate of a drainage basin based on an SCS model;
s2, grid division is carried out on the drainage basin, and water storage capacity of all grid units in the drainage basin is calculated based on the terrain indexes;
obtaining grids corresponding to the watershed storage full area and the non-storage full area based on the water storage capacity of the grid unit, the rainfall at the current moment and the net rainfall at the current moment; calculating the area of the full area and the water content of the soil in the area which is not full at the current moment on the grid scale; combining the runoff yield calculation result and the drainage basin area, and distributing the net rainfall at the current moment to a full storage area;
s3, constructing a time-varying slope flow velocity calculation formula according to the soil water storage state of the grid unit; the grid unit soil water storage state refers to whether the grid is fully stored or not and the soil water content of the grid which is not fully stored;
s4, obtaining dynamic confluence paths of the drainage basins with different storage and fullness ratios based on the areas of the drainage basin storage and fullness areas at different moments;
s5, obtaining a time-varying distributed dynamic unit line based on a time-varying slope flow velocity calculation formula and a dynamic confluence path;
and S6, calculating the flood process of the drainage basin by adopting the time-varying distributed dynamic unit lines and the drainage basin flow rate calculation result.
Further, the water storage capacity WM of the jth grid celljThe calculation formula is as follows:
Figure BDA0003580641380000021
in the formula, WMminIs made ofMinimum water holding capacity in all grids of the watershed; WM (pulse Width modulation)maxThe maximum water storage capacity in all grids of the full basin; TImin＝min{TIj,j＝1,2…,N}；TImax＝max{TIj,j＝1,2…,N}；TIjThe terrain index of the jth grid; n is a parameter to be calibrated and reflects the coefficient of topographic index distribution and water storage capacity distribution; and N is the total number of the basin grid units.
Further, the area of the flow field full area in the t period is as follows:
Figure BDA0003580641380000031
in the formula (I), the compound is shown in the specification,
Figure BDA0003580641380000032
area of the reservoir, αtThe proportion of the basin full area at time t, Wj,0The initial moment water storage capacity of the grid j is obtained; piIs rainfall in period i, RiFor net rainfall i period, AjIs the grid cell area.
Further, a t-period net rainfall RtRedistribute to the reservoir area, the expression is as follows:
Figure BDA0003580641380000033
f is the basin area; rtFor net rainfall over time t, i.e. production rate, Rt' is the net rain depth of the full storage area,
Figure BDA0003580641380000034
further, the time-varying slope flow velocity calculation formula is as follows:
Figure BDA0003580641380000035
k is the flow velocity coefficient, betajIs j grid cell slope, IcIs the average clear rain intensity of the watershed, Wj,tAnd the soil water content of the j grid unit corresponding to the full storage area in the time period t.
Further, the soil water content of the section t of the j grid unit corresponding to the region which is not fully accumulated is as follows:
Wj,t＝Wj,t-1+Pt-Rt
Wj,t-1for j grid t-1 time period water storage, PtRainfall in t time period, RtThe net rainfall, i.e. the production flow, is measured at t.
Further, the dynamic confluence paths under different full-storage ratios are:
Figure BDA0003580641380000041
Figure BDA0003580641380000042
representing a collection of bus paths that are full of grids,
Figure BDA0003580641380000043
Rjand representing the collection of the confluence paths of the grid units to the drainage basin outlet.
Further, step S5 specifically includes:
01. calculating the basin fullness ratio of the t period as alphatWaiting time of water drop in grid
Figure BDA0003580641380000044
When the water flow is in the direction of the grid
Figure BDA0003580641380000045
When the water flow flows along the diagonal direction of the grid
Figure BDA0003580641380000046
LjIs the grid side length;
accumulating along the confluence path to obtain the confluence time of each grid to the drainage basin outlet
Figure BDA0003580641380000047
Figure BDA0003580641380000048
02. Calculating the full storage area of the watershed in the time interval corresponding to the adjacent unit line time period:
Figure BDA0003580641380000049
Figure BDA00035806413800000410
indicates the full grid convergence time is [ (m-1) Δ t, m Δ t]The sum of the areas in the interval satisfies
Figure BDA00035806413800000411
Δ t is the unit line time interval in hours; m is the unit line period, M =1,2, \ 8230, M, M is the total number of unit line periods,
Figure BDA00035806413800000412
03. converting the area of the full storage grid into the flow process of the drainage basin outlet to obtain a distributed unit line at any time period:
Figure BDA00035806413800000413
UH (m) is the unit linear flow of the mth time period in m3S; h is the unit of net rain, and the unit is mm.
In general, the above technical solutions contemplated by the present invention can achieve the following advantageous effects compared to the prior art.
Aiming at the defect that a water storage capacity curve in a traditional model can only qualitatively describe the spatial uneven distribution of the watershed water storage capacity, the invention introduces a terrain index to describe the spatial uneven distribution of the watershed grid water storage capacity, can quantitatively represent each grid water storage capacity, combines a runoff yield calculation result, can further divide a watershed flooding grid and a flooding grid from a grid scale, and can provide a higher-precision input field for the calculation of a grid flow velocity field;
the invention provides a confluence velocity calculation formula considering time-varying rainfall intensity and soil water content, and a space distribution rule of a flow velocity field is more accurately described by dividing four grid states (full grids, not full grids but in confluence path grids and river channel grids);
the time-varying distributed unit line considering the dynamic confluence path is established, and aiming at the unreasonable assumption that the traditional unit line assumes the uniform flow production of the whole basin, the dynamic confluence path under different storage and fullness ratios of the basin is calculated based on the theoretical basis that the flow production of the full basin and the flow production of the non-full basin are realized, so that the theoretical basis of the calculation of the unit line is perfected;
the grid convergence time distribution fields under different accumulation ratios are calculated by combining the improved time-varying flow velocity calculation formula and the dynamic convergence path theory, specifically, the accuracy of convergence time calculation is improved by improving the flow velocity formula, and the convergence path of the convergence method is developed from a static convergence path to a dynamic convergence path by dividing the accumulation areas and the non-accumulation areas, so that the accuracy of the calculation of the distributed unit line convergence time is improved in general terms, and a physical mechanism is provided;
in summary, the invention provides a dynamic path convergence theory, a slope surface flow velocity calculation formula which simultaneously considers rainfall intensity and underlying surface soil water content space-time distribution characteristics is calculated, a drainage basin flow velocity distribution field is more finely described from a grid scale, and on the basis, a time-varying distributed dynamic unit line is calculated, so that the problem that the traditional distributed unit line forecasts larger flood peak is solved, the influence mechanism of drainage basin convergence velocity is analyzed from a physical cause level, and the accuracy of flood forecasting is improved.
Drawings
FIG. 1 is a flow diagram of a time-varying distributed dynamic convergence method of the present invention;
FIG. 2 is a map of a region of interest provided by an embodiment of the present invention;
FIG. 3 is a map of a study area vegetation profile;
FIG. 4 is a plot of a regional terrain slope profile;
FIG. 5 is a plot of regional topographic index distribution;
FIG. 6 is a schematic diagram showing the distribution of the saturation area of the underlying surface at different filling ratios in (a) - (c);
FIG. 7 is a time-varying distributed unit line based on dynamic bus paths;
FIG. 8 is a conventional time varying distributed unit cell;
FIG. 9 is a comparison graph of net rain for the proposed method and the conventional method;
fig. 10 is a comparison graph of flood forecasting effect at a session.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is 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 of the invention and do not limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Referring to fig. 1, the method for calculating a time-varying distributed dynamic convergence provided by the present invention includes the following steps:
(1) Performing basin runoff yield calculation based on the SCS model;
the step (1) of calculating the watershed runoff yield based on the SCS model, wherein the specific expression is as follows:
Figure BDA0003580641380000061
Figure BDA0003580641380000062
in the formula, R is the total runoff of the earth surface in mm; p is total rainfall amount, mm;s is the maximum retention capacity of the basin at present, which is mm; CN value is dimensionless and reflects river basin characteristics in early rainfall; I.C. AaIn terms of initial loss, mm, IaAnd m is a parameter to be calibrated.
Further, the net rainfall for the period t can be calculated by the following equation:
Figure BDA0003580641380000071
in the formula, PiRainfall in the period i; rtNet rainfall (yield) for time t;
(2) Calculating a distributed watershed water storage capacity curve considering the watershed topographic indexes, counting the watershed full storage area at the current moment on the basis, calculating the current soil water content of the grid unit which is not full of the watershed, and further redistributing the average net rain of the watershed to the full storage area by combining with the runoff yield calculation result;
and (2) calculating a distributed watershed water storage capacity curve considering the watershed terrain index, firstly, extracting the terrain index based on the watershed DEM data, wherein the specific expression is as follows:
Figure BDA0003580641380000072
in the formula, TIjA terrain index for the jth grid; asjThe area of the grid unit j is collected to the uphill region through unit contour lines; beta is ajIs the j grid cell slope.
Further, a distributed water storage capacity curve reflecting the heterogeneity of the soil water space of the drainage basin is calculated according to the terrain index of the drainage basin, and the expression is as follows:
Figure BDA0003580641380000073
in the formula, WMjThe water storage capacity of the j grid cell; WM (pulse Width modulation)minThe minimum water storage capacity in all grids of the full watershed; WM (pulse Width modulation)maxIs the most of all grids in the full flow fieldLarge water storage capacity; TImin＝min{TIj,j＝1,2…,N}；TImax＝max{TIjJ =1,2 \ 8230;, N }; n is a parameter to be calibrated, and reflects the coefficient of topographic index distribution and water storage capacity distribution; and N is the total number of the basin grid units.
the full storage area of the drainage basin in the period t is as follows:
Figure BDA0003580641380000081
in the formula, Wj,0The initial moment water storage capacity of the grid j is obtained;
Figure BDA0003580641380000082
the area of the part for storing the drainage basin; a. ThejIs the grid cell area.
Further, the water content of the soil in the non-storage area t period is as follows:
Wj,t＝Wj,t-1+Pt-Rt (7)
in the formula, Wj,tThe water storage capacity is j grid t time period; wj,t-1The water storage amount is the time period of the j grid t-1.
Further, since only the full reservoir occurs, and the SCS model considers the full basin uniform runoff, the t-period net rainfall RtNeed to be redistributed to the storage full area, the expression is as follows:
Figure BDA0003580641380000083
wherein F is the basin area; rt' is the clear rain depth of the full storage area, and the other parameters have the same meanings as above. The net rain depth of the actual full storage area can be expressed as:
Figure BDA0003580641380000084
(3) Considering the time-space variation characteristic of the state of the underlying surface of the drainage basin, providing a time-varying slope flow velocity calculation formula;
Figure BDA0003580641380000085
in the formula (I), the compound is shown in the specification,
Figure BDA0003580641380000086
is the confluence speed of j grid cells when the basin accumulation ratio is alpha; k is a flow velocity coefficient and is determined according to the vegetation and the soil type of the underlying surface; i iscThe average clear rain intensity of the drainage basin is defined as the same as the other parameters.
(4) According to the time-varying slope flow rate calculation formula and the basin full storage area, a distributed dynamic unit line considering the soil water content is calculated;
01. determining the direction of the grid water flow according to a D8 algorithm, and extracting a convergence path set R from the grid to a basin outlet according to the direction of the grid water flowj(the set of grid cells on the jth grid-to-basin exit path), then the set of all grid convergence paths for the full basin can be expressed as:
R＝{Rj|j＝1,2,…,N} (11)
because the path set is static, however, the actual confluence condition is that only the full storage area has the confluence path, for this reason, the invention combines the distributed grid water storage capacity to calculate different full storage ratios alphatCollection of sink paths for a lower-fill grid
Figure BDA0003580641380000091
Satisfies the following conditions:
Figure BDA0003580641380000092
in the formula (I), the compound is shown in the specification,
Figure BDA0003580641380000093
representing a collection of bus paths that are full of grids,
Figure BDA0003580641380000094
Figure BDA0003580641380000095
representation collection
Figure BDA0003580641380000096
Is really contained in the collection
Figure BDA0003580641380000097
The set R represents a set of watershed static convergence paths; the other parameters have the same meaning as above. Due to different storage ratios of drainage basins
Figure BDA0003580641380000098
Different, therefore, it constitutes a dynamic bus path at different fill ratios.
02. Calculating the time-by-time confluence speed of each grid according to the provided flow speed calculation formula
Figure BDA0003580641380000099
Obtaining different basin fullness ratios alphatA lower flow velocity distribution field;
03. calculating the basin fullness ratio of t time period as alphatWaiting time of water drop in grid
Figure BDA00035806413800000910
And accumulating along the confluence path to obtain the confluence time of each grid to the drainage basin outlet
Figure BDA00035806413800000911
Figure BDA00035806413800000912
Figure BDA00035806413800000913
LjTo the length of the grid side, when the water flow is in the direction of the grid
Figure BDA00035806413800000914
When the water flow flows along the diagonal direction of the grid
Figure BDA00035806413800000915
04. Calculating the full area of the drainage basin in the time interval corresponding to the adjacent unit line time period:
Figure BDA0003580641380000101
Figure BDA0003580641380000102
indicates the full grid convergence time is [ (m-1) Δ t, m Δ t]The sum of the areas in the interval satisfies
Figure BDA0003580641380000103
Δ t is the unit line time interval in hours; m is unit line time interval, M =1,2, \8230, M is total time interval number of the unit line,
Figure BDA0003580641380000104
05. the process of converting the area of the full storage grid into the flow of the drainage basin outlet flow is carried out to obtain the distributed unit line at any time period:
Figure BDA0003580641380000105
UH (m) is the unit linear flow of the mth time period in m3S; h is unit net rain, and the unit is mm;
(5) And calculating the flood process of the drainage basin by adopting the time-varying distributed dynamic unit line and combining the runoff yield calculation result.
The agro polder watershed is taken as a research object, and a research area map is shown in fig. 2. As the invention focuses on the calculation accuracy of the drainage basin confluence method, the SCS model is adopted to calculate the drainage basin yield, the historical multi-field typical flood is selected to carry out model parameter calibration, the simulation time step is 1h, the CN value in the drainage basin is determined according to the soil type, the land utilization and the soil wetting condition before precipitation, the value is referred to the CN value taking table of the American SCS model, the initial loss value is 0.25S, and the research of the vegetation coverage condition of the drainage basin is shown in figure 3.
Performing grid division on the drainage basin by taking 30m multiplied by 30m as a unit, performing depression filling, slope extraction, flow direction extraction and grid river network processing on the DEM layer, and researching the slope distribution of the surface of the area as shown in figure 4;
extracting a watershed topographic index, and on the basis, calculating a distributed water storage capacity curve, wherein the distribution of the topographic indexes of the watershed of the dragon and tiger polder is shown in fig. 5, the distribution interval of the topographic indexes is [2.66,21.98], and by taking the water storage capacity distribution curve of the Xinanjiang model as reference, the minimum water storage capacity and the maximum water storage capacity of the watershed grid are respectively 5mm and 103mm through calibration, and the value of the parameter n is 0.95, so that the water storage capacity distribution curve expression is as follows:
Figure BDA0003580641380000111
in the formula, SMjThe water storage capacity of the j-grid cell.
According to the distribution curve of the water storage capacity, when the basin full area proportion is alpha, if the net rain of the next time period is P obtained through calculation of the SCS model, the net rain depth of the next time period full area is P
Figure BDA0003580641380000112
Further, the distribution of the watershed-full regions can be obtained by calculating the distribution of the topographic index, and the distribution of the watershed-full regions is shown in fig. 6 (a) - (c) by taking the watershed-full ratios of 0.25, 0.5 and 0.75 as examples.
The flow velocity coefficient is determined according to the vegetation distribution condition of the underlying surface, and the value of the flow velocity coefficient k of the corresponding vegetation on the slope surface is shown in the table 1.
TABLE 1 flow rate coefficients corresponding to different vegetation types
Figure BDA0003580641380000113
Determining basin reference rain intensity, calculating the reference rain intensity according to the historical average rain intensity of a research area, wherein the target basin reference rain intensity is 10mm/h, and when the basin full area proportion is alpha, the basin grid flow velocity calculation formula at the moment is as follows:
Figure BDA0003580641380000114
according to the formula, when a certain grid belongs to the river channel unit, the flow velocity is fixed to be 2m/s; when the grid is in a full storage area, the flow rate is strongly correlated with rain; when the grid is in an unfilled region but in the flow path of a filled grid, the effect of soil moisture content on the flow rate of the grid is taken into account; when the grid is in the non-full area and has no radial flow, the flow rate of the grid is 0, and the grid does not participate in the statistics of the confluence path.
Further, to simplify the proposed time-varying unit line application and reduce the number of unit lines, the embodiment of the present invention discretizes the rainfall intensity and the basin fullness factor, and the net rainfall and basin fullness factor discretization results are shown in tables 2 and 3:
TABLE 2 rain intensity per time period
Figure BDA0003580641380000121
Corresponding discrete value
Figure BDA0003580641380000122
TABLE 3 soil moisture content status α for each periodtCorresponding to the water content state alpha of the discrete soils
Figure BDA0003580641380000123
Because the basin full-storage proportion and the soil water content can be converted, when the full-storage proportion is given, the soil water content of the region which is not full-storage can be calculated by combining the distributed water storage capacity curve.
And (4) according to the time-varying slope flow rate formula and the basin saturation area, calculating a distributed dynamic unit line considering the soil water content. Combining the dynamic confluence paths obtained in the step (2) under different storage proportions and the time-varying grid flow velocity calculated in the step (3), counting to obtain a basin time-area histogram, wherein the obtained time-varying distributed dynamic unit line is shown in fig. 7, and the traditional time-varying distributed unit line is shown in fig. 8.
The method comprises the steps of forecasting the flood of a field by adopting the proposed time-varying distributed dynamic unit lines, comparing a forecasting result with a traditional distributed unit line, taking the flood of the field 20130713 as an example, taking the parameter CN as 73, calculating the net rainfall of the field as 92mm according to an SCS model, calculating the soil water content of the early stage of the flood of the field as 24mm, knowing that the initial storage proportion of the drainage basin reaches 70% by combining a distributed water storage capacity curve, and distributing the net rainfall of the whole drainage basin to a time-varying storage area by adopting the proposed method and the traditional distributed unit line method, wherein the time-varying storage proportion of the net rainfall is shown in figure 9; the flood forecasting result is shown in fig. 10, and the result shows that the method is superior to the traditional time-varying distributed unit line in the flood whole process and the rising stage, and the forecasting method is superior to the traditional time-varying distributed unit line in accuracy in general.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (8)

1. A time-varying distributed dynamic convergence calculation method is characterized by comprising the following steps:
s1, calculating the drainage basin flow rate based on an SCS model;
s2, grid division is carried out on the drainage basin, and water storage capacity of all grid units in the drainage basin is calculated based on the terrain indexes;
obtaining grids corresponding to the watershed storage full area and the non-storage full area based on the water storage capacity of the grid unit, the rainfall at the current moment and the net rainfall at the current moment; calculating the area of the full area and the water content of the soil in the area which is not full at the current moment on the grid scale; combining the runoff yield calculation result and the drainage basin area, and distributing the net rainfall at the current moment to a full storage area;
s3, constructing a time-varying slope flow velocity calculation formula according to the soil water storage state of the grid unit; the grid unit soil water storage state refers to whether the grid is fully stored or not and the soil water content of the grid which is not fully stored;
s4, obtaining dynamic confluence paths of the drainage basins with different storage and fullness ratios based on the areas of the drainage basin storage and fullness areas at different moments;
s5, obtaining a time-varying distributed dynamic unit line based on a time-varying slope flow velocity calculation formula and a dynamic confluence path;
and S6, calculating the flood process of the drainage basin by adopting the time-varying distributed dynamic unit lines and the drainage basin flow rate calculation result.
2. The time-varying distributed dynamic bus calculation method according to claim 1, wherein the j-th grid cell has a water storage capacity WMjThe calculation formula is as follows:
Figure FDA0003580641370000011
in the formula, WMminThe minimum water storage capacity in all grids of the full watershed; WM (pulse Width modulation)maxThe maximum water storage capacity in all grids of the full watershed; TImin＝min{TIj,j＝1,2…,N}；TImax＝max{TIj,j＝1,2…,N}；TIjThe terrain index of the jth grid; n is ginseng to be calibratedA coefficient reflecting topographic index distribution and water storage capacity distribution; and N is the total number of the basin grid units.
3. The time-varying distributed dynamic confluence computing method according to claim 2, wherein the t-period basin fullness area is:
Figure FDA0003580641370000021
in the formula (I), the compound is shown in the specification,
Figure FDA0003580641370000022
area of the reservoir, αtThe proportion of the basin full area at time t, Wj,0The initial moment water storage capacity of the grid j is obtained; p isiIs rainfall in period i, RiFor net rainfall i period, AjIs the grid cell area.
4. The time-varying distributed dynamic convergence calculation method according to claim 3, wherein a t-period net rainfall RtRedistribute to the area of the full region, the expression is as follows:
Figure FDA0003580641370000023
f is the basin area; rtFor net rainfall over time t, i.e. production rate, Rt' is the net rain depth of the full storage area,
Figure FDA0003580641370000024
5. the time-varying distributed dynamic convergence calculation method according to claim 4, wherein a time-varying slope flow velocity calculation formula is as follows:
Figure FDA0003580641370000025
k is the flow velocity coefficient, betajIs j grid cell slope, IcIs the average clear rain intensity of the watershed, Wj,tAnd the soil water content of the j grid unit corresponding to the full storage area in the time period t.
6. The time-varying distributed dynamic confluence computing method according to claim 2 or 5, wherein the soil moisture content of the j grid unit corresponding to the non-accumulation area in the t period is as follows:
Wj,t＝Wj,t-1+Pt-Rt
Wj,t-1for j grid t-1 time interval water storage, PtIs rainfall in the period of t, RtThe net rainfall, i.e. the production flow, is measured at time t.
7. The time-varying distributed dynamic convergence calculation method according to claim 5, wherein the dynamic convergence paths under different accumulation capacity ratios are:
Figure FDA0003580641370000031
Figure FDA0003580641370000032
indicating a collection of confluent paths that are full of grids,
Figure FDA0003580641370000033
Rjand representing the collection of the confluence paths of the grid units to the drainage basin outlet.
8. The time-varying distributed dynamic convergence calculation method according to claim 7, wherein the step S5 specifically comprises:
01. calculating the basin fullness ratio of t time period as alphatWaiting time of water drop in grid
Figure FDA0003580641370000034
When the water flow is in the direction of the grid
Figure FDA0003580641370000035
When the water flow flows along the diagonal direction of the grid
Figure FDA0003580641370000036
LjThe length of the grid side;
accumulating along the confluence path to obtain the confluence time of each grid to the drainage basin outlet
Figure FDA0003580641370000037
Figure FDA0003580641370000038
02. Calculating the full area of the drainage basin in the time interval corresponding to the adjacent unit line time period:
Figure FDA0003580641370000039
Figure FDA00035806413700000310
indicates that the full grid convergence time is [ (m-1) Δ t, m Δ t]The sum of the areas in the interval satisfies
Figure FDA00035806413700000311
Δ t is the unit line time interval in hours; m is unit line time interval, M =1,2, \8230, M is total time interval number of the unit line,
Figure FDA00035806413700000312
03. converting the area of the full storage grid into the flow process of the drainage basin outlet to obtain a distributed unit line at any time period:
Figure FDA0003580641370000041
UH (m) is the unit linear flow of the mth time period, and the unit is m3/s; h is the unit net rain, and the unit is mm.
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