CN117172142A - Hydrological model water flow along-path distribution considering terrain influence - Google Patents
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Abstract
The hydrological model water flow path-along distribution taking the influence of the terrain into consideration comprises the following steps: 1. the river basin is discretized into a plurality of grid units, the resolution of the grid units is set as the calculation scale of the distributed hydrologic model confluence calculation, and the terrain gradient beta is extracted c The method comprises the steps of carrying out a first treatment on the surface of the 2. Improving the resolution of the grid unit, calculating the gradient of the terrain, upscaling the gradient of the terrain to the calculated scale, and quantifying the terrain fluctuation beta inside the grid unit s The method comprises the steps of carrying out a first treatment on the surface of the 3. The rainfall P and the evaporation E are taken as inputs, the water flow q which can flow out freely in the grid unit is calculated, and the water flow q is divided into water flow q entering the air-packing belt of the downstream grid unit c And a water flow q discharged into the channels inside the grid unit s The method comprises the steps of carrying out a first treatment on the surface of the 4. Water flow q c Supplementing downstream gridThe unit air-packing water continuously flows out after the water quantity is lacking, and water flow q s Through the rapid movement of the channels among different grid units, the water flow along-path redistribution among the grid units is realized. The method has reasonable design, is favorable for better simulating the space-time dynamic distribution of soil water in the rainfall runoff process, and realizes the runoff process simulation with higher precision.
Description
Technical Field
The invention relates to the technical field of hydrology, in particular to a hydrological model water flow along-path distribution method considering the influence of terrain.
Background
Watershed water circulation can be generalized to the processes of precipitation, evapotranspiration, runoff, and watershed water storage capacity change, wherein precipitation is the main input of the circulation process and usually plays a dominant role; the water loss caused by the evaporation is an output item of the water circulation process; the dynamic change of runoff and water storage capacity of a river basin is jointly influenced by precipitation and evapotranspiration, and is a key link influencing natural ecological environment and human society in water circulation of the river basin. The space-time dynamic distribution of the water content of the soil directly influences the evolution of the soil ecosystem, and forms important basis for dividing the Chinese climate and vegetation types together with factors such as rainfall, thereby influencing the crop types and cultivation modes in different regions and indirectly modeling the economic, cultural and social life modes with various characteristics. Therefore, the dynamic change of the water content of the soil is used as a key link of water circulation of the river basin, the influence of meteorological factors and topographical features on the space-time distribution of the water content of the soil is quantized, the method is beneficial to improving the rationality of the rainfall runoff process simulation of the river basin, and important reference bases are provided for the aspects of soil moisture content simulation and forecast, agricultural production practice, ecological environment protection, human society scientific research and the like.
However, the conventional lumped hydrologic model generally takes a river basin as a whole, and it is difficult to realize quantitative simulation of soil water space-time distribution dynamic process inside the river basin. Based on the development of remote sensing, geographic information, digital watershed and other technologies, the grid digital elevation model (DEM, digital Elevation Model) adopting the numerical matrix to describe the elevation change of the ground surface is gradually mature and is widely applied. Based on a digital elevation model, a distributed hydrological model generally divides a river basin into a plurality of calculation units, water flows are moved and collected among different calculation units, and factors such as terrain gradient and the like are combined, so that water flow along-path redistribution is reasonably considered, and the problems of important points and difficulty in guaranteeing hydrological process simulation precision of the distributed model and improving the soil water space-time dynamic distribution simulation refinement level are solved.
In order to further promote the development of the soil water space-time dynamic distribution simulation and improve the simulation precision of the distributed rainfall runoff process, the influence of the terrain gradient on the water flow path distribution needs to be understood more deeply, and the response of the soil water content of each grid unit to the water flow path movement is quantized.
When researching a distributed hydrological model water flow path-along distribution method, the first challenge is to reasonably divide water flow directly entering a channel and water flow for supplementing the soil water content of a downstream grid unit. In the current practical application, the influence of the terrain gradient on the water flow along-path distribution is not considered, and all water flows are directly supplemented and supplemented with the soil water content of the downstream grid unit. Although the method realizes generalized simulation of water flow exchange among grid units to a certain extent, the space-time dynamic distribution process of soil water in the river basin is difficult to reasonably describe, the simulation precision of the distributed rainfall runoff process is reduced to a certain extent, and the simulation refinement level of the rainfall runoff process is restricted.
Therefore, the method for neglecting the influence of the terrain gradient on the water flow along-path redistribution is not beneficial to the improvement of the simulation refinement level of the soil water space-time dynamic distribution. Therefore, it is necessary to design a water flow path-along-distance distribution method of a hydrological model in consideration of the influence of terrain, so as to overcome the above problems.
Disclosure of Invention
In order to avoid the problems, the hydrologic model water flow along-path redistribution method considering the influence of the terrain is provided, the design is reasonable, the soil water space-time dynamic distribution in the rainfall runoff process is well simulated, and the runoff process simulation with higher precision is realized.
The invention provides a hydrological model water flow along-path distribution method considering the influence of terrain, which comprises the following steps:
step 1, based on digital elevation model D c The river basin is discretized into a plurality of grid units, the resolution of the grid units is set as the calculation scale of the distributed hydrologic model confluence calculation, and the terrain gradient beta is extracted c ；
Step 2, selecting resolution higher than D c Digital elevation model D of (2) s Calculating the slope of the terrain and upscaling it to the calculated scale, quantifying the terrain relief beta inside the grid unit s ；
Step 3, calculating the water flow q which can flow out freely in the grid unit by taking rainfall P and evaporation E as input, and taking beta as the input c And beta s The ratio between the two divides q into water flow q entering the downstream grid unit air-packing belt c And a water flow q discharged into the channels inside the grid unit s ；
Step 4 of the process, in which,water flow q c Supplementing the air-packing belt of the downstream grid unit, and continuing to flow out after water shortage, wherein water flow q s Through the rapid movement of the channels among different grid units, the water flow along-path redistribution among the grid units is realized.
Preferably, the step 1 comprises the following sub-steps:
1.1 digital elevation model D c Discretizing the river basin into a plurality of orthogonal grid units, and making the side length of the grid units L c As a calculation scale;
1.2 coding 8 adjacent cells of the grid cells in a clockwise direction, coding adjacent grid cells in the east, southeast, south, southwest, west, northwest, north and northeast directions as 0, 1, 2, 3, 4, 5, 6 and 7, respectively;
1.3 calculating the terrain gradient beta between the grid unit and the downstream grid unit by taking the direction of the grid unit with the lowest relative elevation as the water flow direction and taking the grid unit into which the water flows as the downstream grid unit c The calculation formula is as follows:
wherein: e (E) c Elevation for grid cells; e (E) x Elevation for the downstream grid cell;a straight line distance between the grid unit and the downstream grid unit; when the downstream grid cell codes 0, 2, 4, and 6, the value of ε is 1, otherwise it is 1.414.
Preferably, the step 2 includes the following sub-steps:
2.1 selecting resolution higher than D c Digital elevation model D of (2) s Dispersing the grid unit into a grid unit with a side length L s Is arranged in the middle of the grid;
2.2 in grid cells, calculating the side Length L by the method in steps 1.2 and 1.3 s Terrain gradient beta between small grid units s ；
2.3 calculating the terrain slope beta s Is the first order origin moment of (1)Upscaling to computational dimensions, quantifying topography relief beta inside grid cells σ The calculation formula is as follows:
wherein: i is the inside of the grid unit and the side length is L s Numbering of small grid cells from 1 to n; n is the inside of the grid unit and the side length is L s Is provided, the number of small grid cells of (a).
Preferably, the step 3 includes the following sub-steps:
3.1, using rainfall P and evaporation E as input, and calculating water flow q which can flow out freely in the grid unit by adopting a full-reservoir flow model and a linear reservoir formula;
3.2 beta c And beta s The ratio between them divides the water flow q into water flow q entering the downstream grid unit air-packing belt c And a water flow q discharged into the channels inside the grid unit s The calculation formula is as follows:
q c +q s ＝q；
preferably, the step 4 includes the following sub-steps:
4.1 Water flow q c The water is continuously discharged after supplementing the air-packing belt of the downstream grid unit,
when W+PE+q c When the weight is less than or equal to WM, R=0;
when W+PE+q c At > WM, R=PE+W+q c -WM；
Wherein: WM is the water storage capacity of the tension water; w is tension water content; PE is rainfall after evaporation loss is deducted, namely net rain; r is the generated runoff amount;
the runoff quantity R is converted into a water flow q capable of flowing after being calculated by a water diversion source of a full-reservoir flow model and a linear reservoir method b ；
4.2 Water flow q s Fast movement between different grid cells through the channels is achieved byThe two formulas are solved simultaneously to obtain channel water flow Q, and then the channel water flow Q is gradually accumulated to obtain a runoff process of a drainage basin outlet;
wherein: a is the cross-sectional area of channel water flow, Q is the channel water flow; s is S f Is of hydraulic gradient S o Is the channel gradient; t is a time term, and the value is generally a calculation time interval; x is a spatial term and the value is typically the side length of the grid cell.
Compared with the prior art, the invention has the following beneficial effects: the water flow path redistribution of the hydrological model considering the terrain influence is based on physical factors influencing the water flow path redistribution, so that the influence of the terrain on the water flow path redistribution is quantified, and a distributed hydrological model water flow path redistribution method considering the terrain influence is further provided; the accuracy and the reliability of the calculation result are guaranteed, and meanwhile the problem of along-path redistribution when water flows in the distributed model pass through different calculation grid units is solved. The method mainly uses a basin digital elevation model, has stable and reliable data sources, has definite functional relation among variables in the method, is beneficial to the rapid and automatic execution of the water flow along the course in the basin, simplifies the extraction step by a digital basin technology, ensures the objective rationality of the result, and can further promote the deep development of digital hydrology and a distributed model.
Drawings
FIG. 1 is a flow chart of a hydrological model water flow along-path redistribution method taking into account terrain effects according to a preferred embodiment of the present invention;
FIG. 2 is a digital elevation model of the inter-zone basin on a Pu city-Wu Qiang xi dam;
FIG. 3 is a flow direction encoding schematic;
FIG. 4 is a gradient calculation illustration;
FIG. 5 is an upscale front five strong stream domain slope;
FIG. 6 is a graph of five strong stream domain slopes after upscaling;
FIG. 7 is a water flow division schematic;
FIG. 8 is a graph of the spatial distribution of soil water at 8h in the process of 20200915 flood;
fig. 9 is a soil water spatial distribution at 9h in the 20200915 flood process;
FIG. 10 is a spatial distribution of soil water at 10h of the 20200915 flood process;
FIG. 11 is a graph of the spatial distribution of soil water at 11h in the process of 20200915 flood;
FIG. 12 is a graph of the spatial distribution of soil water at 12h in the process of 20200915 flood;
fig. 13 is a soil water spatial distribution of No. 20200915 flood process 13 h;
fig. 14 is a soil water spatial distribution of 14h in the 20200915 flood process;
fig. 15 is a 15h soil water spatial distribution for a 20200915 flood process;
fig. 16 is a soil water spatial distribution of No. 20200915 flood process, no. 16 h;
fig. 17 is a 20200915 flood process simulation result;
FIG. 18 is a comparison of the five-force stream interval basin LPRM AMSR2 product with the results of a soil water simulation;
FIG. 19 shows the proportion of soil moisture content in the total amount of the river basin in different areas.
Detailed Description
As shown in fig. 1 to 19, the water flow path-along distribution method of the hydrological model taking the influence of terrain into consideration provided by the embodiment includes the following steps:
step 1, based on digital elevation model D c The river basin is discretized into a plurality of grid units, the resolution of the grid units is set as the calculation scale of the distributed hydrologic model confluence calculation, and the terrain gradient beta is extracted c ；
The method comprises the following substeps:
1.1 digital elevation model D c Discretizing the river basin into a plurality of orthogonal grid units, and making the side length of the grid units L c As a calculation scale;
1.2 coding 8 adjacent cells of the grid cells in a clockwise direction, coding adjacent grid cells in the east, southeast, south, southwest, west, northwest, north and northeast directions as 0, 1, 2, 3, 4, 5, 6 and 7, respectively;
1.3 calculating the terrain gradient beta between the grid unit and the downstream grid unit by taking the direction of the grid unit with the lowest relative elevation as the water flow direction and taking the grid unit into which the water flows as the downstream grid unit c The calculation formula is as follows:
wherein: e (E) c Elevation for grid cells; e (E) x Elevation for the downstream grid cell;a straight line distance between the grid unit and the downstream grid unit; when the downstream grid cell codes 0, 2, 4, and 6, the value of ε is 1, otherwise it is 1.414.
Step 2, selecting resolution higher than D c Digital elevation model D of (2) s Calculating the slope of the terrain and upscaling it to the calculated scale, quantifying the terrain relief beta inside the grid unit s ；
The method comprises the following substeps:
2.1 selecting resolution higher than D c Digital elevation model D of (2) s Dispersing the grid unit into a grid unit with a side length L s Is arranged in the middle of the grid;
2.2 in grid cells, calculating the side Length L by the method in steps 1.2 and 1.3 s Terrain gradient beta between small grid units s ；
2.3 calculating the terrain slope beta s Is upscaled to calculated scale to quantify the topography relief beta inside the grid cell σ The calculation formula is as follows:
wherein: i is the inside of the grid unit and the side length is L s Numbering of small grid cells from 1 to n; n is the inside of the grid unit and the side length isL s Is provided, the number of small grid cells of (a).
Step 3, calculating the water flow q which can flow out freely in the grid unit by taking rainfall P and evaporation E as input, and taking beta as the input c And beta s The ratio between the two divides q into water flow q entering the downstream grid unit air-packing belt c And a water flow q discharged into the channels inside the grid unit s ；
The method comprises the following substeps:
3.1, using rainfall P and evaporation E as input, and calculating water flow q which can flow out freely in the grid unit by adopting a full-reservoir flow model and a linear reservoir formula;
3.2 beta c And beta s The ratio between them divides the water flow q into water flow q entering the downstream grid unit air-packing belt c And a water flow q discharged into the channels inside the grid unit s The calculation formula is as follows:
q c +q s ＝q；
step 4, water flow q c Supplementing the air-packing belt of the downstream grid unit, and continuing to flow out after water shortage, wherein water flow q s Through the rapid movement of the channels among different grid units, the water flow along-path redistribution among the grid units is realized;
the method comprises the following substeps:
4.1 Water flow q c The water is continuously discharged after supplementing the air-packing belt of the downstream grid unit,
when W+PE+q c When the weight is less than or equal to WM, R=0;
when W+PE+q c At > WM, R=PE+W+q c -WM；
Wherein: WM is the water storage capacity of the tension water; w is tension water content; PE is rainfall after evaporation loss is deducted, namely net rain; r is the generated runoff amount;
the runoff quantity R is converted into water flow q capable of continuously flowing after being calculated by a water diversion source of a full-reservoir flow model and a linear reservoir method b ；
4.2 Water flow q s The channel water flow Q is obtained by the simultaneous solving of the following two formulas through the rapid movement of the channel among different grid units, and then the runoff process of the drainage basin outlet is gradually accumulated;
wherein: a is the cross-sectional area of channel water flow, Q is the channel water flow; s is S f Is of hydraulic gradient S o Is the channel gradient; t is a time term, and the value is generally a calculation time interval; x is a spatial term and the value is typically the side length of the grid cell.
Taking the area of the river basin in the upper section of the five-strong stream dam in Hunan Phragps as an example, the area of the river basin is 7864km 2 The geographic positions are 28 DEG 02 'N-29 DEG 10' N,109 DEG 44 'E-111 DEG 01' E, and belong to subtropical evergreen and deciduous broad-leaved forest belts. Canyons with different lengths are distributed in intervals, the elevation is between 42 and 1396m, the flow of the water coming from the intervals is short, the flow is rapid, the burst performance is strong, and the canyon has a large influence on the warehouse-in runoff of five strong streams. The area on the Fenghu-Wuqiang river dam is in a wet area, the average rainfall for many years is about 1724mm, and the area is mainly concentrated in the flood season of 4-9 months. There are 23 rainfall stations in the flow area, and the daily rainfall data in 2014-2020 and the period rainfall data of the scene flood are collected.
Taking 20200915 flood process as an example, simulating to obtain a five-strong-stream warehouse-in runoff process after upstream inflow through river channel calculation, applying a distributed hydrological model water flow path redistribution method considering the terrain influence, and outputting the soil water content of No. 20200915 flood process 8-16 h after rainfall begins.
The hydrological model water flow path-along redistribution method taking the influence of terrain into consideration comprises the following steps:
step 1, based on digital elevation model D c The river basin is discretized into a plurality of orthogonal grid units, the resolution of the grid units is set as the calculation scale of the confluence calculation of the distributed hydrologic model, and the terrain gradient beta is extracted c The method specifically comprises the following steps:
1.1 based on the number Gao ChengmoD (D) c Discretizing the river basin into a plurality of orthogonal grid units, and making the side length of the grid units L c As a calculation scale, fig. 2;
1.2 coding 8 adjacent cells of the grid cells in a clockwise direction, coding adjacent grid cells in the east, southeast, south, southwest, northwest, north and northeast directions as 0, 1, 2, 3, 4, 5, 6 and 7, respectively, as shown in fig. 3;
1.3 calculating the terrain gradient beta between the grid unit and the downstream grid unit by taking the direction of the grid unit with the lowest relative elevation as the water flow direction and taking the grid unit into which the water flows as the downstream grid unit c As shown in fig. 4, the gradient spatial distribution in the five strong streams is obtained, as shown in fig. 5, and the calculation formula is as follows:
wherein: e (E) c For grid cell elevation, E x For the downstream grid cell elevation,for the straight line distance between the grid cell and the downstream grid cell, the value of e is 1 when the downstream grid cell is coded as 0, 2, 4 and 6, otherwise 1.414.
Step 2, selecting resolution higher than D c Digital elevation model D of (2) s Calculating the slope of the terrain and upscaling it to the calculated scale, quantifying the terrain relief beta inside the grid unit σ The method specifically comprises the following steps:
2.1 selecting resolution higher than D c Digital elevation model D of (2) s Further dispersing the grid unit into a grid unit with a side length L s Is arranged in the middle of the grid;
2.2 in grid cells, calculating the side Length L by the method in steps 1.2 and 1.3 s Terrain gradient beta between small grid units s ；
2.3 calculating the terrain slope beta s Is upscaled to calculated scale to quantify the topography relief beta inside the grid cell σ As shown in fig. 6, the calculation formula is as follows:
wherein: i is the inside of the grid unit and the side length is L s Numbering of small grid cells from 1 to n; n is the inner part of the grid unit and the side length is L s Is provided, the number of small grid cells of (a).
Step 3, calculating the water flow q which can flow out freely in the grid unit by taking rainfall P and evaporation E as input, and taking beta as the input c And beta s The ratio between the two divides q into water flow q entering the downstream grid unit air-packing belt c And a water flow q discharged into the channels inside the grid unit s The method specifically comprises the following steps:
3.1, taking rainfall P and evaporation E as input, and calculating water flow q which can flow out freely in a grid unit by adopting a full-reservoir flow model and a linear reservoir formula;
3.2 beta c And beta s The ratio between them divides the water flow q into water flow q entering the downstream grid unit air-packing belt c And a water flow q discharged into the channels inside the grid unit s As shown in fig. 7, the calculation formula is as follows:
q c +q s ＝q
step 4, water flow q c Supplementing the air-packing belt of the downstream grid unit, and continuing to flow out after water shortage, wherein water flow q s Through the rapid movement of the channel among different grid units, the water flow along-path redistribution among the grid units is realized, and the method specifically comprises the following steps:
4.1 Water flow q c Supplementing the air-packing belt of the downstream grid unit with water shortage and then continuously flowing out;
when W+PE+q c When the weight is less than or equal to WM, R=0;
when W+PE+q c At > WM, R=PE+W+q c -WM；
Wherein: WM represents the water storage capacity of the tension water; w represents the tension water content; PE represents the rainfall after deducting the evaporation loss, namely the net rain; r represents the generated runoff amount; the runoff quantity R is converted into water flow qb capable of continuously flowing after being calculated by a water diversion source of a full-reservoir current generation model and a linear reservoir method.
4.2 Water flow q s The channel water flow Q is obtained by the simultaneous solving of the following two formulas through the rapid movement of the channel among different grid units, and then the runoff process of the outlet of the river basin is obtained by gradually accumulating and calculating each grid unit;
wherein: a is the cross-sectional area of channel water flow, Q is the channel water flow; s is S f Is of hydraulic gradient S o Is the channel gradient; t is a time term, and the value is generally a calculation time interval; x is a spatial term and the value is typically the side length of the grid cell.
Taking into account the water flow q c And water flow q s The motion process of (2) is simulated to obtain the soil water time-space dynamic change, as shown in figures 8 to 16.
In order to further verify the rationality of the spatial distribution of the simulated soil water content, the comparison analysis of the simulation result and the satellite remote sensing inversion soil aquatic product LPRM AMSR2 is carried out in the river basin. At the earth observation data service website https of NASA: the method comprises the steps of (1) carrying out// cmr, earthdata, nasa, gov/obtaining LPRM AMSR2 soil and aquatic products, and combining with JAVA official data website https: the specific time period of the space above the satellite fly-by research river basin in each flood process is checked according to the record of the satellite trajectory of/(g portal. Jaxa. Jp/disclosure, the soil water space distribution of remote sensing inversion in the corresponding time period is shown in fig. 18a, and the obtained soil water content space distribution is simulated as shown in fig. 18b.
It is worth noting that, because the satellite-mounted AMSR2 sensor mainly carries out remote sensing observation on the water content of the soil layer with the depth of 5cm below the surface, and certain difference exists between the water content of the soil layer and the water content of the model simulation, the example does not pay attention to the difference of the water content values of the soil in a specific place, but divides the river basin into a plurality of areas according to satellite observation results, and analyzes the relative size rules of the water content of the soil in different areas in the river basin and the correlation between the LPRM AMSR2 product and the model simulation results. 52 areas are obtained by dividing the five strong stream intervals with larger areas of the drainage basins, and the proportion of the soil water content in different areas to the total amount of the whole drainage basin is calculated respectively, as shown in figure 18. It can be seen that the simulated soil water in the areas numbered 1 to 5, 43 to 45 and 51 is less than the total amount of the full-basin by about 5.1%, 8% and 3.9%, respectively, compared with the LPRM AMSR2 soil water product. By combining the drainage basin topography distribution characteristics of the five strong stream intervals and the rainfall site observation data, the areas are located at the boundary of the drainage basin and have larger gradient, the rapid movement of water flow is facilitated, and rainfall is less in the period, so that the simulated soil has lower water content. The proportion of the soil water in most areas to the total amount of the full-drainage basin is relatively close, the rank correlation coefficient of the soil water content simulation value and the LPRM AMSR2 product which are changed among different areas is calculated to be 0.47 and higher than the rank correlation coefficient test critical value under the conditions that the sample number is 52 and the significance level is 0.05, and the spatial distribution characteristics of the soil water content simulated by the model can be considered to have positive correlation relation with satellite remote sensing observation results.
Meanwhile, the rainfall runoff process of the river basin obtained based on the simulation of the soil and water products is output and compared with the actual measurement process, as shown in fig. 19. The certainty factor between the simulated rainfall runoff process and the actual measurement process obtained through statistics reaches 0.87, and the error is small.
The comparison analysis of the comprehensive soil water simulation result and the satellite remote sensing inversion soil aquatic product LPRM AMSR2, and the comparison of the basin rainfall runoff process and the actual measurement process can be considered to be reasonable in design, and the distributed hydrologic model water flow along-path redistribution method considering the terrain influence is favorable for better simulating the soil water space-time dynamic distribution in the rainfall runoff process, so that the runoff process simulation with higher precision is realized.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (5)
1. The hydrological model water flow path-along-distance redistribution method considering the terrain influence is characterized by comprising the following steps of:
step 1, based on digital elevation model D c The river basin is discretized into a plurality of grid units, the resolution of the grid units is set as the calculation scale of the distributed hydrologic model confluence calculation, and the terrain gradient beta is extracted c ；
Step 2, selecting resolution higher than D c Digital elevation model D of (2) s Calculating the slope of the terrain and upscaling it to the calculated scale, quantifying the terrain relief beta inside the grid unit s ；
Step 3, calculating the water flow q which can flow out freely in the grid unit by taking rainfall P and evaporation E as input, and taking beta as the input c And beta s The ratio between the two divides q into water flow q entering the downstream grid unit air-packing belt c And a water flow q discharged into the channels inside the grid unit s ；
Step 4, water flow q c Supplementing the air-packing belt of the downstream grid unit, and continuing to flow out after water shortage, wherein water flow q s Through the rapid movement of the channels among different grid units, the water flow along-path redistribution among the grid units is realized.
2. A hydrographic model water flow along path allocation method taking into account terrain effects as claimed in claim 1, wherein: the step 1 comprises the following substeps:
1.1 digital elevation model D c Discretizing the river basin into a plurality of orthogonal grid units, and making the side length of the grid units L c As a calculation scale;
1.2 coding 8 adjacent cells of the grid cells in a clockwise direction, coding adjacent grid cells in the east, southeast, south, southwest, west, northwest, north and northeast directions as 0, 1, 2, 3, 4, 5, 6 and 7, respectively;
1.3 calculating the terrain gradient beta between the grid unit and the downstream grid unit by taking the direction of the grid unit with the lowest relative elevation as the water flow direction and taking the grid unit into which the water flows as the downstream grid unit c The calculation formula is as follows:
wherein: e (E) c Elevation for grid cells; e (E) x Elevation for the downstream grid cell;a straight line distance between the grid unit and the downstream grid unit; when the downstream grid cell codes 0, 2, 4, and 6, the value of ε is 1, otherwise it is 1.414.
3. A hydrographic model water flow along path allocation method taking into account terrain effects as claimed in claim 2, wherein: the step 2 comprises the following substeps:
2.1 selecting resolution higher than D c Digital elevation model D of (2) s Dispersing the grid unit into a grid unit with a side length L s Is arranged in the middle of the grid;
2.2 in grid cells, calculating the side Length L by the method in steps 1.2 and 1.3 s Terrain gradient beta between small grid units s ；
2.3 calculating the terrain slope beta s Is upscaled to calculated scale to quantify the topography relief beta inside the grid cell σ The calculation formula is as follows:
wherein: i is the inside of the grid unit and the side length is L s Numbering of small grid cells from 1 to n; n is the inner part and side length of the grid unitIs L s Is provided, the number of small grid cells of (a).
4. A hydrographic model water flow along path allocation method taking into account terrain effects as claimed in claim 1, wherein: the step 3 comprises the following substeps:
3.1, using rainfall P and evaporation E as input, and calculating water flow q which can flow out freely in the grid unit by adopting a full-reservoir flow model and a linear reservoir formula;
3.2 beta c And beta s The ratio between them divides the water flow q into water flow q entering the downstream grid unit air-packing belt c And a water flow q discharged into the channels inside the grid unit s The calculation formula is as follows:
q c +q s ＝q；
5. a hydrographic model water flow along path allocation method taking into account terrain effects as claimed in claim 1, wherein: the step 4 comprises the following substeps:
4.1 Water flow q c The water is continuously discharged after supplementing the air-packing belt of the downstream grid unit,
when W+PE+q c When the weight is less than or equal to WM, R=0;
when W+PE+q c At > WM, R=PE+W+q c -WM；
Wherein: WM is the water storage capacity of the tension water; w is tension water content; PE is rainfall after evaporation loss is deducted, namely net rain; r is the generated runoff amount;
the runoff quantity R is converted into a water flow q capable of flowing after being calculated by a water diversion source of a full-reservoir flow model and a linear reservoir method b ；
4.2 Water flow q s The channel water flow Q is obtained by the simultaneous solving of the following two formulas through the rapid movement of the channel among different grid units, and then the runoff process of the drainage basin outlet is gradually accumulated;
wherein: a is the cross-sectional area of channel water flow, Q is the channel water flow; s is S f Is of hydraulic gradient S o Is the channel gradient; t is a time term, and the value is a calculation time interval; x is a space term and the value is the side length of the grid cell.
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