CN110751723A - A Sequence Coding Method for Grid Calculation of Channels in the Same Subbasin - Google Patents

Abstract

The invention relates to a river channel grid calculation order coding method for the same sub-basin, which comprises the following steps: and carrying out river channel grid and sub-basin division, sub-basin coding, confluence layer coding, in-layer sequence coding, inflow grid coding and river channel coding. The encoding method can realize the production convergence calculation of the grid-type hydrological model, the encoding rules assign different identification values to each sub-basin of the basin, the parallel calculation is convenient, the river course grids and the non-river course grids are distinguished in the encoding process, the hydraulic connection between the grids is only generated between adjacent layers, the problems in the calculation process can be conveniently searched according to the topological relation through the encoding rules in the calculation process, and the problem of calculation sequence encoding of the river course grids of the same sub-basin is solved.

Description

A Sequence Coding Method for Grid Calculation of Channels in the Same Subbasin

technical field

The application of the present invention is the application date of July 25, 2018, the application number is: 2018108299607, and the divisional application of the invention patent application entitled "A DEM-based grid-type hydrological model grid calculation order coding method". The invention relates to a method for constructing a hydrological model, in particular to a method for coding the order of grid calculation of river channels in the same sub-basin.

Background technique

Hydrological phenomena in nature are intricate and complex, not only including different processes that are interrelated and independent of each other, but also affected by many external conditions. In order to realize the simulation and study of complex hydrological processes in the real world, the concept of hydrological model came into being under the continuous exploration of the pioneers of hydrology. It can be said that the emergence of hydrological models has opened a new door in the field of hydrology, and has become the basis for studying and exploring all processes related to hydrology or analyzing all hydrological phenomena.

In general, hydrological models can be divided into two categories: distributed models and lumped models. The lumped hydrological model regards the watershed as a homogeneous whole, and does not consider the spatial inconsistency of each parameter and each hydrological process in the watershed simulation. The distributed model divides the hydrological cycle process into several computing units on the spatial scale. The parameters and variables of each computing unit are generally different, and some even have different hydrological simulation methods between different units.

According to the method that the runoff process of each computing unit in the distributed hydrological model forms the flow process at the outlet of the basin, the hydrological model can be divided into a coupled type and a loose type. The coupled distributed hydrological model needs to consider the interaction between each computing unit, and solve it through simultaneous differential equations and determination of boundary conditions. In the loose hydrological model, each calculation unit is independent of each other. During the calculation process, the hydrological process in different calculation units can be calculated separately. There is no interaction between the units. The multiplication or superposition principle is used to obtain the final watershed flow process.

The lumped hydrological model ignores the heterogeneity of the temporal and spatial distribution of hydrological elements because it does not consider the changes of hydrological processes in the basin. The coupled distributed hydrological model requires a strict physical basis, and the parameters are distributed, which not only requires that the hydrological process description equation in the model can truly reflect the actual hydrological response process in the basin, but also has spatial variability. The requirements for calculation and data are relatively high. The grid-based hydrological model is a kind of loose model, which can flexibly adjust the size of the grid and realize the discretization of the underlying surface conditions in the watershed. It is a widely used hydrological model.

The grid-type hydrological model based on DEM performs runoff calculation on each grid separately, and then performs confluence calculation between grids. During the calculation process, it is necessary to distinguish the Calculate the order to meet the path of water flow towards the catchment outlet of the watershed. When extracting a digital watershed from DEM data for confluence calculation, due to the nonlinear characteristics of watershed confluence, the confluence process between grids in the watershed is sequential. the order of confluence calculus. The calculation sequence of each computing unit is established on the basis of determining the water flow direction of each grid, and the topological relationship between each grid is described by the water flow direction. In the simulation of production and confluence, in order to allow the computer to identify the topological relationship between the grids represented by the direction of the water flow, it is necessary to build the coding of each grid, and through the coding rules, the calculation sequence of each grid is reflected, which is convenient for the computer to identify and calculate. .

SUMMARY OF THE INVENTION

The present invention designs a grid calculus order coding method for grid hydrological model based on DEM, which solves the problem that river grids and non-river grids cannot be distinguished in the coding process, and the hydraulic connection between grids only occurs. Between adjacent layers, in the calculation process, the problem that occurs in the calculation process cannot be found according to the topological relationship through the coding rules.

In order to solve the above-mentioned technical problem, the present invention adopts the following scheme:

A DEM-based grid-type hydrological model grid calculation sequence coding method, comprising the following steps: step 1, determining grid size; step 2, obtaining grid flow direction; step 3, dividing river grids and sub-basins; 4. Encode each grid.

Further, step 4: generate a 5-digit array for each grid, which is used to store the code of the grid. The coding format is (ID1, ID2, ID3, ID4, ID5), and the initial value is (0,0,0, 0,0); ID1 is the sub-watershed code; ID2 is the confluence layer code; ID3 is the intra-layer sequence code; ID4 is the inflow grid code; ID5 is the river channel code.

Further, the step 4 includes step 41: reading the sub-watershed code from the sub-watershed division obtained in step 3, and assigning the sub-watershed code to ID1.

Further, the step 4 includes step 42: searching for the most downstream outlet grid of each sub-basin, and assigning the grid ID2 as 1.

Further, the step 4 includes step 43: for each sub-basin, start the search from the outlet grid of the most downstream sub-basin, and clockwise search for the ID1 code and the ID1 code of the grid in the 8 grids around the outlet grid For the same grid, if the water flow direction of a grid flows into this grid, the ID2 of this grid will be assigned a value of 2, ID3 will be assigned from 1, and increase one by one, and ID4 will be assigned a value of 1. Coding of conditional grids.

Further, the step 4 includes step 44: for different sub-basins, search for all grids whose ID2 is B (B≥2), and encode them in the order of ID3, assuming that a grid is (A, B, C, D, E), clockwise search (A, B, C, D, E) in the 8 grids around the grid with the same ID1 code as the grid ID1. When the direction of water flow flows into the grid, the ID2 of this grid is assigned B+1, ID3 starts from 1 and increases one by one, and ID4 is assigned D, until all the grids that meet the requirements are coded.

Further, the step 4 includes step 45 : importing the grid information of the river channel, and sequentially accumulating in the order of gradually increasing from the source of the river to the mouth of the river, and encoding the ID5.

Further, the step 1 determines the grid size of the established grid-type hydrological model according to the scope of the research area and research needs, and the size of each grid should be consistent in a modeling process; or/and, the grid size It is 1km×1km, 3km×3km or 9km×9km.

Further, in the step 2, with the aid of a hydrological analysis tool, the water flow direction of each grid is obtained by a single flow direction method.

Further, in step 3, according to the flow direction information of each grid water obtained in step 2, with the help of hydrological analysis tools, set the threshold value of the catchment area, obtain the digital information of the river channel in the study area, and use the hydrological analysis tool to carry out the analysis of the study area. Sub-basin division.

Further, the hydrological analysis tools in the step 2 and the step 3 are the hydrological analysis tools in ArcGIS 10.2.

This DEM-based grid hydrological model grid calculus order coding method has the following beneficial effects:

(1) The coding method of the present invention assigns different identification values to each sub-watershed of the watershed to facilitate parallel computing;

(2) The grid-based hydrological model of the present invention often needs to distinguish between river units and non-river units in the calculation process. This coding method can effectively distinguish river units and non-river units, which is convenient for different types of grids during confluence calculation. Use different confluence methods.

(3) The confluence of the present invention only occurs between adjacent layers. If an abnormal value occurs in a grid during the calculation process, the reason can be found according to the topological relationship through coding rules.

Description of drawings

FIG. 1 is a flow chart of the grid calculus order coding method of the grid type hydrological model based on the DEM of the present invention.

FIG. 2 is a schematic diagram of the present invention after encoding is completed.

Detailed ways

Below in conjunction with Fig. 1 and Fig. 2, the present invention is further described:

As shown in FIG. 1 , this embodiment is a DEM-based grid-type hydrological model grid operation order coding method, and the process is shown in FIG. 1 . The steps of the method described in this embodiment are as follows:

Step 1: Determine the grid size of the established grid-type hydrological model according to the scope of the study area and research needs, such as 1km×1km, 3km×3km or 9km×9km, and the size of each grid should be consistent in one modeling process .

Step 2: With the help of the hydrological analysis tool in ArcGIS 10.2, the water flow direction of each grid is obtained by the single flow direction method.

Step 3: According to the flow direction information of each grid obtained in Step 2, with the help of the hydrological analysis tool in ArcGIS 10.2, set the threshold of the catchment area to obtain the digital information of the river channel in the study area, and with the help of the hydrological analysis tool in ArcGIS 10.2, Divide the study area into sub-watersheds.

Step 4: Generate a 5-digit array for each grid, which is used to store the grid code. The code format is (ID1, ID2, ID3, ID4, ID5), and the initial value is (0,0,0,0, 0).

Step 41: Read the sub-watershed code from the sub-watershed division obtained in step 3, and assign the sub-watershed code to ID1.

Step 42: Find the most downstream outlet grid of each sub-basin, read the information of the outlet grid of the sub-basin, and assign the grid ID2 to 1.

Step 43: For each sub-basin, start the search from the outlet grid of the most downstream sub-basin, and search clockwise in the 8 grids around the outlet grid for grids with the same ID1 code as the grid ID1. When the flow direction of the grid flows into the grid, the ID2 of this grid is assigned a value of 2, ID3 is assigned from 1, and increases one by one, and ID4 is assigned a value of 1 to complete the encoding of all eligible grids around the river outlet grid.

Step 44: For different sub-basins, search for all grids whose ID2 is B (B≥2), and encode them in the order of ID3. Assuming that a grid is (A, B, C, D, E), the order Clockwise search (A, B, C, D, E) grids with the same ID1 code as the grid ID1 code in the 8 grids around the grid. If the water flow direction of a grid flows into the grid, then The ID2 of this grid is assigned B+1, ID3 starts from 1 and increases one by one, and ID4 is assigned D, until all the grids that meet the requirements are coded.

Step 45: Import the grid information of the river channel, accumulate it in order from the source of the river to the mouth of the river, and encode ID5.

As shown in Figure 2, as shown in the above figure, each grid is encoded by a set of five-digit arrays, and the encoding structure is (ID1, ID2, ID3, ID4, ID5), where:

ID1: Sub-watershed code; different sub-watersheds have different coding values, identifying the sub-watershed positions where different grids are located;

ID2: Convergence layer code; the layer number of the grid in a sub-basin, such as the sub-basin outlet grid layer number is 1, the inflow outlet grid layer number is 2, and so on;

ID3: In-layer sequence coding; the grid number in the same layer. In a sub-watershed, as the layer number increases, the number of grids in the same layer also increases. In order to distinguish the grids in the same layer Grids, number these grids to facilitate locking grids in the same layer;

ID4: Inflow grid code; the number of a specific grid in the inflow downstream layer. Since only the hydraulic connection occurs between adjacent layers, in order to locate the confluence target of a grid in the layer with the larger value of the confluence layer, the inflow grid code is used to search for the grid that merges into a grid in the downstream layer;

ID5: river channel code; the code for non-river grid grid is 0, and the channel grid code gradually increases from the river source to the estuary.

The coding rule first determines all the grids in the same sub-basin, and assigns a uniform value to grid ID1. The grids in Figure 2 are all located in sub-basin 1, so the code ID1 is 1; according to the flow direction of each grid and the flow direction network The sub-watershed is layered, the layer number is the code number of ID2, the outlet grid of the watershed is the first layer grid of the watershed, so the ID2 code is 1, the grid of the inflow watershed outlet is the second layer grid, and the ID2 code is 2. There are 5 layers in the sub-watershed in the figure, and the maximum code value of ID2 is 5; ID3 is coded as an intra-layer sequential code. Taking the 3rd layer as an example, it is changed to a total of 3 grids, and the codes of ID3 are 1, 2, 3; The ID4 code determines the grid into which the grid water flow flows. Since only the corresponding layers will have hydraulic connections under this coding rule, and the water flow will only flow from a grid with a large number of layers into a grid with a small number of layers, so It is only necessary to specify the trellis encoding of a grid inflow in trellis encoding, and its layer number information is actually known. Taking the grid of layer 4 and intra-layer coding 2 as an example, the grid will only flow into a grid in the grid of layer 3. From the confluence network, it can be seen that the grid inflow code is (1,3,2, 1, 3) grid, so the ID4 of the grid is coded 2, that is, the grid points to the grid with the order of 2 in the third layer grid, giving it the meaning of the water flow direction; ID5 is the river channel code, as shown in the figure The dark box represents the river grid. It can be seen that there are 5 river grids in the confluence network, and the ID5 codes of the river grids are 5, 4, 3, 2, and 1 in sequence.

The present invention has been exemplarily described above in conjunction with the accompanying drawings. Obviously, the implementation of the present invention is not limited by the above-mentioned manner, as long as various improvements made by the method concept and technical solutions of the present invention are adopted, or the present invention is not modified without improvement. It is within the protection scope of the present invention that the ideas and technical solutions of the invention are directly applied to other occasions.

Claims (5)

1. a same sub-basin river grid calculation sequence coding method, comprising the following steps: Step 1, determine grid size; Step 2, obtain grid flow direction; Step 3, carry out river grid and sub-basin division; Step 4, encode each grid; Step 4: Generate a 5-digit array for each grid, which is used to store the grid code. The code format is (ID1, ID2, ID3, ID4, ID5), and the initial value is (0,0,0,0, 0); ID1 is the sub-watershed code; ID2 is the confluence layer code; ID3 is the sequence code within the layer; ID4 is the inflow grid code; ID5 is the river channel code; The step 4 includes step 41: reading the sub-watershed code from the sub-watershed division obtained in step 3, and assigning the sub-watershed code to ID1; The step 4 includes step 42: searching for the most downstream outlet grid of each sub-basin, and assigning the outlet grid ID2 to 1; The step 4 includes step 43: for each sub-basin, start the search from the outlet grid of the most downstream sub-basin, and search the 8 grids around the outlet grid in a clockwise direction. The ID1 code is the same as the ID1 code of the outlet grid. If the water flow direction of a grid flows into the grid with the same ID1 and the outlet grid code, then the ID2 of the grid with the same ID1 and the outlet grid code will be assigned a value of 2, and ID3 will be assigned from 1, one by one. Increase, assign ID4 to 1, and complete the coding of all qualified grids around the river outlet grid; The step 4 includes step 44 : importing the grid information of the river channel, and sequentially accumulating in the order of increasing gradually from the source of the river to the mouth of the river, and encoding the ID5. 2. according to the described same sub-basin river grid calculation sequence coding method of claim 1, it is characterized in that: described step 1 determines the grid size of the established grid-type hydrological model according to the scope of the study area and research needs, and builds a grid type hydrological model once. The size of each grid should remain the same during the modulo process; or/and, the grid size is 1km×1km, 3km×3km or 9km×9km. 3. The method for coding the order of grid calculation of river grids in the same sub-basin according to claim 1, characterized in that: in the step 2, with the aid of a hydrological analysis tool, the water flow direction of each grid is obtained by a single flow direction method. 4. the same sub-basin river grid calculation sequence coding method according to claim 1, is characterized in that: described step 3 is based on the flow direction information of each grid water obtained in step 2, by means of hydrological analysis tools, set sink The water area threshold value can be obtained to obtain the digital information of the river channel in the study area, and the sub-basin division of the study area can be carried out with the help of hydrological analysis tools. 5 . The method for coding sequence of river grids in the same sub-basin according to claim 3 or 4 , wherein the hydrological analysis tool is a hydrological analysis tool in ArcGIS 10.2. 6 .

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