A distributed watershed runoff simulation model coupled with reservoir operation effects

Abstract

The application discloses a kind of distributed basin runoff simulation model coupled with reservoir regulation influence, it is related to runoff simulation technical field, including the following steps: step one, build the digital reservoir basin of distributed hydrological model;Step two, build climate, soil and vegetation cover database;Step three, formulate reservoir typical regulation rule and extract characteristic parameter;Step four, calculate each grid runoff;Step five, calculate the confluence of coupling reservoir regulation, after upstream grid flow is converged into reservoir, it is converged into river next grid after reservoir regulation and control again.The application uses the above-mentioned one kind of distributed basin runoff simulation model coupled with reservoir regulation influence, traditional lumped hydrological model ignores the influence of spatial heterogeneity of basin underlying surface on hydrological simulation, the spatial distribution information of dam site and corresponding dam area is added in the underlying surface grid data level of distributed hydrological model in the present scheme, when runoff is converged into reservoir, it is regulated by specified regulation rule and then flows to river.

Description

Technical Field

[0001] This invention relates to the field of runoff simulation technology, and in particular to a distributed watershed runoff simulation model that couples the effects of reservoir scheduling. Background Technology

[0002] Runoff simulation and prediction in reservoir basins mainly fall into two categories: data-driven and hydrological simulation methods. Data-driven methods are relatively mature. Common methods include mathematical statistics, artificial neural network models, and support vector machines, which analyze and capture the trends and periodic characteristics of the evolution of various water cycle elements through a large amount of long-term hydrological observation data. However, these methods only perform predictive analysis from a data perspective, mainly relying on simple statistical and regression relationships between variables for simulation. They are difficult to accurately describe nonlinear and non-constant physical hydrological processes and cannot explain complex physical processes such as reservoir regulation within the basin. With the development of computer technology, improved methods such as long short-term memory networks and grey neural networks have emerged. These methods learn patterns from a large amount of basin hydrological data and reservoir inflow and outflow data to simulate runoff under the regulation of reservoirs. However, these deep learning algorithms have high requirements for data samples and are "black box" models, lacking physical mechanisms. They cannot explain the accuracy of simulation results, nor can they analyze the physical change mechanism and spatial characteristics of runoff caused by reservoirs.

[0003] Hydrological models include lumped hydrological models and distributed hydrological models. Lumped hydrological models treat the watershed as a whole, failing to reflect the spatial characteristics of parameters and hydrological elements. They also suffer from sensitivity to runoff parameters and cumbersome manual adjustments, making it difficult to achieve high accuracy. Distributed hydrological models, on the other hand, consider the spatial heterogeneity of parameters. Based on differences in topography, soil, vegetation cover, land use, and precipitation across the watershed, they discretize the watershed into different computational units and output model results according to these simulation units. Currently, some lumped hydrological models consider the regulation and storage effects of reservoirs, mainly by generalizing the reservoir's impact to parameters affecting the underlying surface. However, because they do not consider the spatial distribution of reservoirs and the differences in the regulation and storage processes of different reservoirs, their improvement in the simulation effect of reservoir-watershed runoff is limited. Traditional distributed hydrological models based on rainfall-runoff generation and runoff processes, while possessing strong simulation capabilities for natural runoff, still offer significant advantages. However, more than half of the world's major rivers are currently blocked by reservoirs and dams. The runoff formation process under the regulation of reservoirs (or groups of reservoirs) is more complex, and traditional distributed hydrological models have limited simulation capabilities, facing greater uncertainties in the future. To improve the accuracy of distributed hydrological models in simulating runoff under the regulation of reservoirs (or groups of reservoirs), it is necessary to focus on strengthening the model's characterization of reservoirs: on the one hand, the spatial location information of reservoirs should be effectively coupled into the discretized watershed calculation units; on the other hand, the operating rules of reservoirs need to be accurately described to characterize the timing of storage and release and the discharge process of reservoirs in the model's calculation time step. Summary of the Invention

[0004] The purpose of this invention is to provide a distributed watershed runoff simulation model that couples the effects of reservoir scheduling, constructs a digital reservoir watershed based on a distributed hydrological model, and then formulates typical reservoir scheduling rules and extracts characteristic parameters. This couples the reservoir regulation process into the distributed hydrological model, thereby improving the accuracy of runoff simulation in the reservoir watershed.

[0005] To achieve the above objectives, this invention provides a distributed watershed runoff simulation model that couples the effects of reservoir scheduling, comprising the following steps: Step 1: Construct a digital reservoir watershed using a distributed hydrological model, including creating a water flow direction distribution map and a reservoir location distribution map; Step 2: Construct a database of climate, soil, and vegetation cover; Step 3: Formulate typical reservoir scheduling rules and extract characteristic parameters. Typical reservoir scheduling rules are the key to describing reservoir regulation. Step 4: Calculate the runoff of each grid cell. The total runoff of the grid cells is obtained by using an area-weighted average of surface runoff and baseflow. Step 5: Calculate the confluence process of the coupled reservoir scheduling. After the upstream grid flow flows into the reservoir, it flows into the next grid in the river channel after being regulated by the reservoir.

[0006] Preferably, the construction of the water flow direction distribution map in step one includes: acquiring watershed DEM elevation data; filling depressions in the DEM elevation data in ArcGIS; processing the filled DEM elevation data using hydrological analysis tools, and calculating the maximum downward direction and flow direction data for each grid based on the DEM elevation data.

[0007] Preferably, in step one, the location of the reservoir and the upstream water storage area is determined based on the flow direction data.

[0008] Preferably, one of the typical reservoir scheduling rules in step three is selected, specifically including: The standard curve allows you to set monthly target water levels; the simplified version only requires predefining the highest water level of the year. H 1 and lowest water level H 2. The time points corresponding to these water levels T 1 and T 2. Four parameters; Run the rules, set the rule curve, which consists of four parameters. x 1. x 2. x 3 and x 4. Definitions and operating rules vary monthly; The predefined time series data of reservoir storage capacity is used. The actual discharge volume depends on the physical constraints of the reservoir and the available water volume, while the actual storage volume depends on the physical constraints of the reservoir.

[0009] Preferably, the reservoir characteristic parameters in step three include the check flood level, dead water level, reservoir capacity, water head, design flow rate, year of construction, initial water storage, reservoir name, seepage rate, infiltration rate, irrigation flow rate, reservoir scheduling rules, and water level-storage capacity curve.

[0010] Preferably, in step four, the surface runoff is calculated using a water storage capacity curve, taking into account the impact of uneven soil moisture distribution on surface runoff. The calculation formula is as follows: ; ; In the formula, P For precipitation, W 0 represents the initial soil moisture content. This represents the maximum soil moisture content in the upper layer. b For shape parameters, I 0 represents the initial infiltration rate. I m For maximum infiltration capacity, A s This represents the percentage of soil within the grid that has reached saturation.

[0011] Preferably, the baseflow calculation in step four considers a soil moisture content threshold. Below the soil moisture content threshold, the baseflow declines linearly; above the soil moisture content threshold, the baseflow decline process is non-linear. The calculation formula is as follows: ; In the formula, W s This represents the percentage coefficient of maximum soil moisture content during the nonlinear decay of the baseflow. W 2 represents the soil moisture content of the lower soil layer. This represents the maximum water content of the lower soil layer. d 1 represents the linear outflow coefficient of the lower soil moisture content. d 2 represents the nonlinear decay coefficient of the base current.

[0012] Preferably, step five includes calculating all grids according to the flow direction; for each time step, the reservoir performs water discharge scheduling according to the input specified scheduling scheme, the sum of the flow into the upstream grid is the inflow of the reservoir, and the water discharged from the reservoir after scheduling flows into the next grid of the river channel according to the flow direction of the dam site grid; after the calculation of all time steps is completed, the reservoir scheduling process, reservoir water level, inflow and outflow, and the confluence flow of the specified station are output.

[0013] Preferably, in step five, the linear Saint-Venant equation is used to simulate the river confluence flow at the reservoir dam site and designated stations. The calculation formula is as follows: ; In the formula, Q For traffic,t For time, x Let be the axis along the river channel in the spatial coordinate system. D and C These are the diffusion coefficient and the pulse wave coefficient, respectively.

[0014] Therefore, this invention employs a distributed watershed runoff simulation model coupled with reservoir scheduling effects. The lumped hydrological model conceptualizes reservoir effects as new parameters to adjust runoff simulation results under reservoir (group) regulation. At the watershed raster data level of the distributed hydrological model, spatial distribution information including reservoir dam sites and corresponding dam areas is added. This invention supports multiple methods for characterizing reservoir regulation processes from coarse to fine. The model calculates the target water level that the actual reservoir water level should reach according to the scheduling plan at the current time step, and then uses the principle of water balance to regulate reservoir discharge so that the actual water level reaches or is as close as possible to the target water level, with a clear physical mechanism. The runoff calculation process of this invention is coupled with reservoir scheduling effects. When the model simulates the runoff from upstream to downstream, the runoff sequentially enters the designated reservoir areas and is regulated according to the reservoir's specified plan before flowing into the downstream river channel. Therefore, the model can distinguish different reservoirs within the watershed and characterize the impact mechanism of the cascade reservoir system.

[0015] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0016] Figure 1 This is a flowchart of a distributed watershed runoff simulation model coupled with the effects of reservoir scheduling, according to the present invention. Figure 2 This is a schematic diagram of the flow direction data of distributed watershed runoff coupled with the influence of reservoir scheduling according to the present invention; Figure 3 This is a schematic diagram of reservoir location information for a distributed watershed runoff simulation model that couples the effects of reservoir scheduling according to the present invention. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0019] Example Please see Figures 1-3 This invention provides a distributed watershed runoff simulation model that couples the effects of reservoir scheduling, comprising the following steps: Step 1: Construct a digital reservoir basin using a distributed hydrological model.

[0020] Construction of the water flow direction distribution map: Obtain the watershed DEM elevation data, and fill in depressions in the DEM elevation data in ArcGIS to eliminate depression raster cells in the original DEM elevation data. Process the filled DEM elevation data using hydrological analysis tools, and calculate the maximum downward direction of each raster, i.e., the flow direction data, based on the DEM elevation data. Each raster in the flow direction data is assigned a value of 1, 2, 3, ..., 8, representing the raster where the water flow is in the direction of due north, northeast, due west, ..., northwest.

[0021] Construction of reservoir location distribution map: Based on flow direction data, the locations of reservoirs and upstream water storage areas are determined. The grid uses integer values ​​[0, 9999], where 1-9998 represents grids containing dams, 9999 represents grids belonging to upstream water storage areas, and 0 indicates other land uses. Characteristic parameters can be constructed for each reservoir.

[0022] Step 2: Construct a database of climate, soil, and vegetation cover.

[0023] Construction of the climate-driven database: Each grid cell is named with its own latitude and longitude, and the rainfall, wind speed, maximum temperature, and minimum temperature are arranged in time series to construct a climate-driven dataset.

[0024] Construction of the soil database: Determine the soil properties of each grid cell, such as the thickness of the first to third soil layers.

[0025] Construction of the vegetation cover database: Determine the vegetation cover properties of each grid cell, including the vegetation types contained in the grid cell and their proportions, the attributes of each vegetation type, etc.

[0026] Set Station: Specifies the simulated runoff output raster for the model.

[0027] Step 3: Formulate typical reservoir scheduling rules and extract characteristic parameters.

[0028] Typical reservoir operation rules are key to characterizing reservoir regulation, especially the process of flood control and discharge. There are three schemes to characterize this process, and one of the three schemes must be selected.

[0029] Option 1: Regular Curve. Set a monthly target water level; the simplified version only requires predefining the highest water level of the year. H 1 and lowest water level H 2. And the time points corresponding to reaching these water levels. T 1 and T 2. Four parameters.

[0030] Option 2: Running Rules. Define the rule curve, consisting of four parameters ( x 1. x 2. x 3 and x 4) Definition. The operating rules can be different each month, that is, there are twelve operating rules per year.

[0031] Option 3: Predefined reservoir water storage time series data. Provides time series data of daily reservoir water storage within the simulation period. The actual discharge volume depends on the reservoir's physical limitations (e.g., maximum design discharge) and available water volume.

[0032] Extract reservoir characteristic parameters: including check flood level (m), dead water level (m), and reservoir capacity (1000m³). 3 ), head (m; optional parameter for hydropower calculations), design flow rate (m³ / h) 3 / s), year of construction, initial water storage (1000 m³ / s), 3 ), Reservoir name, seepage rate (m) 3 / s), infiltration rate (m 3 / s), irrigation flow rate (m³) 3 / s), reservoir scheduling rules, and water level-capacity curve.

[0033] Step 4: Calculate the runoff of each grid cell. The total runoff of the grid cells is obtained by using an area-weighted average of surface runoff and baseflow.

[0034] In grid runoff calculations, water sources are separated. The upper soil layer generates surface runoff and infiltration into the lower soil layer, while the lower soil layer generates baseflow. The sum of surface runoff and baseflow constitutes the total grid runoff. Infiltration into the lower soil layer is determined by a function related to soil moisture content and saturated hydraulic conductivity. Surface runoff is calculated using a water storage capacity curve, taking into account the impact of uneven soil moisture distribution on surface runoff. The calculation formula is as follows: In the formula, Surface runoff, P Where W is the precipitation and W0 is the initial soil moisture content. This represents the maximum soil moisture content in the upper layer. b For shape parameters, I 0 represents the initial infiltration rate. I m For maximum infiltration capacity, A s This represents the percentage of soil within the grid that has reached saturation.

[0035] The baseflow calculation considers a soil moisture content threshold. Below the threshold, the baseflow declines linearly; above the threshold, the baseflow decline process is non-linear. The calculation formula is as follows: In the formula ， As the base current, W s This represents the percentage coefficient of maximum soil moisture content during the nonlinear decay of the baseflow. W 2 represents the soil moisture content of the lower soil layer. This represents the maximum water content of the lower soil layer. d 1 represents the linear outflow coefficient of the lower soil moisture content. d 2 represents the nonlinear decay coefficient of the base current.

[0036] Step 5: Calculate the confluence process of the coupled reservoir scheduling. After the upstream grid flow flows into the reservoir, it flows into the next grid in the river channel after being regulated by the reservoir.

[0037] Calculate the number of grid cells according to the flow direction for all grid cells, and count the number of grid cells that flow into each reservoir dam site and designated station.

[0038] For each time step, the reservoir discharges water according to the input specified scheduling scheme. The sum of the flows flowing into the upstream grid is the inflow into the reservoir. After scheduling, the discharged water flows into the next grid cell of the river channel according to the flow direction of the dam site grid. The linear Saint-Venant equation is used to simulate the river channel flow at the dam site and specified stations. The calculation formula is as follows: In the formula, Q For traffic, t For time, x Let be the axis along the river channel in the spatial coordinate system. D and C These are the diffusion coefficient and the pulse wave coefficient, respectively.

[0039] After all time steps are calculated, the reservoir scheduling process is output, including the reservoir water level, inflow and outflow, and the confluence flow at the specified station.

[0040] Therefore, this invention employs a distributed watershed runoff simulation model coupled with reservoir scheduling effects. While the lumped hydrological model conceptualizes reservoir effects as new parameters to adjust runoff simulation results under reservoir (group) regulation, this scheme adds spatial distribution information of reservoir dam sites and corresponding dam areas to the watershed raster data level of the distributed hydrological model. This scheme supports multiple methods for characterizing the reservoir regulation process from coarse to fine. The model calculates the target water level that the actual reservoir water level should reach according to the scheduling plan at the current time step, and then uses the principle of water balance to regulate reservoir discharge so that the actual water level reaches or is as close as possible to the target water level, with a clear physical mechanism. The runoff calculation process in this scheme is coupled with reservoir scheduling effects. When the model simulates the runoff from upstream to downstream, the runoff sequentially enters the designated reservoir areas and is scheduled according to the reservoir's specified plan before flowing into the downstream river channel. Therefore, the model can distinguish between different reservoirs within the watershed, achieving a characterization of the impact mechanism of the cascade reservoir system. Compared with traditional hydrological models, the distributed watershed runoff simulation model coupled with the effects of reservoir scheduling has a better overall simulation effect on daily runoff and hydrological situation indicators of hydrological stations.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A distributed watershed runoff simulation model coupled with the effects of reservoir scheduling, characterized in that, Includes the following steps: Step 1: Construct a digital reservoir watershed using a distributed hydrological model, including creating a water flow direction distribution map and a reservoir location distribution map; Step 2: Construct a database of climate, soil, and vegetation cover; Step 3: Formulate typical reservoir scheduling rules and extract characteristic parameters. Typical reservoir scheduling rules are the key to describing reservoir regulation. Step 4: Calculate the runoff of each grid cell. The total runoff of the grid cells is obtained by using an area-weighted average of surface runoff and baseflow. Step 5: Calculate the confluence process of the coupled reservoir scheduling. After the upstream grid flow flows into the reservoir, it flows into the next grid in the river channel after being regulated by the reservoir.

2. The distributed watershed runoff simulation model coupled with reservoir scheduling effects according to claim 1, characterized in that, The construction of the water flow direction distribution map in step one includes: acquiring the watershed DEM elevation data; filling depressions in the DEM elevation data in ArcGIS; processing the filled DEM elevation data using hydrological analysis tools, and calculating the maximum downward direction and flow direction data for each grid based on the DEM elevation data.

3. The distributed watershed runoff simulation model coupled with reservoir scheduling effects according to claim 2, characterized in that: In step one, based on the flow direction data, the location of the reservoir and the upstream water storage area is determined.

4. The distributed watershed runoff simulation model coupled with reservoir scheduling effects according to claim 3, characterized in that, In step three, one of the typical reservoir operation rules is selected, specifically including: The standard curve allows you to set monthly target water levels; the simplified version only requires predefining the highest water level of the year. H 1 and lowest water level H 2. And the time points corresponding to reaching these water levels. T 1 and T 2. Four parameters; Run the rules, set the rule curve, which consists of four parameters. x 1. x 2. x 3 and x 4. Definitions and operating rules vary monthly; The predefined time series data of reservoir storage capacity is used. The actual discharge volume depends on the physical constraints of the reservoir and the available water volume, while the actual storage volume depends on the physical constraints of the reservoir.

5. A distributed watershed runoff simulation model coupled with reservoir scheduling effects according to claim 4, characterized in that: Step 3 includes the following reservoir characteristic parameters: check flood level, dead water level, reservoir capacity, head, design flow rate, year of construction, initial water storage, reservoir name, seepage rate, infiltration rate, irrigation flow rate, reservoir operation rules, and water level-storage capacity curve.

6. A distributed watershed runoff simulation model coupled with reservoir scheduling effects according to claim 5, characterized in that: In step four, surface runoff is calculated using a water storage capacity curve, taking into account the impact of uneven soil moisture distribution on surface runoff. The calculation formula is as follows: ； ； In the formula, P For precipitation, W 0 represents the initial soil moisture content. This represents the maximum soil moisture content in the upper layer. b For shape parameters, I 0 represents the initial infiltration rate. I m For maximum infiltration capacity, A s This represents the percentage of soil within the grid that has reached saturation.

7. A distributed watershed runoff simulation model coupled with reservoir scheduling effects according to claim 6, characterized in that: In step four, the baseflow calculation considers a soil moisture content threshold. Below the soil moisture content threshold, the baseflow declines linearly; above the soil moisture content threshold, the baseflow decline process is non-linear. The calculation formula is as follows: ； In the formula, W s This represents the percentage coefficient of maximum soil moisture content during the nonlinear decay of the baseflow. W 2 represents the soil moisture content of the lower soil layer. This represents the maximum water content of the lower soil layer. d 1 represents the linear outflow coefficient of the lower soil moisture content. d 2 represents the nonlinear decay coefficient of the base current.

8. A distributed watershed runoff simulation model coupled with reservoir scheduling effects according to claim 7, characterized in that: Step five includes calculating all grids according to the flow direction; for each time step, the reservoir discharges water according to the input specified scheduling scheme, the sum of the flow into the upstream grid is the inflow into the reservoir, and the discharged water after scheduling flows into the next grid in the river channel according to the flow direction of the dam site grid; after the calculation of all time steps is completed, the reservoir scheduling process, reservoir water level, inflow and outflow, and the runoff flow of the specified station are output.

9. A distributed watershed runoff simulation model coupled with reservoir scheduling effects according to claim 8, characterized in that: Step five uses the linear Saint-Venant equation to simulate the river runoff at the reservoir dam site and designated stations. The calculation formula is as follows: ； In the formula, Q For traffic, t For time, x Let be the axis along the river channel in the spatial coordinate system. D and C These are the diffusion coefficient and the pulse wave coefficient, respectively.

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