Method for calculating reservoir inflow of riverway type reservoir based on hydrological and hydrodynamic coupling

Abstract

The invention belongs to the technical field of hydrological forecasting, and discloses a method for calculating the reservoir inflow of a river type reservoir based on hydrological and hydrodynamic coupling. The method comprises the following steps: firstly, constructing a hydrological-hydrodynamic coupling model, including distributed hydrological modeling and one-dimensional hydrodynamic modeling; secondly, river section data are provided by a hydrological and hydrodynamic coupling model, and reservoir capacity change of the river type reservoir is calculated; and finally, according to the reservoir capacity change and the reservoir outlet flow output by the coupling model, calculating the reservoir inlet flow of the riverway type reservoir by adopting a water balance method. According to the method, the dynamic reservoir capacity of the river type reservoir is calculated in combination with the hydrological and hydrodynamic coupling model, the dynamic reservoir capacity change can be accurately reflected, and an accurate and reliable method is provided for calculation of the reservoir inflow of the river type reservoir.

Description

Technical Field

[0001] The invention relates to the technical field of hydrological forecasting, and in particular to a method for calculating inflow into a river-type reservoir based on hydrological and hydrodynamic coupling. Background Art

[0002] A river-type reservoir is a reservoir formed by building a dam in a canyon. Its topography is complex and varied. There are many mountains on both sides of the main river. In addition to the confluence of tributaries, runoff will also flow directly into the main river from the slopes on both sides. In addition, the spatial span of a river-type reservoir is large, and the temporal and spatial distribution of the water flowing into the river is very uneven, so it is difficult to accurately calculate the inflow of a river-type reservoir.

[0003] At present, the inflow of most reservoirs is calculated by back-calculating according to the static reservoir water balance method based on the outflow of the reservoir, the reservoir water level and other data. However, for river-type reservoirs, due to the significant gradient of the reservoir water surface and the large change of the reservoir capacity, the inflow process calculated by this algorithm basically fluctuates in a sawtooth shape, or even negatively, and cannot accurately reflect the actual inflow process. Although the segmented reservoir capacity calculation algorithm based on the principle of the slot storage back-calculation method has solved the problem of excessive fluctuations in the calculation results of the static reservoir capacity calculation to a certain extent, due to the lack of flow data along the river-type reservoir, the number of segments of the segmented reservoir capacity method is insufficient, and the calculation results still have large errors, and it is impossible to scientifically simulate and predict the changes in the reservoir dynamic storage capacity, the water level in front of the dam and the inflow.

[0004] With the advancement of remote sensing monitoring technology, hydrological and hydrodynamic modeling data has gradually accumulated to meet the needs of high-precision coupled modeling of hydrology and hydrodynamics. By coupling the distributed hydrological model with the one-dimensional hydrodynamic model, the spatiotemporal distribution characteristics of rainstorms and floods in different areas of river-type reservoirs can be accurately grasped, providing continuous and efficient along-the-way flow input for the hydrodynamic modeling of river-type reservoirs. Compared with the traditional segmented storage capacity algorithm, the hydrological and hydrodynamic coupling model can subdivide the river-type reservoir into hundreds of sections, reduce the storage capacity calculation error caused by fewer section segments, and accurately simulate the storage capacity changes of river-type reservoirs. Therefore, it is urgent to invent a method for calculating the inflow flow based on the hydrological and hydrodynamic coupling method to provide a river-type reservoir with an inflow flow process that conforms to the actual situation. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention proposes a method for calculating the inflow flow of river-type reservoirs based on hydrological and hydrodynamic coupling to solve the problem of low accuracy in the current calculation of the inflow flow of river-type reservoirs and obtain an inflow flow process that is closer to the actual situation.

[0006] To achieve the above-mentioned purpose, the technical solution provided by the present invention is as follows: a method for calculating the inflow of a river-type reservoir based on hydrological and hydrodynamic coupling, comprising the following steps:

[0007] Step 1: Construct a hydrological-hydrodynamic coupling model;

[0008] Step 2: Calculate the storage capacity change of river-type reservoirs based on the hydrological-hydrodynamic coupling model;

[0009] Step 3: Calculate the inflow into the river-type reservoir by combining the storage capacity change and the water balance method.

[0010] The step 1 is specifically as follows:

[0011] Step 1-1, collecting hydrological and meteorological data and underlying surface data of river-type reservoirs, and constructing a distributed hydrological model; the distributed hydrological model simulates the runoff and base flow of each grid unit according to the meteorological data and surface conditions of the basin; and outputs the river flow process through the confluence method;

[0012] Step 1-2, collecting topographic data of river-type reservoirs and river section data, and constructing a one-dimensional hydrodynamic model; the one-dimensional hydrodynamic model divides the river into hundreds of sections, simulates the water flow in the river, and outputs the changes of water level, water depth and flow velocity over time in each river section;

[0013] Steps 1-3: Use the river flow process simulated by the distributed hydrological model as the boundary condition of the one-dimensional hydrodynamic model to form a hydrological-hydrodynamic coupling model; use the one-dimensional hydrodynamic model to simulate the river flood process in the main river channel of the river-type reservoir.

[0014] The step 2 is specifically as follows:

[0015] Step 2-1, the river section data required for calculating the dynamic reservoir capacity is output from the hydrological-hydrodynamic coupling model, and the river section division scheme of the hydrological-hydrodynamic coupling model is adopted to divide the river into k sections;

[0016] Step 2-2, calculate the average of the water flow areas of two adjacent sections and multiply it by the section spacing to obtain the water volume between the two sections. The calculation formula is as follows:

[0017]

[0018] Where V n is the water volume between the nth section and the n+1th section, A n and A n+1 is the area of ​​the nth cross section and the area of ​​the n+1th cross section; d n is the distance between two sections;

[0019] Step 2-3: After completing the calculation of all sections one by one, the water volume between all sections is accumulated to obtain the instantaneous storage capacity of the reservoir during this period. The storage capacity changes dynamically over time. The calculation formula is as follows:

[0020] V=V1+V2+…+V k

[0021] Where V is the instantaneous storage capacity of the reservoir, V1, V2, …, V k is the water volume between sections;

[0022] Step 2-4: Calculate the instantaneous storage capacity of the reservoir at adjacent times, and make the difference between the two to obtain the reservoir storage capacity change ΔV within the period. The calculation formula is as follows:

[0023] ΔV=V t2 -V t1

[0024] Where V t1 is the instantaneous value of the reservoir capacity at time 1, V t2 is the instantaneous value of the reservoir capacity at time 2, and ΔV is the change in reservoir capacity during the period.

[0025] The step 3 is specifically as follows:

[0026] Based on the principle of water balance, the dam flow output by the hydrological-hydrodynamic coupling model is used as the outflow of the river-type reservoir, the outflow and storage capacity change are used to define the inflow, and the sum of the outflow in a certain period and the storage capacity change in the period is used as the inflow of the period; the calculation formula is as follows:

[0027]

[0028] In the formula, Qin is the inflow flow; Q out is the outflow flow; ΔV is the change in storage capacity; T is the time period corresponding to the change in storage capacity.

[0029] The beneficial effects of the present invention are as follows: the present invention focuses on the difficult problem of low accuracy in calculating the inflow flow of river-type reservoirs, based on the hydrological-hydrodynamic method, combined with the characteristics of dynamic storage capacity and water balance equation, and proposes a method that can accurately calculate the inflow flow of river-type reservoirs. The method has a simple principle and a novel method, and can solve the problem of poor accuracy in the current calculation of inflow flow of river-type reservoirs due to failure to consider dynamic storage capacity, and provides a more effective and practical method for calculating the inflow flow of river-type reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the calculation principle of the storage capacity change value during a period of the present invention;

[0031] Figure 2 It is a comparison diagram of the inflow flow process in the implementation scheme of the present invention;

[0032] Figure 3 It is a 30m resolution DEM elevation map of the study area in the implementation scheme of the present invention. DETAILED DESCRIPTION

[0033] A method for calculating the inflow of a river-type reservoir based on hydrological and hydrodynamic coupling includes the following steps:

[0034] Step 1: Construct a hydrological-hydrodynamic coupling model.

[0035] Step 2: Calculate the storage capacity changes of river-type reservoirs based on the hydrological-hydrodynamic coupling model.

[0036] Step 3: Calculate the inflow into the river-type reservoir by combining the storage capacity change and the water balance method.

[0037] Furthermore, the step 1 is specifically as follows:

[0038] Step 1-1: Collect hydrological and meteorological data, topographic data, underlying surface data and river section data of river-type reservoirs, and compile and analyze the required data collected.

[0039] Step 1-2: Based on the collected data, a distributed hydrological model is constructed. The model simulates the runoff and base flow of each grid unit according to the meteorological data (precipitation, temperature, wind speed, etc.) and surface conditions (topography, land cover, soil type, etc.) of the basin, and outputs the river flow process through the confluence method.

[0040] Step 1-3: Construct a one-dimensional hydrodynamic model, which divides the river into hundreds of sections, simulates the water flow in the river, and outputs the changes in water level, water depth and flow velocity of each river section over time.

[0041] Steps 1-4: Use the flow process simulated by the distributed hydrological model as the boundary condition of the hydrodynamic model, and use the hydrodynamic model to simulate the river flood process in the main river channel of the river-type reservoir.

[0042] Furthermore, the step 2 is specifically as follows:

[0043] Step 2-1: The river channel section data required for calculating the dynamic reservoir capacity is output from the hydrological-hydrodynamic coupling model, and the river channel is divided into k sections using the river channel section division scheme of the hydrological-hydrodynamic coupling model.

[0044] Step 2-2, calculate the average of the water flow areas of two adjacent sections and multiply it by the section spacing to obtain the water volume between the two sections. The calculation formula is as follows:

[0045]

[0046] Where V n is the water volume between the nth section and the n+1th section, A n and An+1 It is the area of ​​the nth cross-section and the area of ​​the n+1th cross-section.

[0047] Step 2-3: After completing the calculation of all sections one by one, the water volume between all sections is accumulated to obtain the instantaneous storage capacity of the reservoir during this period. The storage capacity changes dynamically over time. The calculation formula is as follows:

[0048] V=V1+V2+…+V k

[0049] Where V is the instantaneous storage capacity of the reservoir, V1, V2, …, V k It is the water volume between sections.

[0050] Step 2-4: Calculate the instantaneous storage capacity of the reservoir at adjacent times. The difference between the two is the reservoir storage capacity change ΔV within the time period. The calculation formula is as follows:

[0051] ΔV=V t2 -V t1

[0052] Where V t1 is the instantaneous value of the reservoir capacity at time 1, V t2 is the instantaneous value of the reservoir capacity at time 2, and ΔV is the change in reservoir capacity during the period.

[0053] The calculation principle of storage capacity change value is shown in Figure 1 .

[0054] Furthermore, the step 3 is specifically as follows:

[0055] Based on the principle of water balance, the flow in front of the dam output by the hydrological-hydrodynamic coupling model is used as the outflow of the river-type reservoir, and the inflow is defined by the outflow and storage capacity change. That is, the sum of the outflow in a certain period and the storage capacity change in the period is used as the inflow of the period. This method is more objective in calculating the inflow water volume and conforms to the principle of water balance. It is one of the feasible methods for calculating the actual inflow of the river-type reservoir. The calculation formula is as follows:

[0056]

[0057] In the formula, Qin is the inflow flow; Q out is the outflow flow; ΔV is the change in storage capacity; T is the time period corresponding to the change in storage capacity.

[0058] The method proposed by the present invention is further described below through embodiments and in conjunction with the accompanying drawings.

[0059] The Three Gorges Reservoir is located in the upper reaches of the Yangtze River, with a total area of ​​1,084 km 2 , total storage capacity 3.93×10 10 m 3, and is one of the largest reservoirs in the world. The Three Gorges Reservoir is a typical large river-type reservoir with complex terrain and large storage capacity. At the same time, the Three Gorges reservoir area has a humid subtropical monsoon climate, and the climate is significantly affected by the canyon terrain. The annual rainfall is abundant, and the average rainfall over many years reaches 1150mm. The reservoir area has a developed water system and numerous tributaries. The main stream of the Yangtze River and its many tributaries continuously flow into the main river channel. In addition, the runoff will also flow into the reservoir from the slopes around the reservoir, resulting in a large change in the storage capacity of the Three Gorges Reservoir, which increases the difficulty of accurately calculating the inflow flow. The traditional static storage capacity estimation method is difficult to meet the Three Gorges Reservoir's requirements for the accuracy of the inflow flow. Therefore, the river-type reservoir inflow calculation method based on hydrological-hydrodynamic coupling introduced in the present invention is adopted, and the inflow flow calculation is carried out using this area as an example. The specific steps are as follows:

[0060] The first step is to construct a hydrological-hydrodynamic coupling model of the Three Gorges Reservoir.

[0061] (1) Collect basic data in the region, mainly including hydrological and meteorological data, topographic data, high-precision remote sensing image data and river cross-section data; secondly, compile and analyze the collected data, identify and correct typical erroneous data, and normalize the data to form a set of dedicated data sets, which will provide a solid data foundation for the distributed hydrological modeling and one-dimensional hydrodynamic modeling of the Three Gorges Reservoir area.

[0062] (2) Construct a distributed hydrological model of the Three Gorges Reservoir area. The 30m resolution DEM elevation map of the Three Gorges Reservoir area was selected, and 0.05° was selected as the horizontal resolution. The entire Three Gorges Reservoir area was divided into 2854 orthogonal grids of 0.05°×0.05° as the watershed runoff calculation unit, and the variable infiltration capacity curve was used for runoff calculation; based on the DEM elevation map of the Three Gorges Reservoir area, ArcGIS software was used to divide the watershed into 737 sub-basins as the basic unit for runoff calculation, and the runoff calculation was performed by combining slope and river confluence.

[0063] (3) Construct a hydrological and hydrodynamic coupling model for the Three Gorges Reservoir area. The collected river sections are generalized by dividing the sections into several vertical trapezoids for approximation, and the river network is generalized in the form of channel-node-channel. The flow process obtained by the distributed hydrological model is used as the boundary condition, and the initial water level and initial flow are determined based on the measured data and the simulation results of the hydrological model. A one-dimensional hydrodynamic model is constructed, and the hydrodynamic model is used to simulate the river flood process in the main river channel of the Three Gorges Reservoir.

[0064] The second step is to calculate the changes in the storage capacity of the Three Gorges Reservoir.

[0065] (1) Based on the river section data provided by the hydrological-hydrodynamic coupling model, 401 sections in the Yangtze River mainstream from Cuntan (Zhutuo) to the dam site were selected, with Cuntan as the reservoir entry point.

[0066] (2) Based on the 401 sections in the Yangtze River mainstream from Cuntan (Zhutuo) to the dam site, the reservoir area of ​​the Three Gorges Reservoir is subdivided into 400 sections. The average water flow area of ​​each section and the adjacent sections is multiplied by the distance between the sections, and the instantaneous reservoir capacity is obtained by adding them together. The instantaneous reservoir capacity values ​​at adjacent times are subtracted to obtain the reservoir capacity change during the period.

[0067] The reservoir capacity change value calculated by this method changes dynamically over time and is controlled by the water level in front of the dam and the inflow flow. Compared with the current eight-stage reservoir capacity inverse method, it is more detailed and the calculation result is more in line with the actual situation of the Three Gorges Reservoir.

[0068] The third step is to calculate the inflow into the Three Gorges Reservoir based on the reservoir capacity changes and water balance principles.

[0069] Based on the principle of water balance, the sum of the outflow and the change in reservoir water storage is the reservoir inflow. The change in the Three Gorges Reservoir storage capacity calculated in the first step is used as the change in reservoir water storage, and the dam flow output by the hydrological-hydrodynamic coupling model is used as the outflow. The sum of the two is the Three Gorges Reservoir inflow.

[0070] Figure 2 Shown is a comparison chart of the Three Gorges Reservoir inflow process line calculated by the method of the present invention and the calculation result of the eight-stage reservoir capacity method. The vertical axis represents the inflow, the horizontal axis represents the time series, and the data interval is from 0:00 on June 20, 2022 to 23:00 on July 3. The light solid line in the figure represents the inflow process calculated by the eight-stage reservoir capacity method, and the dark solid line represents the inflow process calculated by the method of the present invention. Compared with the eight-stage reservoir capacity method, the flow process calculated by the method of the present invention is smoother, the calculation result is more accurate, there is no unreasonable minimum value, and the change trend is consistent with the actual inflow situation. In the absence of measured inflow, the inflow process calculated by the method of the present invention can be used as the inflow of the reservoir.

[0071] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for calculating the inflow of a river-type reservoir based on hydrological and hydrodynamic coupling, characterized in that: The following steps are involved: Step 1: Construct a hydrological-hydrodynamic coupling model; Step 2: Calculate the storage capacity change of river-type reservoirs based on the hydrological-hydrodynamic coupling model; Step 3: Calculate the inflow into the river-type reservoir by combining the storage capacity change and the water balance method.

2. The method for calculating the inflow of a river-type reservoir based on hydrological and hydrodynamic coupling according to claim 1 is characterized in that: The step 1 is specifically as follows: Step 1-1, collecting hydrological and meteorological data and underlying surface data of river-type reservoirs, and constructing a distributed hydrological model; the distributed hydrological model simulates the runoff and base flow of each grid unit according to the meteorological data and surface conditions of the basin; and outputs the river flow process through the confluence method; Step 1-2, collecting topographic data of river-type reservoirs and river section data, and constructing a one-dimensional hydrodynamic model; the one-dimensional hydrodynamic model divides the river into hundreds of sections, simulates the water flow in the river, and outputs the changes of water level, water depth and flow velocity over time in each river section; Steps 1-3: Use the river flow process simulated by the distributed hydrological model as the boundary condition of the one-dimensional hydrodynamic model to form a hydrological-hydrodynamic coupling model; use the one-dimensional hydrodynamic model to simulate the river flood process in the main river channel of the river-type reservoir.

3. The method for calculating the inflow of a river-type reservoir based on hydrological and hydrodynamic coupling according to claim 1 or 2, characterized in that: The step 2 is specifically as follows: Step 2-1, the river section data required for calculating the dynamic reservoir capacity is output from the hydrological-hydrodynamic coupling model, and the river section division scheme of the hydrological-hydrodynamic coupling model is adopted to divide the river into k sections; Step 2-2, calculate the average of the water flow areas of two adjacent sections and multiply it by the section spacing to obtain the water volume between the two sections. The calculation formula is as follows: Where V n is the water volume between the nth section and the n+1th section, A n and A n+1 is the area of ​​the nth cross section and the area of ​​the n+1th cross section; d n is the distance between two sections; Step 2-3: After completing the calculation of all sections one by one, the water volume between all sections is accumulated to obtain the instantaneous storage capacity of the reservoir during this period. The storage capacity changes dynamically over time. The calculation formula is as follows: V=V1+V2+…+V k Where V is the instantaneous storage capacity of the reservoir, V1, V2, …, V k is the water volume between sections; Step 2-4: Calculate the instantaneous storage capacity of the reservoir at adjacent times, and make the difference between the two to obtain the reservoir storage capacity change ΔV within the period. The calculation formula is as follows: ΔV=V t2 -V t1 Where V t1 is the instantaneous value of the reservoir capacity at time 1, V t2 is the instantaneous value of the reservoir capacity at time 2, and ΔV is the change in reservoir capacity during the period.

4. The method for calculating the inflow of a river-type reservoir based on hydrological and hydrodynamic coupling according to claim 3 is characterized in that: The step 3 is specifically as follows: Based on the principle of water balance, the dam flow output by the hydrological-hydrodynamic coupling model is used as the outflow of the river-type reservoir, and the inflow is defined by the outflow and storage capacity change. The sum of the outflow in a certain period and the storage capacity change in the period is taken as the inflow of the period. The calculation formula is as follows: In the formula, Qin is the inflow flow; Q out is the outflow flow; ΔV is the change in storage capacity; T is the time period corresponding to the change in storage capacity.

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