Method for determining critical overtopping flood scale of reservoir dam
By acquiring basic reservoir data and fitting the inflow process using Pearson Type III curves, and combining this with the reservoir's discharge capacity curve, the outflow process was calculated time-by-time. This solved the problem of calculating the critical overtopping flood scale of earth-rock dam reservoirs, enabling accurate risk assessment and safety design.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-03-31
AI Technical Summary
Existing technologies lack a system for calculating the critical overtopping flood scale of earth-rock dam reservoirs, which makes it impossible to accurately assess overtopping risks and flood control safety designs. Furthermore, the fitting error of the inflow process is large, failing to meet the safety assessment requirements under extreme flood conditions.
By acquiring key basic data of the reservoir, the flood inflow process was fitted using Pearson Type III curves. Combined with the water level-reservoir capacity-spillway discharge capacity curves, the outflow process was calculated time-by-time. The critical overtopping flood was determined using the surplus deficit function, and a direct quantitative correlation between flood parameters and overtopping status was established.
It achieves a precise quantitative correlation between flood scale and inundation status, reduces calculation errors, and provides a scientific basis for flood control safety design and risk prevention.
Smart Images
Figure CN121765950A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water conservancy project assessment technology, specifically relating to a method for determining the critical overtopping flood scale of a reservoir dam. Background Technology
[0002] As a core infrastructure for flood control, disaster reduction, and water resource allocation, reservoir projects have irreplaceable strategic significance for ensuring flood control safety in river basins and supporting the sustainable socio-economic development of the region.
[0003] Currently, flood control calculation technologies both domestically and internationally largely focus on conventional flood scenarios, with the core revolving around deriving key parameters such as maximum discharge and total flood volume from the water level to verify the conventional flow capacity of reservoir flood discharge facilities. However, for the special engineering type of earth-rock dam reservoirs, a dedicated system for calculating the scale of critical overtopping floods has not yet been established. There is neither a direct quantitative correlation between the "critical overtopping state" (water level reaching the dam crest) and flood parameters, nor a technical path that can accurately output the "flood parameters that just trigger overtopping," which makes it impossible to provide direct support for the overtopping risk prevention and flood control safety design of earth-rock dam reservoirs.
[0004] Furthermore, existing technologies rely on empirical formulas or simplified models to derive the inflow process for floods with different return periods in the inflow process fitting stage. They fail to fully integrate long-term measured runoff data from upstream hydrological stations (such as multi-year measured peak flow and maximum 24-hour runoff) and use scientific methods like Pearson Type III curves to fit key parameters. This results in significant errors in the inflow process characterization, further reducing the reliability of calculating the critical overtopping flood scale. In summary, existing technologies, lacking a dedicated calculation system for the critical overtopping flood scale and deficient in terms of discharge simulation adaptability and inflow fitting data support, are unable to meet the core requirements of earth-rock dam reservoir safety assessment under extreme flood conditions. Summary of the Invention
[0005] This invention proposes a method for determining the critical overtopping flood scale of a reservoir dam, which can establish the relationship between flood parameters and the critical overtopping state, and realize the overtopping risk prevention and flood control safety design of the Shiba Reservoir.
[0006] To achieve the above objectives, the present invention proposes the following technical content: A method for determining the critical overtopping flood scale of a reservoir dam includes the following steps: S1: Obtain key basic data of the reservoir; key basic data include: water level-reservoir capacity-spillage channel discharge capacity curve, flood control level, dam crest elevation, and maximum flood control capacity. W max In addition, peak flow data and detailed flood process data for the upstream basin of the reservoir and floods with different return periods; maximum flood control capacity. W maxThis is expressed as the difference in reservoir capacity between the flood control level and the dam crest elevation; S2: Fit the peak flow data and detailed flood process data of floods with different return periods collected in S1 to obtain the corresponding flood flow process curve. Q in ( t ); S3: A flood discharge process curve Q in ( t By combining the water level-reservoir capacity-spillway discharge capacity curves in S1, the corresponding flood discharge flow process line can be obtained. Q out ( t ); S4: Utilize the corresponding flood flow process curve Q in ( t ) and flood discharge process line Q out ( t To determine whether the flood event is a critical overtopping flood; S5: If yes, output the flood parameters for the critical overtopping flood; if no, adjust the flood process and repeat S3-S4 until the flood parameters for the critical overtopping flood are output.
[0007] Furthermore, step S4 includes the following steps: S4.1: Calculate the reservoir's surplus / deficit water volume function, the formula is:
[0008] In the formula, T This indicates the time from when the flood enters the reservoir until the water level reaches the dam crest elevation; S4.2: Based on the surplus / deficit water function, the relationship between the total reservoir capacity and time is obtained; the formula is:
[0009] In the formula, V 0 represents the inventory corresponding to the flood control level; V ( t () indicates the total reservoir inventory; S4.3: Based on the water level-reservoir capacity-spillway discharge capacity curve, calculate the total reservoir capacity function. V ( t Convert to reservoir water level function Z ( t ); S4.4: Determine whether it is a critical overtopping flood according to the set rules; At a certain moment, the reservoir water level function is satisfied. Z (t The elevation of the dam crest is equal to the elevation of the reservoir, and simultaneously satisfies the following conditions: If the current flood event is critically overtopping, then the flood parameters are adjusted and steps S3-S4 are repeated until a flood event that meets the critical conditions is output. The flood peak parameters include the flood return period, the flood peak discharge, and the total flood volume.
[0010] Furthermore, in step S2, Pearson type III curves are used to fit the peak flow data and detailed flood process data of floods with different return periods.
[0011] Furthermore, in step S3, the flood inflow process is first obtained through step S2. Q in ( t Then, combining initial reservoir capacity and other data, flood control calculations are used to deduce the reservoir's water level change process over time periods. Z ( t For the water level at each time period Z ( t ), query the water level-reservoir capacity-spillway discharge capacity curve to obtain the corresponding flood discharge flow rate. Q out ( t ).
[0012] The beneficial effects that can be achieved by adopting the above technologies are: 1. A quantitative correlation between the critical state of flood inundation and the scale of flood was established through the core formula. For the first time, the critical state of "water level reaching the top of the dam" is directly linked to the scale of the flood, solving the core problem of existing technologies that "cannot define the critical flood level" and avoiding ambiguity in parameter calculation.
[0013] 2. Inflow process Q in ( t Generated based on measured runoff data fitted by Pearson Type III curve, outflow process Q out ( t By combining the dynamic calculation of the "water level - reservoir capacity - flood discharge capacity curve" and calculating time-by-time through a list trial algorithm, data errors are reduced from the source, ensuring the accuracy of parameters such as critical flood return period and peak flow in the final output. Attached Figure Description
[0014] Figure 1 This is a schematic diagram of the flood control and storage principle of a reservoir. Figure 2 This is a diagram showing the relationship between reservoir water level, reservoir capacity, and flood discharge capacity. Figure 3It is a flow duration curve of the reservoir flood regulation process; Figure 4 It is a flood flow process graph; Figure 5 It is a flow chart of the reservoir's flood discharge process; Figure 6 It is a curve showing the relationship between reservoir water level and storage capacity; Figure 7 It is a flow chart of flood discharge capacity for floods with different return periods. Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0016] A method for determining the critical overtopping flood scale of a reservoir dam includes the following steps: S1: Obtain key basic data about the reservoir.
[0017] Key basic data include: water level-reservoir capacity-spillway discharge capacity curve, flood control level (i.e., initial water level), dam crest elevation, and maximum flood control capacity. W max (Defined as: the difference in reservoir capacity between the flood control level and the dam crest elevation), and river runoff data from the upstream basin of the reservoir. Related schematic diagrams are shown below. Figure 1 As shown.
[0018] In this embodiment, Qianping Reservoir (an earth-rock dam reservoir) is used as an example. The water level-reservoir capacity-spillway discharge capacity curves of Qianping Reservoir are collected (see...). Figure 2 ), flood control level (i.e., initial water level set at 415.0m), dam crest elevation (set at 426.0m), and maximum flood control capacity. W max and river runoff data in the upstream basin of the reservoir (see Figure 7 River runoff data includes peak flow data for floods with different return periods and detailed data on flood processes.
[0019] Figure 2 The water level-reservoir capacity-spillway discharge capacity curves are shown in Table 1, with some data provided.
[0020] Table 1. Water Level-Reservoir Capacity-Flood Discharge Capacity Curve of Qianping Reservoir
[0021] Foregoing: Wmax =Dam crest elevation inventory - Flood control level inventory = 644,686,000 m³ 3 - 469.8 million m 3 = 174,886,000 m 3 .
[0022] S2: Determine the flood inflow process.
[0023] The flood inflow process curve satisfies Figure 3 The blue curve.
[0024] In this scheme, the peak discharge data and detailed flood process data of floods with different return periods collected in S1 are used to fit the inflow characteristics of the flood using Pearson Type III curves to generate a flood discharge process curve, see [link to relevant documentation]. Figure 4 Pearson Type III curve fitting is a commonly used curve in hydrological statistics. Based on the characteristic values of floods, it can extract the hydrological characteristics of floods with different return periods. The hydrological characteristics include: peak flow, total flood volume, flood duration, and the temporal distribution of the flood process. Finally, the actual flood flow process line is simplified into a triangular curve, which not only retains the core characteristics of the flood (peak flow, total flood volume, and duration) but also transforms the complex curve into a regular shape, which is convenient for subsequent calculations.
[0025] See Figure 4 Using a 24-hour period as the calculation timeframe, with each hour as a timeframe (a total of 24 timeframes), the inflow rate of the spillway at each timeframe is obtained. Q in ( t (i.e., inbound flow).
[0026] Table 2. Inflow rate of Qianping Reservoir spillway at different times
[0027] S3: Determine the outflow process of the reservoir.
[0028] By combining the flood discharge hydrograph in S2 with the water level-reservoir capacity-spillway discharge capacity curve in S1, the discharge capacity of the reservoir at different water levels caused by a flood with a certain return period is analyzed. The flood discharge hydrograph is shown below. Figure 5 .
[0029] Specifically: Outflow process Q out ( t The core process of flood regulation simulation is as follows: using the flood inflow process generated by S2 fitting. Q in (t)Using the initial reservoir capacity, water level-reservoir capacity-spillway discharge capacity curve obtained from S1 as input, a trial-and-error algorithm is used to extrapolate the data period by period, according to a fixed time interval (e.g., 1 hour). First, the discharge flow rate at the end of the current time interval is assumed. Q out1 By calculating the inflow of water into the reservoir during the time period ( Q in (t) The reservoir capacity change and the reservoir capacity at the end of the period are calculated by multiplying the reservoir capacity by the time period length (× time period length) and the outflow volume (average outflow at the beginning and end of the period × time period length). Then, the outflow capacity curve is queried based on this reservoir capacity to obtain the corresponding actual outflow, which is then compared with the assumed value. If they match, the result is retained; otherwise, the assumption is corrected and the calculation is repeated. The reservoir capacity, water level, and outflow at the end of the current period are used as the initial state for the next period, and this process is iterated until all periods are completed, ultimately forming a complete... Q out (t) Process line.
[0030] In this embodiment, the outflow process is obtained through flood control calculations and trials, specifically represented by the flood control discharge flow rate. Q out ( t (i.e., outbound flow) Figure 5 The data for the middle part is shown in Table 3.
[0031] Table 3. Flood discharge from the spillway of Qianping Reservoir at different times.
[0032] S4: Determine if the flood is a critical overtopping flood. This includes the following steps: S4.1: Inbound flow function in S2 and S3 Q in ( t ) and outbound flow function Q out ( t ), calculate the surplus / deficit water volume of the reservoir; the formula is:
[0033] In the formula, T This indicates the time from when the floodwaters enter the reservoir until the water level reaches the dam crest elevation.
[0034] S4.2: Based on the surplus / deficit water function, the relationship between the total reservoir capacity and time is obtained, expressed as:
[0035] In the formula, V 0 represents the initial inventory, which is the reservoir capacity corresponding to the flood control level, i.e., 469,796,500 m³. 3 ; S4.3: Based on the water level-reservoir capacity-spillway discharge capacity curve, calculate the total reservoir capacity function. V ( t Convert to reservoir water level function Z ( t ),See Figure 6 ; S4.4: Determine whether it is a critical overtopping flood according to the set rules; If there exists a certain moment when the reservoir water level function Z ( t The elevation of the dam crest is equal to the elevation of the reservoir, and simultaneously satisfies the following conditions: If so, the current flood event is a critical overtopping flood.
[0036] If the conditions are not met, adjust the flood parameters and repeat the trial calculation process from steps S4.1 to S4.3 until a flood process that meets the critical conditions is found.
[0037] S5: Output critical overtopping flood parameters. Peak flood parameters include flood return period, peak discharge, and total flood volume.
[0038] In this embodiment, the flood recurrence interval is 5500 years. Peak flow rate: 2.2 × 10⁻⁶ 4 m³ / s; Total flood volume: 1.5 × 10 9 m³.
[0039] Through the aforementioned trial calculation process based on integral equations, this invention accurately determined the critical overtopping flood scale of Qianping Reservoir. This method establishes continuous flood process functions and discharge process functions, and directly solves the water balance equation using integral operations. The theory is rigorous, providing a scientific basis for dam flood control safety design, flood control scheduling optimization, and dam break risk early warning.
[0040] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.
Claims
1. A method for determining the size of a critical overtopping flood for a reservoir dam, characterized in that, Comprising the following steps: S1: obtaining key basic data of the reservoir; Key basic data include: water level-storage-discharge capacity curve of spillway, flood control water level, dam crest elevation, maximum flood control storage W max and flood peak flow data and detailed flood process data of upstream watershed of reservoir and different return period floods; maximum flood control storage W max represented as the difference in storage between the flood control water level and the dam crest elevation; S2: fitting the flood peak flow data and flood process detailed data of different return period floods collected in S1 to obtain the corresponding flood flow hydrograph Q in ( t ) S3: a certain flood discharge hydrograph Q in ( t ) combined with the water level-storage-discharge capacity curve in S1, a corresponding flood regulation discharge hydrograph is obtained Q out ( t ); S4: using the corresponding flood discharge hydrograph Q in ( t ) and the flood regulation discharge hydrograph Q out ( t ) to determine whether the flood process is a critical overtopping flood; S5: if yes, output the flood parameters of the critical overtopping flood; if no, repeat S3-S4 after adjusting the flood process until the flood parameters of the critical overtopping flood are output.
2. The method for determining the critical overtopping flood size of a reservoir dam according to claim 1, characterized in that, In step S4, comprising the following steps: S4.1: calculating the residual deficit function of the reservoir, the formula being: ； In the formula, T represents the time for the flood to enter the reservoir to the water level reaching the dam crest elevation; S4.2: obtaining the relationship formula of the total reservoir capacity with time based on the residual deficit function; the formula being: ； In the formula, V 0 represents the inventory corresponding to the flood control water level; V t represents the total inventory of the reservoir. S4.3: According to the water level-storage-discharge capacity curve, convert the reservoir total storage function V ( t ) into a reservoir water level function Z ( t ); S4.4: judging whether it is a critical overtopping flood according to the set rules; At a certain moment, the reservoir water level function is satisfied. Z ( t The elevation of the dam crest is equal to the elevation of the reservoir, and simultaneously satisfies the following conditions: If yes, the current flood process is a critical overtopping flood; if not, adjust the flood parameters, repeat steps S3-S4 until the flood process that meets the critical condition is output; the flood peak parameters include flood return period, flood peak flow, and total flood volume.
3. The method for determining the critical overtopping flood size of a reservoir dam according to claim 1, characterized in that, In step S2, the Pearson III curve fitting is adopted to fit the flood peak flow data and detailed flood process data of different recurrence period floods.
4. The method for determining the critical overtopping flood size of a reservoir dam according to claim 1, characterized in that, In step S3, the flood inflow process obtained in step S2 is combined with initial reservoir capacity data, and the reservoir water level change process is derived through flood regulation calculation Q in ( t ) for each time period Z t ). For each time period water level Z t , the water level-capacity-discharge capacity curve is queried to obtain the corresponding flood regulation discharge Q out ( t ).