Reservoir drought-resistant scheduling risk identification and evaluation method considering multiple targets

Abstract

The invention discloses a reservoir drought-resistant scheduling risk identification and evaluation method considering multiple targets, and the method comprises the steps: building a first-stage risk index, decomposing the first-stage risk index into a second-stage risk index, and constructing an evaluation index system; performing long-series simulation on the reservoir drought-resisting scheduling scheme by adopting a reservoir scheduling model, and calculating a second-level risk index value according to the obtained reservoir basic elements; performing normalization processing on the second-level risk index values, listing the second-level risk index values as an advantage matrix, endowing the second-level risk indexes with corresponding weights, and calculating first-level risk index values based on the advantage matrix and the corresponding weights; assigning a corresponding weight to each first-level risk index, and calculating a comprehensive risk based on each first-level risk index value and the corresponding weight; and carrying out risk grade division on the first-level risk index and the comprehensive risk index. The method has the advantages that a basis is provided for risk early warning, scientific decision-making in the reservoir drought-resisting dispatching process is supported, and a solid technical foundation is provided for efficient management and coping with multiple risks in a complex environment.

Description

Technical Field

[0001] The invention relates to the technical field of reservoir drought relief dispatching, and in particular to a reservoir drought relief dispatching risk identification and assessment method considering multiple objectives. Background Art

[0002] Many regions around the world are facing increasingly severe drought conditions. The prevalence and frequency of droughts have significantly increased, and climate change has become one of the main factors causing droughts. Taking the middle and lower reaches of the Yangtze River Basin in China as an example, with the rapid development of the economy and society, the demand for water resources and the degree of security have continued to increase. Since the establishment of the reservoir, as the impact of climate change has become more and more obvious, especially in September 2009, the water flow in the main and tributary rivers of the Yangtze River was less than normal, and the middle and lower reaches of the main stream had a rare low water level during the same period, showing the intensification of the contradiction between water supply and demand. In 2022, the Yangtze River Basin suffered the most severe drought event in history, and the regulation capacity of the reservoir urgently needs to be exerted to cope with the continued water shortage. This series of events highlights the importance and urgency of reservoir drought control in the context of climate change, and water resources management must be strengthened.

[0003] Reservoirs play a multifaceted role in drought relief. In terms of water resource management, reservoirs can store water during the flood season to ensure water supply during drought and reduce the impact of drought on the social economy. In terms of agricultural production, they can ensure irrigation and stabilize the agricultural economy. In terms of the ecological environment, they can improve water quality. In terms of social economy, the most direct link is the problem of water resource allocation in water-scarce areas. While reservoirs improve the efficiency of water resource utilization in drought relief scheduling, they may also trigger competition and influence among multiple goals such as flood control, power generation, water supply and shipping. The implementation of drought relief strategies has led to an increase in reservoir water storage, but it may also lead to an increase in flood control risks, especially when the water storage reaches its limit, the potential risk of dam failure is significantly enhanced. In addition, the rise in water storage levels has a suppressive effect on hydropower generation capacity and affects the peak-shaving performance of the power grid. Due to the priority of water supply demand during drought, it may lead to insufficient water supply during the flood season and have a negative impact on the water supply in subsequent seasons. In terms of shipping, the dynamic adjustment of reservoir water levels may also have an adverse impact on the navigation capacity of waterways. In order to effectively alleviate these potential management conflicts, it is urgent to implement comprehensive planning and scheduling and build a decision support system. The concept of scheduling risk was proposed in the 1980s. In the early days, reservoir scheduling was only analyzed for a certain type of risk, and the research on risk theory in hydrological science was mainly presented in flood control analysis. Researchers have conducted in-depth discussions on risk analysis methods in reservoir scheduling and proposed risk decision-making strategies suitable for reservoir scheduling. Among them, the risk analysis of dynamic flood limit water level control scheduling takes into account the impact of flood forecast errors and emphasizes the key role of forecast uncertainty in flood control scheduling. In addition, the study also established a comprehensive reservoir risk assessment index system and a comprehensive evaluation model for scheduling schemes, and applied them in Danjiangkou Reservoir. There are few studies on reservoir drought-resistant scheduling risks, and there are few comprehensive research results that take into account various risks, or the existing evaluation methods are difficult to meet actual needs. Summary of the invention

[0004] The purpose of the present invention is to provide a reservoir drought relief scheduling risk identification and assessment method taking multiple objectives into consideration, thereby solving the above-mentioned problems existing in the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A multi-objective reservoir drought dispatch risk identification and assessment method includes the following steps:

[0007] S1. Construction of index system: Establish first-level risk indicators from five perspectives: flood control, power generation, water supply, shipping, and ecology, and decompose each first-level risk indicator into corresponding second-level risk indicators to build a well-structured and hierarchical index system for reservoir drought dispatch risk identification and assessment;

[0008] S2. Quantitative calculation of secondary risk indicators: Use the reservoir operation model to simulate the reservoir drought relief operation plan in a long series to obtain the basic elements of the reservoir; calculate the secondary risk indicator value based on the basic elements of the reservoir;

[0009] S3. Quantitative calculation of primary risk indicators: normalize the calculated secondary risk indicator values ​​and list them as an advantage matrix, assign corresponding weights to each secondary risk indicator, and calculate the corresponding primary risk indicator values ​​based on the advantage matrix and corresponding weights of the secondary risk indicators;

[0010] S4. Comprehensive risk assessment: assign corresponding weights to each first-level risk indicator, and calculate the comprehensive risk based on the calculated first-level risk indicator values ​​and corresponding weights;

[0011] S5. Risk level classification: Use the equal frequency method to classify the primary risk indicators and comprehensive risk indicators into five levels: no risk, low risk, medium risk, medium-high risk, and high risk.

[0012] Preferably, in step S1,

[0013] The secondary risk indicators obtained by decomposing the primary risk indicator flood control include the reservoir's own risk rate, flood control risk rate, flood control storage capacity failure risk rate, and downstream river flood control risk rate;

[0014] The secondary risk indicators obtained by decomposing the primary risk indicator power generation include the risk rate of insufficient power generation, the risk rate of insufficient output, and the risk rate of water abandonment;

[0015] The secondary risk indicators obtained by decomposing the primary risk indicator water supply include the risk rate of insufficient urban water supply, the risk rate of insufficient industrial water supply, and the risk rate of insufficient agricultural irrigation water supply;

[0016] The secondary risk indicators obtained by decomposing the primary risk indicator shipping include the upstream shipping shortage risk rate and the downstream shipping shortage risk rate;

[0017] The secondary risk indicators obtained from the ecological decomposition of the primary risk indicators include the risk rate of insufficient ecological assurance in downstream sections.

[0018] Preferably, the calculation method of the secondary risk index of the primary risk index flood control is:

[0019] Reservoir's own risk rate:

[0020]

[0021] Among them, A1 is the risk rate of the reservoir itself; a1 is the number of floods exceeding the design flood level of the reservoir; a is the total number of floods;

[0022] Flood risk rate:

[0023]

[0024] Among them, A2 is the flood control risk rate; a2 is the number of times the water level upstream of the reservoir exceeds the established flood limit water level; a is the total number of times;

[0025] Risk rate of flood control storage capacity failure:

[0026]

[0027] Among them, A3 is the risk rate of reservoir flood control failure; a i is the reservoir water level and storage capacity corresponding to time i; a3 is the storage capacity corresponding to the flood control limit water level; a4 is the design flood level;

[0028] Downstream river flood risk rate:

[0029]

[0030] Among them, A4 is the flood control risk rate of the downstream river; a5 is the number of times the safe discharge of the downstream river is exceeded; a 泄流 It is the total number of reservoir discharge events.

[0031] Preferably, the calculation method of the secondary risk index of the primary risk index power generation is:

[0032] Risk rate of insufficient power generation:

[0033]

[0034] Among them, B1 is the risk rate of insufficient power generation; b1 is the number of times the actual power generation is less than the planned target power generation; b2 is the total number of power generation;

[0035] Risk rate of insufficient output:

[0036]

[0037] Among them, B2 is the risk rate of insufficient output; b3 is the number of times the actual output is less than the planned output; b4 is the total number of outputs;

[0038] Risk rate of water abandonment:

[0039]

[0040] Among them, B3 is the risk rate of water abandonment; b5 is the number of times the reservoir discharge is greater than the power generation flow; and b2 is the total number of power generation times.

[0041] Preferably, the calculation method of the secondary risk index of the primary risk index water supply is,

[0042] Risk rate of insufficient urban water supply:

[0043]

[0044] Among them, C1 is the risk rate of insufficient urban water supply; c1 is the number of reservoir discharges corresponding to the urban water supply level / flow; c is the total number of reservoir discharges;

[0045] Risk rate of insufficient industrial water supply:

[0046]

[0047] Among them, C2 is the risk rate of insufficient industrial water supply; c2 is the number of reservoir discharges corresponding to the industrial water supply level / flow; c is the total number of reservoir discharges;

[0048] Risk rate of insufficient water supply for agricultural irrigation:

[0049]

[0050] Among them, C3 is the risk rate of insufficient water supply for agricultural irrigation; c3 is the number of reservoir discharge flows corresponding to the agricultural irrigation water supply water level / flow; and c is the total number of reservoir discharges.

[0051] Preferably, the calculation method of the secondary risk index of the primary risk index shipping is:

[0052] Risk rate of insufficient upstream shipping:

[0053]

[0054] Among them, D1 is the risk rate of insufficient upstream navigation; d1 is the number of reservoir discharges that do not meet the upstream navigation water level / flow; c is the total number of reservoir discharges;

[0055] Downstream shipping shortage risk rate:

[0056]

[0057] Among them, D2 is the risk rate of insufficient downstream navigation; d2 is the number of reservoir discharge flow events that do not meet the downstream navigation water level / flow; c is the total number of reservoir discharge events.

[0058] Preferably, the calculation method of the secondary risk indicator of the primary risk indicator ecosystem is:

[0059] Risk rate of insufficient ecological guarantee in downstream sections:

[0060]

[0061] Among them, E2 is the risk rate of insufficient downstream navigation; e1 is the number of reservoir discharge flow events that does not meet the ecological guarantee flow of the downstream section; and e is the total number of reservoir discharge events.

[0062] Preferably, the calculation formula for comprehensive risk is:

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069] Among them, B is the comprehensive risk; B1, B2, B3, B4, B5 are the first-level risk indicators of flood control, power generation, water supply, shipping, and ecology; w1, w2, w3, w4, w5 are the weights of the first-level risk indicators of flood control, power generation, water supply, shipping, and ecology; R1, R2, R3, R4, R5 are the second-level risk indicators corresponding to each first-level risk indicator converted to obtain the advantage matrix; w 11 、w 12 、w 13 、w 14 are the weights of the secondary risk indicators, namely, the reservoir’s own risk rate, flood control risk rate, flood control storage capacity failure risk rate, and downstream river flood control risk rate; w 21 、w 22 、w 23 are the weights of the secondary risk indicators: insufficient power generation risk rate, insufficient output risk rate, and water abandonment risk rate; w 31 、w 32 、w 33 are the weights of the secondary risk indicators: urban domestic water supply shortage risk rate, industrial water supply shortage risk rate, and agricultural irrigation water supply shortage risk rate; w 41 、w 42 are the weights of the secondary risk indicators upstream shipping shortage risk rate and downstream shipping shortage risk rate; w 51 、w 52 ,…,w 5t are the weights of the risk rate of insufficient ecological assurance of each downstream section, and t is the number of downstream sections.

[0070] Preferably, step S5 specifically comprises: classifying the primary risk indicators by using an equal frequency method based on the secondary risk indicator values, and classifying the comprehensive risk indicators by using an equal frequency method based on the primary risk indicator values.

[0071] Preferably, the equal frequency method is used to divide the risk indicators, specifically including the following contents:

[0072] S51, sort the indicator results and arrange all sample data from small to large;

[0073] S52. Divide the sample data into multiple groups according to the research purpose;

[0074] S53, calculating the upper bound of each interval according to the determined number of intervals;

[0075]

[0076] Among them, Q k is the kth upper bound, k = 1, 2, ..., (n-1); n is the number of intervals; N is the total number of data points;

[0077] S54, using the upper bound of each interval, determining the boundary of each interval;

[0078] edges=[Q0, Q1, Q2,…,Q n ]

[0079] Among them, edges are boundaries; Q0 is the minimum value of the sample data; Q n is the maximum value of the sample data;

[0080] S55. Determine the interval range of each group based on the sorted sample data; the upper limit of each category or group is the value of the last data sample of the group, and the lower limit is the upper limit of the previous group.

[0081] The beneficial effects of the present invention are as follows: 1. The present invention can identify and evaluate the risks generated in multiple dimensions such as water supply, power generation, flood control, shipping, and ecology when the reservoir is dispatched for drought resistance, which can provide a basis for risk warning, support scientific decision-making in the process of reservoir drought resistance dispatch, and provide a solid technical foundation for efficient management and response to multiple risks in complex environments. 2. The present invention can effectively identify potential risk factors and conduct quantitative and qualitative evaluations on them, thereby comprehensively evaluating the feasibility and safety of drought resistance dispatch. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 is a flow chart of a method in an embodiment of the present invention;

[0083] Figure 2 It is an overall technical framework diagram of the method in the embodiment of the present invention;

[0084] Figure 3 It is a multi-objective risk assessment index system in an embodiment of the present invention;

[0085] Figure 4 is a schematic diagram of secondary risk indicators in an embodiment of the present invention;

[0086] Figure 5 It is a schematic diagram of the first-level risk indicator in an embodiment of the present invention. DETAILED DESCRIPTION

[0087] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0088] Embodiment 1

[0089] like Figure 1 As shown in FIG. 1 , in this embodiment, a set of methods is proposed to identify and evaluate the conversion relationship of the risk quantification generated in multiple dimensions such as water supply, power generation, flood control, shipping, and ecology when the reservoir is drought-resistant. The method includes the construction of an indicator system, the quantitative calculation of secondary risk indicators, the quantitative calculation of primary risk indicators, the comprehensive risk assessment, the risk level classification, and the risk characteristic analysis (the process is shown in FIG. 1 ). Figure 1 It provides a basis for risk warning, supports scientific decision-making in the process of reservoir drought relief dispatch, and provides a solid technical foundation for efficient management and response to multiple risks in complex environments.

[0090] During droughts, the rational allocation of water resources is directly related to the water supply security and navigation in downstream areas. Faced with complex climate change and growing population demand, reservoir scheduling strategies face multiple risks, such as reservoir water level fluctuations and socio-economic factors. In the drought-resistant scheduling of reservoirs, it is crucial to carry out risk identification and assessment. Through a systematic approach, potential risk factors can be effectively identified and quantitatively and qualitatively assessed, covering data collection, risk indicator establishment, model construction and risk assessment, so as to comprehensively assess the feasibility and safety of drought-resistant scheduling. The overall technical framework of the reservoir drought-resistant scheduling risk identification and assessment method of the present invention is shown in the figure below: Figure 2 shown.

[0091] I. Construction of the indicator system

[0092] Cascade reservoirs usually have comprehensive utilization functions, and their tasks include flood control, power generation, water supply, shipping, ecology, etc. Against the background of global climate change and increasing water scarcity, the frequency and intensity of drought events are gradually increasing, bringing unprecedented challenges to the management and dispatch of reservoirs. The effectiveness of drought-resistant dispatch depends on the comprehensive identification and assessment of risk factors, including changes in meteorological conditions, fluctuations in water demand, and the impact of social and economic activities. Establishing a sound drought-resistant dispatch risk identification system can provide data support and decision-making basis for the daily management and emergency response of reservoirs.

[0093] In this embodiment, first-level risk assessment indicators are established from five perspectives, namely, flood control, power generation, water supply, shipping, and ecology. Each first-level indicator is decomposed into second-level indicators to form a reservoir drought dispatch risk identification and assessment system with a structural hierarchy, such as Figure 3shown.

[0094] In reservoir management and operation, comprehensive identification and assessment of risks is an important part of ensuring their safety and effective operation. Comprehensive risk management involves the assessment of multiple risk factors, which include not only flood control, power generation, and water supply, but also shipping and other aspects.

[0095] For the identification of primary risk indicators:

[0096] Comprehensive risk = {flood control risk, power generation risk, water supply risk, shipping risk, ecological risk}

[0097] In the formula: comprehensive risk is recorded as B, flood control risk is recorded as B1, power generation risk is recorded as B2, water supply risk is recorded as B3, shipping risk is recorded as B4, and ecological risk is recorded as B5.

[0098] The four first-level indicators are decomposed into second-level risk indicators:

[0099] Flood control = {reservoir’s own risk rate, flood control risk rate, flood control storage capacity failure risk rate, downstream river flood control risk rate}.

[0100] Power generation = {risk rate of insufficient power generation, risk rate of insufficient output, risk rate of water abandonment}.

[0101] Water supply = {risk rate of insufficient water supply for urban life, risk rate of insufficient water supply for industrial industry, risk rate of insufficient water supply for agricultural irrigation}.

[0102] Shipping = {upstream shipping shortage risk rate, downstream shipping shortage risk rate}.

[0103] Ecology = {Risk rate of insufficient ecological assurance in downstream sections}.

[0104] II. Quantitative calculation of secondary risk indicators

[0105] The calculation of the secondary risk indicators is based on the reservoir scheduling simulation. The reservoir scheduling model is used to conduct a long series of simulations on the reservoir drought relief scheduling plan to obtain basic elements such as reservoir water level, downstream flow, power generation, power generation output, and downstream section flow, which are used to calculate the secondary risk indicators. The algorithms for each secondary risk indicator are as follows.

[0106] 1. Calculation method of secondary risk indicators for flood control

[0107] Flood control is a key link in ensuring the safety of reservoirs. It aims to reduce the threat of floods to reservoirs and their surrounding environment and ensure that reservoirs can remain safe and functional when floods come. The flood control objectives of reservoirs can be roughly divided into ensuring dam safety and downstream flooding safety. The flood control risk design in this paper consists of four evaluation indicators: the reservoir's own risk rate, flood control risk rate, reservoir flood control capacity failure risk rate, and downstream river flood control risk rate.

[0108] 1) Reservoir risk rate: the percentage of times when the reservoir water level exceeds the design flood level in the total number of times.

[0109]

[0110] In the above formula, A1 is the risk rate of the reservoir itself; a1 is the number of floods exceeding the design flood level of the reservoir; and a is the total number of floods.

[0111] 2) Flood control risk rate: the percentage of times the water level upstream of the reservoir exceeds the established flood limit water level in the total number of times.

[0112]

[0113] In the above formula, A2 is the flood risk rate; a2 is the number of times the water level upstream of the reservoir exceeds the established flood limit water level; and a is the total number of times.

[0114] 3) Risk rate of flood control reservoir failure: the proportion of reservoir capacity that exceeds the flood control limit water level to the difference between the design flood level and the flood control limit water level.

[0115]

[0116] In the above formula, A3 is the risk rate of reservoir flood control failure; a i is the reservoir water level and storage capacity corresponding to time i; a3 is the storage capacity corresponding to the flood control limit water level; a4 is the design flood level.

[0117] 4) Downstream river flood control risk rate: the percentage of times the downstream river discharge exceeds the safe discharge volume to the total number of reservoir discharges.

[0118]

[0119] In the above formula, A4 is the flood control risk rate of the downstream river; a5 is the number of times the safe discharge of the downstream river is exceeded; a 泄流 It is the total number of reservoir discharge events.

[0120] 2. Calculation method of secondary risk indicators for power generation

[0121] Power generation is an important criterion that affects the benefits of reservoirs. The design and operation of reservoirs are not only for water storage and flood control, but also for making full use of water resources to achieve power generation goals. The amount of power generation directly affects the benefits of the reservoir group. Power generation risk is composed of three evaluation indicators: insufficient power generation risk rate, insufficient output risk rate, and water abandonment risk rate. They are important indicators for evaluating the power generation capacity and operating efficiency of reservoirs, and reflect the potential risks and challenges in the power generation process of reservoirs from different angles.

[0122] 1) Risk rate of insufficient power generation: the percentage of the number of times the actual power generation is less than the planned target power generation in the total number of power generation times.

[0123]

[0124] In the above formula, B1 is the risk rate of insufficient power generation; b1 is the number of times the actual power generation is less than the planned target power generation; and b2 is the total number of power generation.

[0125] 2) Risk rate of insufficient output: the percentage of times the actual output of a reservoir is less than the planned output of the reservoir in the total output times.

[0126]

[0127] In the above formula, B2 is the risk rate of insufficient output; b3 is the number of times the actual output is less than the planned output; and b4 is the total number of outputs.

[0128] 3) Risk rate of water abandonment: the percentage of times when the reservoir outflow is greater than the power generation flow in the total power generation times.

[0129]

[0130] In the above formula, B3 is the risk rate of water abandonment; b5 is the number of times the reservoir discharge is greater than the power generation flow; and b2 is the total number of power generation times.

[0131] 3. Calculation method of secondary risk indicators for water supply

[0132] For cascade reservoirs with water supply requirements, it is crucial to ensure the stability and sufficiency of water supply, and to strike a balance between multiple goals such as power generation, flood control, and ecological protection to meet downstream water demand, while improving the operating efficiency and sustainability of the overall reservoir system. The more days of normal water supply, the lower the water supply risk. The water supply risk is composed of the risk rate evaluation indicators of insufficient water supply in three different industries: life, industry, and irrigation.

[0133] 1) Risk rate of insufficient urban water supply: the percentage of reservoir discharge events that do not meet the urban water supply water level / flow to the total discharge events.

[0134]

[0135] In the above formula, C1 is the risk rate of insufficient urban domestic water supply; c1 is the number of reservoir discharge flows corresponding to the urban domestic water supply water level / flow; and c is the total number of reservoir discharge events.

[0136] 2) Risk rate of insufficient industrial water supply: The percentage of reservoir discharge events that do not meet the industrial water supply level / flow rate to the total discharge events

[0137]

[0138] In the above formula, C2 is the risk rate of insufficient industrial water supply; c2 is the number of reservoir discharge flows corresponding to the industrial water supply water level / flow; and c is the total number of reservoir discharge events.

[0139] 3) Risk rate of insufficient water supply for agricultural irrigation: The percentage of reservoir discharge events that do not meet the industrial water supply level / flow rate to the total discharge events

[0140]

[0141] In the above formula, C3 is the risk rate of insufficient water supply for agricultural irrigation; c3 is the number of reservoir discharge flows corresponding to the agricultural irrigation water supply level / flow; and c is the total number of reservoir discharges.

[0142] 4. Calculation method of secondary risk indicators for shipping

[0143] For reservoirs with navigation requirements, navigation is also an important manifestation of the comprehensive benefits of cascade reservoirs. The more days of normal navigation are guaranteed, the smaller the navigation risk is. The navigation risk is composed of two evaluation indicators: the upstream navigation risk rate and the downstream navigation risk rate.

[0144] 1) Risk rate of insufficient upstream navigation: the percentage of reservoir discharge events that do not meet the upstream navigation water level / flow of the reservoir to the total number of reservoir discharge events.

[0145]

[0146] In the above formula, D1 is the risk rate of insufficient upstream navigation; d1 is the number of reservoir discharge flows that do not meet the upstream navigation water level / flow; and c is the total number of reservoir discharge flows.

[0147] 2) Risk rate of insufficient downstream navigation: the percentage of reservoir discharge events that do not meet the downstream navigation water level / flow of the reservoir to the total number of reservoir discharge events.

[0148]

[0149] In the above formula, D2 is the risk rate of insufficient downstream navigation; d2 is the number of reservoir discharge flows that do not meet the downstream navigation water level / flow; and c is the total number of reservoir discharge flows.

[0150] 5. Calculation method of secondary ecological risk indicators

[0151] When the reservoir is regulating, it should not only meet the full regulation of water resources, but also take into account the protection of the ecological environment, so as to ensure that the ecological flow of the downstream river can meet the needs of the survival and reproduction of aquatic organisms. The higher the degree of guarantee, the smaller the ecological risk. The ecological risk is composed of the risk rate of insufficient ecological guarantee in the downstream section.

[0152] Risk rate of insufficient ecological guarantee in downstream sections: the percentage of total reservoir outflow events at the reservoir outflow station that does not meet the ecological guarantee flow in the downstream section.

[0153]

[0154] In the above formula, E2 is the risk rate of insufficient downstream navigation; e1 is the number of reservoir discharge flows that do not meet the ecological guarantee flow of the downstream section; and e is the total number of reservoir discharge flows.

[0155] III. Quantitative calculation of primary risk indicators

[0156] For the decomposed secondary indicators, numerical calculation and normalization are performed. First, the indicators are arranged into a matrix, and then the relative advantage is calculated, and the indicators are dimensionless so that they are all between 0 and 1.

[0157] 1. Column as matrix:

[0158]

[0159] 2. Normalization processing:

[0160]

[0161] For r ij The smaller (larger) the risk (benefit) index is, the better. In the formula: m2 is the maximum value among x; m1 is the minimum value among x.

[0162] 3. Relative advantage matrix:

[0163]

[0164] 4. Determine the weight of evaluation indicators:

[0165] The four secondary risk indicators of flood control are assigned weights, namely w 11 、w 12 、w 13 、w 14 The three secondary risk indicators of power generation are assigned weights, namely w 21 、w 22 、w 23 ; Assign weights to the three secondary risk indicators of water supply, namely w 31 、w 32 、w 33 ; Assign weights to the two secondary risk indicators of shipping, namely w 41 、w 42 ; Assign weights to the secondary risk indicators of the ecology, which are w 51 、w 52 ,…,w 5t (If there are t sections, then record it as w5t ).

[0166] 5. Using the normalized secondary risk index values, primary risk index weights, and secondary risk index weights, a comprehensive risk assessment index for reservoir drought resistance scheduling is constructed.

[0167] Calculation of each first-level risk indicator:

[0168]

[0169]

[0170]

[0171]

[0172]

[0173] IV. Comprehensive Risk Assessment

[0174]

[0175] The five first-level risk indicators B1, B2, B3, B4, and B5 (flood control, power generation, water supply, shipping, and ecology) are assigned weights of w1, w2, w3, w4, and w5 respectively.

[0176] V. Risk Level Classification

[0177] Construct risk level identification standards. Use the equal frequency method to divide the primary risk indicators and comprehensive risk indicators into five levels, namely no risk, low risk, medium risk, medium-high risk, and high risk.

[0178] 1. Data sorting: Sort the indicator results and arrange all sample data from small to large.

[0179] 2. Determine the number of groups: Divide the sample data into multiple categories or groups according to the research purpose.

[0180] 3. Calculate the quantile: Based on the determined number of intervals, calculate the upper bound (i.e., quantile) of each interval.

[0181] If the data is divided into n intervals, then n quantiles of the data need to be calculated, and the kth quantile Q k It can be defined as:

[0182]

[0183] Where k = 1, 2, ..., (n-1); n is the number of intervals; N is the total number of data points.

[0184] 4. Boundary calculation: For the boundary of each interval, use the quantile calculation as follows:

[0185] Assuming that the data is divided into n intervals, the boundaries can be determined by the following formula:

[0186] edges=[Q0, Q1, Q2,…,Q n ]

[0187] Among them, edges are boundaries; Q0 is the minimum value of the sample data; Q n is the maximum value of the sample data;

[0188] 5. Divide the interval: Determine the interval range of each group based on the sorted sample data; the upper limit of each category or group is the value of the last data sample of the group, and the lower limit is the upper limit of the previous group.

[0189] VI. Risk Characteristics Analysis

[0190] The risk level classification results of the first-level risk indicators and the comprehensive risk level classification results are statistically analyzed to form a risk characteristic table.

[0191] Embodiment 2

[0192] This embodiment takes a reservoir as an example to specifically illustrate the execution process of the method of the present invention. The reservoir has flood control, power generation, navigation, ecology and water supply functions. The average flow of the reservoir over the years is 14300m 3 / s, the flood season is from June 11th to September 10th, and the dry season is from January to May. The normal water level and design flood level of the reservoir are 175m, and the total storage capacity is 39.3 billion m 3 The flood control limit water level is 145m, the dry season drawdown water level is 155m, and the navigation requirement upstream of the reservoir in the non-flood season is not lower than the dry season drawdown water level of 155m.

[0193] I. Construction of the indicator system

[0194] Against the backdrop of intensified climate change and frequent natural disasters, a reservoir is an important infrastructure for water resource management. In its construction and management, drought resistance ensures the water demand of farmland and cities during droughts; flood control safety reduces flood risks by rationally regulating water levels; power generation optimizes water flow utilization and improves the stability of power supply; ecological protection can maintain aquatic habitats and ecological diversity; and shipping convenience ensures smooth inland water transportation by regulating water levels.

[0195] Therefore, a certain reservoir comprehensively considers flood control, power generation, water supply, shipping, and ecology as the first-level indicators; the second-level indicators of flood control risk include the reservoir's own risk rate, flood control risk rate, flood control storage capacity failure risk rate, and downstream river flood control risk rate; the power generation risk includes the risk rate of insufficient power generation, the risk rate of insufficient output, and the risk rate of water abandonment; the water supply risk includes the risk rate of insufficient urban water supply, the risk rate of insufficient industrial water supply, and the risk rate of insufficient agricultural irrigation water supply; the shipping risk includes the upstream shipping risk rate and the downstream shipping risk rate; the ecological risk includes the risk rate of insufficient ecological guarantee of downstream river section a and the risk rate of insufficient ecological guarantee of downstream river section b.

[0196] II. Quantitative calculation of secondary risk indicators

[0197] The reservoir operation model is used to simulate the drought-resistant operation plan of the reservoir in a long series, and the daily water level above the dam, the discharge flow, the power generation, the output, the flow of the downstream key section a and the downstream key section b of the reservoir are obtained. The results of the secondary risk values ​​are as follows:

[0198] 1) Flood risk

[0199] According to formulas (1), (2), (3) and (4), the four secondary flood risk indicators are calculated. The calculation results are shown in the following table:

[0200] Table 1 Risk calculation of secondary flood control indicators

[0201] Reservoir's own risk rate Flood risk rate Risk rate of flood control storage capacity failure Downstream river flood risk rate 5％ 65％ 32％ 5％

[0202] 2) Power generation risks

[0203] According to formulas (5), (6) and (7), the three secondary power generation risk indicators are calculated, and the calculation results are shown in the following table:

[0204] Table 2 Risk calculation of secondary power generation indicators

[0205] Risk rate of insufficient power generation Risk rate of insufficient output Water abandonment risk rate 25％ 5％ 20％

[0206] 3) Water supply risk

[0207] It is known that to ensure water for life, industry and irrigation downstream of the reservoir, the reservoir is required to discharge at least 5758.06m 3 / s、7888.19m 3 / s、6227.04m 3 / s, and then calculate the three secondary water supply risk indicators according to formulas (8), (9) and (10). The calculation results are shown in the following table:

[0208] Table 3 Risk calculation of secondary water supply indicators

[0209] Risk of insufficient urban water supply Risk of insufficient industrial water supply Risk of insufficient water supply for agricultural irrigation 5％ 20％ 15％

[0210] 4) Shipping risks

[0211] It is known that to ensure upstream navigation, the reservoir water level must not be lower than 155m, and to ensure downstream navigation, the reservoir outflow must not be lower than 6345.16m 3 / s, and then calculate the secondary shipping risk index according to formulas (11) and (12). The calculation results are shown in the following table:

[0212] Table 4 Risk calculation of secondary shipping indicators

[0213] Risk rate of insufficient upstream shipping Downstream shipping shortage risk rate 60％ 15％

[0214] 5) Ecological risks

[0215] To ensure the ecological protection of the downstream section, the outflow of the reservoir is required to be no less than 8000m 3 / s, to ensure the ecological protection of the downstream section b, the outflow of the reservoir is required to be no less than 6000m 3 / s, and then calculate the secondary ecological risk index according to formula (13). The calculation results are shown in the following table:

[0216] Table 5 Risk calculation of secondary ecological indicators

[0217] Risk rate of insufficient ecological guarantee in downstream section a Risk rate of insufficient ecological guarantee for downstream section b 20％ 5％

[0218] Summarize the calculation results of all secondary risk indicators, such as Figure 4 shown.

[0219] III. Quantitative calculation of primary risk indicators

[0220] 1) The statistical secondary risk indicators are classified into matrices according to the four primary indicators:

[0221]

[0222] 2) The relevant formula in Example 1 is used to normalize the secondary indicators and list them as an advantage matrix:

[0223]

[0224] 3) Determine weights: Priority is given to urban domestic water supply in water supply risks, with a weight of 4:3:3, and the others are all given equal weights.

[0225]

[0226]

[0227]

[0228]

[0229]

[0230]

[0231] 4) The first-level index is calculated using the relevant formula in Example 1:

[0232]

[0233]

[0234]

[0235]

[0236]

[0237] Summarize the calculation results of all first-level risk indicators, such as Figure 5 shown.

[0238] IV. Comprehensive Risk Assessment

[0239] Comprehensive risks:

[0240]

[0241] V. Risk Level Classification

[0242] According to the normalized secondary indicators, the equal frequency method is used to divide the primary indicators. The calculation results are shown in the following table:

[0243] Table 6 Classification of first-level risk levels

[0244]

[0245]

[0246] According to the results of the first-level risk index, the equal frequency method is used again to divide the comprehensive risk. The calculation results are shown in the following table:

[0247] Table 7 Classification of comprehensive risk indicators

[0248] grade No risk Low risk Medium risk Medium to high risk High risk Comprehensive Risk X<0.36 0.36<＝X<0.44 0.44<＝X<0.51 0.51<＝X<0.58 X>＝0.58

[0249] VI. Risk Characteristics Analysis

[0250] Risks 1 to 5 are classified according to the first-level risk level in Table 5, and comprehensive risk No. 6 is classified according to the comprehensive risk index level in Table 6. The results are shown in Table 6 below. The comprehensive risk is a medium risk level.

[0251] Table 8 Risk characteristics

[0252] Serial number risk Value at Risk grade 1 Flood risk 0.36 Medium risk 2 Power generation risks 0.58 Medium risk 3 Water supply risks 0.5 Medium risk 4 Shipping risks 0.5 Medium risk 5 Ecological risks 0.5 Medium risk 6 Comprehensive Risk 0.49 Medium risk

[0253] By adopting the above technical solution disclosed in the present invention, the following beneficial effects are obtained:

[0254] The present invention provides a multi-objective reservoir drought dispatch risk identification and assessment method, which quantitatively identifies and assesses the risks generated in multiple dimensions such as water supply, power generation, flood control, shipping, and ecology when the reservoir is drought dispatched, and can provide a basis for risk warning, support scientific decision-making in the process of reservoir drought dispatch, and provide a solid technical foundation for efficient management and response to multiple risks in complex environments. The present invention can effectively identify potential risk factors and conduct quantitative and qualitative assessments on them, thereby comprehensively assessing the feasibility and safety of drought dispatch.

[0255] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the scope of protection of the present invention.

Claims

1. A multi-objective reservoir drought dispatch risk identification and assessment method, characterized by: The following steps are included: S1. Construction of index system: Establish first-level risk indicators from five perspectives: flood control, power generation, water supply, shipping, and ecology, and decompose each first-level risk indicator into corresponding second-level risk indicators to build a well-structured index system for identifying and evaluating reservoir drought relief scheduling risks; S2. Quantitative calculation of secondary risk indicators: Use the reservoir operation model to simulate the reservoir drought relief operation plan in a long series to obtain the basic elements of the reservoir; calculate the secondary risk indicator value based on the basic elements of the reservoir; S3. Quantitative calculation of primary risk indicators: normalize the calculated secondary risk indicator values ​​and list them as an advantage matrix, assign corresponding weights to each secondary risk indicator, and calculate the corresponding primary risk indicator value based on the advantage matrix and corresponding weights of the secondary risk indicators; S4. Comprehensive risk assessment: assign corresponding weights to each first-level risk indicator, and calculate the comprehensive risk based on the calculated first-level risk indicator values ​​and corresponding weights; S5. Risk level classification: Use the equal frequency method to classify the primary risk indicators and comprehensive risk indicators into five levels: no risk, low risk, medium risk, medium-high risk, and high risk.

2. The multi-objective reservoir drought dispatch risk identification and assessment method according to claim 1 is characterized by: In step S1, The secondary risk indicators obtained by decomposing the primary risk indicator flood control include the reservoir's own risk rate, flood control risk rate, flood control storage capacity failure risk rate, and downstream river flood control risk rate; The secondary risk indicators obtained by decomposing the primary risk indicator power generation include the risk rate of insufficient power generation, the risk rate of insufficient output, and the risk rate of water abandonment; The secondary risk indicators obtained by decomposing the primary risk indicator water supply include the risk rate of insufficient urban water supply, the risk rate of insufficient industrial water supply, and the risk rate of insufficient agricultural irrigation water supply; The secondary risk indicators obtained by decomposing the primary risk indicator shipping include the upstream shipping shortage risk rate and the downstream shipping shortage risk rate; The secondary risk indicators obtained from the ecological decomposition of the primary risk indicators include the risk rate of insufficient ecological assurance in downstream sections.

3. The multi-objective reservoir drought dispatch risk identification and assessment method according to claim 2 is characterized by: The calculation method of the secondary risk index of flood control for the primary risk index is: Reservoir's own risk rate: Among them, A1 is the risk rate of the reservoir itself; a1 is the number of floods exceeding the design flood level of the reservoir; a is the total number of floods; Flood risk rate: Among them, A2 is the flood control risk rate; a2 is the number of times the water level upstream of the reservoir exceeds the established flood limit water level; a is the total number of times; Risk rate of flood control storage capacity failure: Among them, A3 is the risk rate of reservoir flood control failure; a i is the reservoir water level and storage capacity corresponding to time i; a3 is the storage capacity corresponding to the flood control limit water level; a4 is the design flood level; Downstream river flood risk rate: Among them, A4 is the flood control risk rate of the downstream river; a5 is the number of times the safe discharge of the downstream river is exceeded; a 泄流 It is the total number of reservoir discharge events.

4. The multi-objective reservoir drought dispatch risk identification and assessment method according to claim 2 is characterized by: The calculation method of the secondary risk index of primary risk index power generation is: Risk rate of insufficient power generation: Among them, B1 is the risk rate of insufficient power generation; b1 is the number of times the actual power generation is less than the planned target power generation; b2 is the total number of power generation; Risk rate of insufficient output: Among them, B2 is the risk rate of insufficient output; b3 is the number of times the actual output is less than the planned output; b4 is the total number of outputs; Risk rate of water abandonment: Among them, B3 is the risk rate of water abandonment; b5 is the number of times the reservoir discharge is greater than the power generation flow; and b2 is the total number of power generation times.

5. The multi-objective reservoir drought dispatch risk identification and assessment method according to claim 2 is characterized by: The calculation method of the secondary risk index of the primary risk index water supply is, Risk rate of insufficient urban water supply: Among them, C1 is the risk rate of insufficient urban water supply; c1 is the number of reservoir discharges corresponding to the urban water supply level / flow; c is the total number of reservoir discharges; Risk rate of insufficient industrial water supply: Among them, C2 is the risk rate of insufficient industrial water supply; c2 is the number of reservoir discharges corresponding to the industrial water supply level / flow; c is the total number of reservoir discharges; Risk rate of insufficient water supply for agricultural irrigation: Among them, C3 is the risk rate of insufficient water supply for agricultural irrigation; c3 is the number of reservoir discharge flows corresponding to the agricultural irrigation water supply water level / flow; and c is the total number of reservoir discharges.

6. The multi-objective reservoir drought dispatch risk identification and assessment method according to claim 2 is characterized by: The calculation method of the secondary risk index of shipping is as follows: Risk rate of insufficient upstream shipping: Among them, D1 is the risk rate of insufficient upstream navigation; d1 is the number of reservoir discharges that do not meet the upstream navigation water level / flow; c is the total number of reservoir discharges; Downstream shipping shortage risk rate: Among them, D2 is the risk rate of insufficient downstream navigation; d2 is the number of reservoir discharge flow events that do not meet the downstream navigation water level / flow; c is the total number of reservoir discharge events.

7. The multi-objective reservoir drought dispatch risk identification and assessment method according to claim 2 is characterized by: The calculation method of the secondary risk indicator of the primary risk indicator ecosystem is: Risk rate of insufficient ecological guarantee in downstream sections: Among them, E2 is the risk rate of insufficient downstream navigation; e1 is the number of reservoir discharge flow events that does not meet the ecological guarantee flow of the downstream section; and e is the total number of reservoir discharge events.

8. The multi-objective reservoir drought dispatch risk identification and assessment method according to claim 1 is characterized by: The formula for calculating the comprehensive risk is: Among them, B is the comprehensive risk; B1, B2, B3, B4, B5 are the first-level risk indicators of flood control, power generation, water supply, shipping, and ecology; w1, w2, w3, w4, w5 are the weights of the first-level risk indicators of flood control, power generation, water supply, shipping, and ecology; R1, R2, R3, R4, R5 are the second-level risk indicators corresponding to each first-level risk indicator converted to obtain the advantage matrix; w 11 、w 12 、w 13 、w 14 are the weights of the secondary risk indicators, namely, the reservoir’s own risk rate, flood control risk rate, flood control storage capacity failure risk rate, and downstream river flood control risk rate; w 21 、w 22 、w 23 are the weights of the secondary risk indicators: insufficient power generation risk rate, insufficient output risk rate, and water abandonment risk rate; w 31 、w 32 、w 33 are the weights of the secondary risk indicators: urban domestic water supply shortage risk rate, industrial water supply shortage risk rate, and agricultural irrigation water supply shortage risk rate; w 41 、w 42 are the weights of the secondary risk indicators upstream shipping shortage risk rate and downstream shipping shortage risk rate; w 51 、w 52 ,…,w 5t are the weights of the risk rate of insufficient ecological assurance of each downstream section, and t is the number of downstream sections.

9. The multi-objective reservoir drought dispatch risk identification and assessment method according to claim 1 is characterized by: Step S5 specifically comprises: classifying the primary risk indicators by using the equal frequency method based on the secondary risk indicator values, and classifying the comprehensive risk indicators by using the equal frequency method based on the primary risk indicator values.

10. The multi-objective reservoir drought dispatch risk identification and assessment method according to claim 9 is characterized in that: The equal frequency method is used to divide the risk indicators, including the following contents: S51, sort the indicator results and arrange all sample data from small to large; S52. Divide the sample data into multiple groups according to the research purpose; S53, calculating the upper bound of each interval according to the determined number of intervals; Among them, Q k is the kth upper bound, k=1,2,…,(n-1); n is the number of intervals; N is the total number of data points; S54, using the upper bound of each interval, determining the boundary of each interval; edges=[Q0,Q1,Q2,…,Q n ] Among them, edges are boundaries; Q0 is the minimum value of the sample data; Q n is the maximum value of the sample data; S55. Determine the interval range of each group based on the sorted sample data; the upper limit of each category or group is the value of the last data sample of the group, and the lower limit is the upper limit of the previous group.

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