CN111460674B - Flood pulse design method for ecological flow process - Google Patents

Abstract

The invention discloses a flood pulse design method for an ecological flow process, which belongs to the technical field of ecological hydrological branches in geophysical environment and comprises the following steps: 1) according to the long series daily average flow data, calculating the average value of the flood pulse indexes in the past year and the average flow in the past year; 2) respectively constructing joint probability distribution between the average value of the historical flood pulse indexes and the annual average flow by using a Copula function, and further calculating the conditional probability of different hydrological annual pulse indexes; 3) and for the basic ecological flow process, establishing the correlation between the conditional probabilities and the joint probabilities of flood pulse indexes of different hydrologic years according to the definition of the conditional probabilities, and calculating the corresponding index values as the design values of the flood pulses. The invention makes up the defect that the existing ecological flow analysis method system lacks a flood pulse design method, improves the utilization efficiency of hydrological observation data, and improves the rationality of ecological flow analysis results and the river ecological environment protection capability.

Description

Flood pulse design method for ecological flow process

Technical Field

The invention belongs to the technical field of ecological hydrological branches in geophysical, and particularly relates to a flood pulse design method in an ecological flow process.

Background

The river and lake ecological environment water demand calculation specification (SL/Z712-2014) indicates that river and lake ecological environment water demand comprises river channel ecological environment water demand and river channel external ecological environment water demand. The ecological environment water demand in the river channel refers to an ecological environment protection target given for maintaining rivers, lakes and marshes, and the water quantity in the river channel needs to be reserved. The water requirement of the ecological environment in the river channel can be subdivided into the water requirement of the basic ecological environment in the river channel and the water requirement of the target ecological environment in the river channel. The water demand of the basic ecological environment in the river channel maintains the ecological environment function corresponding to the given ecological environment protection target of rivers, lakes and marshes without losing, and the minimum water quantity required to be reserved in the river channel is a lower limit value of the water demand requirement of the ecological environment in the river channel. The water demand of the target ecological environment in the river channel is the normal play of the ecological environment function corresponding to the ecological environment protection target given by rivers, lakes and marshes, and the water quantity required to be reserved in the river channel is a control value of the water consumption of rivers and lakes in the economic society outside the river channel. For convenience of expression, the basic ecological environment water demand in the river and the target ecological environment water demand in the river are simplified and expressed as basic ecological flow and target ecological flow.

At present, the analysis methods of ecological flow are hundreds of types, and can be roughly divided into a hydrology method, a hydraulics method, a habitat simulation method, an overall analysis method and the like according to the method type attributes. And a corresponding ecological flow analysis method is provided aiming at the specific ecological environment characteristics or functions of the river. For example, "an ecological water demand season difference rapid analysis method (CN 101650763 a)", "an ecological water demand month scale visual analysis method (CN 105808947 a) based on sand transportation water demand", "a tidal river reach ecological environment water demand calculation method (CN 107908888A)", "a river mouth ecological water demand calculation method (CN 108830033 a) considering ecological system net productivity", "an ecological water demand accounting method (CN 110414051 a) for inhibiting river water bloom", and the like.

River flood pulses are an important ecological hydrological process and play an important role in conveying silt and nutrients to the downstream of a river, flushing the river, shaping the shape of the river bed and purifying water quality. Flood pulses are the primary driving force for the survival, productivity and interaction of river and riparian systems, promoting mass transfer, energy exchange and information transfer in aquatic, land-water and land systems. The water flow and the water level fluctuation change cause the change of the water flow velocity and the flow state, and the associated adaptive biological behavior and ecological process directly or indirectly influence the composition and population density of aquatic or terrestrial biological communities. The flood pulse process can be regarded as interference on a river ecosystem, the ecological effects generated by the flood pulse processes with different magnitudes are different, and especially, the huge and rare flood can damage the river ecosystem and even cause disastrous results. According to the moderate interference hypothesis, moderate interference generated by the medium and small flood pulse processes has more beneficial influence on the biological community diversity of the river ecosystem.

When the ecological flow process is analyzed, a flood pulse process needs to be considered, and the flood peak flow, the water rising rate, the water falling rate, the duration and the occurrence frequency of the flood pulse are determined, but a flood pulse design method is not available in the current ecological flow analysis method system. For this reason, flood pulse design methods for ecological flux processes need to be developed.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a flood pulse design method in an ecological flow process, which overcomes the defect that the existing ecological flow analysis method system lacks a flood pulse design method, improves the utilization efficiency of hydrological observation data, and improves the rationality of ecological flow analysis results and the river ecological environment protection capability.

The technical scheme is as follows: in order to achieve the purpose, the invention provides the following technical scheme:

a flood pulse design method for an ecological flow process comprises the following steps:

1) according to the long series daily average flow data, calculating the average value of the flood pulse indexes in the past year and the average flow in the past year;

2) respectively constructing joint probability distribution between the average value of the historical flood pulse indexes and the annual average flow by using a Copula function, and further calculating the conditional probability of different hydrological annual pulse indexes;

3) for the basic ecological flow process, establishing the correlation between the conditional probability and the joint probability of flood pulse indexes of different hydrological years according to the definition of the conditional probability, setting the 90% conditional probability of the dry year as the conditional probability target of the pulse indexes, and calculating the corresponding index value as the design value of the flood pulse; and for the target ecological flow process, setting the 50% conditional probability of the open water year as the conditional probability target of the pulse index, and calculating the corresponding index value as the design value of the flood pulse.

Further, in step 1), the average value of the historical flood pulse indexes includes:

peak flow X₁: peak flow in single flood pulse process, unit m³/s；

Pulse water expansion rate X₂: starting from the water rise of the base flow, the flow rate is increased until the peak flow rate and the average water rise rate of flood pulses are reached, and the unit m is³/s/day；

Pulse water falling rate X₃: starting from the flood peak discharge, the flow decreases until it falls back to the base flow, the average discharge rate of the flood pulse, in m³/s/day；

Duration of pulse X₄: the number of days, in units of days, during which the complete fluctuation process of a single flood pulse lasts;

frequency of pulses X₅: the times of flood pulses in a certain year are dimensionless;

the annual average flow of the past years is the annual average flow X₆: annual average of flow process, unit m³/s。

Further, in step 2), the step of respectively constructing a joint probability distribution between the average value of the historical flood pulse indexes and the annual average flow rate by using the Copula function includes the following steps:

2.1) respectively carrying out hydrological frequency analysis based on the flood peak flow sequence, the pulse water rise rate sequence, the pulse water fall rate sequence, the pulse duration sequence, the pulse frequency sequence and the annual average flow sequence to determine the edge distribution function of the flood peak flow

Edge distribution function of pulse water expansion rate

Edge distribution function of pulse water falling rate

Duration of pulseEdge distribution function of

Edge distribution function of pulse frequency

Edge distribution function of annual average flow

Pearson type III (P-III) distribution functions are often employed for univariate hydrological frequency analysis;

2.2) based on the edge distribution function of 2.1), adopting Copula function to respectively construct a two-dimensional combined distribution function of flood peak flow and annual average flow

Two-dimensional joint distribution function of pulse water expansion rate and annual average flow

Two-dimensional joint distribution function of pulse water falling rate and annual average flow

Two-dimensional joint distribution function of pulse duration and annual average flow

Two-dimensional joint distribution function of pulse frequency and annual average flow

The Copula function is applied to multivariate hydrological frequency analysis, and edge distribution of a plurality of random variables is combined to obtain combined distribution of the multivariate hydrological frequency analysis, wherein the combined distribution mainly comprises 3 types, namely an elliptic type, an Archimedes type and a quadratic type; analyzing common Archimedes type Copula functions in hydrological frequency, wherein the common Archimedes type Copula functions comprise Gumbel Copula functions, Frank Copula functions, Clayton Copula functions, Ali-Mikhail-Haq Copula functions and the like; the Copula function is expressed as:

in the formula (I), the compound is shown in the specification,

copula function of flood peak flow and annual average flow;

copula function of pulse water expansion rate and annual average flow;

copula function of pulse water falling rate and annual average flow;

copula function of pulse duration and annual average flow;

copula function of pulse frequency and annual average flow.

Further, in step 2), the conditional probabilities of different hydrological annual pulse indexes are calculated, and different hydrological annual types are established according to the definition of the conditional probabilitiesCorrelation between the conditional probability and joint probability of flood pulse indexes; the hydrologic year type refers to the dry year and the open year, and the average flow of the dry year is taken to obtain the annual average flow x with 90 percent of guarantee rate_6,90％Annual average flow of 50% guarantee rate of annual average flow measurement in open water_6,50％(ii) a Specifically, the method comprises the following steps:

2.3) for dry year, take P (x)₆≥x_6,90％) 0.9; establishing a correlation relation between the conditional probability and the joint probability of flood pulse indexes in the dry year:

P(x₁≥x_{1, design value of dry year},x₆≥x_6,90％)＝P(x₁≥x_{1, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₂≥x_{2, design value of dry year},x₆≥x_6,90％)＝P(x₂≥x_{2, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₃≥x_{3, design value of dry year},x₆≥x_6,90％)＝P(x₃≥x_{3, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₄≥x_{4, design value of dry year},x₆≥x_6,90％)＝P(x₄≥x_{4, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₅≥x_{5, design value of dry year},x₆≥x_6,90％)＝P(x₅≥x_{5, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

In the formula, P (x)₁≥x_{1, design value of dry year},x₆≥x_6,90％) Is the peak flow x₁≥x_{1, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₁≥x_{1, dry year facilityEvaluating value}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Peak flow x under occurrence conditions₁≥x_{1, design value of dry year}The conditional probability of occurrence; p (x)₂≥x_{2, design value of dry year},x₆≥x_6,90％) Is the pulse water expansion rate x₂≥x_{2, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₂≥x_{2, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Pulse water expansion rate x under generating condition₂≥x_{2, design value of dry year}The conditional probability of occurrence; p (x)₃≥x_{3, design value of dry year},x₆≥x_6,90％) As pulse water fall rate x₃≥x_{3, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₃≥x_{3, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Pulse water falling rate x under occurrence conditions₃≥x_{3, design value of dry year}The conditional probability of occurrence; p (x)₄≥x_{4, design value of dry year},x₆≥x_6,90％) For a pulse duration x₄≥x_{4, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₄≥x_{4, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Duration of pulse under generating conditions x₄≥x_{4, design value of dry year}The conditional probability of occurrence; p (x)₅≥x_{5, design value of dry year},x₆≥x_6,90％) Is the pulse frequency x₅≥x_{5, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₅≥x_{5, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Frequency of pulses x under the occurrence conditions₅≥x_{5, design value of dry year}The conditional probability of occurrence;

2.4) for open water years, take P (x)₆≥x_6,50％) 0.5; establishing a correlation relation between the conditional probability and the joint probability of the flood pulse indexes in the open water:

P(x₁≥x_{1, design value in open water},x₆≥x_6,50％)＝P(x₁≥x_{1, design value in open water}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₂≥x_{2, design value in horizontal year},x₆≥x_6,50％)＝P(x₂≥x_{2, design value in horizontal year}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₃≥x_{3, design value in open water year},x₆≥x_6,50％)＝P(x₃≥x_{3, design value in open water year}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₄≥x_{4, open water annual design value},x₆≥x_6,50％)＝P(x₄≥x_{4, open water annual design value}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₅≥x_{5, design value in open water},x₆≥x_6,50％)＝P(x₅≥x_{5, design value in open water}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

In the formula, P (x)₁≥x_{1, design value in open water},x₆≥x_6,50％) Is the peak flow x₁≥x_{1, design value in open water}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₁≥x_{1, design value in open water}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Peak flow x under occurrence conditions₁≥x_{1, design value in open water}The conditional probability of occurrence; p (x)₂≥x_{2, design value in horizontal year},x₆≥x_6,50％) Is the pulse water expansion rate x₂≥x_{2, design value in horizontal year}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₂≥x_{2, design value in horizontal year}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Pulse water expansion rate x under generating condition₂≥x_{2, design value in horizontal year}The conditional probability of occurrence; p (x)₃≥x_{3, design value in open water year},x₆≥x_6,50％) As pulse water fall rate x₃≥x_{3, design value in open water year}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₃≥x_{3, design value in open water year}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Pulse water falling rate x under occurrence conditions₃≥x_{3, design value in open water year}The conditional probability of occurrence; p (x)₄≥x_{4, open water annual design value},x₆≥x_6,50％) For a pulse duration x₄≥x_{4, open water annual design value}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₄≥x_{4, open water annual design value}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Duration of pulse under generating conditions x₄≥x_{4, open water annual design value}The conditional probability of occurrence; p (x)₅≥x_{5, design value in open water},x₆≥x_6,50％) Is the pulse frequency x₅≥x_{5, design value in open water}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₅≥x_{5, design value in open water}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Frequency of pulses x under the occurrence conditions₅≥x_{5, design value in open water}Conditional probability of occurrence.

Further, in the step 3), for the basic ecological flow process, setting the 90% conditional probability of the dry year as a conditional probability target of a flood pulse index, and calculating a corresponding index value as a flood pulse design value; for the target ecological flow process, setting the 50% conditional probability of the open water year as the conditional probability target of the flood pulse index, and calculating the corresponding index value as the design value of the flood pulse; specifically, the method comprises the following steps:

3.1) for the basic ecological flow process, setting the conditional probability of 90% in dry year as the conditional probability target of the flood pulse index:

P(x₁≥x_{1, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₂≥x_{2, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₃≥x_{3, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₄≥x_{4, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₅≥x_{5, design value of dry year}|x₆≥x_6,90％)＝0.9；

Solving for P (x) from the formula in 2.3)₁≥x_{1, design value of dry year},x₆≥x_6,90％)、P(x₂≥x_{2, design value of dry year},x₆≥x_6,90％)、P(x₃≥x_{3, design value of dry year},x₆≥x_6,90％)、P(x₄≥x_{4, design value of dry year},x₆≥x_6,90％)、P(x₅≥x_{5, design value of dry year},x₆≥x_6,90％)；

Solving P (x) by Copula joint distribution function in 2.2)₁≥x_{1, design value of dry year},x₆≥x_6,90％) Corresponding peak flow assurance rate P (x)₁≥x_{1, design value of dry year})、P(x₂≥x_{2, design value of dry year},x₆≥x_6,90％) Corresponding pulse water expansion rate guarantee rate P (x)₂≥x_{2, design value of dry year})、P(x₃≥x_{3, design value of dry year},x₆≥x_6,90％) Corresponding pulse water falling rate guarantee rate P (x)₃≥x_{3, design value of dry year})、P(x₄≥x_{4, design value of dry year},x₆≥x_6,90％) Corresponding pulse duration guarantee rate P (x)₄≥x_{4, design value of dry year})、P(x₅≥x_{5, design value of dry year},x₆≥x_6,90％) Corresponding pulse frequency guarantee rate P (x)₅≥x_{5, design value of dry year})；

Solving for P (x) from the edge distribution function in 2.1)₁≥x_{1, design value of dry year}) Corresponding peak flow design value x_{1, design value of dry year}That is, the peak flow design value x in the basic ecological flow process_{1, basic ecological flux}；P(x₂≥x_{2, design value of dry year}) Corresponding design value x of pulse water expansion rate_{2, design value of dry year}That is, the design value x of the pulse water expansion rate in the basic ecological flow process_{2, basic ecological flux}；P(x₃≥x_{3, design value of dry year}) Corresponding design value x of pulse water falling rate_{3, design value of dry year}That is, the design value x of the pulse water falling rate in the basic ecological flow process_{3, basic ecological flux}；P(x₄≥x_{4, design value of dry year}) Design value x of corresponding pulse duration_{4, design value of dry year}I.e. the design value x of the pulse duration of the basic ecological flow process_{4, basic ecological flux}；P(x₅≥x_{5, design value of dry year}) Corresponding pulse frequency design value x_{5, design value of dry year}I.e. the design value x of the pulse frequency of the basic ecological flow process_{Basic ecological flux}；

3.2) for the target ecological flow process, setting the 50% conditional probability of the open water year as the conditional probability target of the flood pulse index:

P(x₁≥x_{1, design value in open water}|x₆≥x_6,50％)＝0.5；

P(x₂≥x_{2, design value in horizontal year}|x₆≥x_6,50％)＝0.5；

P(x₃≥x_{3, design value in open water year}|x₆≥x_6,50％)＝0.5；

P(x₄≥x_{4, open water annual design value}|x₆≥x_6,50％)＝0.5；

P(x₅≥x_{5, design value in open water}|x₆≥x_6,50％)＝0.5；

Solving for P (x) from the formula in 2.4)₁≥x_{1, design value in open water},x₆≥x_6,50％)、P(x₂≥x_{2, design value in horizontal year},x₆≥x_6,50％)、P(x₃≥x_{3, design value in open water year},x₆≥x_6,50％)、P(x₄≥x_{4, open water annual design value},x₆≥x_6,50％)、P(x₅≥x_{5, design value in open water},x₆≥x_6,50％)；

Solving P (x) by Copula joint distribution function in 2.2)₁≥x_{1, design value in open water},x₆≥x_6,50％) Corresponding peak flow assurance rate P (x)₁≥x_{1, design value in open water})、P(x₂≥x_{2, design value in horizontal year},x₆≥x_6,50％) Corresponding pulse water expansion rate guarantee rate P (x)₂≥x_{2, design value in horizontal year})、P(x₃≥x_{3, design value in open water year},x₆≥x_6,50％) Corresponding pulse water falling rate guarantee rate P (x)₃≥x_{3, design value in open water year})、P(x₄≥x_{4, open water annual design value},x₆≥x_6,50％) Corresponding pulse duration guarantee rate P (x)₄≥x_{4, open water annual design value})、P(x₅≥x_{5, design value in open water},x₆≥x_6,50％) Corresponding pulse frequency guarantee rate P (x)₅≥x_{5, design value in open water})；

Solving for P (x) from the edge distribution function in 2.1)₁≥x_{1, design value in open water}) Corresponding peak flow design value x_{1, design value in open water}That is, the peak flow design value x of the target ecological flow process_{1, target ecological flux}；P(x₂≥x_{2, design value in horizontal year}) Corresponding design value x of pulse water expansion rate_{2, design value in horizontal year}Namely the design value x of the pulse water expansion rate of the target ecological flow process_{2, target ecological flux}；P(x₃≥x_{3, design value in open water year}) Corresponding design value x of pulse water falling rate_{3, design value in open water year}That is, the design value x of the pulse water falling rate in the target ecological flow process_{3, target ecological flux}；P(x₄≥x_{4, open water annual design value}) Design value x of corresponding pulse duration_{4, open water annual design value}I.e. the design value x of the pulse duration of the target ecological traffic process_{4, target ecological flux}；P(x₅≥x_{5, design value in open water}) Corresponding pulse frequency design value x_{5, design value in open water}I.e. the design value x of the pulse frequency of the target ecological flow process_{Target ecological flux}。

Has the advantages that: compared with the prior art, the flood pulse design method for the ecological flow process has the advantages that different protection targets of ecological environment are considered in the flood pulse design of the ecological flow process, flood pulse index values including flood peak flow, pulse water rising rate, pulse water falling rate, pulse duration and pulse frequency are designed aiming at the basic ecological flow process and the target ecological flow process, and different requirements of reservoir ecological scheduling, river health regulation, water resource optimization configuration and the like can be met; on the other hand, in the flood pulse index design, different conditional probabilities are set for different hydrological years such as a dry year and an open year, the annual rich and lean change characteristics of the natural hydrological situation and the river habitat diversity are favorably maintained, the defect that the existing ecological flow analysis method system is lack of the flood pulse design method is overcome, the utilization efficiency of hydrological observation data is improved, the rationality of ecological flow analysis results and the river ecological environment protection capability are improved, and the protection effect of a river ecological system is improved.

Drawings

FIG. 1 is a flow chart of a flood pulse design method for an ecological flow process;

FIG. 2 is the average flow of Majinxi in Zhejiang province, month by month, over many years;

FIG. 3 is the annual average flow and annual average flood pulse indexes of Majinxi in Zhejiang province;

fig. 4 is a probability distribution of the ma jinxi flood impulse index and the annual average flow rate in zhejiang.

Detailed Description

The invention will be further described with reference to the following drawings and specific embodiments.

A flood pulse design method for ecological flow process, the flood pulse changes with the hydrology, the characteristics of flood peak flow, pulse change rate, pulse duration and frequency also present a certain fluctuation change characteristic, for the basic ecological flow and target ecological flow process, the design value of flood pulse index has a difference, figure 1 is the flow chart of the invention, the concrete steps are as follows:

(1) daily average flow (m) according to long series³And/s) data, counting average values of flood pulse indexes over the years, including flood peak flow, pulse water rising rate, pulse water falling rate, pulse duration and pulse frequency, and counting average flow over the years. The specific meanings of each flood pulse index and the annual average flow are as follows:

peak flow X₁: peak flow in single flood pulse process, unit m³/s；

Pulse water expansion rate X₂: starting from the water rise of the base flow, the flow rate is increased until the peak flow rate and the average water rise rate of flood pulses are reached, and the unit m is³/s/day；

Pulse water falling rate X₃: starting from the flood peak discharge, the flow decreases until it falls back to the base flow, the average discharge rate of the flood pulse, in m³/s/day；

Duration of pulse X₄: the number of days, in units of days, during which the complete fluctuation process of a single flood pulse lasts;

frequency of pulses X₅: the times of flood pulses in a certain year are dimensionless;

average annual flow X₆: annual average of flow process, unit m³/s；

(2) Respectively constructing combined probability distribution among peak flow, pulse water rising rate, pulse water falling rate, pulse duration, pulse frequency and annual average flow by utilizing a Copula function; specifically, the method comprises the following steps:

respectively carrying out hydrological frequency analysis based on a flood peak flow sequence, a pulse water rise rate sequence, a pulse water fall rate sequence, a pulse duration sequence, a pulse frequency sequence and an annual average flow sequence to determine an edge distribution function of the flood peak flow

Edge distribution function of pulse water expansion rate

Edge distribution function of pulse water falling rate

Edge distribution function of pulse duration

Edge distribution function of pulse frequency

Edge distribution function of annual average flow

In the hydrological frequency analysis of China, a Pearson III type (P-III) distribution function is often adopted for univariate hydrological frequency analysis;

secondly, based on the edge distribution function of the first step, a Copula function is adopted to respectively construct a two-dimensional combined distribution function of the flood peak flow and the annual average flow

Two-dimensional joint distribution function of pulse water expansion rate and annual average flow

Two-dimensional combined distribution of pulse water falling rate and annual average flowFunction(s)

Two-dimensional joint distribution function of pulse duration and annual average flow

Two-dimensional joint distribution function of pulse frequency and annual average flow

The Copula function is applied to multivariate hydrological frequency analysis, and can combine edge distribution of a plurality of random variables to obtain combined distribution of the random variables, wherein the combined distribution mainly comprises 3 types, namely an elliptic type, an Archimedes type and a quadratic type. Commonly used Archimedes-type Copula functions in the hydrological frequency analysis include Gumbel Copula functions, Frank Copula functions, Clayton Copula functions, Ali-Mikhail-Haq Copula functions, and the like. The Copula function can be expressed as:

in the formula (I), the compound is shown in the specification,

the peak flow and the annual averageCopula function of the flow;

copula function of pulse water expansion rate and annual average flow;

copula function of pulse water falling rate and annual average flow;

copula function of pulse duration and annual average flow;

copula function of pulse frequency and annual average flow;

(3) and establishing the correlation between the conditional probabilities and the joint probabilities of the flood pulse indexes of different hydrologic years according to the definition of the conditional probabilities. The hydrologic year type refers to the dry year and the open year, and the annual average flow rate of the dry year can be 90 percent of the guarantee rate x_6,90％The annual average flow of the average flow in the horizontal year can be taken as 50 percent of guarantee rate annual average flow x_6,50％(ii) a Specifically, the method comprises the following steps:

for dry water year, P (x) can be taken₆≥x_6,90％) 0.9. Establishing a correlation relation between the conditional probability and the joint probability of flood pulse indexes in the dry year:

P(x₁≥x_{1, design value of dry year},x₆≥x_6,90％)＝P(x₁≥x_{1, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₂≥x_{2, design value of dry year},x₆≥x_6,90％)＝P(x₂≥x_{2, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₃≥x_{3, design value of dry year},x₆≥x_6,90％)＝P(x₃≥x_{3, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₄≥x_{4, design value of dry year},x₆≥x_6,90％)＝P(x₄≥x_{4, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₅≥x_{5, design value of dry year},x₆≥x_6,90％)＝P(x₅≥x_{5, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

In the formula, P (x)₁≥x_{1, design value of dry year},x₆≥x_6,90％) Is the peak flow x₁≥x_{1, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₁≥x_{1, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Peak flow x under occurrence conditions₁≥x_{1, design value of dry year}The conditional probability of occurrence; p (x)₂≥x_{2, design value of dry year},x₆≥x_6,90％) Is the pulse water expansion rate x₂≥x_{2, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₂≥x_{2, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Pulse water expansion rate x under generating condition₂≥x_{2, design value of dry year}The conditional probability of occurrence; p (x)₃≥x_{3, design value of dry year},x₆≥x_6,90％) As pulse water fall rate x₃≥x_{3, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₃≥x_{3, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Pulse water falling rate x under occurrence conditions₃≥x_{3, design value of dry year}The conditional probability of occurrence; p (x)₄≥x_{4, design value of dry year},x₆≥x_6,90％) For a pulse duration x₄≥x_{4, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₄≥x_{4, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Duration of pulse under generating conditions x₄≥x_{4, design value of dry year}The conditional probability of occurrence; p (x)₅≥x_{5, design value of dry year},x₆≥x_6,90％) Is the pulse frequency x₅≥x_{5, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₅≥x_{5, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Frequency of pulses x under the occurrence conditions₅≥x_{5, design value of dry year}The conditional probability of occurrence;

② for the horizontal year, P (x) can be taken₆≥x_6,50％) 0.5. Establishing a correlation relation between the conditional probability and the joint probability of the flood pulse indexes in the open water:

P(x₁≥x_{1, design value in open water},x₆≥x_6,50％)＝P(x₁≥x_{1, design value in open water}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₂≥x_{2, design value in horizontal year},x₆≥x_6,50％)＝P(x₂≥x_{2, design value in horizontal year}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₃≥x_{3, design value in open water year},x₆≥x_6,50％)＝P(x₃≥x_{3, design value in open water year}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₄≥x_{4, open water annual design value},x₆≥x_6,50％)＝P(x₄≥x_{4, open water annual design value}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₅≥x_{5, design value in open water},x₆≥x_6,50％)＝P(x₅≥x_{5, design value in open water}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

In the formula, P (x)₁≥x_{1, design value in open water},x₆≥x_6,50％) Is the peak flow x₁≥x_{1, design value in open water}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₁≥x_{1, design value in open water}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Peak flow x under occurrence conditions₁≥x_{1, design value in open water}The conditional probability of occurrence; p (x)₂≥x_{2, design value in horizontal year},x₆≥x_6,50％) Is the pulse water expansion rate x₂≥x_{2, design value in horizontal year}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₂≥x_{2, design value in horizontal year}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Pulse water expansion rate x under generating condition₂≥x_{2, design value in horizontal year}The conditional probability of occurrence; p (x)₃≥x_{3, design value in open water year},x₆≥x_6,50％) As pulse water fall rate x₃≥x_{3, design value in open water year}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₃≥x_{3, design value in open water year}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Pulse water falling rate x under occurrence conditions₃≥x_{3, design value in open water year}The conditional probability of occurrence; p (x)₄≥x_{4, open water annual design value},x₆≥x_6,50％) For a pulse duration x₄≥x_{4, open water annual design value}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₄≥x_{4, open water annual design value}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Duration of pulse under generating conditions x₄≥x_{4, open water annual design value}The conditional probability of occurrence; p (x)₅≥x_{5, design value in open water},x₆≥x_6,50％) Is the pulse frequency x₅≥x_{5, design value in open water}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₅≥x_{5, design value in open water}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Frequency of pulses x under the occurrence conditions₅≥x_{5, design value in open water}The conditional probability of occurrence;

(4) for the basic ecological flow process, the condition probability of 90% in dry year can be set as the condition probability target of the flood pulse index, and the corresponding index value is calculated to be used as the design value of the flood pulse; for the target ecological flow process, the 50% conditional probability in the open water year can be set as the conditional probability target of the flood pulse index, and the corresponding index value is calculated to be used as the design value of the flood pulse; specifically, the method comprises the following steps:

for the basic ecological flow process, the conditional probability of 90% in dry year can be set as the conditional probability target of the flood pulse index:

P(x₁≥x_{1, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₂≥x_{2, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₃≥x_{3, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₄≥x_{4, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₅≥x_{5, design value of dry year}|x₆≥x_6,90％)＝0.9；

Solving P (x) by the formula in the step (3) (r)₁≥x_{1, design value of dry year},x₆≥x_6,90％)、P(x₂≥x_{2, design value of dry year},x₆≥x_6,90％)、P(x₃≥x_{3, design value of dry year},x₆≥x_6,90％)、P(x₄≥x_{4, design value of dry year},x₆≥x_6,90％)、P(x₅≥x_{5, design value of dry year},x₆≥x_6,90％)；

Solving P (x) by the Copula joint distribution function in the step (2)₁≥x_{1, design value of dry year},x₆≥x_6,90％) Corresponding peak flow assurance rate P (x)₁≥x_{1, design value of dry year})、P(x₂≥x_{2, design value of dry year},x₆≥x_6,90％) Corresponding pulse water expansion rate guarantee rate P (x)₂≥x_{2, design value of dry year})、P(x₃≥x_{3, design value of dry year},x₆≥x_6,90％) Corresponding pulse water falling rate guarantee rate P (x)₃≥x_{3, design value of dry year})、P(x₄≥x_{4, design value of dry year},x₆≥x_6,90％) Corresponding pulse duration guarantee rate P (x)₄≥x_{4, design value of dry year})、P(x₅≥x_{5, design value of dry year},x₆≥x_6,90％) Corresponding pulse frequency guarantee rate P (x)₅≥x_{5, design value of dry year})；

Solving P (x) by the edge distribution function in the step (2) (-)₁≥x_{1, design value of dry year}) Corresponding peak flow design value x_{1, design value of dry year}That is, the peak flow design value x in the basic ecological flow process_{1, basic ecological flux}；P(x₂≥x_{2, design value of dry year}) Corresponding design value x of pulse water expansion rate_{2, design value of dry year}That is, the design value x of the pulse water expansion rate in the basic ecological flow process_{2, basic ecological flux}；P(x₃≥x_{3, design value of dry year}) Corresponding design value x of pulse water falling rate_{3, design value of dry year}That is, the design value x of the pulse water falling rate in the basic ecological flow process_{3, basic ecological flux}；P(x₄≥x_{4, design value of dry year}) Design value x of corresponding pulse duration_{4, design value of dry year}I.e. the design value x of the pulse duration of the basic ecological flow process_{4, basic ecological flux}；P(x₅≥x_{5, design value of dry year}) Corresponding pulse frequency design value x_{5, design value of dry year}I.e. the design value x of the pulse frequency of the basic ecological flow process_{Basic ecological flux}；

Secondly, for the target ecological flow process, the condition probability of 50% in the open water year can be set as the condition probability target of the flood pulse index:

P(x₁≥x_{1, design value in open water}|x₆≥x_6,50％)＝0.5；

P(x₂≥x_{2, design value in horizontal year}|x₆≥x_6,50％)＝0.5；

P(x₃≥x_{3, design value in open water year}|x₆≥x_6,50％)＝0.5；

P(x₄≥x_{4, open water annual design value}|x₆≥x_6,50％)＝0.5；

P(x₅≥x_{5, design value in open water}|x₆≥x_6,50％)＝0.5；

Solving P (x) by the formula in the step (3)₁≥x_{1, design value in open water},x₆≥x_6,50％)、P(x₂≥x_{2, design value in horizontal year},x₆≥x_6,50％)、P(x₃≥x_{3, design value in open water year},x₆≥x_6,50％)、P(x₄≥x_{4, open water annual design value},x₆≥x_6,50％)、P(x₅≥x_{5, design value in open water},x₆≥x_6,50％)；

Solving P (x) by the Copula joint distribution function in the step (2)₁≥x_{1, design value in open water},x₆≥x_6,50％) Corresponding peak flow assurance rate P (x)₁≥x_{1, design value in open water})、P(x₂≥x_{2, design value in horizontal year},x₆≥x_6,50％) Corresponding pulse water expansion rate guarantee rate P (x)₂≥x_{2, design value in horizontal year})、P(x₃≥x_{3, design value in open water year},x₆≥x_6,50％) Corresponding pulse water falling rate guarantee rate P (x)₃≥x_{3, design value in open water year})、P(x₄≥x_{4, open water annual design value},x₆≥x_6,50％) Corresponding pulse duration guarantee rate P (x)₄≥x_{4, open water annual design value})、P(x₅≥x_{5, design value in open water},x₆≥x_6,50％) Corresponding pulse frequency guarantee rate P (x)₅≥x_{5, design value in open water})；

Solving P (x) by the edge distribution function in the step (2) (-)₁≥x_{1, design value in open water}) Corresponding peak flow design value x_{1, design value in open water}That is, the peak flow design value x of the target ecological flow process_{1, target ecological flux}；P(x₂≥x_{2, design value in horizontal year}) Corresponding design value x of pulse water expansion rate_{2, design value in horizontal year}Namely the design value x of the pulse water expansion rate of the target ecological flow process_{2, target ecological flux}；P(x₃≥x_{3, design value in open water year}) Corresponding design value x of pulse water falling rate_{3, design value in open water year}That is, the design value x of the pulse water falling rate in the target ecological flow process_{3, target ecological flux}；P(x₄≥x_{4, open water annual design value}) Design value x of corresponding pulse duration_{4, open water annual design value}I.e. the design value x of the pulse duration of the target ecological traffic process_{4, target ecological flux}；P(x₅≥x_{5, design value in open water}) Corresponding pulse frequency design value x_{5, design value in open water}I.e. the design value x of the pulse frequency of the target ecological flow process_{Target ecological flux}。

Examples

Fig. 1 is a flow chart of a flood pulse design method of an ecological flow process according to the present invention. Qiantang river is the first big river of Zhejiang province, and the watershed area above Hangzhou sluice gate is 41945km². Majinxi is a source of Qiantangjiang south,the Qixi Yangyuan is originated from Qingzhi in Banguo warehouse of Hunning county of Anhui province dam, passes through Jiangtan, a purification Tianling, a south field, a jade pond and a peach forest, is injected into a Qixi river reservoir from northwest to southeast at a west pithead, and is called a Changshan port after being discharged from the reservoir and converged by Xixia, Majin, a bottom book, a sound pit and a city gate. Majinxi total length 102.2km, drainage basin area 1067.46km²The river channel ratio is reduced to 7.1 per thousand, the natural fall is 1047m, the hills in the drainage basin are continuous, the mountain vigor is steep, the canyons are more, and the valley landform gradually widens and flattens below the urban area and town. The average temperature of the Majinxi basin is 16.3 ℃ in many years, the average maximum wind speed of the Majinxi basin is 17.0m/s in many years, the average wind speed of the Majinxi basin is 1.0m/s in many years, the wind direction is NNE, the average precipitation of the Majinxi basin is 1908mm in many years, and the precipitation is mainly concentrated in spring and summer. Table 1 shows the basic and target ecological flows of majinxi in zhejiang province according to the example of the present invention.

TABLE 1 basic and target ecological flow Processes of Majinxi in Zhejiang province

The first step is as follows: long series daily average flow data were collected from Majinxi Dry flow Tinsei hydrology station 1957 and 1996 for 40 years. Marjinxi river basin area controlled by hydrology station of dense race is about 797km². FIG. 2 shows the average flow of Majinxi in Zhejiang province of the invention for many years, with flood pulses concentrated in 3-7 months.

The second step is that: according to the long series daily average flow data, the average values of annual average flow and historical flood pulse indexes are counted, wherein the average values comprise flood peak flow, pulse water rising rate, pulse water falling rate, pulse duration and pulse frequency. Fig. 3(1) - (6) are the indexes of the average annual flow and average annual flood pulse of ma jinxi in zhejiang province according to the embodiment of the invention.

The third step: by utilizing a Copula function, in the embodiment of the invention, Clayton functions of a two-dimensional Copula function family are adopted to respectively construct joint probability distribution among peak flow, pulse water rising rate, pulse water falling rate, pulse duration, pulse frequency and annual average flow; wherein, the hydrologic year type refers to the dry year and the open water year, and respectively corresponds to the annual average flow rate with the 90% guarantee rate and the annual average flow rate with the 50% guarantee rate. Fig. 4(1) - (5) are the probability distribution of the pulse index of ma jinxi flood and the average annual flow rate in zhejiang, according to the embodiment of the present invention.

The fourth step: for the basic ecological flow process, setting the condition probability of 90% in dry year as the condition probability target of the pulse index, and calculating the corresponding index value as the design value of the flood pulse; and for the target ecological flow process, setting the 50% conditional probability of the open water year as the conditional probability target of the pulse index, and calculating the corresponding index value as the design value of the flood pulse. Table 1 shows the design results of flood pulses during the basic ecological flow and target ecological flow of majinxi in zhejiang province according to the example of the present invention.

The application of the flood pulse design method in the ecological flow process is as follows: the method can be used for analyzing flood pulse design values in the ecological flow process, providing design values of flood peak flow, pulse water rising rate, pulse water falling rate, pulse duration and pulse frequency in the basic ecological flow process and the target ecological flow process, refining and enriching analysis results of river ecological water demand, and supporting reservoir ecological scheduling and water resource optimal allocation.

It should be noted that the above description is only a preferred embodiment of the present invention, and it should be understood that various changes and modifications can be made by those skilled in the art without departing from the technical idea of the present invention, and these changes and modifications are included in the protection scope of the present invention.

Claims (5)

1. A flood pulse design method for an ecological flow process is characterized by comprising the following steps: the basic ecological flow refers to the water demand of the basic ecological environment in the river channel, and the target ecological flow refers to the target ecological water demand in the river channel, and the method comprises the following steps:

1) according to the long series daily average flow data, calculating the average value of the flood pulse indexes in the past year and the average flow in the past year;

2) respectively constructing joint probability distribution between the average value of the historical flood pulse indexes and the annual average flow by using a Copula function, further deducing the conditional probability of different hydrological annual pulse indexes, and establishing the correlation between the conditional probability and the joint probability of the different hydrological annual flood pulse indexes according to the definition of the conditional probability;

3) for the basic ecological flow process, setting the condition probability of 90% in dry year as the condition probability target of the pulse index, and calculating the corresponding index value as the design value of the flood pulse; and for the target ecological flow process, setting the 50% conditional probability of the open water year as the conditional probability target of the pulse index, and calculating the corresponding index value as the design value of the flood pulse.

2. The flood pulse design method for the ecological flow process according to claim 1, wherein the flood pulse design method comprises the following steps: in step 1), the average value of the historical flood pulse indexes includes:

peak flow X₁: peak flow in single flood pulse process, unit m³/s；

Pulse water expansion rate X₂: starting from the water rise of the base flow, the flow rate is increased until the peak flow rate and the average water rise rate of flood pulses are reached, and the unit m is³/s/day；

Pulse water falling rate X₃: starting from the flood peak discharge, the flow decreases until it falls back to the base flow, the average discharge rate of the flood pulse, in m³/s/day；

Duration of pulse X₄: the number of days, in units of days, during which the complete fluctuation process of a single flood pulse lasts;

frequency of pulses X₅: the times of flood pulses in a certain year are dimensionless;

the annual average flow of the past years is the annual average flow X₆: annual average of flow process, unit m³/s。

3. The flood pulse design method for the ecological flow process according to claim 2, wherein the flood pulse design method comprises the following steps: in step 2), the method for constructing the joint probability distribution between the average value of the historical flood pulse indexes and the annual average flow rate by using the Copula function comprises the following steps:

2.1) flow sequence based on flood peak, pulse riseRespectively carrying out hydrological frequency analysis on a water rate sequence, a pulse water falling rate sequence, a pulse duration sequence, a pulse frequency sequence and an annual average flow sequence to determine an edge distribution function of flood peak flow

Edge distribution function of pulse water expansion rate

Edge distribution function of pulse water falling rate

Edge distribution function of pulse duration

Edge distribution function of pulse frequency

Edge distribution function of annual average flow

For univariate hydrological frequency analysis, a Pearson type III (P-III) distribution function is adopted;

2.2) based on the edge distribution function of 2.1), adopting Copula function to respectively construct a two-dimensional combined distribution function of flood peak flow and annual average flow

Two-dimensional joint distribution function of pulse water expansion rate and annual average flow

Two-dimensional joint distribution function of pulse water falling rate and annual average flow

Duration of pulse and annual average flow rateDimension union distribution function

Two-dimensional joint distribution function of pulse frequency and annual average flow

The Copula function is expressed as:

in the formula (I), the compound is shown in the specification,

copula function of flood peak flow and annual average flow;

copula function of pulse water expansion rate and annual average flow;

the pulse water falling rate and the annual average flowCopula function of (a);

copula function of pulse duration and annual average flow;

copula function of pulse frequency and annual average flow.

4. A flood pulse design method for ecological flow process according to claim 3, characterized in that: in step 2), the conditional probabilities of different hydrological annual type pulse indexes are calculated, and the correlation between the conditional probabilities and the joint probabilities of the different hydrological annual type flood pulse indexes is established according to the definition of the conditional probabilities; the hydrologic year type refers to the dry year and the open year, and the average flow of the dry year is taken to obtain the annual average flow x with 90 percent of guarantee rate_6,90％Annual average flow of 50% guarantee rate of annual average flow measurement in open water_6,50％(ii) a Specifically, the method comprises the following steps:

2.3) for dry year, take P (x)₆≥x_6,90％) 0.9; establishing a correlation relation between the conditional probability and the joint probability of flood pulse indexes in the dry year:

P(x₁≥x_{1, design value of dry year},x₆≥x_6,90％)＝P(x₁≥x_{1, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₂≥x_{2, design value of dry year},x₆≥x_6,90％)＝P(x₂≥x_{2, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₃≥x_{3, design value of dry year},x₆≥x_6,90％)＝P(x₃≥x_{3, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₄≥x_{4, design value of dry year},x₆≥x_6,90％)＝P(x₄≥x_{4, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

P(x₅≥x_{5, design value of dry year},x₆≥x_6,90％)＝P(x₅≥x_{5, design value of dry year}|x₆≥x_6,90％)P(x₆≥x_6,90％)；

In the formula, P (x)₁≥x_{1, design value of dry year},x₆≥x_6,90％) Is the peak flow x₁≥x_{1, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₁≥x_{1, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Peak flow x under occurrence conditions₁≥x_{1, design value of dry year}The conditional probability of occurrence; p (x)₂≥x_{2, design value of dry year},x₆≥x_6,90％) Is the pulse water expansion rate x₂≥x_{2, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₂≥x_{2, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Pulse water expansion rate x under generating condition₂≥x_{2, design value of dry year}The conditional probability of occurrence; p (x)₃≥x_{3, design value of dry year},x₆≥x_6,90％) As pulse water fall rate x₃≥x_{3, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₃≥x_{3, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Pulse water falling rate x under occurrence conditions₃≥x_{3, design value of dry year}The conditional probability of occurrence; p (x)₄≥x_{4, design value of dry year},x₆≥x_6,90％) For a pulse duration x₄≥x_{4, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₄≥x_{4, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Duration of pulse under generating conditions x₄≥x_{4, design value of dry year}The conditional probability of occurrence; p (x)₅≥x_{5, design value of dry year},x₆≥x_6,90％) Is the pulse frequency x₅≥x_{5, design value of dry year}Average annual flow x₆≥x_6,90％Joint probability of simultaneous occurrence, P (x)₅≥x_{5, design value of dry year}|x₆≥x_6,90％) Mean flow x for year₆≥x_6,90％Frequency of pulses x under the occurrence conditions₅≥x_{5, design value of dry year}The conditional probability of occurrence;

2.4) for open water years, take P (x)₆≥x_6,50％) 0.5; establishing a correlation relation between the conditional probability and the joint probability of the flood pulse indexes in the open water:

P(x₁≥x_{1, design value in open water},x₆≥x_6,50％)＝P(x₁≥x_{1, design value in open water}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₂≥x_{2, design value in horizontal year},x₆≥x_6,50％)＝P(x₂≥x_{2, design value in horizontal year}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₃≥x_{3, design value in open water year},x₆≥x_6,50％)＝P(x₃≥x_{3, design value in open water year}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₄≥x_{4, open water annual design value},x₆≥x_6,50％)＝P(x₄≥x_{4, open water annual design value}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

P(x₅≥x_{5, design value in open water},x₆≥x_6,50％)＝P(x₅≥x_{5, design value in open water}|x₆≥x_6,50％)P(x₆≥x_6,50％)；

In the formula, P (x)₁≥x_{1, design value in open water},x₆≥x_6,50％) Is the peak flow x₁≥x_{1, design value in open water}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₁≥x_{1, design value in open water}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Peak flow x under occurrence conditions₁≥x_{1, design value in open water}The conditional probability of occurrence; p (x)₂≥x_{2, design value in horizontal year},x₆≥x_6,50％) Is the pulse water expansion rate x₂≥x_{2, design value in horizontal year}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₂≥x_{2, design value in horizontal year}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Pulse water expansion rate x under generating condition₂≥x_{2, design value in horizontal year}The conditional probability of occurrence; p (x)₃≥x_{3, design value in open water year},x₆≥x_6,50％) As pulse water fall rate x₃≥x_{3, design value in open water year}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₃≥x_{3, design value in open water year}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Pulse water falling rate x under occurrence conditions₃≥x_{3, design value in open water year}The conditional probability of occurrence; p (x)₄≥x_{4, open water annual design value},x₆≥x_6,50％) For a pulse duration x₄≥x_{4, open water annual design value}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₄≥x_{4, open water annual design value}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Duration of pulse under generating conditions x₄≥x_{4, open water annual design value}The conditional probability of occurrence; p (x)₅≥x_{5, design value in open water},x₆≥x_6,50％) Is the pulse frequency x₅≥x_{5, design value in open water}Average annual flow x₆≥x_6,50％Joint probability of simultaneous occurrence, P (x)₅≥x_{5, design value in open water}|x₆≥x_6,50％) Mean flow x for year₆≥x_6,50％Frequency of pulses x under the occurrence conditions₅≥x_{5, design value in open water}Conditional probability of occurrence.

5. The flood pulse design method for the ecological flow process according to claim 4, wherein the flood pulse design method comprises the following steps: in the step 3), for the basic ecological flow process, setting the 90% conditional probability of the dry year as the conditional probability target of the flood pulse index, and calculating the corresponding index value as the design value of the flood pulse; for the target ecological flow process, setting the 50% conditional probability of the open water year as the conditional probability target of the flood pulse index, and calculating the corresponding index value as the design value of the flood pulse; specifically, the method comprises the following steps:

3.1) for the basic ecological flow process, setting the conditional probability of 90% in dry year as the conditional probability target of the flood pulse index:

P(x₁≥x_{1, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₂≥x_{2, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₃≥x_{3, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₄≥x_{4, design value of dry year}|x₆≥x_6,90％)＝0.9；

P(x₅≥x_{5, design value of dry year}|x₆≥x_6,90％)＝0.9；

Solving for P (x) from the formula in 2.3)₁≥x_{1, design value of dry year},x₆≥x_6,90％)、P(x₂≥x_{2, design value of dry year},x₆≥x_6,90％)、P(x₃≥x_{3, design value of dry year},x₆≥x_6,90％)、P(x₄≥x_{4, design value of dry year},x₆≥x_6,90％)、P(x₅≥x_{5, design value of dry year},x₆≥x_6,90％)；

Solving P (x) by Copula joint distribution function in 2.2)₁≥x_{1, design value of dry year},x₆≥x_6,90％) Corresponding peak flow assurance rate P (x)₁≥x_{1, design value of dry year})、P(x₂≥x_{2, design value of dry year},x₆≥x_6,90％) Corresponding pulse water expansion rate guarantee rate P (x)₂≥x_{2, design value of dry year})、P(x₃≥x_{3, design value of dry year},x₆≥x_6,90％) Corresponding pulse water falling rate guarantee rate P (x)₃≥x_{3, design value of dry year})、P(x₄≥x_{4, design value of dry year},x₆≥x_6,90％) Corresponding pulse duration guarantee rate P (x)₄≥x_{4, design value of dry year})、P(x₅≥x_{5, design value of dry year},x₆≥x_6,90％) Corresponding pulse frequency guarantee rate P (x)₅≥x_{5, design value of dry year})；

Solving for P (x) from the edge distribution function in 2.1)₁≥x_{1, design value of dry year}) Corresponding peak flow design value x_{1, design value of dry year}That is, the peak flow design value x in the basic ecological flow process_{1, basic ecological flux}；P(x₂≥x_{2, design value of dry year}) Corresponding design value x of pulse water expansion rate_{2, design value of dry year}That is, the design value x of the pulse water expansion rate in the basic ecological flow process_{2, basic ecological flux}；P(x₃≥x_{3, design value of dry year}) Corresponding design value x of pulse water falling rate_{3, design value of dry year}That is, the design value x of the pulse water falling rate in the basic ecological flow process_{3, basic ecological flux}；P(x₄≥x_{4, design value of dry year}) To pairDesign value of pulse duration x_{4, design value of dry year}I.e. the design value x of the pulse duration of the basic ecological flow process_{4, basic ecological flux}；P(x₅≥x_{5, design value of dry year}) Corresponding pulse frequency design value x_{5, design value of dry year}I.e. the design value x of the pulse frequency of the basic ecological flow process_{Basic ecological flux}；

3.2) for the target ecological flow process, setting the 50% conditional probability of the open water year as the conditional probability target of the flood pulse index:

P(x₁≥x_{1, design value in open water}|x₆≥x_6,50％)＝0.5；

P(x₂≥x_{2, design value in horizontal year}|x₆≥x_6,50％)＝0.5；

P(x₃≥x_{3, design value in open water year}|x₆≥x_6,50％)＝0.5；

P(x₄≥x_{4, open water annual design value}|x₆≥x_6,50％)＝0.5；

P(x₅≥x_{5, design value in open water}|x₆≥x_6,50％)＝0.5；

Solving for P (x) from the formula in 2.4)₁≥x_{1, design value in open water},x₆≥x_6,50％)、P(x₂≥x_{2, design value in horizontal year},x₆≥x_6,50％)、P(x₃≥x_{3, design value in open water year},x₆≥x_6,50％)、P(x₄≥x_{4, open water annual design value},x₆≥x_6,50％)、P(x₅≥x_{5, design value in open water},x₆≥x_6,50％)；

Solving P (x) by Copula joint distribution function in 2.2)₁≥x_{1, design value in open water},x₆≥x_6,50％) Corresponding peak flow assurance rate P (x)₁≥x_{1, design value in open water})、P(x₂≥x_{2, design value in horizontal year},x₆≥x_6,50％) Corresponding pulse water expansion rate guarantee rate P (x)₂≥x_{2, design value in horizontal year})、P(x₃≥x_{3, design value in open water year},x₆≥x_6,50％) Corresponding pulse water falling rate guarantee rate P (x)₃≥x_{3, design value in open water year})、P(x₄≥x_{4, open water annual design value},x₆≥x_6,50％) Corresponding pulse duration guarantee rate P (x)₄≥x_{4, open water annual design value})、P(x₅≥x_{5, design value in open water},x₆≥x_6,50％) Corresponding pulse frequency guarantee rate P (x)₅≥x_{5, design value in open water})；

Solving for P (x) from the edge distribution function in 2.1)₁≥x_{1, design value in open water}) Corresponding peak flow design value x_{1, design value in open water}That is, the peak flow design value x of the target ecological flow process_{1, target ecological flux}；P(x₂≥x_{2, design value in horizontal year}) Corresponding design value x of pulse water expansion rate_{2, design value in horizontal year}Namely the design value x of the pulse water expansion rate of the target ecological flow process_{2, target ecological flux}；P(x₃≥x_{3, design value in open water year}) Corresponding design value x of pulse water falling rate_{3, design value in open water year}That is, the design value x of the pulse water falling rate in the target ecological flow process_{3, target ecological flux}；P(x₄≥x_{4, open water annual design value}) Design value x of corresponding pulse duration_{4, open water annual design value}I.e. the design value x of the pulse duration of the target ecological traffic process_{4, target ecological flux}；P(x₅≥x_{5, design value in open water}) Corresponding pulse frequency design value x_{5, design value in open water}I.e. the design value x of the pulse frequency of the target ecological flow process_{Target ecological flux}。

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