A hydrological regime change analysis method for quantifying reservoir impacts

Abstract

The application provides a hydrological regime change analysis method for quantifying reservoir influence, which comprehensively evaluates the hydrological regime change under the influence of reservoir operation by adopting a threshold variation method and a deviation-distance weight method. Annual maximum flood discharge, monthly average discharge during the storage period, base flow during the dry period, ecological surplus, ecological deficit, pulse during the storage period, pulse during the dry period and annual extreme value occurrence time are selected as the evaluation factors of the hydrological regime; the threshold variation method is proposed to compare the threshold variation of the natural and measured series to calculate the variation degree of different evaluation factors; and the deviation-distance weight method is proposed to calculate the overall change level after revaluing the evaluation factors.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of river and lake hydrological regime analysis, and particularly relates to a hydrological regime change analysis method for quantifying the influence of reservoirs. BACKGROUND

[0002] Hydrological element change has been a hot research direction in the field of hydrology and water resources. The construction and operation of large-scale water conservancy and hydropower projects and the frequent occurrence of extreme hydro-meteorological events under the background of climate change have greatly increased the complexity of research. The variation characteristics of river and lake hydrological regime under the operation of water conservancy projects have been a research difficulty in hydrology and water ecological protection.

[0003] Currently, the research and analysis of the hydrological regime of the river section under the operation of water conservancy projects mainly take the operation time of the reservoir as the mutation node to study the variation characteristics of the long series of measured daily runoff before and after the operation of the reservoir. The evaluation results are often affected by multiple factors such as human activities and climate change, and it is difficult to eliminate the influence of hydrological period, climate change and other factors on the hydrological regime. The operation of the reservoir has gradually become the main influencing factor in human activities. How to separate this factor and consider it alone and use an appropriate hydrological variation calculation method to quantitatively evaluate the change of the downstream river hydrological regime caused by the operation of the reservoir (group) is a key technical problem that needs to be solved at present. SUMMARY

[0004] The present application aims to overcome the deficiencies of the prior art and provides a hydrological regime change analysis method for quantifying the influence of reservoirs.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] The present application provides a hydrological regime change analysis method for quantifying the influence of reservoirs, comprising the following steps:

[0007] S1, using the water balance principle to restore the long series of daily runoff data of the research station to the natural state, and selecting the natural and measured series of the same period after the operation of the cascade reservoir group in the study area as the research objects before and after human disturbance;

[0008] S2, selecting the annual maximum flood discharge, monthly average discharge during the storage period, base flow during the dry period, ecological surplus, ecological deficit, pulse during the storage period, pulse during the dry period, and annual extreme value occurrence time as the evaluation factors of the hydrological regime, and comprehensively representing the variation characteristics of the hydrological regime under the influence of the reservoir operation in the basin;

[0009] S3, proposing a threshold variation method to calculate the variation degree of different evaluation factors by comparing the threshold variation of the natural series and the measured series;

[0010] S4, the deviation-distance weight method is proposed, and the overall change level is calculated after reassigning the evaluation factors.

[0011] Further, in S1, the long series of daily runoff data of the research station is restored to the natural state by using the water balance principle:

[0012] According to the actual operation data of the reservoir, the water level in front of the dam, the reservoir capacity curve and the discharge flow, the inflow is calculated by water balance, and the formula is:

[0013]

[0014] Among them, is the average inflow of the period; is the average outflow of the period; ΔV 损 is the loss of water in the reservoir; ΔV is the change value of the reservoir storage at the beginning and end of the period; Δt is the calculation period; I is the inflow.

[0015] Further, in S2, the change characteristics of hydrological regime are as follows:

[0016] Q max = max{Q1, Q2, …, Q day};

[0017]

[0018] E cp = A s / A 50％ ;

[0019] E cf = A l / A 50％ ;

[0020]

[0021] Among them, Q max is the annual maximum flood flow; Q day is the daily flow of each year; Q a,im is the monthly average flow during the storage period; Q i,im is the daily average flow of the i-th month during the storage period; Q d is the base flow during the dry period; Q min,7d is the minimum flow for 7 consecutive days; is the annual average flow; E cp is the ecological surplus; A s is the area surrounded by the PDC curve of the specified annual flow duration curve exceeding 75% percentile; A 50％ is the annual flow corresponding to 50% percentile; E cf is the ecological deficit; Al is the area of the region enclosed by the PDC curve below the 25th percentile of the designated year PDC curve; P im is the impulsive pulse in the storage period; P dry is the impulsive pulse in the dry period; N im , N dry are the numbers of high and low pulses in the storage and dry periods, respectively; x is the daily average flow; T e is the occurrence time of the annual extreme value; is the occurrence time of the annual maximum flood peak flow, ranging from [1, 365 / 366].

[0022] Further, the S3 is specifically:

[0023] Two sets of threshold systems under the conditions of 25% and 75% frequencies of the natural series and the measured series before being artificially disturbed are established, and by comparing the threshold range of the measured series with the threshold range of the natural series at the same period, the effect of the reservoir operation on the river hydrological regime is studied;

[0024] The annual evaluation factors obtained by the natural series and the measured series are arranged in descending order and frequency calculation is performed, wherein the values obtained at the frequencies of 25% and 75% are the frequency thresholds of the natural series and the measured series;

[0025]

[0026] wherein D n is the hydrological change degree based on the threshold variation method, N u is the threshold difference of the evaluation factor of the measured series not falling into the natural series, N t is the threshold difference of the evaluation factor of the measured series itself.

[0027] Further, the threshold comparison of the natural series and the measured series in the S3 mainly includes the following cases:

[0028] 1) When the threshold range of the measured series is within the threshold range of the natural series,

[0029] that is, I′ 25％ ≤ I 25％ , I′ 75％ ≥ I 75％ , at this time, the measured series after being artificially disturbed changes less than the natural series:

[0030]

[0031] 2) When the lower limit I′ 75％ of the threshold range of the measured series is within the threshold range of the natural series, the upper limit I′ 25％ of the threshold range of the measured series is higher than the upper limit I 25％ of the threshold range of the natural series,

[0032] i.e. I 75％ ≤ I' 75％ < I 25％ , I' 25％ > I 25％ :

[0033]

[0034] 3) When the upper limit of the measured series threshold range I' 25％ is between the natural series threshold range, the lower limit of the measured series threshold range I' 75％ is lower than the lower limit of the natural series threshold range I 75％ ,

[0035] i.e. I 75％ < I' 25％ ≤ I 25％ , I' 75％ < I 75％ :

[0036]

[0037] 4) When the measured series threshold range contains the natural series threshold range, i.e. I' 75％ < I 75％ , I' 25％ > I 25％ :

[0038]

[0039] 5) When the lower limit of the measured series threshold range I' 75％ are all higher than the corresponding natural series threshold range, i.e. I' 75％ ≥ I 25％ :

[0040]

[0041] 6) When the upper limit of the measured series threshold range I' 25％ are all lower than the corresponding natural series threshold range, i.e. I' 25％ ≤ I 75％ :

[0042]

[0043] Further, the S4 is specifically:

[0044] S401, weight calculation: first, the deviation of the same scene of the natural series and the measured series is calculated, then the distance between the corresponding years of the natural series and the measured series under the three flow threshold values is logarithmically discriminated, the weight coefficient of each evaluation factor is obtained, and normalization processing is performed:

[0045]

[0046]

[0047] w=d p ×d dis ;

[0048]

[0049] wherein γ and γ' are the bias coefficients in the natural series and the measured series respectively; X 10％ , X 50％ , X 90％ are the flow values at 10%, 50% and 90% frequencies in the natural series; X' 10％ , X' 50％ , X' 90％ are the flow values at 10%, 50% and 90% frequencies in the measured series; d p is the bias degree of the natural series and the measured series; d dis is the distance between the corresponding years in the natural series and the measured series at the flow threshold value; k is the number of the corresponding years when the distance difference between the corresponding years at 10%, 50% and 90% threshold values exceeds 1 / 10 of the total number of years; A1(A2, A3), A'1(A'2, A'3) are the corresponding years at 10% (50%, 90%) threshold value in the natural series and the measured series respectively, and if the distances of the corresponding years at the three threshold values are all less than 1 / 10 of the total number of years, then d dis = 0; w is the weight coefficient; is the weight normalization result; b is the number of evaluation factors; w j is the weight of the jth evaluation factor;

[0050] S402, comprehensive change degree calculation:

[0051]

[0052] In the formula, D t is the comprehensive change degree based on the index bias; is the comprehensive weight coefficient of each evaluation factor, and Dm is the hydrological change degree of different evaluation factors;

[0053] wherein the change degree range threshold values of D n and D t are 33% and 67%, i.e. [0, 33% ), [33%, 67% ), [67% ~ 100% ] are low, medium and high change degrees respectively.

[0054] The beneficial effect of the present application is that: the measured and natural (reduced to before human disturbance) flow in the same period (after the library) is taken as the research object, the reservoir operation factor is considered separately on the premise of fixing other consistent factors, the threshold variation method and the corresponding evaluation factor are proposed, and finally the deviation-distance weight method is used to avoid the uniformization weight of the evaluation factor to comprehensively evaluate the change degree of the hydrological regime affected only by the reservoir operation in the research basin. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 The flowchart of the hydrological regime change analysis method for quantifying the influence of the reservoir. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application will be further described in detail below with reference to the drawings. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0057] The embodiment takes the daily average flow of the control station in the middle and lower reaches of the Yangtze River as the implementation object, uses the threshold variation method to calculate and analyze the change degree of the evaluation factor of the hydrological station in the research area, and then uses the deviation-distance weight method to calculate the comprehensive change degree, so as to comprehensively evaluate the change characteristics of the hydrological regime in the middle and lower reaches of the Yangtze River.

[0058] As shown in Figure 1 A hydrological regime change analysis method for quantifying the influence of the reservoir, comprising the following steps:

[0059] The long series of daily runoff data of the research station is restored to the natural state by using the water balance principle, and the natural and measured series in the same period after the operation of the cascade reservoir group in the research area are selected as the research objects before (after) human disturbance;

[0060] In the present example, the control station in the middle and lower reaches of the Yangtze River is selected as the implementation object, and the implementation example period of the natural series and the measured series after the operation of the cascade reservoir group in the middle and lower reaches of the Yangtze River (2008-2021) is selected after the water balance principle.

[0061] S2, the annual maximum flood flow, the monthly average flow in the storage period, the base flow in the dry period, the ecological surplus, the ecological deficit, the pulse in the storage period, the pulse in the dry period, and the occurrence time of the annual extreme value are selected as the evaluation factors of the hydrological regime, and the change characteristics of the hydrological regime under the influence of the reservoir operation in the basin are comprehensively represented;

[0062] S3, the threshold variation method is proposed, and the change degree of different evaluation factors is calculated by comparing the threshold variation of the natural series and the measured series;

[0063] Among them, after calculating the different evaluation factor data of Yichang station river section, the natural series and the measured series are arranged in descending order, and the values with frequency of 25% and 75% are selected as the series threshold, then the difference between the threshold range of natural series and measured series is calculated to calculate the hydrological change degree of different evaluation factors;

[0064] S4, propose the deviation-distance weight method, revalue the evaluation factors and calculate the overall change level.

[0065] In S1, the reduction method of long series daily runoff data of the research station to the natural state is:

[0066] According to the actual operation data of the reservoir, the water level in front of the dam, the reservoir capacity curve and the discharge flow, the inflow is calculated by water balance, and the formula is:

[0067]

[0068] Among them, is the period average inflow; is the period average outflow; ΔV 损 is the reservoir loss; ΔV is the period initial and final reservoir water storage change value; Δt is the calculation period; I is the inflow.

[0069] In S2, the change characteristics of hydrological regime are:

[0070] Q max = max{Q1, Q2, …, Q day};

[0071]

[0072] E cp = A s / A 50％ ;

[0073] E cf = A l / A 50％ ;

[0074]

[0075] Among them, Q max is the annual maximum flood discharge; Q day is the daily flow Q a,im is the monthly average flow in the storage period; Q i,im is the daily average flow of the i-th month in the storage period; Q d is the base flow in the dry period; Q min,7d is the minimum flow for 7 consecutive days; is the annual average flow; E cpEcological surplus; A s Area of the region enclosed by the PDC curve of the specified annual flow duration curve exceeding the 75th percentile; A 50％ Annual flow corresponding to the 50th percentile; E cf Ecological deficit; A l Area of the region enclosed by the PDC curve of the specified annual PDC curve below the 25th percentile; P im Pulse in the wet period; P dry Pulse in the dry period; N im , N dry Number of high and low pulses in the wet and dry periods, respectively; x is the daily average flow; T e Time of occurrence of annual extreme value; Time of occurrence of the annual maximum flood flow, ranging from [1, 365 / 366].

[0076] The S3 is specifically:

[0077] Two sets of threshold systems under the conditions of 25% and 75% frequencies of the measured series before and after human disturbance are established, and the range of the threshold of the measured series in the same period accounts for the range of the threshold of the natural series, so as to study the effect of only reservoir operation on river hydrological regime;

[0078] The annual evaluation factors obtained by the natural series and the measured series are arranged in descending order and frequency calculation is performed, wherein the values obtained by 25% and 75% frequencies are the frequency thresholds of the natural series and the measured series;

[0079]

[0080] Among them, D n Hydrological change degree based on threshold variation method, N u Threshold difference of the evaluation factor of the measured series not falling into the natural series, N t Threshold difference of the evaluation factor of the measured series itself.

[0081] The threshold comparison of the natural series and the measured series in the S3 mainly includes the following cases:

[0082] 1), when the threshold range of the measured series is within the threshold range of the natural series,

[0083] I.e. I' 25％ ≤ I 25％ , I' 75％ ≥ I 75％ At this time, the measured series after human disturbance changes less than the natural series:

[0084]

[0085] 2) when the measured series threshold range lower limit I' 75％ is within the natural series threshold range, the measured series threshold range upper limit I' 25％ is higher than the natural series threshold range upper limit I 25％ ,

[0086] i.e. I 75％ ≤ I' 75％ < I 25％ , I' 25％ > I 25％ :

[0087]

[0088] 3) when the measured series threshold range upper limit I' 25％ is within the natural series threshold range, the measured series threshold range lower limit I' 75％ is lower than the natural series threshold range lower limit I 75％ ,

[0089] i.e. I 75％ < I' 25％ ≤ I 25％ , I' 75％ < I 75％ :

[0090]

[0091] 4) when the measured series threshold range contains the natural series threshold range, i.e. I' 75％ < I 75％ , I' 25％ > I 25％ :

[0092]

[0093] 5) when the measured series threshold range lower limit I' 75％ is higher than the corresponding natural series threshold range, i.e. I' 75％ ≥ I 25％ :

[0094]

[0095] 6) when the measured series threshold range upper limit I' 25％ is lower than the corresponding natural series threshold range, i.e. I' 25％ ≤ I 75％ :

[0096]

[0097] The S4 is specifically:

[0098] S401, weight calculation: firstly, the deviation of the natural series and the measured series under the same scenario is calculated, then the distance between the corresponding years of the natural series and the measured series under three flow thresholds (10%, 50%, 90%) is logarithmically discriminated to obtain the weight coefficient of each evaluation factor, and normalization processing is performed:

[0099]

[0100]

[0101] w=d p ×d dis ;

[0102]

[0103] wherein, γ and γ' are the deviation coefficients of the natural series and the measured series respectively; X 10％ , X 50％ , X 90％ are the flow values under the 10%, 50% and 90% frequencies of the natural series respectively; X' 10％ , X' 50％ , X' 90％ are the flow values under the 10%, 50% and 90% frequencies of the measured series respectively; d p is the deviation degree of the natural series and the measured series; d dis is the distance between the corresponding years of the natural series and the measured series under the flow threshold; k is the number of corresponding years when the distance difference between the corresponding years of the natural series and the measured series under the 10%, 50%, 90% threshold exceeds 1 / 10 of the total number of years; A1(A2, A3), A'1(A'2, A'3) are the corresponding years of the natural series and the measured series under the 10% (50%, 90%) threshold respectively, if the distances of the corresponding years under the three thresholds are all less than 1 / 10 of the total number of years, then d dis =0; w is the weight coefficient; is the weight normalization result; b is the number of evaluation factors; is the weight of the jth evaluation factor; S402, comprehensive change degree calculation:

[0104]

[0105] In the formula, D t is the comprehensive change degree based on the index deviation; is the comprehensive weight coefficient of each evaluation factor, and D m is the hydrological change degree of different evaluation factors;

[0106] wherein, D n and D tThe variation degree range defining threshold is 33% and 67%, that is, [0, 33%], [33%, 67%], and [67%~100%] are low L, medium M, and high H variation degrees, respectively.

[0107] Table 1 Yichang Station Related Parameter Achievement Table

[0108]

[0109] The above-described embodiments only express the implementation of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be based on the appended claims.

Claims

1. A method for analyzing hydrological changes to quantify the impact of a reservoir, characterized by: The following steps are involved: S1. Using the water balance principle, the long series of daily runoff data from the research station were restored to their natural state. The natural and measured series of the same period after the operation of the cascade reservoir group in the study area were selected as the research objects before or after artificial interference. S2. Select annual maximum flood peak flow, average monthly flow during the impoundment period, base flow during the dry season, ecological surplus, ecological deficit, impoundment period pulse, dry season pulse, and the time of occurrence of annual extreme values ​​as hydrological evaluation factors to comprehensively characterize the changing characteristics of the hydrological situation under the influence of reservoir operation in the basin; S3. A threshold variation method is proposed to compare the threshold changes of the natural series and the measured series to calculate the degree of change of different evaluation factors; S4. Deviation-distance weighting method is proposed to re-assign the evaluation factors and calculate the overall change level; The S3 is specifically: Two threshold systems were established at 25% and 75% frequencies for the measured series before and after artificial disturbance. By comparing the threshold range of the measured series with the threshold range of the natural series during the same period, the effect of reservoir operation alone on the river hydrological regime was studied. The annual evaluation factor results obtained from the natural series and the measured series were arranged in descending order and the frequencies were calculated. The values ​​obtained at the 25% and 75% frequencies were the frequency thresholds of the natural series and the measured series. ； in, is the hydrological change degree based on the threshold variation method, is the threshold difference of the measured series evaluation factor that does not fall into the natural series, is the threshold difference of the measured series evaluation factor itself; The S4 is specifically: S401. Weight calculation: First, calculate the deviations of the natural series and the measured series under the same scenario. Then, perform logarithmic discrimination on the distances between the natural series and the measured series in corresponding years under the three flow thresholds to obtain the weight coefficients of each evaluation factor and perform normalization processing: ； ； ； ； ； ； in, and are the deviation coefficients under the natural series and measured series conditions, respectively; 、 、 These are the flow rates at 10%, 50% and 90% frequencies of the natural series; 、 、 These are the flow rates at 10%, 50% and 90% frequencies of the measured series respectively; is the degree of deviation between the natural series and the measured series; is the distance between the corresponding years of the natural series and the measured series under the flow threshold; It is the number of years corresponding to the 10%, 50%, and 90% thresholds between the natural series and the measured series when the distance difference exceeds 1 / 10 of the total number of years; 、 These are the years corresponding to the 10% threshold for the natural series and the measured series, respectively; 、 These are the years corresponding to the 50% threshold for the natural series and the measured series, respectively; 、 These are the years corresponding to the 90% threshold for the natural series and the measured series, respectively; If the distances between the years corresponding to the three thresholds are all less than 1 / 10 of the total number of years, then =0; is the weight coefficient; is the weight normalization result; is the number of evaluation factors; For the The weight of each evaluation factor; S402, calculation of comprehensive change degree: ； Where, is the comprehensive change degree based on the indicator deviation; is the comprehensive weight coefficient of each evaluation factor, and ; is the degree of hydrological change for different evaluation factors; in, and The thresholds for defining the range of variability are 33% and 67%, i.e., [0,33%), [33%,67%), and [67%~100%] represent low, medium, and high variability, respectively.

2. A hydrological regime change analysis method for quantifying reservoir impact according to claim 1, characterized in that: In S1, the method for restoring the daily runoff data of the research station to the natural state using the water balance principle is as follows: Based on the actual reservoir operation data, the water level in front of the reservoir dam, the reservoir capacity curve and the outflow flow, the water balance method is used to reversely calculate the inflow flow. The formula is: ； in, is the average inflow flow during the period; is the average outbound flow during the period; Loss of water to reservoirs; The change in reservoir water storage at the beginning and end of the time period; The calculation period.

3. A hydrological regime change analysis method for quantifying reservoir impact according to claim 2, characterized in that: In S2, the changing characteristics of the hydrological situation are specifically as follows: ； ； ； ； ; ; ; ； in, is the annual maximum flood peak flow; is the daily flow rate for each year; is the average monthly flow during the impoundment period; For the water storage period Average daily traffic volume; is the base flow during the dry season; The minimum flow rate for 7 consecutive days; is the average annual flow; for ecological surplus; The area enclosed by the PDC curves where the duration curve of a given annual flow exceeds the 75% quantile; is the annual flow corresponding to the 50% quantile; for ecological deficit; The area enclosed by the PDC curves for a given year that are below the 25% quantile; is the water storage period pulse; It is the dry season pulse; is the number of high and low pulses during the water storage period; is the number of high and low pulses in the dry season; is the average daily flow; is the time when the annual extreme value occurs; The time of occurrence of the annual maximum flood peak flow is in the range of [1, 365 / 366].

4. A hydrological regime change analysis method for quantifying reservoir impact according to claim 3, characterized in that: The threshold comparison between the natural series and the measured series in S3 mainly includes the following situations: 1) When the measured series threshold range is within the natural series threshold range, Right now , at this time, the measured series after artificial interference changes less than the natural series: ； 2) When the lower limit of the measured series threshold range When within the natural series threshold range, the upper limit of the measured series threshold range Above the upper limit of the natural series threshold range hour, Right now : ； 3) When the upper limit of the measured series threshold range Between the natural series threshold range and the lower limit of the measured series threshold range Below the lower limit of the natural series threshold range hour, Right now : ； 4) When the measured series threshold range contains the natural series threshold range, that is, : ； 5) When the lower limit of the measured series threshold range When both are higher than the corresponding natural series threshold range, that is, : ； 6) When the upper limit of the measured series threshold range When both are lower than the corresponding natural series threshold range, that is, : 。

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