CN-122022336-A - River channel ecological water demand multi-scale dynamic assessment method considering environmental change

CN122022336ACN 122022336 ACN122022336 ACN 122022336ACN-122022336-A

Abstract

The invention discloses a river channel ecological water demand multi-scale dynamic assessment method considering environmental changes. The method comprises the steps of obtaining historical runoff data of a target river reach, taking a minimum value of the sequence as the dry runoff of the period, periodically identifying the time sequence of the dry runoff, simultaneously carrying out correlation analysis and drawing a periodic chart, selecting three periods with highest correlation as main periods, constructing a time period function, constructing a candidate model, estimating parameters, selecting an optimal model to calculate dynamic ecological flow, calculating traditional ecological flow based on a time-invariant model, carrying out abundant judgment on a survey period to obtain abundant judgment, combining the abundant judgment, the dynamic ecological flow and the traditional ecological flow to generate recommended thresholds, and respectively executing each step on a plurality of scales of year, season and month to output the recommended thresholds of the corresponding scales. The dynamic model is combined with the traditional fixed value to generate the recommended threshold, so that the scientific frontier of the method is ensured, and the feasibility and the robustness of the management decision are enhanced.

Inventors

ZHANG XUAN
WANG YIXUAN
LIU XIAOMIN
GAO RUIZHONG
DUAN LIMIN
LIU TINGXI
JI JIANGUO
ZHANG SHIYU
SONG WENBO

Assignees

内蒙古农业大学

Dates

Publication Date: 20260512
Application Date: 20260130

Claims (8)

1. The multi-scale dynamic assessment method for the ecological water demand of the river channel taking environmental change into consideration is characterized by comprising the following steps of: S1, acquiring historical runoff data of a target river reach, forming an N-day sliding average flow sequence based on a preset investigation period, and forming a time sequence of the runoff with the minimum value of the N-day sliding average flow sequence as the runoff with the period; S2, periodically identifying the time sequence of the dead water runoff by adopting Fourier analysis, generating trigonometric function sequences corresponding to different periods, carrying out correlation analysis by taking the time sequence of the dead water runoff as a dependent variable and drawing a periodic chart by taking the trigonometric function sequence as the independent variable, and selecting three periods with highest correlation as main periods to construct a time period function; S3, constructing a candidate model in a preset probability distribution parameter set and estimating parameters, wherein the candidate model comprises a time-invariant model, a trend time-varying model and a period time-varying model embedded in the time period function; s4, selecting an optimal model based on the fitting goodness and an information criterion, calculating dynamic ecological flow under a target guarantee rate, and calculating traditional ecological flow under the target guarantee rate based on the time-invariant model, wherein the traditional ecological flow is a single fixed value in the same investigation period; S5, carrying out abundant and separate judgment on the investigation period to obtain a abundant criterion, and combining the abundant criterion, the dynamic ecological flow and the traditional ecological flow to generate a recommended threshold.
2. The multi-scale dynamic assessment method for river channel ecological water demand taking environmental changes into consideration as defined in claim 1, wherein in step S1, the historical runoff data of the target river reach is preprocessed data; the pretreatment process comprises missing value filling, outlier robustness treatment and sequence consistency check.
3. The method for multi-scale dynamic assessment of river channel ecological water demand in consideration of environmental changes as set forth in claim 1, wherein in step S2, the expression of the time period function is: Wherein the expression of a 0 ,a k ,b k is: Where a 0 、a k 、b k is a fourier coefficient determined by history sequence fitting, T i is the i-th main period, k denotes the number of periods, and T is a time variable.
4. The method for multi-scale dynamic assessment of river channel ecological water demand in consideration of environmental changes as set forth in claim 1, wherein in step S3, the specific process of constructing candidate models and estimating parameters in a preset probability distribution parameter set comprises: the probability morphology to which the data is likely to be subjected is widely captured by adopting a set containing a plurality of distribution parameters; Respectively establishing a time invariant model, a trend time variant model and a period time variant model for each time sequence of the dead water runoff, and comparing the time invariant model with the period time variant model; The time invariant model is formed by assuming that the distribution parameters are constant; a trend time-varying model, which is to assume that the distribution parameter is a polynomial function of time; and (3) a periodic time-varying model, namely, assuming that the distribution parameter is a linear function of the time period function.
5. The method for multi-scale dynamic assessment of river channel ecological water demand in consideration of environmental changes as set forth in claim 1, wherein in step S4, the specific process of calculating the dynamic ecological flow comprises: bringing the time covariates corresponding to each time scale into the selected optimal model to obtain probability distribution of the year; Calculating the quantiles of the probability distribution under the target guarantee rate; calculating quantiles year by year to obtain dynamic ecological flow changing with time.
6. The method for multi-scale dynamic assessment of river channel ecological water demand in consideration of environmental changes as set forth in claim 1, wherein in step S4, the specific process of calculating the traditional ecological flow comprises: Estimating fixed distribution parameters by adopting a dead water runoff time sequence fitting time invariant probability model; And calculating the quantile number of the fixed distribution parameters under the target guarantee rate to obtain the fixed traditional ecological flow value in the investigation period.
7. The method for dynamically estimating ecological water demand in river channels according to claim 1, wherein in step S5, the withering score is determined by calculating a long-term average value of the moving average curve as a threshold value through a moving average curve of the longest period in the main period, and a time period higher than the threshold value is determined as a water-rich period, and a time period lower than the threshold value is determined as a dead water period.
8. The method for dynamically evaluating the ecological water demand of the river channel in a multi-scale manner by considering environmental changes according to claim 1, wherein the recommended threshold value satisfies the following conditions: When C (P) =dead water, let Then When C (P) =water enlargement, let Then Wherein C (P) is a withered criterion, A p is a withered water year subset, B p is a plump water year subset, t is a time variable, P is a withered water runoff time sequence investigation period, For a dynamic ecological flow rate that varies with time, Is the traditional ecological flow in the same investigation period, For the recommended threshold, mean is the average of the dynamic ecological flow values that meet the specified annual conditions.

Description

River channel ecological water demand multi-scale dynamic assessment method considering environmental change Technical Field The invention relates to the technical field of ecological flow scheduling decision making, in particular to a river channel ecological water demand multi-scale dynamic assessment method considering environmental changes. Background In recent years, ecological traffic scheduling needs continue to grow. The existing ecological flow calculation mostly adopts a fixed threshold method and is generally established on the premise of stability. The method is difficult to reflect the instability caused by climate change and human activities, and also does not fully describe the obvious difference of runoffs in the annual season scale, so that the ecological flow target is insufficient in pertinence and the adaptability to management practice is weak. But at the same time, the rapid development of the social economy of the river basin makes the contradiction between life, production and ecological water increasingly prominent, and the problems of difficult guarantee of ecological flow, flow interruption, damaged biodiversity, reduced ecological service function and the like occur in part of river reach. Under the background, how to scientifically define and effectively ensure the ecological water demand in a river channel and maintain the ecological-hydrologic benign relationship of a river basin becomes a key problem to be solved urgently. The existing method starts from the annual scale, the influence of intra-season changes on ecological water demand and process maintenance is not fully considered, and an executable threshold basis is difficult to provide for ecological scheduling in seasons and months. Therefore, it is necessary to construct a dynamic ecological flow framework that can change with time and can run on a year/season/month scale, and simultaneously organically link the dynamic result with the traditional fixed ecological flow to form an executable recommended threshold so as to improve the engineering application feasibility and the refinement level of management decisions while ensuring scientificity. Disclosure of Invention In view of the above, the present invention has been made in order to provide a method for multi-scale dynamic assessment of river ecological water demand taking environmental changes into consideration, which overcomes or at least partially solves the above-mentioned problems. In order to achieve the above purpose, the present invention adopts the following technical scheme: The embodiment of the invention provides a river channel ecological water demand multi-scale dynamic assessment method considering environmental changes, which comprises the following steps: s1, acquiring historical runoff data of a target river reach, forming a seven-day sliding average flow sequence based on a preset investigation period, and forming a sequence of time of the runoff with the minimum value of the sequence as the runoff with the same period; S2, periodically identifying the time sequence of the dead water runoff by adopting Fourier analysis, generating trigonometric function sequences corresponding to different periods, carrying out correlation analysis by taking the hydrologic sequence as a dependent variable and drawing a periodic chart by taking the trigonometric function sequence as the independent variable, and selecting three periods with highest correlation as main periods to construct a time period function; S3, constructing a candidate model in a preset probability distribution parameter set and estimating parameters, wherein the candidate model comprises a time-invariant model, a trend time-varying model and a period time-varying model embedded in the time period function; s4, selecting an optimal model based on the fitting goodness and an information criterion, calculating dynamic ecological flow under a target guarantee rate, and calculating traditional ecological flow under the target guarantee rate based on the time-invariant model, wherein the traditional ecological flow is a single fixed value in the same investigation period; S5, carrying out abundant and separate judgment on the investigation period to obtain a abundant criterion, and combining the abundant criterion, the dynamic ecological flow and the traditional ecological flow to generate a recommended threshold. Further, in step S1, the historical runoff data of the target river reach is preprocessed data; the pretreatment process comprises missing value filling, outlier robustness treatment and sequence consistency check. Further, in step S2, the expression of the time period function is: Wherein the expression of a 0,ak,bk is: Where a 0、ak、bk is a fourier coefficient determined by history sequence fitting, T i is the i-th main period, k denotes the number of periods, and T is a time variable. Further, in step S3, the specific process of constructing the candidate model and estimating the par