CN111898097A - Ecological flow determination method combining probability density and guarantee rate - Google Patents

Ecological flow determination method combining probability density and guarantee rate Download PDF

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CN111898097A
CN111898097A CN202010748090.8A CN202010748090A CN111898097A CN 111898097 A CN111898097 A CN 111898097A CN 202010748090 A CN202010748090 A CN 202010748090A CN 111898097 A CN111898097 A CN 111898097A
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吴贞晖
梅亚东
程贝
朱迪
余姚果
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Abstract

The invention relates to an ecological flow determining method combining probability density and guarantee rate, which comprises the following steps: collecting daily flow data of multiple years, and sorting to obtain a daily flow frequency curve of 12 months; adopting a self-adaptive kernel density function method, and regarding the flow at the position with the maximum probability density as the optimum flow of the month to obtain the optimum ecological flow process all year round; determining a monthly lower proper ecological flow threshold and a yearly lower proper ecological flow threshold flow process; and determining the monthly upper threshold value of the suitable ecological flow and the annual upper threshold value flow process of the suitable ecological flow. The invention firstly provides an ecological flow determination method combining probability density and guarantee rate, the calculation result can ensure that the designed ecological flow can reflect the change process of the annual and seasonal changes, and simultaneously adapts to the aquatic organism demand and the water demand requirement of human society, the balance between river health and social water is maintained to the maximum extent, and the method has certain popularization and use values.

Description

Ecological flow determination method combining probability density and guarantee rate
Technical Field
The invention relates to the technical field of ecological flow formulation and environmental protection, in particular to an ecological flow determination method combining probability density and guarantee rate.
Background
At present, more than 200 ecological flow calculation methods exist at home and abroad, and the methods can be divided into a hydrological method, a hydraulic method, a habitat method, an integral analysis method and the like on the whole. Among them, the hydrology method is widely used because of its simple data type and simple calculation. According to the 'nature-society' binary water circulation theory, the water flow change in the river channel is not only influenced by natural environment boundaries such as climate change and the like, but also related to the increasing water taking behaviors of human beings, the river ecological flow relates to a plurality of beneficial subjects, and contradiction exists between the river ecological flow and the traditional water demand for production and life. However, the current ecological flow determination is rarely related to the degree of utilization of human development. Meanwhile, the defining subjectivity and the experientiality of the hydrological method (such as Tennant method, monthly frequency method and the like) to the ecological grade standard are too strong, the ecological flow rate is more emphasized on the aspects of aquatic organisms, natural hydrological situation and the like, and the water demand of the human society is not balanced by combining the ecological management target. In view of this, it is considered to perfect and develop an ecological traffic determination method based on the combination of probability density and guarantee rate. The flow at the position with the maximum probability density is regarded as the proper flow of the aquatic organisms and is used for reflecting the change of natural hydrological situation; the social and economic targets are embodied in the form of the guarantee rate to set the upper threshold and the lower threshold of the appropriate ecological flow, and then the influence of natural and social activities on the ecological flow is considered at the same time. The method is not only beneficial to coordinating the ecological water demand binary contradiction of different beneficiaries, but also is rich and supplementary to the ecological flow formulation theory and method.
Disclosure of Invention
The invention aims to provide an ecological flow determining method combining probability density and guarantee rate, which can more accurately reflect and evaluate annual and annual changes of ecological flow, has better regional applicability and portability, and can consider both optimum ecological runoff required by aquatic organisms and corresponding water resource development and utilization degree.
The scheme adopted by the invention for solving the technical problems is as follows:
an ecological flow determining method combining probability density and guarantee rate comprises the following steps:
step 1, collecting daily flow data of multiple years, and sorting to obtain a daily runoff frequency curve of 12 months;
step 2, adopting a self-adaptive kernel density function method, and regarding the flow at the position with the maximum probability density as the optimum flow of the month to obtain the optimum ecological flow process all the year round;
step 3, determining a monthly proper ecological flow lower threshold value, and obtaining a yearly proper ecological flow lower threshold value flow process according to the monthly proper ecological flow lower threshold value;
and 4, determining the monthly suitable ecological flow upper threshold value, and obtaining the annual suitable ecological flow upper threshold value flow process according to the monthly suitable ecological flow upper threshold value.
Further, daily traffic data of not less than 10 years is collected in step 1.
Further, the method for obtaining the daily runoff frequency curve of 12 months in the step 1 comprises the following steps:
firstly, arranging and designing daily runoff data of a plurality of years of a hydrological station, and setting the daily runoff of the jth month and the kth day of the ith year as xi，j，kWherein i 1, 2, N, J1, 2, 1, K1, 2jN is total number of years, J is monthly (J-12) per year, KiTotal days corresponding to month j; set the daily runoff sequence of the ith year and the jth month
Figure BDA0002609372460000021
Then daily runoff of multiple years can be arranged into a daily runoff matrix M:
Figure BDA0002609372460000022
then, a theoretical frequency curve of the 1 month day runoff sequence is plotted: the 1 st column (X) in the M matrix11，X21，...，XN1) Sorting the daily runoff values from large to small, and fitting the daily runoff sequence by using a Pearson III-type curve to obtain a theoretical frequency curve of the daily runoff in 1 month;
and repeating the steps on the remaining 11 rows of daily runoff sequences of the M matrix to obtain a daily runoff theoretical frequency curve of each month, and finally, sorting to obtain a daily runoff theoretical frequency curve of 12 months.
Further, the method for establishing the annual optimum ecological flow rate process in the step 2 comprises the following steps:
firstly, extracting a 1-month long series daily flow sequence in the M matrix obtained in the step 1, and defining a fixed bandwidth density function of the month; sequence of daily flow (y)1，y2，...，yt，...，ym)＝(x1，1，1，...，x1，1，K，x2，1，1，...，x2，1，K，...，xN，1，1，...，xN，1，K) The distribution density function obeyed by the method is f (y), y belongs to R, and the function is defined as:
Figure BDA0002609372460000031
wherein f ish(y; h) an estimate of the nuclear density as a function of the density f (y);
Figure BDA0002609372460000032
is a kernel function; h is a window width or smoothness parameter; m is the length of the daily flow sequence;
then, on the basis of the fixed wide kernel density function, the window width parameter h is corrected to be w lambdatAn adaptive kernel density estimate is obtained, which is of the form:
Figure BDA0002609372460000033
in the formula, λjIs a local bandwidth factor, w is a window width parameter;
then the parameter lambda is carried outtAnd determination of w when λ is obtainedtAfter the value of w, substituting into formula(3) In (1), calculating to obtain a nuclear density estimated value fh(y，yt)；
Whereby the daily flow sequence y is in accordance with the 1 month long seriestGet the corresponding kernel density estimation sequence { f ═ 1, 2h(yt) Obtaining a density function graph of the daily flow sequence of 1 month, and selecting the maximum value f of the density function in the graphmax(yt) The daily flow rate value thereof
Figure BDA0002609372460000034
The flow rate is proper for 1 month;
and finally, repeating the steps for the daily flow sequence of 2-12 months to obtain the proper flow of 2-12 months, and forming a suitable ecological flow process of the whole year by the optimal ecological flow of each month.
Further, the expression of the kernel function is:
Figure BDA0002609372460000035
wherein S is a sample set { y }tThe variance of (f) to consider each sample point ytData scatter in different directions and ranges.
Further, in determining the parameter λtThe method for summing the values of w is:
initially selecting a bandwidth h0And substituted into formula (2) to obtain a preliminary estimate
Figure BDA0002609372460000036
Thereby, the local bandwidth factor λtThe solving formula of (2) is as follows:
Figure BDA0002609372460000037
wherein T is more than or equal to 0 and less than or equal to 1 and is taken as a sensitive factor, T is 0.5,
the solution formula of the window width parameter w is:
Figure BDA0002609372460000041
in the formula, MdIs the number of mutually different flow values appearing in the time series, and Md≤m；
Thereby obtaining lambdatAnd the value of w.
Further, the method for determining the lower threshold value of the monthly suitable ecological flow rate in the step 3 comprises the following steps:
after the theoretical frequency curve of each month is obtained in the step 1, a lower threshold value guarantee rate P is setdAnd selecting a flow value corresponding to the lower threshold guarantee rate as the ecological water requirement lower threshold of the month, and forming a suitable ecological flow lower threshold flow process of the whole year by using the suitable ecological flow lower threshold of each month.
Further, a lower threshold guarantee rate PdIs Pd90% or 95%.
Further, the method for determining the monthly suitable ecological flow upper threshold in the step 4 comprises the following steps:
after the theoretical frequency curve of each month is obtained in the step 1, an upper threshold guarantee rate P is setuAnd selecting a flow value corresponding to the upper threshold guarantee rate as the ecological water demand upper threshold of the month, and forming a suitable ecological flow upper threshold flow process of the whole year by using the suitable ecological flow upper threshold of each month.
Further, an upper threshold guarantee rate PuIs selected as P u10% or 20%.
Compared with the prior art, the invention has at least the following beneficial effects: the ecological flow determining method based on the combination of the probability density and the guarantee rate is different from the traditional hydrology method in ecological flow determination, the traditional hydrology method generally takes the percentage or the guarantee rate of the flow as the ecological flow grading standard, has larger subjectivity and experience, focuses more on the change situation of the natural habitat, and considers less influences of the water demand of human society and the development and utilization degree of water resources during design; the invention provides an ecological flow determining method based on the combination of probability density and guarantee rate, which can reflect the ecological flow demand of the 'natural side' by selecting the flow value corresponding to the maximum probability density position in the daily flow sequence as the proper ecological flow most suitable for the survival and reproduction of aquatic organisms, and set the guarantee rate meeting the development requirement of human social economy at the same time, and select the daily flow value corresponding to the specific guarantee rate as the upper and lower thresholds of the proper ecological flow to reflect the ecological flow demand of the 'social side', and can maintain the balance between river health and social water to the maximum extent, the result is simple and clear, and the implementation is simple and easy; compared with the prior art, the ecological flow determination method combining the self-adaptive probability density and the guarantee rate is provided for the first time and is applied to river ecological flow calculation, the method is an important innovation in the technical field, the calculation result can guarantee the problem of annual and seasonal change of the ecological flow, the method is suitable for aquatic organism requirements and human society water demand requirements, and the method has certain popularization and use values.
Drawings
FIG. 1 is a flow chart of an embodiment of the present invention.
FIG. 2 is a 1-month daily flow length series theoretical frequency curve of a total stream station in an embodiment of the present invention;
FIG. 3 is a 1-month daily flow length series probability density curve for a total stream station in an embodiment of the present invention;
fig. 4 is a graph comparing the process in the general stream station with the Tennant process in an example of the present invention.
Detailed Description
The following examples are provided to further illustrate the present invention for better understanding, but the present invention is not limited to the following examples.
The invention provides an ecological flow determination method combining probability density and guarantee rate, which takes a total stream river hydrological station of a river basin of a certain province as an example, and explains a process of designing the monthly average ecological flow of the total stream river station by adopting the ecological flow determination method based on the combination of the probability density and the guarantee rate. As shown in fig. 1, an embodiment of the present invention includes the steps of:
step 1, data arrangement:
selecting the daily runoff data of the general stream station 2002-And measuring the basic data of calculation. Let the daily runoff of the ith year, jth month and kth day be xi，j，kWherein i 1, 2, N, J1, 2, 1, K1, 2jN is total number of years, J is monthly (J-12) per year, KjThe total number of days for month j. Set the daily runoff sequence of the ith year and the jth month
Figure BDA0002609372460000051
Then the daily runoff of many years can be arranged into a daily runoff matrix M:
Figure BDA0002609372460000052
then, drawing a theoretical frequency curve of the daily runoff sequence of 1 month, wherein the specific method comprises the following steps: will M the 1 st column (X) of the matrix11，X21，...，XN1) Sorting the daily runoff values from large to small, and fitting the daily runoff series by using a Pearson type III curve to obtain a daily runoff theoretical frequency curve of 1 month, which is shown in figure 2.
And repeating the steps on the remaining 11 rows of daily runoff sequences of the M matrix to obtain a daily runoff theoretical frequency curve of each month, and finally, sorting to obtain a daily runoff theoretical frequency curve of 12 months.
Step 2, adopting a self-adaptive kernel density function method, regarding the flow at the position with the maximum probability density as the optimum flow in the month, and obtaining the optimum ecological flow process all year round, wherein the specific realization method is as follows:
firstly, extracting the daily runoff sequence of 1 month in the M matrix obtained by sorting in the step 1, and defining the fixed bandwidth density function of the month. For convenience of description, let the daily flow sequence (y)1，y2，...，yt，...，ym)＝(x1，1，1，...，x1，1，K，x2，1，1，...，x2，1，K，...，xN，1，1，...，xN，1，K) The distribution density function obeyed by the method is f (y), y belongs to R, and the function is defined as:
Figure BDA0002609372460000061
wherein f ish(y; h) an estimate of the nuclear density as a function of the density f (y);
Figure BDA0002609372460000062
is a kernel function; h is a window width or smoothness parameter; and m is the length of the daily flow sequence. There are many kernel functions, but the functions of different kernel functions are equivalent, and this embodiment takes a gaussian kernel function as an example:
Figure BDA0002609372460000063
wherein S is a sample set { y }tThe variance of (f) to consider each sample point ytData scatter in different directions and ranges.
Then, on the basis of the fixed wide kernel density function, the window width parameter h is corrected to be w lambdatAn adaptive kernel density estimate is obtained, which is of the form:
Figure BDA0002609372460000064
in the formula, λjIs the local bandwidth factor, w is the window width parameter.
Next, a parameter λ is performedtAnd the specific method for determining w is as follows: initially selecting a bandwidth h0And substituted in formula (ii), a preliminary estimate can be obtained
Figure BDA0002609372460000065
Thereby, the local bandwidth factor λtThe solving formula of (2) is as follows:
Figure BDA0002609372460000071
in the formula, T is 0 ≦ T ≦ 1 as a sensitivity factor, and T is usually 0.5.
The solution formula of the window width parameter w is:
Figure BDA0002609372460000072
in the formula, MdIs the number (M) of mutually different flow values appearing in the time seriesdM is less than or equal to m). From which λ is calculatedtW, and then substituting in formula (iV) to determine the nuclear density estimated value fh(y，yt)。
Therefore, the daily flow sequence { y) can be obtained according to the long series of 1 monthtGet the corresponding kernel density estimation sequence { f ═ 1, 2h(yt) Thus, a density function plot of the 1 month day flow sequence is obtained, see FIG. 3. Selecting the maximum value f of the density function in the graphmax(yt) The daily flow rate value thereof
Figure BDA0002609372460000073
I.e. a suitable flow for month 1.
And finally, repeating the steps for the daily flow sequence of 2-12 months to obtain the appropriate flow of 2-12 months. The optimum ecological flow rate in each month constitutes the suitable ecological flow rate process throughout the year.
And 3, determining a monthly lower threshold value of suitable ecological flow and a yearly lower threshold value flow process of suitable ecological flow.
After the theoretical frequency curve of each month is obtained in step 1, the lower threshold guarantee rate P is set in this embodimentdOf course, in other embodiments, the lower threshold guarantee rate P may be selected to be 90%d95%, the specific lower threshold guarantee rate is determined according to actual conditions; selecting a flow value corresponding to the lower threshold guarantee rate as an ecological water demand lower threshold of the month, and forming a year-round suitable ecological flow lower threshold flow process by using the suitable ecological flow lower threshold of each month
And 4, determining monthly suitable ecological flow upper threshold value and annual suitable ecological flow upper threshold value flow process.
After the theoretical frequency curve of each month is obtained in step 1, the upper threshold guarantee rate P is set in this embodiment according to the local economic and social requirements u10% (ten years flood standard), in other regions or embodiments, the upper threshold guarantee rate P may also be setu20% (flood standard in five years), the actual selection is subject to the local situation; and selecting a flow value corresponding to the upper threshold guarantee rate as an ecological water demand upper threshold of the month, and forming an appropriate ecological flow upper threshold flow process of the whole year by using the appropriate ecological flow upper threshold of each month.
Through model solution, the monthly suitable ecological flow of the total brook station and the processes of the upper threshold and the lower threshold of the total brook station can be calculated. To analyze whether the ecological flux process designed by the method of the present invention is rational, the results obtained are compared with Tennant, and the comparison figure is shown in FIG. 4. The calculated flow rate of the suitable ecological water for the river in 10 months to 3 months next year accounts for 52 percent of the average annual flow rate, and reaches the standard of 'optimal range' of the Tennant method; the suitable ecological water flow of the river in 4-9 months accounts for 140% of the average annual flow, and the ecological condition is good. The upper threshold value of the river suitable ecological water flow calculated by the method of the embodiment from 10 months to 3 months in the next year accounts for 92% of the annual average flow, and reaches the standard of 'optimal range' of the Tennant method; the upper threshold value of the flow rate of the river suitable for ecological water in 4-9 months accounts for 200% of the average annual flow rate, and the ecological condition is good. The lower threshold value of the river suitable ecological water flow of 10 months to 3 months in the next year calculated by the method of the embodiment accounts for 34 percent of the annual average flow, and reaches the 'very good' standard of the Tennant method; the lower threshold value of the river suitable ecological water flow of 4-9 months accounts for 46% of the average annual flow, and the ecological condition is good. In conclusion, the lower threshold set by the method of the embodiment is more important for guaranteeing the ecological target in the dry season, and can reach a better flow grade when the water is rich; both the adaptive flow process and the upper threshold process can provide an excellent survival condition for the ecological system. Meanwhile, the method of the embodiment sets an upper threshold and a lower threshold for the appropriate ecological flow, rather than setting a subjective ecological flow level like the Tennant method, in comparison, the feasible range of the ecological flow set by the new method is larger, and the flow is controlled to be above a certain threshold or below the threshold in actual operation.
In conclusion, compared with the Tennant method, the method can more accurately reflect and evaluate the annual and annual change of the ecological flow, has better regional applicability and transplantability, can consider the optimum ecological runoff required by aquatic organisms and can also consider the corresponding water resource development and utilization degree. The invention is innovative in that an ecological flow determination method combining probability density and guarantee rate is firstly provided and applied to the determination time of the river monthly ecological flow, and a new thought is provided for the ecological flow formulation comprehensively considering natural conditions and social water demand.
While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims (10)

1. An ecological flow determining method combining probability density and guarantee rate is characterized by comprising the following steps:
step 1, collecting daily flow data of multiple years, and sorting to obtain a daily runoff frequency curve of 12 months;
step 2, adopting a self-adaptive kernel density function method, and regarding the flow at the position with the maximum probability density as the optimum flow of the month to obtain the optimum ecological flow process all the year round;
step 3, determining a monthly proper ecological flow lower threshold value, and obtaining a yearly proper ecological flow lower threshold value flow process according to the monthly proper ecological flow lower threshold value;
and 4, determining the monthly suitable ecological flow upper threshold value, and obtaining the annual suitable ecological flow upper threshold value flow process according to the monthly suitable ecological flow upper threshold value.
2. The ecological traffic determining method combining probability density and securing rate according to claim 1, wherein daily traffic data of not less than 10 years is collected in step 1.
3. The ecological flux determining method combining probability density and guarantee rate according to claim 1, wherein the method for obtaining the daily runoff frequency curve of 12 months in step 1 comprises the following steps:
firstly, arranging and designing daily runoff data of a plurality of years of a hydrological station, and setting the daily runoff of the jth month and the kth day of the ith year as xi，j，kWherein i 1, 2, N, J1, 2, 1, K1, 2jN is total number of years, J is monthly (J-12) per year, KjTotal days corresponding to month j; set the daily runoff sequence of the ith year and the jth month
Figure FDA0002609372450000011
Then daily runoff of multiple years can be arranged into a daily runoff matrix M:
Figure FDA0002609372450000012
then, a theoretical frequency curve of the 1 month day runoff sequence is plotted: the 1 st column (X) in the M matrix11，X21，...，XN1) Sorting the daily runoff values from large to small, and fitting the daily runoff sequence by using a Pearson III-type curve to obtain a theoretical frequency curve of the daily runoff in 1 month;
and repeating the steps on the remaining 11 rows of daily runoff sequences of the M matrix to obtain a daily runoff theoretical frequency curve of each month, and finally, sorting to obtain a daily runoff theoretical frequency curve of 12 months.
4. The ecological flux determining method combining probability density and guarantee rate according to claim 1, wherein the method of step 2 for establishing the annual optimum ecological flux process is as follows:
firstly, extracting a 1-month long series daily flow sequence in the M matrix obtained in the step 1, and defining a fixed bandwidth density function of the month; sequence of daily flow (y)1，y2，...，yt，...，ym)＝(x1，1，1，...，x1，1，K，x2，1，1，...，x2，1，K，...，xN，1，1，...，xN，1，K) The distribution density function obeyed by the method is f (y), y belongs to R, and the definition function teaches that:
Figure FDA0002609372450000021
wherein f ish(y; h) an estimate of the nuclear density as a function of the density f (y);
Figure FDA0002609372450000022
is a kernel function; h is a window width or smoothness parameter; m is the length of the daily flow sequence;
then, on the basis of the fixed wide kernel density function, the window width parameter h is corrected to be w lambdatAn adaptive kernel density estimate is obtained, which is of the form:
Figure FDA0002609372450000023
in the formula, λjIs a local bandwidth factor, w is a window width parameter;
then the parameter lambda is carried outtAnd determination of w when λ is obtainedtW, substituting the value of w into formula (3), and calculating to obtain a nuclear density estimated value fh(y，yt)；
Whereby the daily flow sequence y is in accordance with the 1 month long seriestGet the corresponding kernel density estimation sequence { f ═ 1, 2h(yt) Obtaining a density function graph of the daily flow sequence of 1 month, and selecting the maximum value f of the density function in the graphmax(yt) The daily flow rate value thereof
Figure FDA0002609372450000024
The flow rate is proper for 1 month;
and finally, repeating the steps for the daily flow sequence of 2-12 months to obtain the proper flow of 2-12 months, and forming a suitable ecological flow process of the whole year by the optimal ecological flow of each month.
5. The ecological traffic flow determination method combining probability density and guarantee rate according to claim 4, characterized in that the expression of the kernel function is:
Figure FDA0002609372450000025
wherein S is a sample set { y }tThe variance of (f) to consider each sample point ytData scatter in different directions and ranges.
6. The ecological traffic flow determination method combining probability density and assurance rate according to claim 4, characterized in that in determining the parameter λtThe method for summing the values of w is:
initially selecting a bandwidth h0And substituted into formula (2) to obtain a preliminary estimate
Figure FDA0002609372450000031
Thereby, the local bandwidth factor λtThe solving formula of (2) is as follows:
Figure FDA0002609372450000032
wherein T is more than or equal to 0 and less than or equal to 1 and is taken as a sensitive factor, T is 0.5,
the solution formula of the window width parameter w is:
Figure FDA0002609372450000033
in the formula, MdIs the number of mutually different flow values appearing in the time series, and Md≤m；
Thereby obtaining lambdatAnd the value of w.
7. The ecological flow rate determining method combining the probability density and the guarantee rate as claimed in claim 1, wherein the method for determining the monthly-appropriate ecological flow rate lower threshold in the step 3 comprises:
after the theoretical frequency curve of each month is obtained in the step 1, a lower threshold value guarantee rate P is setdAnd selecting a flow value corresponding to the lower threshold guarantee rate as the ecological water requirement lower threshold of the month, and forming a suitable ecological flow lower threshold flow process of the whole year by using the suitable ecological flow lower threshold of each month.
8. The ecological traffic flow determination method combining probability density and guarantee rate as claimed in claim 7, wherein: lower threshold guarantee rate PdIs Pd90% or 95%.
9. The ecological traffic flow determination method combining probability density and guarantee rate as claimed in claim 1, wherein: the method for determining the monthly suitable ecological flow upper threshold in the step 4 comprises the following steps:
after the theoretical frequency curve of each month is obtained in the step 1, an upper threshold guarantee rate P is setuAnd selecting a flow value corresponding to the upper threshold guarantee rate as the ecological water demand upper threshold of the month, and forming a suitable ecological flow upper threshold flow process of the whole year by using the suitable ecological flow upper threshold of each month.
10. The method for determining ecological traffic according to claim 9, wherein the upper threshold guarantee rate P is higher than the probability densityuIs selected as Pu10% or 20%.
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