Multi-element collaborative cascade reservoir discharged water temperature variation degree evaluation method
By constructing a multi-factor collaborative method for assessing the variability of water temperature in cascade reservoirs, the problem of assessing the degree of water temperature change in cascade reservoir groups has been solved. This method enables accurate assessment of water temperature variability in cascade reservoir groups and quantification of water ecological impacts, providing a scientific reference for cascade reservoir scheduling.
Patent Information
- Application Number
- CN202511348510.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-21
- Publication Date
- 2026-01-06
AI Technical Summary
Existing technologies lack methods suitable for assessing the degree of water temperature change in cascade reservoir groups, and the assessment of the impact of the construction and operation of a single reservoir on downstream water temperature is limited to single factors, failing to fully consider multi-factor indicators and the cumulative effect of cascade reservoir groups.
A multi-factor collaborative method for assessing the variability of water temperature in cascade reservoir discharge was established. By constructing an assessment system that includes multiple water temperature indicators and combining it with the IHA indicator system, the range and degree of change of water temperature indicators were calculated, water temperature variability was classified, the degree of water temperature variability during the fish spawning period was considered, and the RVA method was used to assess the degree of water temperature change.
It enables accurate assessment of the temperature variability of water released during the dynamic construction of cascade reservoir groups, quantifies the impact of water temperature changes on the aquatic ecosystem, improves the scientificity and accuracy of the assessment method, and provides a reference for the scheduling of cascade reservoirs.
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Figure CN121279581A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of hydraulic engineering and relates to ecological regulation of reservoirs, in particular to a method for evaluating variation degree of water temperature discharged by cascade reservoirs in coordination with multiple factors. BACKGROUND
[0002] Water temperature is one of the important parameters of river water ecological environment, which is not only a key factor affecting the physical and chemical processes of water body, but also controls the life cycle and population distribution of aquatic organisms, and has a significant impact on the growth and development, spawning, foraging and overwintering of index organisms such as fish. After the construction and operation of cascade reservoirs, the hydrodynamic and thermal conditions of river water body are changed, resulting in differences in water temperature rhythm, which is often manifested as water temperature homogenization phenomenon of reduced water temperature in summer and increased water temperature in winter. The delay of water temperature cycle changes the spawning time of fish. When the environmental water temperature decreases, the growth rate of fish cells stops or decreases, and the oocyte proliferates and develops; when the water temperature increases, the formation speed of fish reproductive cells increases, but too high water temperature will increase the embryonic malformation rate and shorten the spawning time. Changes in river water temperature will affect the physicochemical properties of water body, which may disturb the growth and development, spawning and distribution of fish, and further affect the biodiversity of river ecological system to a certain extent.
[0003] With the gradual construction of reservoir group systems in various domestic river basins, more and more attention and efforts are paid to environmental protection and ecological construction. The disturbance of reservoir construction and operation to natural water temperature rhythm has become an important environmental problem related to water conservancy and hydropower engineering. It is of great significance to protect river water environment and river ecological system to study the influence of reservoir construction and operation on downstream river. In the field of hydrology, the IHA (Indicators of Hydrologic Alteration) index system has been widely used in the study of the degree of hydrological change caused by reservoir construction, and has been recognized by most scholars in the field. However, in the field of analysis of water temperature discharged by reservoirs, there are great differences between the influence of single reservoir construction and cascade reservoir construction on downstream. The influence of single reservoir construction and operation on the river section and aquatic ecology is local, while the influence of cascade hydropower development is basin-wide. In different basins and under the influence of different reservoirs, the cumulative effect of cascade reservoirs on the variation degree of discharged water temperature is different, which may appear to be superimposed or slowed down. At present, the status quo of the evaluation of the variation degree of water temperature discharged by cascade reservoirs is as follows: ① For the local water temperature change caused by single reservoir, there are many index systems for evaluating the change of water temperature, but they are not widely used, and such evaluation methods are limited to single reservoir, lacking methods suitable for evaluating the change degree of water temperature of cascade reservoirs; ② Most evaluation methods of discharged water temperature are limited to annual and monthly statistical indicators of water temperature, lacking consideration of water ecological impact indicators.
[0004] Therefore, it is necessary to design a multi-element cooperative cascade reservoir water temperature variation evaluation method to overcome the above problems. SUMMARY
[0005] The purpose of the present application aims at the defects of the existing cascade reservoir water temperature variation evaluation method, which only targets a single reservoir and a single element, and lacks comprehensive consideration of the cumulative effect of cascade reservoir groups and multi-element indicators, and provides a multi-element cooperative cascade reservoir water temperature variation evaluation method, which is suitable for dynamic construction of cascade reservoir groups, selects water temperature indicators with ecological significance for cascade reservoir water temperature variation evaluation.
[0006] The invention idea of the present application is: based on the variation characteristics of the discharged water temperature under the dynamic construction and operation of the cascade reservoir group, a set of cascade reservoir discharged water temperature variation system considering multiple water temperature statistical value indicators and water ecological evaluation indicators is established, and from the time and space variation dimension, the discharged water temperature variation of different stages and different sections is analyzed, which provides a reference for the cascade reservoir dispatching.
[0007] Based on the above invention concept, the present application provides a multi-element cooperative cascade reservoir discharged water temperature variation evaluation method, which comprises the following steps: S1, according to the construction location and construction time of the hydropower station, the evaluation section and the operation stage are determined; S2, a water temperature change degree evaluation index system including multiple water temperature indicators is constructed; S3, the change range of each water temperature indicator of each evaluation section in different operation stages is calculated; S4, according to the change range of each water temperature indicator, the change degree corresponding to each water temperature indicator of each evaluation section in different operation stages is determined; S5, the comprehensive change degree of each evaluation section in different operation stages is determined according to the change degree corresponding to all water temperature indicators; S6, according to the change degree division standard, the discharged water temperature variation degree of each evaluation section in different operation stages is determined.
[0008] In the above step S1, according to the construction time of the cascade reservoir group and the development and operation of each cascade reservoir, the joint operation of different cascade reservoirs is taken as the division standard of different stages, and different operation stages are determined. According to the construction location of the reservoir group, typical monitoring sections are set at the upstream and downstream of the cascade reservoir as the evaluation sections, and the reservoir inflow and discharged water temperature are monitored.
[0009] In the step S2, the indicators of temperature alteration (ITA) are proposed by mainly referring to the IHA index system, and the variation degree of water temperature during the spawning period of fish is considered, and one or more than one of the monthly average water temperature, extreme water temperature and occurrence time, extreme temperature difference, extreme temperature rising rate and rising time, and the date when the water temperature reaches a specified temperature are selected. Specifically, the water temperature indicators include one or more than one of the 3-month average water temperature, 4-month average water temperature, 5-month average water temperature, 6-month average water temperature, minimum water temperature, minimum water temperature occurrence time, maximum water temperature, maximum water temperature occurrence time, extreme temperature difference (i.e. the difference between the maximum water temperature and the minimum water temperature), extreme temperature rising rate, minimum temperature rising to maximum temperature time, water temperature reaching 15°C date, water temperature reaching 17°C date, water temperature reaching 18°C date, and water temperature reaching 20°C date. Among them, the monthly average water temperature is an important statistical value representing the water temperature of the river; the extreme water temperature and other related indicators affect the length of each life cycle of aquatic organisms, the length of the feeding, spawning, and overwintering periods of fish, and the suitability of fish survival, etc. The specific water temperature mainly considers the minimum suitable water temperature required for the spawning and reproduction of main fish in the river, and the water temperature required for the spawning and reproduction of each fish is determined by analyzing and investigating the water monitoring data of the river, and the specific water temperature is determined according to the number and adaptability of fish in the river.
[0010] In the step S3, long sequence continuous data of daily average water temperature of the river are collected, and the water temperature data are analyzed in time sequence according to the division standard in the previous step, and the water temperature indicators before and after the construction of the cascade reservoir are calculated. For any to-be-evaluated section, the calculation method of the variation range of each water temperature indicator is as follows: ; ; ; Among them, is the reference value of the i-th water temperature indicator; is the number of years in the natural state stage of the to-be-evaluated section; is the i-th water temperature indicator in the natural state stage of the to-be-evaluated section; is the standard deviation of the i-th water temperature indicator of the to-be-evaluated section; is the upper limit value and the lower limit value of the i-th water temperature indicator of the to-be-evaluated section, , constitute the variation range of the water temperature indicator.
[0011] In step S4 above, the Range of Variability (RVA) approach is used. The RVA method is often used to assess changes in river hydrological conditions caused by human activities. It primarily calculates the degree of change of a single indicator after the river is affected, relative to the RVA threshold before the impact. The formula for calculating the degree of change corresponding to the i-th water temperature indicator at the assessed cross section and the assessed operational stage is as follows: ; in, The degree of change corresponding to the i-th water temperature index; The number of years in which the i-th indicator of the cross section to be evaluated falls within the range of water temperature variation during the operational phase to be evaluated. The section to be evaluated and the number of years of operation to be evaluated.
[0012] In step S5 above, the formula for calculating the comprehensive change degree of each cross section to be evaluated at different operational stages is as follows: ; in, To comprehensively change the degree; This refers to the quantity of water temperature indicators.
[0013] In step S6 above, the water temperature variability of the cascade reservoirs is classified according to the variability classification standard: when D0 is between 0% and 33%, the corresponding operating stage of the section to be evaluated belongs to low variability (L); when D0 is between 33% and 67%, the corresponding operating stage of the section to be evaluated belongs to medium variability (M); when D0 is between 67% and 100%, the corresponding operating stage of the section to be evaluated belongs to high variability (H).
[0014] Through the above steps S1-S5, the degree of change of each water temperature index and the comprehensive degree of change of each section at different operating stages can be calculated, and the degree of change of the outflow water temperature (i.e. the degree of change of outflow water temperature) of each section at different operating stages can be determined according to step S6.
[0015] By assessing the changes in downstream water temperature at different construction and operation stages of cascade reservoirs, we can better study the cumulative impact of the combined operation of cascade reservoirs on downstream water temperature, including the degree of change in downstream water temperature after cascade reservoir operation compared to the natural water temperature. Furthermore, by assessing the changes in downstream water temperature at typical cross-sections along the downstream river after cascade reservoir operation, we can better study the extent of the impact of cascade reservoir operation on downstream water temperature and the natural recovery process of the river.
[0016] Compared with existing technologies, the multi-factor coordinated method for assessing the temperature variability of cascade reservoir discharge provided by this invention has the following beneficial effects: (1) Based on river aquatic monitoring data and the development sequence of cascade reservoirs, this invention establishes a method for evaluating the temperature variability of water discharged from cascade reservoirs; (2) The water temperature index proposed in this invention takes into account the relationship between the aquatic ecological suitability of fish in rivers and water temperature. Based on the relationship between fish spawning and reproduction and water temperature change response, the degree of influence of water temperature change on aquatic ecology is further quantified. (3) This invention takes into account the different construction sequence of cascade reservoirs and uses the inlet and outlet sections of the cascade reservoir group as typical sections for cumulative impact assessment, which improves the accuracy and scientific nature of the assessment method. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the multi-factor collaborative method for assessing the temperature variability of cascade reservoir discharge provided in an embodiment of the present invention.
[0018] Figure 2 This describes the construction and cross-sectional distribution of the hydropower station according to an embodiment of the present invention.
[0019] Figure 3 This is a diagram showing the water temperature parameters and changes at section A.
[0020] Figure 4 This is a diagram showing the water temperature index and its change at section D. Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. The invention will be specifically described below in conjunction with the accompanying drawings and specific embodiments. An example is selected as the scheduling object, consisting of a cascade reservoir system composed of several reservoirs in the middle and upper reaches of the Yangtze River. The water temperature at each typical cross-section is analyzed in stages according to different reservoir operating conditions. Based on the calculated water temperature variability evaluation system indicators, the changes in water temperature are comprehensively evaluated in conjunction with the changes in each indicator.
[0022] Example
[0023] like Figure 1 As shown in this embodiment, the method for assessing the temperature variability of cascade reservoirs based on multi-factor collaboration includes the following steps:
[0024] S1. Based on the location and construction time of the hydropower station, determine the cross section to be evaluated and the operational stage.
[0025] In this step, based on the construction time of the cascade reservoir group and the development and operation status of each cascade reservoir, the joint operation of different cascade reservoirs is used as the standard for dividing different stages, thus determining different operation stages. Typical monitoring sections are set up upstream and downstream of the cascade reservoirs as evaluation sections according to their construction locations, to monitor the inflow and outflow water temperatures.
[0026] For example, for Figure 2 The given cascade reservoir group is constructed with typical monitoring sections set up upstream and downstream of the reservoirs, including sections A, B, C, and D. At section A, hydropower development was mainly concentrated between 2011 and 2023, with peak operation periods from 2014 to 2015 (hydropower station 2) and from 2021 to 2023 (hydropower station 3). Therefore, to analyze the degree to which the inflow water temperature in the study area is affected by upstream hydropower development, the analysis is divided into four periods: natural water temperature (2000-2010), the first operational stage (2011-2015), the second operational stage (2016-2020), and the third operational stage (2021-2023). Section B primarily examines the impact of the dynamic construction process of hydropower stations 4-7, therefore, the analysis is divided into three periods: natural water temperature (2000-2011), two-stage operation (2014-2019), and four-stage operation (2022-2023). Similarly, Section C is also divided into three periods: natural water temperature (2000-2011), two-stage operation (2014-2019), and four-stage operation (2022-2023). Section D mainly considers the joint operation of hydropower station 8 and hydropower stations 4-7, and is divided into four stages: natural water temperature (1984-2002), first operational stage development (2008-2011), second operational stage (2014-2019), and third operational stage (2022-2023).
[0027] S2, construct a water temperature change assessment index system that includes multiple water temperature indicators.
[0028] This step proposes an ITA (Index to Assess) system for water temperature variability in cascade reservoirs. It primarily considers the degree of water temperature variability during fish spawning season, taking into account factors such as monthly average water temperature, extreme temperatures and their occurrence times, extreme temperature differences and the rate and duration of extreme temperature rises, and the date the water temperature reaches a specified temperature. The specified water temperature mainly considers the minimum stable water temperature required for the spawning and reproduction of important fish species in the river. This is determined through analysis and investigation of aquatic monitoring data of the river, identifying the required spawning and reproduction temperatures for each fish species, and further defining the specified water temperature based on the fish population and adaptability in the river.
[0029] In this embodiment, for Figure 2The typical fish species in the downstream section of the cascade reservoirs listed in the report mainly include the four major freshwater fish species, the Chinese paddlefish, the copper carp, the common carp, the perch, and the mandarin fish. Based on their spawning and reproduction types, they can be divided into drift-spawning fish and sticky-spawning fish. Analysis of aquatic monitoring data shows that the initial water temperature for spawning of drift-spawning and sticky-spawning fish is 17℃ and 15℃, respectively, and the suitable spawning period before reservoir construction is from March to June. Based on the aquatic analysis results, 15 water temperature indicators are proposed: average water temperature from March to June (4 in total), minimum / maximum water temperature, time of occurrence of minimum / maximum water temperature, extreme temperature difference, extreme temperature rise rate, time from minimum to maximum temperature, date when water temperature reaches 15℃, date when water temperature reaches 17℃, date when water temperature reaches 18℃, and date when water temperature reaches 20℃. For section A, the water temperature indicators include the average water temperature from March to June (4 in total), the lowest / highest water temperature, the time when the lowest / highest water temperature occurred, the extreme temperature difference, the rate of temperature rise from the lowest to the highest temperature, the date when the water temperature reaches 15℃, and the date when the water temperature reaches 17℃. For section D, the water temperature indicators include the average water temperature from March to June (4 in total), the lowest / highest water temperature, the time when the lowest / highest water temperature occurred, the extreme temperature difference, the rate of temperature rise from the lowest to the highest temperature, the date when the water temperature reaches 18℃, and the date when the water temperature reaches 20℃.
[0030] S3, calculate the range of water temperature index changes for each section to be evaluated at different operating stages.
[0031] In this step, long-term continuous data of the river's daily average water temperature are collected. Based on the classification criteria from the previous step, time-series analysis is performed on the water temperature data to calculate water temperature indicators before and after the construction of the cascade reservoirs. For any cross-section to be evaluated, the calculation method for the range of variation of each water temperature indicator is as follows: ; ; ; in, This is the baseline value for the i-th water temperature index; The number of years in the natural state stage of the section to be evaluated; The i-th water temperature index in the natural state stage of the cross section to be evaluated; Let be the standard deviation of the i-th water temperature index at the cross section to be evaluated; Let i be the upper and lower limits of the water temperature index of the i-th cross section to be evaluated. , This constitutes the range of water temperature index changes.
[0032] S4. Based on the range of change of each water temperature index, determine the degree of change of each cross section to be evaluated at different operating stages and corresponding to the water temperature index.
[0033] The Range of Variability (RVA) approach is frequently used to assess changes in river hydrological conditions caused by human activities. It primarily calculates the degree of change of a single indicator relative to its pre-affected RVA threshold. The formula for calculating the degree of change corresponding to the i-th water temperature indicator at the assessed cross section and during the assessed operational phase is as follows: ; in, The degree of change corresponding to the i-th water temperature index; The number of years in which the i-th indicator of the cross section to be evaluated falls within the range of water temperature variation during the operational phase to be evaluated. For the cross section to be evaluated, the number of years of the operational phase to be evaluated (i.e., the total number of years of the water temperature index sequence during the operational phase after water storage; for example, for cross section A, the first operational phase is 2011-2015, then...) ).
[0034] For section A, the calculation results of the change in water temperature index at each operating stage are as follows: Figure 3 As shown in the figure. For section D, the calculation results of the change in water temperature index at each operating stage are as follows. Figure 4 As shown.
[0035] S5, determine the comprehensive change of each section to be evaluated at different operating stages based on the change of all water temperature indicators.
[0036] In step S5 above, the formula for calculating the comprehensive change degree of each cross section to be evaluated at different operational stages is as follows: ; in, To comprehensively change the degree; For the number of water temperature indicators, here .
[0037] The calculation results of the comprehensive change degree of cross-sections A and D at different operating stages are shown in Table 1.
[0038] Table 1. Statistical Table of Water Temperature Variation at Typical Cross-Sections
[0039]
[0040] S6. Based on the change degree classification standard, determine the degree of temperature variation of the outflow water at different operating stages of each section to be evaluated.
[0041] According to the classification standard for the degree of change, the water temperature variability of cascade reservoirs is classified as follows: when D0 is between 0% and 33%, the corresponding operating stage of the section to be evaluated belongs to low degree of change (L); when D0 is between 33% and 67%, the corresponding operating stage of the section to be evaluated belongs to medium degree of change (M); when D0 is between 67% and 100%, the corresponding operating stage of the section to be evaluated belongs to high degree of change (H).
[0042] As shown in Table 1, the increase in the number of cascade reservoirs under construction and operation leads to a greater variability in water temperature. This is related to the cumulative effects of the cascade reservoirs' construction and operation, as well as the transmission of the cumulative impact on water temperature. From a temporal perspective, section A, as the inlet section of the study area, saw its overall change in water temperature indicators increase from 33.3% (first operational stage) to 58.5% (third operational stage). Section D, as the outlet section of the study area, experienced an increase in overall variability in water temperature indicators from 48.5% (first operational stage) to 67.9% (third operational stage) due to the cumulative impact of the cascade reservoirs. From a spatial perspective, the variability in water temperature intensifies further along the river as the number of reservoirs increases, increasing from moderate change (section A) to significant change (section D). The construction and operation of cascade reservoirs have caused changes in water temperature in both time and space. This method can better quantify the degree of water temperature variability, providing a reference for assessing the impact of reservoirs at different operational stages on the downstream river ecosystem.
[0043] Therefore, this invention establishes a method for assessing the water temperature variability of cascade reservoirs based on the reproductive needs of river fish and the construction sequence of cascade reservoirs. This method considers the relationship between fish aquatic ecological suitability and water temperature, quantifies the impact of water temperature changes on the aquatic ecosystem based on the needs of fish spawning and reproduction for key water temperature indicators, and effectively assesses the contribution of cascade construction to water temperature variability by considering different construction sequences of cascade reservoirs and selecting typical cross-sections.
[0044] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.
[0045] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.
Claims
1. A method for evaluating the variation degree of water temperature discharged from a cascade reservoir in a multi-element synergy, characterized in that, The method comprises the following steps: S1, determining the to-be-evaluated sections and operation stages according to the construction location and construction time of the hydropower station; S2, constructing a water temperature change degree evaluation index system comprising multiple water temperature indexes; S3, calculating the change ranges of the water temperature indexes of each to-be-evaluated section in different operation stages; S4, determining the change degrees corresponding to the water temperature indexes of each to-be-evaluated section in different operation stages according to the change ranges of the water temperature indexes; S5, determining the comprehensive change degrees of each to-be-evaluated section in different operation stages according to the change degrees corresponding to all the water temperature indexes; S6, determining the water temperature variation degrees of each to-be-evaluated section in different operation stages according to the change degree division standard.
2. The method for evaluating the temperature variation degree of the water released from the cascade reservoirs according to claim 1, characterized in that, In step S2, the water temperature indexes comprise one or more of the following: monthly average water temperature, extreme water temperature and occurrence time, extreme temperature difference, extreme temperature rising rate and rising time, and the date when the water temperature reaches a specified temperature.
3. The method of claim 2, wherein the method further comprises: The water temperature indexes comprise one or more of the following: 3-month average water temperature, 4-month average water temperature, 5-month average water temperature, 6-month average water temperature, minimum water temperature, minimum water temperature occurrence time, maximum water temperature, maximum water temperature occurrence time, extreme temperature difference, extreme temperature rising rate, minimum temperature rising to maximum temperature time, water temperature reaching 15℃ date, water temperature reaching 17℃ date, water temperature reaching 18℃ date, and water temperature reaching 20℃ date.
4. The method for evaluating the temperature variation degree of the cascade reservoirs according to any one of claims 1 to 3, characterized in that, In step S3, for any to-be-evaluated section, the calculation method of the change range of each water temperature index is as follows: ； ； ； wherein, is the reference value for the i-th water temperature indicator; is the number of years in the natural state phase of the section to be evaluated; is the i-th water temperature indicator of the natural state phase of the section to be evaluated; is the standard deviation of the i-th water temperature indicator of the section to be evaluated; are the upper and lower limit values of the i-th water temperature indicator of the section to be evaluated, , ) constitute the range of variation of the water temperature indicator.
5. The method of claim 4, wherein the method further comprises: In step S4, the change degree corresponding to the i-th water temperature index of the to-be-evaluated section and the to-be-evaluated operation stage is calculated according to the following formula: ； wherein, is the change degree corresponding to the i-th water temperature index; is the number of years in which the i-th index of the section to be evaluated and the operation stage to be evaluated falls within the change range of the water temperature index; is the number of years of the section to be evaluated and the operation stage to be evaluated.
6. The method for evaluating the temperature variation degree of the water released from the cascade reservoirs according to claim 5, characterized in that, In step S5, the comprehensive change degree of each to-be-evaluated section in different operation stages is calculated according to the following formula: ； wherein, is the overall change degree; is the water temperature index number.
7. The method of claim 6, wherein the method further comprises: In step S6, according to the change degree division standard, the water temperature variation degrees of the cascade hydropower stations are divided: when D0 is 0-33%, the corresponding operation stage of the to-be-evaluated section belongs to low change L; when D0 is 33%-67%, the corresponding operation stage of the to-be-evaluated section belongs to medium change M; and when D0 is 67%-100%, the corresponding operation stage of the to-be-evaluated section belongs to high change H.