High dam reservoir water temperature prototype monitoring and evaluation method

Abstract

The invention provides a high dam reservoir water temperature prototype monitoring and evaluating method. The method comprises the steps that water temperature instruments are arranged in tail water in a reservoir, in front of a dam and behind the dam for surveying and arranging water temperature instruments, data are stored in an information box through a remote transmission instrument, maintenance is carried out when the data are abnormal, daily water temperature is processed through an IHA program and a change range method, monthly water temperature is analyzed through a monthly flow state analysis method, and results are compared. According to the method, synchronous prototype monitoring of the water temperature of the high dam reservoir and the downstream river channel is carried out, a numerical analysis method is carried out on observation data, the measured water temperature data are faster and more accurate, synchronous data of the vertical water temperature structure of the reservoir and the water temperature of the downstream river channel can be determined, and the real water temperature, temperature and structure can be better restored.

Description

Technical Field

[0001] The invention relates to the technical field of water conservancy and hydropower engineering, and in particular to a prototype monitoring and evaluation method for water temperature of a high dam reservoir. Background Art

[0002] Since the 20th century, large-scale power stations and reservoirs have begun to be built in the world. Although they have brought conveniences to human life such as power generation, irrigation, water storage, and regulation, they have also brought many harms to the natural environment and changed the original water flow state of the river. The change in hydrological conditions has a great impact on the fish in the water body, especially the change in water temperature directly interferes with the living habits of fish, resulting in a decrease in the reproductive capacity of many fish and destroying the natural reproduction laws of ecological species. The establishment of high dam reservoirs has a huge impact on the temperature of downstream water. The study of the evolution of water temperature in the reservoir area of ​​cascade power stations and rivers below the dam has always been the focus of domestic and foreign water conservancy scholars. It is mainly based on in-depth exploration of the research area, research methods, prototype observations, numerical analysis, and numerical model simulation. It is concluded that the deeper the reservoir built on the river, the larger the volume and the better the adjustability. However, one of the biggest impacts brought about by it is the change of river water temperature. The original summer water temperature will gradually increase with the temperature, but the deep water body of the reservoir cannot receive solar radiation, and the water temperature will be greatly reduced. The location of the reservoir discharge is almost at the bottom layer, which will cause low-temperature water to flow into the river. Fish cannot receive normal water temperature changes and cannot judge whether it is the spawning season. The construction of the Three Gorges Project has a huge impact on the downstream ecological and hydrological situation, directly interfering with the spawning environment of the four major carps. The researchers mainly used the hydrological index method, the range of variation method, and the ecological flow group method to study the hydrological situation before and after the completion of the dam, and constructed a conceptual model of the influence of hydrological situation on the reproduction of the four major carps.

[0003] Studying how to change the interference of the lowered temperature of the downstream water caused by the reservoir on fish is the current key problem. There have been many studies on the evolution trend of the water temperature of single-stage reservoirs. The cumulative effect of the joint operation of cascade power stations on the water temperature of the river is more significant. For example, the bottom water temperature of large domestic hydropower stations such as Ertan Hydropower Station will increase when the joint operation is relatively compared with the single-stage power station operation, while the surface water temperature will decrease. In addition, the water temperature stratification structure is unstable, and the evolution trend of the downstream water temperature is delayed in time sequence. The cumulative effect has a more significant impact on the ecological environment. Prototype observation of water temperature before and after the dam of each power station is one of the effective methods to study the specific evolution trend of river water temperature. The original hydrological station observation data can only roughly observe the water temperature at a fixed river position, and cannot be combined with the water temperature changes brought about by the regulation and operation of cascade power stations. Although there have been a lot of studies on the water temperature model prediction of high-dam reservoirs, few can use the actual observation data of the long-term synchronous changes in the temperature structure inside the reservoir and the downstream river water temperature to analyze. Due to the lack of detailed measured data in this regard, it will become difficult to predict and evaluate the water temperature changes of the cascade power stations built in the basin.

[0004] Therefore, it is necessary to design a prototype monitoring and evaluation method for high-dam reservoir water temperature to solve the problem that most existing technologies focus on theoretical model construction or short-term observations in local areas. Very few studies can successfully obtain and deeply analyze the actual observation data of the long-term temperature structure inside the reservoir and the synchronous changes in the water temperature of the downstream river channel, which makes researchers in a dilemma when facing the water temperature change problem caused by the construction of cascade power stations in the basin. Due to the lack of key data support, it is difficult to accurately grasp the dynamic changes of water temperature at different time scales, whether it is diurnal fluctuations, seasonal cycles or annual trends, they cannot be accurately described. In the spatial dimension, it is also impossible to clearly understand the correlation and differences between water temperatures at different depths, different regions of the reservoir and various sections of the downstream river channel. When predicting the water temperature changes of cascade power stations, the model lacks accuracy due to the lack of reliable data calibration, and it is difficult to effectively simulate key factors such as the reservoir water storage process, the complex relationship between the discharge flow and water temperature, and the synergistic impact between cascade power stations. In the evaluation phase, due to insufficient data, it is impossible to fully consider the various impacts of water temperature changes on river ecosystems, including potential interference with fish reproduction, aquatic plant growth, and microbial community structure. This makes it extremely difficult to formulate reasonable hydropower development strategies to ensure ecological balance, seriously hindering the sustainable development of water conservancy and hydropower projects. Summary of the invention

[0005] In view of this, the present invention proposes a prototype monitoring and evaluation method for water temperature in a high-dam reservoir, aiming to solve the problem that the existing technology is rarely able to utilize the actual observation data of long-term synchronous changes in the temperature structure inside the reservoir and the water temperature in the downstream river to analyze, making it difficult to predict and evaluate the water temperature changes of the cascade power stations built in the basin.

[0006] In one aspect, the present invention provides a prototype monitoring and evaluation method for water temperature of a high dam reservoir, comprising:

[0007] Set up monitoring points in the reservoir, in front of the dam and in the tailwater behind the dam, and conduct on-site surveys;

[0008] A water temperature monitoring instrument is installed at each monitoring point, and the casings of the water temperature monitoring instruments in the tailwater in front of the dam and behind the dam are placed in the water;

[0009] The remote real-time transmission water temperature monitoring instrument uploads the water temperature data to the information box and stores it. When abnormal data is detected, maintenance is carried out in time;

[0010] The IHA program is used to extract the hydrological variation index from the measured long series of daily water temperatures, and the variation range method is used to calculate the water temperature change degree.

[0011] The monthly flow pattern analysis method was used to analyze the trend of the measured long series of monthly water temperatures, and the water temperature change trend analysis results of the high dam reservoir obtained by the variation range method were compared with the water temperature change trend analysis results of the high dam reservoir obtained by the monthly flow pattern analysis method.

[0012] Furthermore, the monitoring point in front of the dam is located at a right angle between the spillway in front of the reservoir dam and the dam body;

[0013] The monitoring point in the reservoir is located in the center of the reservoir;

[0014] The monitoring point of the tailwater behind the dam is located at the bank of the tailwater;

[0015] The monitoring frequency in the library is once a week in summer, and the monitoring frequency in the library is once a month in autumn and winter.

[0016] Furthermore, remote real-time transmission water temperature monitors are arranged at monitoring points in front of the dam, fixed to the cables at intervals of 3 m, and sleeved on the cables;

[0017] Portable water temperature sensors are installed at monitoring points in the reservoir and fixed on cables at intervals of 3 m, without casings on the cables;

[0018] A remote real-time transmission water temperature monitor is set at the monitoring point of the tail water behind the dam.

[0019] Further, the calculation object of the IHA program is water temperature;

[0020] The hydrological change index is 27 water temperature change indexes extracted from the measured long series of daily water temperatures using the IHA program;

[0021] The variation range method is used to calculate the water temperature change degree for the 27 water temperature variation indices, and the data corresponding to 25% and 75% of the water temperature variation indices are selected as the upper and lower limits of the variation range method.

[0022] Further, the 27 water temperature change indicators include: average water temperature in January, average water temperature in February, average water temperature in March, average water temperature in April, average water temperature in May, average water temperature in June, average water temperature in July, average water temperature in August, average water temperature in September, average water temperature in October, average water temperature in November, average water temperature in December, annual minimum water temperature on one day, annual minimum water temperature on three days, annual minimum water temperature on seven days, annual minimum water temperature on thirty days, annual minimum water temperature on ninety days, annual maximum water temperature on one day, annual maximum water temperature on three days, annual maximum water temperature on seven days, annual maximum water temperature on thirty days, annual maximum water temperature on ninety days, annual maximum water temperature on the date of occurrence of annual maximum water temperature, annual minimum water temperature date, number of high water temperature pulses, number of low water temperature pulses, number of temperature rises;

[0023] The calculation formula of the water temperature change is:

[0024]

[0025] Where D i is the change degree of the ith IHA index; N obi is the number of years for calculation, which refers to the number of years after the completion of the reservoir when the i-th IHA index falls within the target range; N e The expected number of years refers to the number of years after the reservoir is built that is expected to fall within the target range of the water temperature change index in the natural state before the reservoir was built.

[0026] Furthermore, the research object of the monthly flow pattern analysis method is water temperature, and the magnitude influencing factor, time series influencing factor, and variation influencing factor are used to quantify the change of water temperature, and the comprehensive river influencing factor is used to judge the overall change of the river. The specific formula is as follows:

[0027] RI=MIF×(TIF+VIF)

[0028] MIF=AT post / AT pre

[0029] VIF=(50-0.5×I RR ) / 100

[0030]

[0031] IF 0<<T<<8.33:MRRP=-12×T+100

[0032] IF 8.333<<T<<13.333:MRRP=+12×T-100

[0033] IF 13.333<<T<<100:MRRP=0.46×T+53.85

[0034] TIF = (50-0.274×TF) / 100

[0035]

[0036] In the formula, RI is the comprehensive impact factor of the river; MIF is the magnitude impact factor; AT post is the annual water temperature after the dam is built; AT pre is the annual water temperature in the natural state before the dam was built; VIF is the variation influencing factor; I RR is the percentage deviation of RRI; RRI is the river water temperature index before and after the dam construction; MRRP is the monthly water temperature characteristic point, representing the river where the monthly water temperature varies from the annual mean to 0; k is the number of months; T is the long-term monthly mean water temperature calculated under the unit river concept; TIF is the time series influencing factor; TT maxis the time shift of the maximum monthly water temperature; TT min is the time shift of the minimum monthly water temperature; TT median is the time shift of the median monthly water temperature.

[0037] Furthermore, RI varies between 0 and 1. 0 represents the natural water temperature state of the river, and 1 represents the river with a completely changed water temperature. The impact levels are divided into low impact (0.8 < RI < 1), initial impact (0.6 < RI < 0.8), medium impact (0.4 < RI < 0.6), severe impact (0.2 < RI < 0.4), and drastic impact (0 < RI < 0.2);

[0038] VIF shows the temperature homogenization after the dam is built. VIF is obtained by scaling IRR to a value between 0 and 0.5, where the maximum impact is 0.5;

[0039] TIF quantifies the impact of the water temperature change time series on the water temperature distribution, where the maximum impact is 0.5.

[0040] Furthermore, D is the overall change value between the corresponding time series. When D is in the range of 0% - 33%, it belongs to low change; when it is in the range of 33% - 67%, it belongs to medium change; when it is in the range of 67% - 100%, it belongs to high change;

[0041] Compare D with RI numerically to contrast the analysis results of the water temperature change trend of high - dam reservoirs obtained by the range - of - change method and the analysis results of the water temperature change trend of high - dam reservoirs obtained by the monthly flow regime analysis method.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows: A method and system for prototype monitoring and evaluation of the water temperature of a high - dam reservoir in the present invention systematically carry out synchronous prototype monitoring of the water temperature of the high - dam reservoir and the downstream river channel, and perform a numerical analysis method on the observed data. The measured water temperature data is faster and more accurate, and the synchronous data of the vertical water temperature structure of the reservoir and the water temperature of the downstream river channel can be determined, and the real water temperature and structure can be restored more. The water temperature data is calculated by combining three methods: the hydrological change index method, the range - of - change method, and the monthly flow regime analysis to obtain the comprehensive evaluation result of the water temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered as a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0044] Figure 1 is the functional block diagram of the method for prototype monitoring and evaluation of the water temperature of a high - dam reservoir in the embodiment of the present invention;

[0045] Figure 2It is a classification map of river conditions before and after dam construction;

[0046] Figure 3 This is a comparison chart between the comprehensive change degree of the RVA method and the RI value. DETAILED DESCRIPTION

[0047] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to be able to fully convey the scope of the present invention to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the implementation regulations.

[0048] Reference Figure 1 As shown, in some embodiments of the present application, a prototype monitoring and evaluation method for water temperature of a high dam reservoir includes:

[0049] Set up monitoring points in the reservoir, in front of the dam and in the tailwater behind the dam, and conduct on-site surveys;

[0050] A water temperature monitoring instrument is installed at each monitoring point, and the casings of the water temperature monitoring instruments in the tailwater in front of the dam and behind the dam are placed in the water;

[0051] The remote real-time transmission water temperature monitoring instrument uploads the water temperature data to the information box and stores it. When abnormal data is detected, maintenance is carried out in time;

[0052] The IHA program is used to extract the hydrological variation index from the measured long series of daily water temperatures, and the variation range method is used to calculate the water temperature change degree.

[0053] The monthly flow pattern analysis method was used to analyze the trend of the measured long series of monthly water temperatures, and the water temperature change trend analysis results of the high dam reservoir obtained by the variation range method were compared with the water temperature change trend analysis results of the high dam reservoir obtained by the monthly flow pattern analysis method.

[0054] Specifically, the monitoring point is located near the spillway in front of the reservoir dam and at a right angle to the dam body. This is a dead corner of the water flow, and the flow is relatively stable when the spillway is opened. Since there are no fixed buildings in the reservoir for the remote real-time transmission water temperature monitoring instrument to attach to, the staff can only rely on sailing to the reservoir to use portable water temperature sensors to monitor the data in real time. The basic water temperature of the reservoir is monitored at different frequencies in different seasons. The water temperature changes greatly in spring and summer, so it is monitored once a week. The water temperature changes less in autumn and winter, so it is monitored once a month. The monitoring data in the reservoir can be used as supplementary data for the water temperature in front of the reservoir dam. The tailwater of the reservoir is generally extremely unstable during flood discharge, and the water flow under normal operating conditions is relatively stable. The remote real-time transmission water temperature monitoring instrument can be placed at a suitable water depth on the shore of the tailwater, and the power station maintenance and operation personnel can be arranged to pull out the equipment when the spillway is opened to avoid damage to the equipment.

[0055] It is understandable that the monitoring points in front of the dam are located at the right angles between the spillway in front of the reservoir and the dam body, in the center of the reservoir, and at the tailwater bank behind the dam. The monitoring frequency in the reservoir is adjusted according to the season, which can comprehensively and accurately capture water temperature data, effectively reflect the law of water temperature changes, and help scientifically assess the impact of the reservoir on the ecological environment.

[0056] Specifically, a remote real-time transmission water temperature monitor is set at the monitoring point in front of the dam, fixed on the cable at intervals of 3m, and a casing is set on the cable; a portable water temperature sensor is set at the monitoring point in the reservoir, fixed on the cable at intervals of 3m, and no casing is set on the cable; a remote real-time transmission water temperature monitor is set at the monitoring point of the tail water behind the dam.

[0057] It can be understood that by setting up specific water temperature monitoring instruments in front of the dam, in the reservoir, and in the tailwater behind the dam, the remote real-time transmission instruments in front of the dam are fixed at 3m intervals and casing, the portable instruments in the reservoir are fixed at 3m intervals and without casing, and a single remote instrument is set in the tailwater behind the dam. It is possible to accurately, efficiently and specifically obtain water temperature data at different locations, provide strong support for a comprehensive assessment of the changing patterns and impacts of reservoir water temperature, greatly improve the scientificity and reliability of monitoring, and effectively assist subsequent research and management decisions.

[0058] Specifically, the remote real-time transmission water temperature monitoring instrument uploads the measured water temperature data to the information box according to the time node and stores it. The staff can monitor the data in real time on the computer terminal to see if there are any abnormalities. If any abnormalities are found, they will be processed and repaired in time.

[0059] Specifically, the IHA program generally calculates the hydrological situation. The present invention also applies it to water temperature. The water temperature has a minimum value of 0°C, so the annual minimum water temperature is not judged. Only 27 water temperature change indicators are extracted from the measured long series of daily water temperatures. The specific indicators are shown in Table 1.

[0060] The range method is used to calculate the water temperature change for the above 27 water temperature change indicators. The data corresponding to 25% and 75% of the water temperature change indicators are selected as the upper and lower limits of the range method. Similarly, the formula used for the water temperature change (RVA) is as follows:

[0061]

[0062] Di: the degree of change of the ith IHA index; Nobi: the number of calculated years, which refers to the number of years after the completion of the reservoir that the ith IHA index falls within the target range; Ne: the expected number of years, which refers to the number of years after the completion of the reservoir that the water temperature change index in the natural state before the completion of the reservoir is expected to fall within the target range; D: the overall change value between the corresponding time series. D between 0% and 33% is a low change (L), 33% to 67% is a moderate change (M), and 67% to 100% is a high change (H).

[0063] It is understandable that by applying the IHA program to water temperature calculations, extracting 27 key water temperature change indicators, and using the range of change method to calculate the degree of water temperature change based on specific proportion data, and accurately judging the degree of change based on the formula, the water temperature change trend of the reservoir can be systematically and scientifically analyzed, providing solid data support and scientific basis for effectively evaluating the impact of reservoirs on the ecological environment and water temperature, and effectively promoting the coordinated progress of hydropower development and ecological protection.

[0064] Specifically, the monthly flow pattern analysis method is used to analyze the trend of the measured long series of monthly water temperatures. Initially, the research object of the monthly flow pattern analysis method is flow. In this invention, the research object is changed to water temperature. The magnitude impact factor (MIF), time series impact factor (TIF), and variation impact factor (VIF) are mainly used to quantify the change of water temperature. Finally, the comprehensive river impact factor (RI) is a combination of the above three impact factors to comprehensively judge the overall change of the river. The specific formula is as follows:

[0065] RI=MIF×(TIF+VIF)

[0066] MIF=AT post / AT pre

[0067] VIF=(50-0.5×I RR ) / 100

[0068]

[0069] IF 0<<T<<8.33:MRRP=-12×T+100

[0070] IF 8.333<<T<<13.333:MRRP=+12×T-100

[0071] IF 13.333 << T << 100: MRRP = 0.46×T + 53.85

[0072] TIF = (50 - 0.274×TF) / 100

[0073]

[0074] RI: River comprehensive impact factor, RI varies between 0 and 1. 0 represents the natural water temperature state of the river, and 1 represents the river with completely changed water temperature. The influence of human factors is divided into low influence (0.8 < RI < 1), initial influence (0.6 < RI < 0.8), medium influence (0.4 < RI < 0.6), severe influence (0.2 < RI < 0.4), and drastic influence (0 < RI < 0.2); MIF: Magnitude influence factor; ATpost: Annual water temperature (°C) after the dam is built; ATpre: Annual water temperature (°C) in the natural state before the dam is built; VIF: Variation influence factor, which shows the water temperature change after the dam is built and is obtained by scaling IRR to a value between 0 and 0.5, with the maximum influence being 0.5. IRR: Percentage deviation of RRI; RRI: River channel water temperature index before and after dam construction; MRRP: Monthly water temperature characteristic point, representing the river where the monthly water temperature varies from the annual average value to 0; k: Number of months; T: Long-term monthly average water temperature (°C) calculated under the unit river concept; TIF: Temporal influence factor, which quantifies the influence of the water temperature change time sequence on the water temperature distribution, with the maximum influence being 0.5; TTmax: Time shift of the maximum monthly water temperature / d; TTmin: Time shift of the minimum monthly water temperature / d; TTmedian: Time shift of the monthly water temperature median / d.

[0075] It can be understood that by focusing on water temperature research with the monthly flow pattern analysis method, quantifying and evaluating water temperature changes through magnitude, temporal, variation influence factors and comprehensive river influence factors, accurately defining the influence level according to the formula, it is possible to comprehensively understand the water temperature dynamics before and after reservoir construction, provide a key basis for scientifically evaluating the impact of water temperature changes on the river ecosystem, and effectively ensure the ecological sustainability of water conservancy projects.

[0076] Specifically, compare the values of D and RI to compare the analysis results of the water temperature change trend of high dam reservoirs obtained by the change range method and the analysis results of the water temperature change trend of high dam reservoirs obtained by the monthly flow pattern analysis method.

[0077] Example 1

[0078] Taking the Longyangxia Reservoir in the upper reaches of the Yellow River as the research object of this invention, a prototype monitoring scheme was made for the long series of daily water temperature monitoring of the Longyangxia Reservoir. The monitoring points were set on the side wall of the water inlet platform in front of the dam of the Longyangxia Reservoir. The water flow here is relatively gentle, which is convenient for later data collection and equipment maintenance; the points behind the dam are arranged 1km away from the tailwater of the Longyangxia Reservoir and placed in the water along the left bank. When the flood discharge gate is opened, the staff needs to use a winch to pull the cable out of the instrument to prevent the equipment from being impacted and lost by the flood; the water temperature monitoring in the reservoir also uses a portable water temperature sensor to be fixed on the cable at intervals of 3m. Because the measurement time is short and no casing is required, it is directly lowered into the water by the staff for measurement. Measurements are made twice in the beginning and middle of the month in spring, summer and autumn, and once a month in winter.

[0079] Based on the historical monitored water temperature data of the Longyangxia Reservoir, 27 IHA water temperature indicators were extracted, and the water temperature change before and after the reservoir was built was analyzed according to the range of variation method (RVA). The results are shown in Table 1.

[0080] Table 1 List of water temperature index changes

[0081]

[0082]

[0083] The comprehensive change degree of human factors on the river after the dam construction is 79%, which is a high impact level.

[0084] Based on the monthly series of water temperature data previously monitored downstream of the Longyangxia Reservoir, the monthly flow pattern analysis method (RI) was used to analyze the changes in river water temperature. According to the changes in the second term (VIF+TIF) in the RI formula, it was classified into low impact, initial impact, medium impact, severe impact, and drastic impact. The results are as follows: Figure 2 shown.

[0085] By comparing the water temperature data under the dam monitored by the Longyangxia Reservoir before using the above two methods, it can be seen that the impact of the dam construction on the river from 2006 to 2020 using the monthly flow state analysis method (RI) was between medium and severe impact levels, while the comprehensive change degree using the range of variation method (RVA) was 79%, which is a high level of change. The range of variation method (RVA) is more serious than the monthly flow state analysis method (RI). Figure 3 shown.

[0086] It should be noted that:

[0087] In the description provided herein, a large number of specific details are described. However, it is understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known structures and technologies are not shown in detail so as not to obscure the understanding of this description.

[0088] Furthermore, those skilled in the art will appreciate that although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features from different embodiments is meant to be within the scope of the present application and to form different embodiments.

[0089] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A prototype monitoring and evaluation method for water temperature in a high dam reservoir, characterized in that: include: Set up monitoring points in the reservoir, in front of the dam and in the tailwater behind the dam, and conduct on-site surveys; A water temperature monitoring instrument is installed at each monitoring point, and the casings of the water temperature monitoring instruments in the tailwater in front of the dam and behind the dam are placed in the water; The remote real-time transmission water temperature monitoring instrument uploads the water temperature data to the information box and stores it. When abnormal data is detected, maintenance is carried out in time; The IHA program is used to extract the hydrological variation index from the measured long series of daily water temperatures, and the variation range method is used to calculate the water temperature change degree. The monthly flow pattern analysis method was used to analyze the trend of the measured long series of monthly water temperatures, and the water temperature change trend analysis results of the high dam reservoir obtained by the variation range method were compared with the water temperature change trend analysis results of the high dam reservoir obtained by the monthly flow pattern analysis method.

2. A high dam reservoir water temperature prototype monitoring and evaluation method according to claim 1, characterized in that: The monitoring point in front of the dam is located at a right angle between the spillway in front of the reservoir dam and the dam body; The monitoring point in the reservoir is located in the center of the reservoir; The monitoring point of the tailwater behind the dam is located at the bank of the tailwater; The monitoring frequency in the library is once a week in summer, and the monitoring frequency in the library is once a month in autumn and winter.

3. A prototype monitoring and evaluation method for water temperature of a high dam reservoir according to claim 1, characterized in that: Remote real-time transmission water temperature monitors are set at monitoring points in front of the dam, fixed on cables at intervals of 3m, and sleeved on the cables; Portable water temperature sensors are installed at monitoring points in the reservoir and fixed on cables at intervals of 3 m, without casings on the cables; A remote real-time transmission water temperature monitor is set at the monitoring point of the tail water behind the dam.

4. A prototype monitoring and evaluation method for water temperature of a high dam reservoir according to claim 1, characterized in that: The calculation object of the IHA program is water temperature; The hydrological change index is 27 water temperature change indexes extracted from the measured long series of daily water temperatures using the IHA program; The variation range method is used to calculate the water temperature change degree for the 27 water temperature variation indices, and the data corresponding to 25% and 75% of the water temperature variation indices are selected as the upper and lower limits of the variation range method.

5. A prototype monitoring and evaluation method for water temperature of a high dam reservoir according to claim 4, characterized in that: The 27 water temperature change indicators include: average water temperature in January, average water temperature in February, average water temperature in March, average water temperature in April, average water temperature in May, average water temperature in June, average water temperature in July, average water temperature in August, average water temperature in September, average water temperature in October, average water temperature in November, average water temperature in December, annual minimum water temperature on one day, annual minimum water temperature on three days, annual minimum water temperature on seven days, annual minimum water temperature on thirty days, annual minimum water temperature on ninety days, annual maximum water temperature on one day, annual maximum water temperature on three days, annual maximum water temperature on seven days, annual maximum water temperature on thirty days, annual maximum water temperature on ninety days, date of occurrence of annual maximum water temperature, date of occurrence of annual minimum water temperature, number of high water temperature pulses, number of low water temperature pulses, number of temperature rises; The calculation formula of the water temperature change is: Where D i is the change degree of the ith IHA index; N obi is the number of years for calculation, which refers to the number of years after the completion of the reservoir when the i-th IHA index falls within the target range; N e The expected number of years refers to the number of years after the reservoir is built that is expected to fall within the target range of the water temperature change index in the natural state before the reservoir was built.

6. A prototype monitoring and evaluation method for the water temperature of a high dam reservoir according to claim 1, characterized in that The research object of the monthly flow pattern analysis method is water temperature, and magnitude influence factors, time series influence factors, and variation influence factors are used to quantify the water temperature change, and the overall change of the river is judged by using the comprehensive river influence factor. The specific formula is as follows: RI = MIF × (TIF + VIF) MIF=AT post / AT pre VIF=(50-0.5×I RR ) / 100 IF 0 << T << 8.33: MRRP = -12 × T + 100 IF 8.333 << T << 13.333: MRRP = +12 × T - 100 IF 13.333 << T << 100: MRRP = 0.46 × T + 53.85 TIF = (50 - 0.274 × TF) / 100 In the formula, RI is the comprehensive impact factor of the river; MIF is the magnitude impact factor; AT post is the annual water temperature after the dam is built; AT pre is the annual water temperature in the natural state before the dam was built; VIF is the variation influencing factor; I RR is the percentage deviation of RRI; RRI is the river water temperature index before and after the dam construction; MRRP is the monthly water temperature characteristic point, representing the river where the monthly water temperature varies from the annual mean to 0; k is the number of months; T is the long-term monthly mean water temperature calculated under the unit river concept; TIF is the time series influencing factor; TT max is the maximum monthly water temperature time shift; TT min is the minimum monthly water temperature time shift; TT median is the time shift of the median monthly water temperature.

7. A prototype monitoring and evaluation method for the water temperature of a high dam reservoir according to claim 6, characterized in that RI varies between 0 and 1. 0 represents the natural water temperature state of the river, and 1 represents the river with completely changed water temperature. The influence levels are divided into low influence (0.8 < RI < 1), initial influence (0.6 < RI < 0.8), medium influence (0.4 < RI < 0.6), severe influence (0.2 < RI < 0.4), and drastic influence (0 < RI < 0.2); VIF shows the water temperature homogenization after the dam is built. VIF is obtained by scaling IRR to a value between 0 and 0.5, where the maximum influence is 0.5; TIF quantifies the influence of the water temperature change time series on the water temperature distribution, where the maximum influence is 0.

5.

8. A prototype monitoring and evaluation method for the water temperature of a high dam reservoir according to claim 7, characterized in that D is the overall change value calculated between the corresponding time series. When D is in the range of 0% to 33%, it belongs to low change; when it is in the range of 33% to 67%, it belongs to medium change; when it is in the range of 67% to 100%, it belongs to high change; Compare the value of D with RI to compare the water temperature change trend analysis results of the high dam reservoir obtained by the change range method and the water temperature change trend analysis results of the high dam reservoir obtained by the monthly flow pattern analysis method.

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