Method for calculating water intake guarantee rate of nuclear power users at downstream of multi-gate dam river

Abstract

The invention discloses a method for calculating the water intake guarantee rate of nuclear power users at the downstream of a multi-gate-dam river. The method comprises the following steps that 1, the water delivery reach, gate dam distribution and the initial water storage capacity of the multi-gate-dam river are determined; 2, constructing a distributed water circulation model to obtain a sub-basin dynamic flow process; 3, calculating the outflow of a water delivery point by considering the drainage basin upstream convergence process and the drainage basin outside water delivery process; 4, from the upstream to the downstream of the water delivery river section, the water storage capacity and the outflow capacity of each gate dam unit are calculated in an echelon mode; 5, determining the water intake guarantee rate requirement of the downstream nuclear power user, and calculating the water demand and the available water intake; and step 6, based on a long series calculation result, giving a nuclear power user water taking guarantee rate. According to the method, organic fusion of the distributed water circulation model, hydraulic engineering scheduling and the human drainage taking process is achieved, quantitative calculation is conducted on the water taking guarantee rate, and technical support can be provided for multi-gate dam river ecological protection and water resource development, utilization and management.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrology and water resources utilization, and particularly relates to a calculation method of a nuclear power user water guarantee rate in a downstream of a multi-dam river. BACKGROUND

[0002] Building dams (such as flat gates, hydraulic lifting gates, rubber dams and other hydraulic structures) on rivers is an important way for human beings to develop and utilize water resources. For a long time, people have regulated river water by means of dam systems to achieve comprehensive service functions such as flood control, water supply, irrigation, power generation and navigation. Using the natural channel of the river to transport water for downstream users does not occupy land resources and does not require the construction of large-scale infrastructure (such as water supply pipelines), which can significantly reduce the construction investment and operating costs of water supply, and can also improve the conditions of hydropower generation, navigation and agricultural irrigation of the dam, which is conducive to the maintenance of the river ecosystem along the line and has significant social and economic benefits.

[0003] Due to the influence of the barrier of the dam project, the multi-dam river is influenced by a variety of complex factors such as river inflow process, water transport scale, dam scheduling, evaporation and leakage, and human use and drainage in the interval when transporting water for downstream users. The downstream water user, such as a nuclear power plant, produces heat through nuclear fission. This heat must be continuously removed through cooling water to maintain the normal operation and safety of the reactor. Once the cooling is interrupted, the reactor may lose control due to the inability to dissipate heat, causing serious safety accidents. Therefore, the downstream nuclear power user has the characteristics of large water demand (cooling water) and uninterrupted water use. Scientifically calculating the water guarantee rate of the downstream nuclear power user of the multi-dam river is of great significance to the water resources management of the dam river. At present, when using the multi-dam river for water transport, the water guarantee rate of the downstream water user is mostly based on hydrological analysis, which does not fully reflect the scheduling process of the dam and human activity decisions. Therefore, how to scientifically and efficiently calculate the water guarantee rate of the downstream nuclear power user of the multi-dam river is a technical problem that needs to be solved in the field at present. SUMMARY

[0004] The purpose of the present application is to provide a calculation method of a nuclear power user water guarantee rate in a downstream of a multi-dam river to solve the above technical problems.

[0005] To achieve the above purpose, the present application provides the following technical scheme: the present application discloses a calculation method of a nuclear power user water guarantee rate in a downstream of a multi-dam river, which comprises the following steps:

[0006] Step 1, determining the water delivery river section, dam distribution and initial storage of the multi-dam river: according to the water delivery engineering planning or design scheme of the multi-dam river basin or region, the location of the upstream water delivery point of the multi-dam river and the location of the downstream water user are identified, and the range of the multi-dam river water delivery river section is determined; then according to the relevant planning and water conservancy engineering data of the basin, the number, spatial distribution and characteristic parameters of the dams in the water delivery river section are determined; and the initial storage of each dam is determined;

[0007] Step 2, constructing a distributed water cycle model to obtain the dynamic flow process of the sub-basin: a distributed water cycle model of the basin where the multi-dam river is located is constructed, and then the constructed distributed water cycle model is used for calculation to obtain the daily dynamic flow process of all sub-basins in the basin where the multi-dam river is located;

[0008] Step 3, considering the upstream inflow and external water delivery process of the basin, calculating the outflow of the water delivery point: the water delivery river section and the sub-basin are spatially superimposed and analyzed to identify the sub-basin corresponding to the upstream of the water delivery point of the water delivery river section; based on the simulation results of the distributed water cycle model, the flow process of each sub-basin in the upstream of the basin corresponding to the water delivery point is read and summarized as the upstream inflow; combined with the basic demand of the downstream water user of the multi-dam river, the external water delivery amount of the basin corresponding to the water delivery point is determined according to the water source engineering planning and related design scheme of the basin; without considering the mixing loss of water flow, the sum of the upstream inflow and the external water delivery amount of the basin is taken as the outflow of the water delivery point of the water delivery river section, and the calculation formula is:

[0009]

[0010] In the formula, QM t is the outflow of the water delivery point of the water delivery river section at the t time, m 3 ; Qm i,t is the upstream inflow of the basin corresponding to the water delivery point of the i sub-basin at the t time, which is obtained by reading the calculation results of the distributed water cycle model, m 3 ; Nm is the number of sub-basins in the upstream of the basin corresponding to the water delivery point, pieces; Qb t is the external water delivery amount of the basin corresponding to the water delivery point at the t time, m 3 ;

[0011] Step 4, from upstream to downstream of the water conveyance reach, the storage and outflow of each dam unit are calculated in stages: first, the number and range of dam units of the water conveyance reach are determined; then, each dam unit is spatially superimposed with all sub-basins of the basin to identify the sub-basins corresponding to each dam unit of the water conveyance reach, read the calculation results of the distributed water cycle model, and aggregate and calculate the interval inflow of the dam unit as the interval inflow; according to the calculated outflow of the upstream water conveyance point, combined with the interval inflow, considering the water consumption loss in the evaporation, seepage process and human activity water taking process, combined with the dam scheduling water level limit requirement and the downstream ecological flow index, the storage and outflow at different times are calculated, and the specific calculation formula is:

[0012] Vm j,t =max(Qi j,t +Qr j,t -Qz j,t -Ql j,t -Qu j,t -Qe j,t ,0) (2)

[0013] V j,t =max(Vm j,t +V j,t-1 ,Vl j,t ) (3)

[0014] Vl j,t =fv j (Hl j,t ) (4)

[0015] O j,t =Vm j,t -V j,t +V j,t-1 (5)

[0016] In the formula, Qi j,t is the inflow of the jth dam unit at the tth time, such as j = 1, which is the outflow of the water conveyance point; if j > 1, it is the outflow of the upstream dam unit, m 3 , j = 1, 2, 3…J+1, J is the number of dam units of the water conveyance reach, m j,t ; Qr 3 is the interval inflow of the jth dam unit at the tth time, which comes from the calculation results of the distributed water cycle model, m j,t ; Qz j,t and Ql 3 are the net evaporation and seepage of the jth dam unit at the tth time, m j,t ; Qu 3 is the water consumption in the human activity water taking process of the jth dam unit at the tth time, m j,t ; Qeis the ecological flow index requirement for the jth dam unit at time t, m 3 ;Vm j,t is the water storage capacity of the jth dam unit at time t, m 3 ; V j,t and V j,t-1 are the actual water storage capacity of the jth dam unit at time t and time t-1, m 3 , when t=1, V j,t-1 is the initial water storage in step 1; Vl j,t Hl is the limited water storage capacity of the jth dam unit at time t, j,t The limited water level of the jth dam unit at time t; fv j () function is the water level-storage capacity curve of the j-th dam unit; j,t is the outflow of the jth dam unit at time t, m 3 ;

[0017] Step 5: Clarify the water withdrawal guarantee rate requirements of downstream nuclear power users and calculate the water demand and available water volume: First, clarify the water withdrawal guarantee rate requirements of downstream nuclear power users. The water withdrawal guarantee rate of downstream nuclear power users represents the probability that water withdrawal can be met at the time of withdrawal. Then, calculate the water demand based on the living and production characteristics of downstream nuclear power users. The calculation formula is:

[0018] QN t =Qna t +Qnb t +Qnv t +Qnd t (twenty three)

[0019] Where QN t is the water demand of nuclear power users at time t, m 3 ;Qna t 、Qnb t 、Qnc t 、Qnd t They are the cooling tower make-up water volume, in-plant water system make-up water volume, desalination, industrial and domestic make-up water volume, and the water demand for unforeseen and leakage at time t, m 3 ;

[0020] Then, based on the location characteristics of the water intake project of the downstream nuclear power user and the outflow of the sluice dam unit where the water is taken, the available water volume is determined and divided into two types:

[0021] a) When a nuclear power user draws water from the last sluice gate unit in a water diversion section, the amount of water that can be drawn is less than the water withdrawal capacity limit and the outflow of the sluice gate unit. The specific calculation formula is as follows:

[0022] QX t=min(QNl t ,O j＝J,t ) (twenty four)

[0023] Where, QX t is the available water volume for downstream nuclear power users at time t, m 3 ;QNl t is the water intake capacity limit of downstream nuclear power users at time t, m 3 , such as unlimited time QNl t =∞;O j＝J,t is the outflow of the dam unit where the nuclear power user takes water upstream at time t, m 3 ;

[0024] b) Nuclear power users draw water downstream of the last dam in the water transfer section. The amount of water that the nuclear power user can draw is less than the water withdrawal capacity limit and the outflow of the dam unit minus the downstream flow requirement of the water withdrawal section. The specific calculation formula is as follows:

[0025] QX t =min(QNl t ,O 1＝J,t -Qe j+1,t ) (25)

[0026] In the formula, Qe j+1,t is the discharge flow requirement of the downstream nuclear power user water intake section at time t, m 3 ;

[0027] According to the relevant technical specifications and industry standards for nuclear power plant engineering hydrology, the data used to calculate the water withdrawal guarantee rate for downstream nuclear power users is a long series of data with a length of more than 30 years. Based on steps 2 to 5 above, the daily calculation of the water withdrawal capacity for long-term nuclear power users is performed until the required number of years for the long-term calculation is met.

[0028] Step 6: Based on the long series calculation results, the water withdrawal guarantee rate for nuclear power users is given: Based on the long series daily calculation results of the available water for nuclear power users obtained in the above steps, and taking into account the continuity and reliability requirements of nuclear power users, when the available water cannot meet the water demand on any day in a year, it is determined that the water demand for that year is not met. Based on this criterion, the water withdrawal guarantee rate is calculated. The specific calculation formula is:

[0029]

[0030] Where, P is the water intake guarantee rate of downstream nuclear power users, %; Y is the number of years for long series data calculation, year; ty represents the year number, ty = 1, 2, 3...Y; N1 ty The starting date of the tyth year; N2 ty The end date of year ty.

[0031] Further, the determination of the range of the water delivery river section of the multi-gate dam in step 1 is specifically: if the water delivery point and the water intake point are both located in the main stream of the river, the water delivery river section is located in the main stream of the river; if the water delivery point is located in the branch stream and the water intake point is located in the main stream, the water delivery river section is located in the main and branch streams of the river;

[0032] The characteristic parameters of the dam of the water delivery river section specifically include a water level-area curve, i.e., a functional relationship between the water level of the reservoir and the corresponding water storage area, a water level-storage capacity curve, i.e., a functional relationship between the water level of the reservoir and the corresponding water storage volume, the water level limit for dam regulation in different periods including the flood period and the non-flood period, and the ecological flow discharge index requirement;

[0033] The specific process of determining the initial water storage of each dam is: if there are long series of observation data of the dam, the actual water storage of the reservoir in the starting year calculated by the long series is directly taken as the initial value; if there is a lack of long series of observation data of the dam, the water storage corresponding to the dead storage water level is taken as the initial value; the long series is more than 30 years of data.

[0034] Further, the construction of the distributed water cycle model in step 2 specifically includes the following steps:

[0035] 1) Collect and process multi-source data: specifically including collecting and processing river system, meteorological hydrological, land use, topography, soil geology, vegetation cover, water conservancy and water conservation engineering, human activity water intake and drainage data;

[0036] 2) Spatial discretization and unit division: based on high-resolution DEM data, spatial discretization is performed by means of spatial analysis, and regular grid, hydrological response unit or sub-basin is divided; sub-basin is preferred, and in actual simulation, sub-basin is further divided according to contour belt to reflect the influence of terrain on precipitation, evapotranspiration and confluence; the sub-basin division process includes the steps of depression filling, water flow direction determination, confluence accumulation calculation, threshold determination and river network vector generation, and sub-basin catchment range extraction;

[0037] 3) Perform water cycle module calculation: including precipitation interception and evapotranspiration, infiltration and soil movement, runoff generation, confluence, human activity water intake and drainage, and special process;

[0038] 4) Parameter calibration and model verification: based on the historical measured data of the water delivery river section hydrological station, the soil hydrological parameters, runoff generation parameters and confluence parameters in the model are identified; by comparing the simulation value and the measured value of the model, the Nash coefficient is calculated, the calibration period is required to be not less than 0.6, the verification period is required to be not less than 0.5, and the reliability of the distributed water cycle model is verified.

[0039] Further, the calculation process of the net evaporation and leakage of each dam unit in step 4 is specifically:

[0040] 1) Dam collapse period: During this period, each dam unit is a river section, which has the basic characteristics of a river, so the evaporation and seepage are calculated according to the river:

[0041] Qz j,t = S j,t × (E j,t × Ke-P j,t ) × 10 -3 (6)

[0042] S j,t = L j × B j,t (7)

[0043] In the formula, S j,t is the water surface area of the jth dam unit at the tth time, m 2 ; E j,t is the water surface evaporation pan observation value of the jth dam unit at the tth time, mm; Ke is the evaporation conversion coefficient, taking a value of 0.7-0.8; P j,t is the rainfall intensity of the jth dam unit at the tth time, mm; L j is the river length of the jth dam unit, m; B j,t is the river surface width of the jth dam unit, m; Under specific inflow conditions, the river surface width is affected by many factors such as river cross-section parameters, terrain and slope. According to the remote sensing monitoring results, the average width of the river is taken for simplified calculation;

[0044] The river seepage is the water loss caused by the seepage of river flow from the riverbed to the soil during the flow process, which is calculated by using an empirical formula, which is specifically:

[0045] Ql j,t = (Qi j,t + Qr j,t ) × Km j × kq (8)

[0046] In the formula, Km j is the seepage coefficient of the jth dam unit river section, dimensionless, which is determined according to the actual survey data of the river, and is 0.01-0.05 for clay soil riverbed and 0.1-0.3 for sandy soil; kq is the flow conversion unit, which converts the inflow of the jth dam unit at the tth time into m 3 / s, and the time step is daily, so the coefficient is equal to 1 / 86400;

[0047] 2) Dam operation period: During this period, each dam unit has a specific length of river section in addition to the dam reservoir section in the river. Quantitative identification of the length of the reservoir section and the river section is the basis, and the specific calculation formula is as follows:

[0048] La j,t = L j -Lb j,t (9)

[0049] Sb j,t = fs j (V j,t ) (10)

[0050]

[0051] Qzb j,t = Sb j,t × (E j,t × Ke - P j,t ) × 10 -3 (12)

[0052] Sa j,t = La j,t × Ba j,t (13)

[0053] Qza j,t = Sa j,t × (E j,t × Ke - P j,t ) × 10 -3 (14)

[0054] Qz j,t = Qza j,t + Qzb j,t (15)

[0055] In the formula, La j,t and Lb j,t are the lengths of the river section and the reservoir section of the jth gate dam unit, m; Qza j,t and Qzb j,t are the net evaporation amounts of the river section and the reservoir section of the jth gate dam unit at the tth time, m 3 ; Sa j,t and Sb j,t are the water surface areas of the river section and the reservoir section of the jth gate dam unit at the tth time, m 2 ; fs j is the storage-volume-area curve of the reservoir section of the jth gate dam unit, which is determined according to the engineering design data; Ba j,t and Bb j,t are the average widths of the river section and the reservoir section of the jth gate dam unit, m, which are simplified by taking the average widths of the river section and the gate dam end according to the remote sensing monitoring results;

[0056] The leakage of the river section in this period is the water loss caused by the river flow penetrating from the riverbed to the soil in the flowing process. The leakage is calculated by using an empirical formula, which is as follows:

[0057] Ql j,t = Qla j,t + Qlb j,t (16)

[0058] Qla j,t = (Qi j,t + Qr j,t ) x Kma j x kq (17)

[0059] Qlb j,t = V j,t x Kv j (18)

[0060] In the formula, Kma j is the leakage coefficient of the river section in the jth gate dam unit, which is dimensionless and determined according to the actual survey data of the river section. The leakage coefficient of the river section in the jth gate dam unit is 0.01-0.05 for a clay soil riverbed and 0.1-0.3 for a sandy soil riverbed; Qla j,t and Qlb j,t are the leakage of the river section and the reservoir section of the jth gate dam unit, respectively, m 3 ; Kv j is the leakage coefficient of the reservoir section of the jth gate dam unit, which is dimensionless and determined according to the geology, soil and anti-seepage characteristics of the area where the gate dam is located. The leakage coefficient of the reservoir section of the jth gate dam unit is between 1% and 5%.

[0061] Further, the water consumption of the human activities in the jth gate dam unit in step 4 includes the water consumption of agricultural irrigation, life, industry and ecological users. The calculation formula is as follows:

[0062] Qu j,t = Qua j,t x (1-Ta j ) + Qub j,t x (1-Tb j ) + Quc j,t x (1-Tc j ) + Qud j,t x (1-Td j ) (19)

[0063] In the formula, Qua j,t , Qub j,t , Quc j,t and Qud j,t are the water consumption of agricultural irrigation, life, industry and ecological users in the jth gate dam unit, respectively, m 3 ; Ta j , Tbj , Tc j and Tc j are the proportional coefficients of agricultural irrigation, domestic, industrial and ecological water users drainage or effluent in the jth gate dam unit, dimensionless;

[0064] If the water user takes water in the jth gate dam unit and discharges into the j+1th or j+2th gate dam unit after use, then Ta j , Tb j , Tc j and Tc j are set to zero, and the effluent is put into the water balance of the j+1th or j+2th gate dam unit. If the water user takes water in the jth gate dam unit and discharges into the j+1th gate dam unit and so on after use, the calculation formula is as follows:

[0065] Qu j,t = Qua j,t + Qub j,t + Quc j,t + Qud j,t (20)

[0066] Qu j+1,t = -Qua j,t × Ta j - Qub j,t × Tb j - Quc j,t × Tc j - Qud j,t × Td j (21)

[0067] In the formula, Qu j+1,t is the water consumption in the process of human activity taking water in the j+1th gate dam unit at time t, m 3 .

[0068] Further, the ecological flow discharge index requirement of each gate dam unit in step 4 is quantitatively calculated by hydrological method, hydrodynamic method, habitat simulation method and overall analysis method according to relevant technical standards, specifications or guidelines, combined with the life process demand of downstream ecological protection target; if the local water management department has determined the minimum ecological flow discharge of the gate dam, then the larger value of the two is taken as the ecological flow discharge index requirement of the gate dam unit, which is as follows:

[0069] Qe j,t = max(Re j,t , Se j,t ) (22)

[0070] In the formula, Re j,t is the minimum ecological flow discharge determined by the water management department of the jth gate dam unit at time t; Sej,t The calculated ecological discharge of the tth time jth gate dam unit.

[0071] Further, the explicit downstream nuclear power user water intake guarantee rate requirement in step 5 is: according to the continuity requirement of water in the nuclear power production process, the time step of the water intake guarantee rate is calculated at least daily, and the downstream nuclear power user water intake guarantee rate reaches 97%.

[0072] The beneficial effects of the present application are: the method described in the present application starts from the perspective of the river basin, embeds a distributed water cycle model, can effectively depict the inflow process, evaporation, leakage, gate dam storage, inter-zone human water intake and drainage process, downstream nuclear power user water demand and available water, and dynamically deduces and calculates the river basin inflow, water quantity transportation, storage and water intake process. The method described in the present application realizes the organic integration of the distributed water cycle model and the water conservancy dispatching and human water intake and drainage process, which not only considers the natural side of the river basin water cycle runoff, confluence, evaporation and leakage process, but also considers the influence of the social side of the water conservancy dispatching and human water intake and drainage activity on the river water quantity process, and combines the downstream nuclear power user water intake capacity and water demand requirement to quantitatively calculate the water intake guarantee rate, which can provide technical support for the ecological protection and water resources development and utilization management of the multi-gate dam river.

[0073] The present application will be further described in detail below in combination with the drawings and specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0074] Figure 1 The flow chart of the method described in the present application;

[0075] Figure 2 The water transportation river section and gate dam distribution diagram of the multi-gate dam river in example one;

[0076] Figure 3 The corresponding relationship diagram of the water transportation river section and sub-basin in example one;

[0077] Figure 4 The reservoir section water storage-area curve diagram of gate A in example one;

[0078] Figure 5 The monthly process calculation result diagram of the downstream nuclear power user water demand in example one;

[0079] Figure 6 The daily process comparison diagram of the downstream nuclear power user available water and water demand in example one. DETAILED DESCRIPTION

[0080] The present application discloses a kind of calculation methods of downstream nuclear power user water intake guarantee rate of multi-gate dam river, as shown in Figure 1 The method comprises the following steps:

[0081] Step 1, determine the water conveyance river section, dam distribution and initial storage of the multi-dam river.

[0082] 1) Determine the water conveyance river section. According to the water conveyance engineering planning or design scheme of the multi-dam river basin or region, identify the location of the upstream water conveyance point and the location of the downstream water user on the multi-dam river, and determine the main range of the multi-dam river water conveyance section; if the water conveyance point and the water intake point are located in the main stream of the river, the water conveyance section is located in the main stream of the river; if the water conveyance point is located in the tributary and the water intake point is located in the main stream, the water conveyance section is located in the main and tributary of the river.

[0083] 2) Determine the spatial distribution and characteristic parameters of each dam. On the basis of determining the water conveyance river section, according to the relevant planning of the basin, the research, design or construction data of water conservancy project, determine the number and spatial distribution of the main dams in the water conveyance river section. According to the engineering design data of the dams in the water conveyance river section, determine the basic characteristics of each dam, including the water level-area curve (the functional relationship between the reservoir water level and the corresponding storage area), the water level-storage capacity curve (the functional relationship between the reservoir water level and the corresponding storage volume), the limiting water level of dam regulation in different periods (including flood season and non-flood season), and the ecological flow discharge index requirements, etc.

[0084] 3) Determine the initial storage of each dam. Determine the initial storage of each dam, if there are long series of dam observation data (such as 30 years of measured data), the actual reservoir storage (such as the initial storage) of the starting year can be directly taken as the initial value. If there is a lack of long series of dam observation data, the storage corresponding to the dead storage water level can be used as the initial value to test the reliability of water intake in drought conditions.

[0085] Step 2, build a distributed water cycle model to obtain the dynamic flow process of the sub-basin.

[0086] Build a distributed water cycle model for the basin where the multi-dam river is located, which integrates the comprehensive influence of river system, meteorological and hydrological, land use, topography, soil geology, vegetation cover, water conservancy and water conservation engineering, human activities, water cycle, etc. on water cycle, and carefully simulates the natural and social water cycle processes such as evaporation, infiltration, surface runoff, interflow and artificial water use and drainage, etc. to reflect the spatial heterogeneity and physical mechanism driven characteristics of water cycle process. Representative distributed water cycle models include WEP-L, VIC, SWAT and TOPMODEL models.

[0087] The main steps of building a distributed water cycle model are as follows:

[0088] 1) Multi-source data collection and processing: This includes the collection and processing of basic data related to river systems, meteorological and hydrological data, land use, topography, soil geology, vegetation cover, water conservancy and soil conservation projects, and human activities such as water intake and drainage.

[0089] 2) Spatial discretization and unit division: Based on high-resolution DEM data (e.g., 10 m, 30 m, etc.), spatial analysis methods are used for spatial discretization, which can be divided into regular grids, hydrological response units (HRU), or sub-basins. Sub-basins are preferred, and within the sub-basin, further segmentation can be performed according to elevation zones to reflect the influence of topography on precipitation, evapotranspiration, and confluence. The sub-basin division process typically includes steps such as depression filling, flow direction determination, confluence accumulation calculation, threshold determination and river network vector generation, and sub-basin catchment area extraction.

[0090] 3) Water cycle module calculation: This typically includes precipitation interception and evapotranspiration, infiltration and soil movement, runoff generation, confluence, and human activities such as water intake and drainage, as well as special processes such as snowmelt and reservoir operation.

[0091] 4) Parameter calibration and model verification: Based on historical measured data from water transfer river stations, key parameters such as soil hydrological parameters (e.g., saturated hydraulic conductivity, porosity), runoff parameters (e.g., CN value, water storage capacity), and confluence parameters (e.g., Manning roughness, river slope) are identified. By comparing the model simulation values and measured values, the Nash coefficient (not less than 0.6 in the calibration period and not less than 0.5 in the verification period) is calculated to verify the reliability of the distributed water cycle model.

[0092] Then, using the completed distributed water cycle model, the daily dynamic flow process of all sub-basins in the multi-dam river basin is obtained.

[0093] Step 3: Considering the upstream inflow and external water transfer process of the basin, calculate the outflow of the water transfer point.

[0094] Using the spatial analysis function of GIS, the water transfer river section and sub-basins are spatially overlaid and analyzed to identify the sub-basins corresponding to the upstream of the water transfer point of the water transfer river section. Based on the simulation results of the distributed water cycle model, the flow process of each sub-basin upstream of the water transfer point is read and summarized as the upstream inflow of the basin. Combined with the basic demand of the downstream water users of the multi-dam river, and based on the planning and relevant design scheme of external water source projects, the external water transfer amount of the water transfer point is determined. Without considering the water mixing loss, the sum of the upstream inflow and the external water transfer amount is taken as the outflow of the water transfer point of the multi-dam river water transfer section, and the main calculation formula is as follows:

[0095]

[0096] where QMt Qm 3 is the outflow of the water delivery point of the water delivery river section at the t time, m i,t ; Qm 3 is the upstream inflow of the water delivery point of the i sub-basin at the t time, which is obtained by reading the calculation results of the distributed water cycle model, m t ; Nm 3 is the number of sub-basins upstream of the water delivery point, units; Qb j,t is the water delivery amount outside the basin corresponding to the water delivery point at the t time, m j,t .

[0097] Step 4: Calculate the storage capacity and outflow of each gate dam unit from upstream to downstream of the water delivery river section.

[0098] 1) Determine the number and range of gate dam units of the water delivery river section: comprehensively consider the water delivery position of the water delivery river section, the distribution of the gate dam, the water intake position of the downstream user, etc., determine the number of gate dam units (i.e. the number of gate dams) from the water delivery point to the downstream water user along the water delivery river section, and determine the river section range of each gate dam unit.

[0099] 2) Dynamically calculate the storage capacity and outflow of each gate dam: with the help of the spatial analysis function of GIS, spatial overlay analysis is performed on each gate dam unit and all sub-basins of the basin, the corresponding sub-basins of each gate dam unit of the water delivery river section are identified, the calculation results of the distributed water cycle model are read, and the interval inflow of the gate dam unit is calculated. According to the calculated outflow of the upstream water delivery point, combined with the interval inflow, considering the evaporation, seepage process and water consumption loss in the process of human activity water use, combined with the requirements of gate dam regulation water level limit and downstream ecological flow index, the storage capacity and outflow at different times are calculated, and the specific calculation formula is:

[0100] Vm j,t = max(Qi j,t + Qr j,t - Qz j,t - Ql j,t - Qu j,t - Qe j,t , 0) (2)

[0101] V j,t = max(Vm j,t + V j,t-1 , Vl j,t ) (3)

[0102] Vl j,t = fv j (Hl j,t ) (4)

[0103] O j,t = Vm j,t - V j,t + Vj,t-1 (5)

[0104] Qi j,t = the inflow of the jth gate dam unit at the tth time, m 3 , j = 1, 2, 3…J+1, J is the number of gate dam units in the water delivery river section, m j,t Qr 3 = the interval inflow of the jth gate dam unit at the tth time, m j,t Qz j,t and Ql 3 = the net evaporation and leakage of the jth gate dam unit at the tth time, m j,t Qu 3 = the water consumption of the jth gate dam unit in the human activity water taking process at the tth time, m j,t Qe 3 = the ecological flow discharge index requirement of the jth gate dam unit at the tth time, m j,t Vm 3 = the storable water of the jth gate dam unit at the tth time, m j,t V j,t-1 and V 3 = the actual storage of the jth gate dam unit at the tth and t-1th times, m j,t-1 , when t = 1, V j,t is the initial storage in step 1; Vl j,t = the limiting storage of the jth gate dam unit at the tth time, Hl j = the limiting water level of the jth gate dam unit at the tth time; fv j,t () function = the water level-storage curve of the jth gate dam unit; O 3 = the outflow of the jth gate dam unit at the tth time, m

[0105] The calculation of the net evaporation and leakage of each gate dam unit is influenced by the river characteristics, gate dam construction engineering parameters, and gate dam regulation, and the calculation methods are different in different periods, as follows:

[0106] 1) Gate dam collapse period: each gate dam unit is a river section in this period, and has the basic characteristics of a river, so the evaporation and leakage are calculated according to the river:

[0107] Qz j,t = S j,t ×(E j,t × Ke-P j,t )×10 -3 (6)

[0108] S j,t = L j × B j,t (7)

[0109] In the formula, S j,t is the water surface area of the jth gate dam unit at the tth time, m 2 ; E j,t is the water surface evaporation pan observation value (such as an E601 evaporation pan) of the jth gate dam unit at the tth time, mm; Ke is an evaporation conversion coefficient, usually taking a value of 0.7-0.8; P j,t is the rainfall intensity of the jth gate dam unit at the tth time, mm; L j is the river length of the jth gate dam unit, m; B j,t is the river water surface width of the jth gate dam unit, m, which is mainly affected by river section parameters, terrain, and slope under specific inflow conditions, and is simplified by taking the average width of the river according to the remote sensing monitoring results.

[0110] The river leakage is the water loss caused by the seepage of river flow from the riverbed to the soil during the flow process, which can be calculated by using an empirical formula, as follows:

[0111] Ql j,t = (Qi j,t + Qr j,t ) × Km j × kq (8)

[0112] In the formula, Km j is the leakage coefficient of the jth gate dam unit river section, dimensionless, which is determined according to the actual survey data of the river, such as 0.01-0.05 for a clay riverbed and 0.1-0.3 for a sandy soil; kq is a flow conversion unit, which converts the inflow of the jth gate dam unit at the tth time into m 3 / s, and the time step is a day, so the coefficient is equal to 1 / 86400.

[0113] 2) Gate dam operation period: In this period, each gate dam unit may have a specific length of river section in addition to the gate dam reservoir section in the river. Quantitative identification of the lengths of the reservoir section and the river section is the basis, and the specific calculation formula is as follows:

[0114] La j,t = L j -Lb j,t (9)

[0115] Sb j,t = fs j (V j,t ) (10)

[0116]

[0117] QUR j,t =Sb j,t ×(E j,t ×Ke-P j,t )×10 -3 (12)

[0118] Sa j,t =La j,t ×Ba j,t (13)

[0119] Qza j,t =Sa j,t ×(E j,t ×Ke-P j,t )×10 -3 (14)

[0120] QZ j,t =Qza j,t +Qzb j,t (15)

[0121] Where, La j,t and Lb j,t are the lengths of the river section and reservoir section of the j-th dam unit, m; Qza j,t and Qzb j,t are the net evaporation of the river section and reservoir section of the jth dam unit at time t, m 3 ;Sa j,t and Sb j,t are the water surface areas of the river section and reservoir section of the jth dam unit at time t, m 2 ;fs j () function is the water storage capacity-area curve of the j-th dam unit reservoir section, which is mainly determined based on engineering design data; Ba j,t and Bb j,t are the average water surface widths of the river section and reservoir section of the jth sluice dam unit, m. According to the remote sensing monitoring results, the average widths of the river section and the sluice dam end are taken for simplified calculation.

[0122] Similarly, the seepage of the river section during this period is the amount of water loss caused by the infiltration of river water from the riverbed into the soil during the flow of the river. It can be calculated using the empirical formula as follows:

[0123] QI j,t =Qla j,t +Qlb j,t (16)

[0124] Qla j,t =(Qi j,t +Qr j,t) x Kma j x kq (17)

[0125] Qlb j,t = V j,t x Kv j (18)

[0126] where Kma j is the leakage coefficient of the river section in the jth gate dam unit, dimensionless, determined according to the actual survey data of the river section, such as 0.01-0.05 for a clay river bed and 0.1-0.3 for a sandy soil river bed; Qla j,t and Qlb j,t are the leakage amounts of the river section and the reservoir section of the jth gate dam unit, respectively, m 3 ; Kv j is the leakage coefficient of the reservoir section of the jth gate dam unit, dimensionless, determined according to the geology, soil and anti-seepage characteristics of the area where the gate dam is located, and is usually between 1% and 5%.

[0127] The water consumption of the human activities in the water taking process of each gate dam unit mainly includes the water consumption of agricultural irrigation, life, industry and ecology users, and the calculation formula is:

[0128] Qu j,t = Qua j,t x (1-Ta j ) + Qub j,t x (1-Tb j ) + Quc j,t x (1-Tc j ) + Qud j,t x (1-Td j ) (19)

[0129] where Qua j,t , Qub j,t , Quc j,t and Qud j,t are the water taking amounts of the agricultural irrigation, life, industry and ecology users in the jth gate dam unit, m 3 ; Ta j , Tb j , Tc j and Tc j are the proportion coefficients of the drainage (or backwater) of the agricultural irrigation, life, industry and ecology water users in the jth gate dam unit, dimensionless.

[0130] It should be noted that if the water users take water in the jth gate dam unit and backwater to the j+1th, j+2th, etc. gate dam units after taking water, Ta j , Tb j , Tcj and Tc j is set to zero and is put into the water balance of the j+1 or j+2 gate dam unit. If the water user takes water from the jth gate dam unit and returns the water to the j+1th gate dam unit after use, the calculation formula is as follows:

[0131] Qu j,t = Qua j,t + Qub j,t + Quc j,t + Qud j,t (20)

[0132] Qu j+1,t = -Qua j,t × Ta j - Qub j,t × Tb j - Quc j,t × Tc j - Qud j,t × Td j (21)

[0133] In the formula, Qu j+1,t is the water consumption during the water taking process of human activities in the j+1th gate dam unit at the tth time, m 3 .

[0134] The ecological flow discharge index requirement of each gate dam unit is quantitatively calculated by hydrological method, hydrodynamic method, habitat simulation method and overall analysis method according to relevant technical standards, norms or guidelines and in combination with the life process demand of downstream ecological protection targets. If the local water management department has determined the minimum ecological flow discharge of the gate dam, the larger value of the two is taken as the ecological flow discharge index requirement of the gate dam unit, which is specifically as follows:

[0135] Qe j,t = max(Re j,t , Se j,t ) (22)

[0136] In the formula, Re j,t is the minimum ecological flow discharge determined by the water management department of the jth gate dam unit at the tth time; and Se j,t is the calculated ecological flow discharge of the jth gate dam unit at the tth time.

[0137] Step 5: Determine the water taking guarantee rate requirement of the downstream nuclear power user, calculate the water demand and the water taking capacity.

[0138] This step mainly determines the water taking guarantee rate requirement of the downstream nuclear power user, the water demand and the maximum water taking capacity, calculates the water taking capacity, which is specifically as follows:

[0139] 1) Define the downstream nuclear power user water intake guarantee rate requirement. The downstream nuclear power user water intake guarantee rate represents the probability of being fully satisfied in the water intake time (duration), which is an important indicator to ensure the safety of downstream nuclear power user water intake. According to the continuity requirement of water use in the nuclear power production process, the time step of the water intake guarantee rate should be calculated at least daily. Nuclear power users have very high requirements for water intake reliability, usually requiring a guarantee rate of 97%.

[0140] 2) Calculate the nuclear power user water demand. According to the characteristics of downstream nuclear power user life and production, carry out water demand calculation. Generally, the water demand of nuclear power users includes cooling tower replenishment water, plant water system replenishment water, desalination, industrial and living replenishment water, unforeseen and leakage, etc. Due to the large difference in circulating replenishment water under different working conditions of nuclear power plant construction, factors such as secondary circulating cooling mode, warm water discharge mode, and air temperature change should be considered to modify and adjust the water demand. The formula for calculating the water storage capacity of nuclear power users is:

[0141] QN t = Qna t + Qnb t + Qnc t + Qnd t (23)

[0142] QN t is the water demand of the nuclear power user at time t, m 3 ; Qna t , Qnb t , Qnc t , Qnd t are the cooling tower replenishment water, plant water system replenishment water, desalination, industrial and living replenishment water, and unforeseen and leakage water demand at time t, m 3 .

[0143] 3) Calculate the available water intake of nuclear power users. According to the location characteristics of the nuclear power user water intake project, and according to the outflow of the gate dam unit where the water is taken, determine the available water intake. There are two main types:

[0144] a) The nuclear power user takes water in the last gate dam unit of the water conveyance river section, and its available water intake should be less than the water intake capacity limit and the outflow of the gate dam unit. According to the calculation in the previous step, the outflow has deducted the guaranteed industrial and agricultural water demand and river ecological water demand. Further, if the user has water intake capacity limit, consider the impact of this factor on the available water intake. The specific calculation formula is as follows:

[0145] QX t = min(QNl t , O j＝J,t ) (24)

[0146] wherein QX t is the available water intake of the downstream nuclear power user at the tth time, m 3 ; QNl t is the water intake capacity limit of the downstream nuclear power user at the tth time, m 3 QNl t =∞ if no limit; O j＝J,t is the outflow of the gate dam unit upstream of the nuclear power user at the tth time, m 3 .

[0147] b) The nuclear power user takes water downstream of the last gate dam in the water conveyance river reach. The available water intake of the nuclear power user should be less than the water intake capacity limit and the outflow of the gate dam unit minus the discharge requirement at the water intake section. The discharge requirement at the water intake section usually needs to consider the ecological water requirement of the downstream river ecological protection target and the basic water requirement of downstream production and life, so as to maintain the health of the river ecological system, ensure the basic water requirement of human society survival, health and economic activities in the downstream area. Similar to the calculation of the ecological flow of the gate dam unit, the ecological water requirement of the downstream river ecological protection target can be quantitatively calculated by hydrological method, hydrodynamic method, habitat simulation method and overall analysis method according to relevant technical standards, specifications or guidelines, combined with the life process requirements of the downstream ecological protection target. The basic water requirement of downstream production and life is usually determined according to the relevant production and life basic water survey or relevant water resources comprehensive planning. The specific calculation formula is as follows:

[0148] QX t = min(QNl t , O j＝J,t -Qe j+1,t ) (25)

[0149] wherein Qe j+1,t is the discharge requirement at the water intake section of the downstream nuclear power user at the tth time, m 3 . In order to meet the safety requirements of nuclear power, according to the relevant technical specifications and industry standards of nuclear power plant engineering hydrology, the data for the calculation of the water intake guarantee rate of the nuclear power user is long series data, and the data length should be more than 30 years. Under the condition of complete basic data, it is recommended to use longer series (such as 50 years). Based on steps 2 to 5 above, the daily calculation of the available water intake of the nuclear power user is carried out until the number of calculation years of the long series is met.

[0150] Step 6: Based on the long series calculation results, the water intake guarantee rate of the nuclear power user is given.

[0151] Based on the calculation results of the long series of daily nuclear power user water intake obtained in the above steps, the continuity and reliability requirements of nuclear power user water are considered comprehensively, and when the water intake cannot meet the water demand of any day in a year, it is determined that the water demand in the year is not met, and the water intake guarantee rate is calculated according to the above criteria. The specific calculation formula of the water intake guarantee rate is as follows:

[0152]

[0153] In the formula, P is the water intake guarantee rate of the downstream nuclear power user, %; Y is the number of years calculated by the long series data, years; ty represents the year number, ty = 1, 2, 3…Y; N1 ty is the starting day of the ty year; N2 ty is the end day of the ty year.

[0154] Example 1

[0155] This embodiment is a specific application example of the above method.

[0156] The multi-gate dam river in this embodiment is a certain river into the sea in Shandong Province, China. The upstream water delivery point is located at point M of the main stream of the river, and the downstream water intake point is located at point N. The water delivery section (M-N) is about 35 km long, and the average width of the river is 260 m. There are three main river sluices (i.e. sluices A, B and C) in the water delivery section. The water intake point of the downstream nuclear power user is located at sluice C, and the water intake guarantee rate requirement is 97%, as shown in Figure 2 .

[0157] From the perspective of the basin of the multi-gate dam river, basic data such as river system, meteorological hydrology, land use, topography, soil geology, vegetation coverage, water conservancy and water conservation engineering, human activities of water intake and drainage are collected. On the basis of data processing, a distributed water cycle model (WEP-L model) of the basin where the multi-gate dam river is located is constructed, 39 sub-basin control units are divided, as shown in Figure 3 , which can simulate the daily water cycle process of the long series (65 years from 1957 to 2021). Select a typical hydrological station (located between sluices A and B), and calibrate and verify the distributed water cycle model.

[0158] Through spatial superposition analysis, the sub-basin units corresponding to the water delivery point M are identified as two, i.e. sub-basin units 13 and 8. Based on the calculation results of the distributed water cycle model, the daily inflow process of the two sub-basin units is obtained. According to the relevant water source engineering planning and design scheme, the external water delivery of the basin is 3.47m 3 / s, and the annual water delivery is about 109 million m 3 .

[0159] Since there are three sluices in the conveyance reach, combined with the location of the upstream conveyance point and the downstream user intake point, three sluice units are determined, namely sluice unit 1 (from the conveyance point M to the sluice A), sluice unit 2 (from the sluice A to the sluice B) and sluice unit 3 (from the sluice B to the sluice C). The dispatching rules of each sluice in the conveyance reach are shown in Table 1. Among them, the reservoir section water level-storage capacity curve and the storage capacity-area curve are obtained according to the preliminary design scheme of each sluice reinforcement, such as the storage capacity-area curve of sluice A as shown in Figure 4 .

[0160] Table 1 Dispatching rules of each sluice in the conveyance reach

[0161]

[0162] Since the evaporation measured data of the basin is missing, the daily evaporation measured data of the hydrological station of the adjacent surrounding basin with similar underlying surface conditions is used for calculation according to the adjacent principle. The human activity water of each sluice unit is mainly agricultural irrigation, and according to the investigation results of the agricultural irrigation area, irrigation quota (gross) and irrigation system of the surrounding towns (see Table 2 and Table 3), the daily water consumption of the human activity water process of the sluice unit is calculated.

[0163] Table 2 Irrigation area, quota and irrigation water of each sluice

[0164] Name Irrigation area (ten thousand mu) Irrigation water requirement (m 3 per acre) Irrigation water (million m 3 )]]> River barrage A 1.5 256.3 384.5 River barrage B 1.0 257.0 257.0 River barrage C 9.5 253.5 2408.3

[0165] Table 3 Irrigation system of each sluice

[0166]

[0167]

[0168] Since there are no sensitive species in the downstream of the conveyance reach, the ecological flow control indicators of each sluice determined by the water management department using hydrological methods are shown in Table 4.

[0169] Table 4 Ecological flow requirements of each sluice

[0170] Name River barrage A (10 km 3 )]]> River barrage B (km 3 )]]> River barrage C (km 3 )]]> January 14.1 14.9 15.3 February 14.1 14.9 15.3 March 14.1 14.9 15.3 April 14.1 14.9 15.3 May 14.1 14.9 15.3 June 14.1 14.9 15.3 July 122.3 129.5 132.9 August 209.6 222 227.7 September 93.3 98.8 101.4 October 14.1 14.9 15.3 November 14.1 14.9 15.3 December 14.1 14.9 15.3 Total 551.9 584.6 599.7

[0171] The design assurance rate requirement of the downstream nuclear power user is 97%. The water use process of the nuclear power user is greatly affected by temperature, and the water demand increases significantly in summer (June-August). Considering the cooling tower make-up water, plant water system make-up water, desalination, industrial and domestic make-up water, unforeseen and leakage, etc., the monthly water demand process of the user is calculated as shown in Figure 5 , and the monthly water demand is evenly distributed to the day. The summary results show that the annual water demand of the user is about 52 million m 3According to the nuclear power water supply and drainage engineering design scheme, the water intake capacity is limited to 2m 3 / s.

[0172] Using the method of the present application, the comparison of the long series of daily downstream user water intake capacity (water intake point located at the sluice C) and water demand calculated is shown in Figure 6 The statistical results show that the number of days when the downstream nuclear power user water intake capacity meets the water demand is 23714 days, and the water intake capacity does not meet the water demand for 27 days. Summarized to years, the number of years in which the daily water intake capacity meets the water demand in the long series of 65 years is 44 years, and the water intake guarantee rate is 67.7%, which does not meet the 97% water intake guarantee rate requirement.

[0173] Overall, although the use of multi-dam river water transmission reduces the pipeline laying cost, it is affected by the water consumption of agricultural irrigation along the way, river evaporation, dam evaporation, and river seepage and dam seepage, resulting in significant water loss along the way, which cannot guarantee the water safety of downstream nuclear power users. Further analysis shows that the time when the nuclear power user water intake capacity cannot meet the water demand is mainly concentrated on September 1 and September 2 (as shown in Table 5), during which the sluices along the water transmission river change from dam collapse to normal operation, and the water is trapped in the dam reservoir section, making it difficult to effectively transmit to downstream water users, resulting in the water intake capacity failing to meet the water demand. The water intake guarantee rate can be improved by increasing the basin water transmission capacity and increasing water regulation.

[0174] Table 5 Long series of annual water user water intake meeting water demand at sluice C

[0175]

[0176]

[0177] Finally, it should be noted that the above description is only used to illustrate the technical solutions of the present application and is not limiting. Although the present application has been described in detail with reference to the preferred arrangement, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for calculating the water intake guarantee rate for nuclear power users downstream of a river with multiple dams and sluice gates, characterized in that: The method comprises the following steps: Step 1: Determine the water delivery reach, dam distribution, and initial water storage capacity of rivers with multiple dams: Based on the water delivery project planning or design for the river basin or region where the river is located, identify the locations of upstream water delivery points and downstream water users, and determine the scope of the water delivery reach of the river with multiple dams. Then, based on relevant basin planning and water conservancy project data, determine the number, spatial distribution, and characteristic parameters of the dams in the water delivery reach; and determine the initial water storage capacity of each dam. Step 2: Construct a distributed water cycle model to obtain the dynamic flow process of the sub-basins: Construct a distributed water cycle model for the basin where the multi-dam river is located, and then use the constructed distributed water cycle model to perform calculations to obtain the daily dynamic flow process of all sub-basins in the basin where the multi-dam river is located; Step 3. Considering the upstream inflow and out-of-basin water transfer processes, calculate the outflow at the water transfer point: perform spatial overlay analysis on the water transfer river section and sub-basins to identify the sub-basins corresponding to the upstream water transfer point of the water transfer river section; based on the results of the distributed water cycle model, read the flow processes of each sub-basin upstream of the water transfer point in the results and summarize them as the upstream inflow of the water transfer point; based on the basic needs of water users downstream of the multi-sluice dam river and the planning and relevant design schemes of the out-of-basin water source project, determine the outflow of the water transfer point corresponding to the water transfer point; without considering water mixing losses, take the sum of the upstream inflow and the out-of-basin water transfer as the outflow of the water transfer point of the multi-sluice dam river section, and calculate it using the following formula: Where QM t is the outflow of the water delivery point in the water delivery section at time t, m 3 ;Qm i,t is the upstream inflow corresponding to the water transfer point at time t in the i-th sub-basin, which is obtained by reading the calculation results of the distributed water cycle model, m 3 ; Nm is the number of upstream sub-basins corresponding to the water transfer point, Qb t is the water delivery outside the basin corresponding to the water delivery point at time t, m 3 ; Step 4: Calculate the water storage and outflow of each dam unit in stages from upstream to downstream of the water transfer section: First, determine the number and range of dam units in the water transfer section; then perform spatial overlay analysis on each dam unit and all sub-basins in the basin, identify the sub-basins corresponding to each dam unit in the water transfer section, read the calculation results of the distributed water cycle model, and summarize and calculate the interval inflow of the dam unit; based on the calculated outflow of the upstream water transfer point, combined with the interval inflow, considering evaporation, leakage and water consumption losses during human activities, combined with the water level limit requirements of the dam scheduling and the downstream ecological flow index, calculate the water storage and outflow at different times. The specific calculation formula is: Wm j,t =max(Qi j,t +Qr j,t -Qz j,t -Ql j,t -Qu j,t -What? j,t ,0) (2) V j,t =max(Vm j,t +V j,t-1 ,Vl j,t ) (3) Vl j,t =fv j (Hl j,t ) (4) O j,t =Vm j,t -V j,t +V j,t-1 (5) Where Qi j,t is the water inflow of the jth dam unit at time t. If j = 1, it is the outflow of the water delivery point; if j> 1, it is the outflow of the upstream dam unit, m 3 , j=1,2,3…J+1, J is the number of dam units in the water delivery section, Qr j,t is the interval inflow of the jth dam unit at time t, which comes from the calculation results of the distributed water cycle model, m 3 ;Qz j,t and Ql j,t are the net evaporation and leakage of the jth dam unit at time t, respectively, m 3 ; Qu j,t is the water consumption during human activities in the j-th sluice dam unit at time t, m 3 ;Qe j,t is the ecological flow index requirement for the jth dam unit at time t, m 3 ;Vm j,t is the water storage capacity of the jth dam unit at time t, m 3 ; V j,t and V j,t-1 are the actual water storage capacity of the jth dam unit at time t and time t-1, m 3 , when t=1, V j,t-1 is the initial water storage in step 1; Vl j,t Hl is the limited water storage capacity of the jth dam unit at time t, j,t The limited water level of the jth dam unit at time t; fv j () function is the water level-storage capacity curve of the j-th dam unit; j,t is the outflow of the jth dam unit at time t, m 3 ; Step 5: Clarify the water withdrawal guarantee rate requirements of downstream nuclear power users and calculate the water demand and available water volume: First, clarify the water withdrawal guarantee rate requirements of downstream nuclear power users. The water withdrawal guarantee rate of downstream nuclear power users represents the probability that water withdrawal can be met at the time of withdrawal. Then, calculate the water demand based on the living and production characteristics of downstream nuclear power users. The calculation formula is: QN t =Qna t +Qnb t +Qnc t +Qnd t (23) Where QN t is the water demand of nuclear power users at time t, m 3 ;Qna t 、Qnb t 、Qnc t 、Qnd t They are the cooling tower make-up water volume, in-plant water system make-up water volume, desalination, industrial and domestic make-up water volume, and the water demand for unforeseen and leakage at time t, m 3 ; Then, based on the location characteristics of the water intake project of the downstream nuclear power user and the outflow of the sluice dam unit where the water is taken, the available water volume is determined and divided into two types: a) When a nuclear power user draws water from the last sluice gate unit in a water diversion section, the amount of water that can be drawn is less than the water withdrawal capacity limit and the outflow of the sluice gate unit. The specific calculation formula is as follows: QX t =min(QNl t ,O j＝J,t ) (24) Where, QX t is the available water volume for downstream nuclear power users at time t, m 3 ;QNl t is the water intake capacity limit of downstream nuclear power users at time t, m 3 , such as unlimited time QNl t =∞;O j＝J,t is the outflow of the dam unit where the nuclear power user takes water upstream at time t, m 3 ; b) Nuclear power users draw water downstream of the last dam in the water transfer section. The amount of water that the nuclear power user can draw is less than the water withdrawal capacity limit and the outflow of the dam unit minus the downstream flow requirement of the water withdrawal section. The specific calculation formula is as follows: QX t =min(QNl t ,Oh j＝J,t JP j+1,t ) (25) In the formula, Qe j+1,t is the discharge flow requirement of the downstream nuclear power user water intake section at time t, m 3 ; According to the relevant technical specifications and industry standards for nuclear power plant engineering hydrology, the data used to calculate the water withdrawal guarantee rate for downstream nuclear power users is a long series of data with a length of more than 30 years. Based on steps 2 to 5 above, the daily calculation of the water withdrawal capacity for long-term nuclear power users is performed until the required number of years for the long-term calculation is met. Step 6: Based on the long series calculation results, the water withdrawal guarantee rate for nuclear power users is given: Based on the long series daily calculation results of the available water for nuclear power users obtained in the above steps, and taking into account the continuity and reliability requirements of nuclear power users, when the available water cannot meet the water demand on any day in a year, it is determined that the water demand for that year is not met. Based on this criterion, the water withdrawal guarantee rate is calculated. The specific calculation formula is: Where, P is the water intake guarantee rate of downstream nuclear power users, %; Y is the number of years for long series data calculation, year; ty represents the year number, ty = 1, 2, 3...Y; N1 ty is the starting date of the tyth year; N2 ty The end date of year ty.

2. The method for calculating the water intake guarantee rate for nuclear power users downstream of a river with multiple dams and locks according to claim 1 is characterized in that: The scope of the water delivery section of the multi-dam river determined in step 1 is specifically as follows: if the water delivery point and the water intake point are both located in the main stream of the river, the water delivery section is located in the main stream of the river; if the water delivery point is located in a tributary and the water intake point is located in the main stream, the water delivery section is located in the main stream or tributary of the river; The characteristic parameters of the dams and gates in the water transfer river section specifically include the water level-area curve, i.e., the functional relationship between the reservoir water level and its corresponding water storage area; the water level-storage capacity curve, i.e., the functional relationship between the reservoir water level and its corresponding water storage capacity; the dam and gate scheduling limit water levels in different periods, including flood season and non-flood season; and the ecological flow release index requirements; The specific process of determining the initial water storage capacity of each dam is as follows: if there is a long series of observation data on dams, the actual water storage capacity of the reservoir in the starting year of the long series calculation is directly taken as the initial value; if there is a lack of long series of observation data on dams, the water storage capacity corresponding to the dead storage capacity water level is used as the initial value; the long series refers to data of more than 30 years.

3. The method for calculating the water intake guarantee rate for nuclear power users downstream of a river with multiple dams and locks according to claim 1 is characterized in that: The construction of the distributed water cycle model described in step 2 specifically includes the following steps: 1) Carry out multi-source data collection and processing: specifically, collecting and processing data on river systems, meteorology and hydrology, land use, topography and geomorphology, soil geology, vegetation cover, water conservancy and water conservation projects, and human activities; 2) Spatial discretization and unit division: Based on high-resolution DEM data, spatial discretization is performed using spatial analysis methods to divide the space into regular grids, hydrological response units, or sub-basins. Sub-basins are preferred, and in actual simulations, they are further divided according to contour zones to reflect the influence of topography on precipitation, evapotranspiration, and runoff. The sub-basin division process includes depression filling, flow direction determination, runoff accumulation calculation, threshold determination and river network vector generation, and sub-basin catchment area extraction. 3) Conduct calculations of the water cycle modules: including precipitation interception and evapotranspiration, infiltration and soil movement, runoff generation, runoff confluence, human activities, and drainage, as well as special processes; 4) Parameter calibration and model verification: Based on the historical measured data from the hydrological stations in the water supply section, the soil hydrological parameters, runoff parameters, and confluence parameters in the model are identified; by comparing the simulated values ​​and measured values ​​of the model, the Nash coefficient is calculated, requiring the calibration period to be no less than 0.6 and the verification period to be no less than 0.5, to verify the reliability of the distributed water cycle model.

4. The method for calculating the water intake guarantee rate for nuclear power users downstream of a river with multiple dams and locks according to claim 1 is characterized in that: The calculation process of the net evaporation and leakage of each dam unit in step 4 is as follows: 1) Dam collapse period: During this period, all dam units are river sections with the basic characteristics of rivers. Evaporation and seepage are calculated based on rivers: Qz j,t =S j,t ×(E j,t ×Ke-P j,t )×10 -3 (6) S j,t =L j ×B j,t (7) Where S j,t The water surface area of ​​the jth dam unit at time t, m 2 ;E j,t is the water surface evaporation pan observation value of the meteorological station near the j-th dam unit at time t, mm; Ke is the evaporation conversion coefficient, ranging from 0.7 to 0.8; P j,t is the rainfall intensity of the jth dam unit at time t, mm; L j The length of the river in the jth dam unit, m; B j,t is the river surface width of the jth sluice dam unit, in m. Under specific water inflow conditions, the river surface width is affected by multiple factors such as river section parameters, topography, and slope. Based on remote sensing monitoring results, the average width of the river is used for simplified calculation. River leakage refers to the amount of water loss caused by the infiltration of riverbed into the soil during the flow of river water. It is calculated using the empirical formula, specifically: QI j,t =(Qi j,t +Qr j,t )×Km j ×kq (8) Where, Km j is the leakage coefficient of the river section of the j-th dam unit, dimensionless, determined based on the actual survey data of the river, and is 0.01-0.05 for clay riverbeds and 0.1-0.3 for sandy soils; kq is the flow conversion unit, which converts the inflow of the j-th dam unit at time t into m 3 / s, the time step is day, then the coefficient is equal to 1 / 86400; 2) Dam operation period: During this period, each dam unit has not only a dam reservoir section in the river channel, but also a river section of a specific length. Quantitative identification of the length of the reservoir section and the river section is the basis. The specific calculation formula is as follows: La j,t =L j -Lb j,t (9) Sb j,t =fs j (V j,t ) (10) Qzb j,t =Sb j,t ×(E j,t ×Ke-P j,t )×10 -3 (12) Saddle j,t =At j,t ×BNa j,t (13) Qza j,t =Sa j,t ×(E j,t ×Ke-P j,t )×10 -3 (14) Qz j,t =Qza j,t +Qzb j,t (15) Where, La j,t and Lb j,t are the lengths of the river section and reservoir section of the j-th dam unit, m; Qza j,t and Qzb j,t are the net evaporation of the river section and reservoir section of the jth dam unit at time t, m 3 ;Sa j,t and Sb j,t are the water surface areas of the river section and reservoir section of the jth dam unit at time t, m 2 ;fs j () function is the water storage capacity-area curve of the j-th dam unit reservoir section, which is determined according to the engineering design data; Ba j,t and Bb j,t are the average water surface widths of the river section and reservoir section of the jth dam unit, m. Based on the remote sensing monitoring results, the average widths of the river section and dam end are taken for simplified calculation; The seepage volume of the river section during this period is the amount of water loss caused by the infiltration of river water from the riverbed into the soil during the flow of the river. It is calculated using the empirical formula as follows: Ql j,t =Gla j,t +Heart j,t (16) LEA j,t =(Qi j,t +Qr j,t )×Kmax j ×kq (17) Heart j,t =V j,t ×Kv j (18) Where, Kma j is the leakage coefficient of the river section in the jth dam unit, dimensionless, determined based on the actual survey data of the river section, with a value of 0.01-0.05 for clay riverbed and 0.1-0.3 for sandy soil; j,t and Qlb j,t are the seepage amounts of the river section and reservoir section of the j-th dam unit, m 3 ;Kv i is the leakage coefficient of the jth dam unit reservoir section, dimensionless, determined according to the geological, soil and anti-seepage characteristics of the area where the dam is located, and is between 1% and 5%.

5. The method for calculating the water intake guarantee rate for nuclear power users downstream of a river with multiple dams and locks according to claim 1 is characterized in that: The water consumption during the human activities of each dam unit in step 4 includes the water consumption of agricultural irrigation, domestic, industrial and ecological users, and the calculation formula is: Dog j,t =Qua j,t ×(1-Ta j )+Qub j,t ×(1-Tb j )+Country j,t ×(1-Tc j )+Qud j,t ×(1-Td j ) (19) Where, Qua j,t , Qub j,t 、Quc j,t and Qud j,t are the water intakes of agricultural irrigation, domestic, industrial and ecological users in the jth dam unit, m 3 ; Ta j , Tb j , Tc j and Tc j are the proportional coefficients of drainage or withdrawal of agricultural irrigation, domestic, industrial and ecological water users in the jth sluice dam unit, dimensionless; If the water user takes water from the jth dam unit and the water is returned to the j+1th and j+2th dam units after use, then the Ta in the jth dam unit j , Tb j , Tc j and Tc j Set it to zero and put its water back into the water balance of the j+1th or j+2th dam unit; if the water user draws water at the jth dam unit and the water is returned to the j+1th dam unit after use, the calculation formula is as follows: What j,t =Which j,t +When j,t +This j,t +What j,t (20) What j+1,t =-Which j,t ×Ta j -When j,t ×Tb j -This j,t ×Tc j -What j,t ×Td j (21) Where, Qu j+1,t is the water consumption during human activities in the j+1th sluice dam unit at time t, m 3 .

6. The method for calculating the water intake guarantee rate for nuclear power users downstream of a river with multiple dams and locks according to claim 1 is characterized in that: In step 4, the ecological flow index requirements for each dam unit are quantitatively calculated based on relevant technical standards, specifications, or guidelines, combined with the life process requirements of downstream ecological protection targets, using hydrological methods, hydrodynamic methods, habitat simulation methods, and holistic analysis methods. If the local water management department has determined the minimum ecological flow for the dam, the larger of the two values ​​will be used as the ecological flow index requirement for the dam unit, as follows: oxen j,t =max(Re j,t ,That j,t ) (22) Where, Re j,t Se is the minimum ecological discharge determined by the water management department for the j-th dam unit at time t; j,t It is the ecological discharge calculated for the jth dam unit at time t.

7. The method for calculating the water intake guarantee rate for nuclear power users downstream of a river with multiple dams and locks according to claim 1, characterized in that: The specific requirements for the water guarantee rate for downstream nuclear power users as described in step 5 are as follows: based on the continuity requirement of water use in the nuclear power production process, the minimum time step of the water guarantee rate is calculated on a daily basis, and the water guarantee rate for downstream nuclear power users is required to reach 97%.

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