Method for estimating diversion rate of small watershed diversion project based on daily precipitation

Abstract

The method for estimating diversion rate of small watershed diversion project based on daily rainfall belongs to the field of water conservancy engineering, and particularly relates to a method for calculating diversion rate. The method calculates flood processes corresponding to different daily rainfall by using comprehensive unit line method, establishes the relationship between daily rainfall and diversion rate corresponding to different flow capacities, calculates daily diversion rate of design representative year, calculates annual diversion amount of design representative year, analyzes annual diversion amount corresponding to different flow capacities by using the same method, and determines diversion scale by technical and economic comparison and selection. The method solves the problem of lacking measured daily flow data in calculation of diversion rate of small watershed. The daily flow process is analyzed by using comprehensive unit line method, the influence of topography, landform and watershed characteristics of small watershed on flow process is considered, the flow process of small watershed is more truly reflected, the influence of large daily change of flow process of small watershed on calculation of diversion rate is avoided, and the method is more practical.

Description

Technical Field

[0001] This invention belongs to the field of water conservancy engineering, and in particular relates to a method for calculating water diversion rate. Background Technology

[0002] In calculating the water diversion rate for water conservancy projects, due to the characteristics of hydrological station network construction, flow data is often unavailable during the design process of water diversion projects in small watersheds. The water diversion rate is typically calculated based on daily flow data from reference stations, obtained by scaling the data proportionally to the daily flow process of the project cross-section. Then, based on the maximum flow capacity of the water diversion project, the annual water diversion rate is calculated by dividing the daily flow process of the project cross-section. The portion of the inflow exceeding the maximum flow capacity of the water diversion project is considered as wastewater, while the portion less than the maximum flow capacity is considered as the diverted water volume. The ratio of the annual diverted water volume to the inflow water volume is the water diversion rate.

[0003] Typically, small watersheds lack measured daily flow monitoring data, while the reference stations with measured daily flow data often have large watershed areas. Due to the regulating effects of the river channel, soil, and reservoirs within the watershed, the baseflow is large, the flood process is relatively short and wide, and the intra-day flow variation is small. Small watersheds, on the other hand, have smaller areas, shorter river lengths, larger channel gradients, and less flattening, resulting in smaller baseflows and relatively sharper flood processes. Therefore, existing methods that use daily flow data from reference stations scaled at the same ratio to obtain daily flow data for engineering sections cannot accurately reflect the characteristics of flow processes in small watersheds. Furthermore, because these reference data do not consider the impact of intra-day flow processes on water diversion, the calculated water diversion rate will be overestimated, leading to uneconomical water conservancy engineering designs. Summary of the Invention

[0004] This invention proposes a method for estimating the water diversion rate of small watershed water diversion projects based on daily precipitation. This method solves the problem of lack of measured daily flow data in small watersheds and is more operable. At the same time, it takes into account the influence of the watershed's own topography and geomorphology and watershed characteristics on the flow process, and can more realistically reflect the flow process of small watersheds.

[0005] Example 1: A method for estimating the water diversion rate of a small watershed water diversion project based on daily precipitation. The specific steps are as follows:

[0006] S1, using the composite unit hydrograph method to calculate the flood process corresponding to different daily precipitation:

[0007] S1-1, Based on the collected daily precipitation data from the reference stations, determine the range of daily precipitation;

[0008] S1-2. Based on the typical annual daily precipitation range of the reference stations, select a representative set of daily precipitation Hi. The selected Hi data should be able to represent the typical annual daily precipitation range, and the selected data intervals should be relatively uniform. The flow process Qit and the maximum 24-hour flood volume Wi corresponding to this daily precipitation are calculated using the integrated unit hydrograph method. Qit should be able to reflect the flood process and correspond to the maximum 24-hour flood volume.

[0009] S2, Establish the relationship between daily precipitation and water diversion rate for different flow capacities:

[0010] Determine the maximum flow capacity Q′j of a set of water diversion projects, and calculate the water diversion volume by cutting the flow rate:

[0011] Qit≤Q′j, water diversion volume W′ijt=Qit×Δt;

[0012] Qit>Q′j, water diversion volume W′ijt=Q′j×Δt;

[0013]

[0014] Water diversion rate ηij=W′ij / Wi;

[0015] The relationship between daily precipitation Hi, maximum flow capacity Q′j, and water diversion rate ηij was obtained;

[0016] S3, Calculate the daily water diversion rate representing the design year:

[0017] S3-1, the daily precipitation process of a typical year is scaled up and down according to the design representative annual precipitation to obtain the daily precipitation process of the design representative year;

[0018] S3-2, based on the daily precipitation process of the design representative year and the relationship between (Hi, Q′j, ηij), the daily water diversion rate of the design representative year is calculated by interpolation;

[0019] S4, Calculates the representative annual water diversion volume:

[0020] S4-1, Calculate the daily runoff of the design representative year: Based on the daily precipitation of the design representative year obtained in S3-1, subtract the baseflow from the design annual runoff and distribute it to the day according to the precipitation, then add the baseflow back to obtain the daily runoff process of the design representative year.

[0021] S4-2, Calculate the design representative year's annual water diversion rate: Multiply the daily runoff of the design representative year by the corresponding daily water diversion rate to obtain the daily water diversion volume, and sum them up to obtain the annual water diversion volume. The ratio of the annual water diversion volume to the design runoff volume is the design annual water diversion rate.

[0022] S5. Then, using the same method, we analyze the annual water diversion volume corresponding to different flow capacities and conduct technical and economic comparisons to determine the water diversion scale.

[0023] The method of this invention solves the problem of lacking measured daily flow data for calculating the water diversion rate in small watersheds. By employing the integrated unit hydrograph method to analyze the intraday flow process, it considers the influence of the small watershed's own topography and watershed characteristics on the flow process, thus more accurately reflecting the flow process in the small watershed and avoiding the impact of large intraday variations in the flow process on the calculation of the water diversion rate, making it more realistic. Attached Figure Description

[0024] Figure 1 This is a graph showing the relationship between daily precipitation, water diversion scale, and water diversion rate.

[0025] Figure 2 To design a water diversion rate diagram corresponding to the representative annual water diversion scale. Detailed Implementation

[0026] Example 1: A method for estimating the water diversion rate of a small watershed water diversion project based on daily precipitation. The specific steps are as follows:

[0027] S1, using the composite unit hydrograph method to calculate the flood process corresponding to different daily precipitation:

[0028] S1-1, Based on the collected daily precipitation data from the reference stations, determine the range of daily precipitation;

[0029] Taking a certain reference station as an example, the daily average flow and daily precipitation data from 1999 to 2006 were obtained. Based on the data of the reference station, 2004 was selected as the typical year with P=75%. The daily precipitation of the typical year is shown in Table 1-1.

[0030] Table 1-1 Typical Annual Daily Precipitation Data (Unit: mm):

[0031]

[0032]

[0033] S1-2, Select a representative set of daily precipitation Hi from the typical annual daily precipitation data of the reference station. The selected Hi data should be able to represent the range of daily precipitation in a typical year, and the selected data should be relatively evenly spaced.

[0034] Daily precipitation values ​​Hi were selected as 18.2 mm, 27.3 mm, 36.4 mm, 45.5 mm, 54.6 mm, 74.6 mm, 93.8 mm, and 112.3 mm, respectively.

[0035] The flow process Qit corresponding to the daily precipitation and the maximum 24-hour flood volume Wi are calculated using the integrated unit hydrograph method. Qit should reflect the flood process and correspond to the maximum 24-hour flood volume.

[0036] The catchment area above the project section is 12.2 km². 2The river is 8.1 km long and has a channel gradient of 82‰. The daily precipitation of 18.2 mm, 27.3 mm, 36.4 mm, 45.5 mm, 54.6 mm, 74.6 mm, 93.8 mm, and 112.3 mm corresponds to the flow process and the maximum 24-hour flood volume, as shown in Table 1-2.

[0037] Table 1-2 Precipitation-to-Flow Rate Process Table:

[0038]

[0039]

[0040] S2, Establish the relationship between daily precipitation and water diversion rate for different flow capacities:

[0041] A set of maximum flow capacity Q′j for water diversion projects is proposed, Q′=[0.7, 0.8, 0.9, 1.0, 1.1], and the corresponding water diversion volume is calculated by cutting the flow rate;

[0042] For example, the maximum overcurrent capacity Q′=1.0m 3 / s, compare Q 27.3 mm flow rate process:

[0043] When t=9, Q 27.3 If mm ≤ Q′, the inflow is less than the maximum flow capacity, and the diversion flow rate is the same as the inflow flow rate, which is 0.92 m³ / s. 3 / s, water diversion volume W′=0.92×Δt;

[0044] At t=2, Q 27.3 mm>Q′, incoming water 1.88m 3 / s is greater than the maximum overcurrent capacity of 1.0m 3 / s, the water diversion flow rate is the maximum flow capacity, and the water diversion flow rate is 1.0m³ / s. 3 / s, water diversion volume W′=1.0×Δt;

[0045] When the maximum current capacity Q′=1.0m 3 At a daily rainfall of 27.3 mm, the corresponding water diversion rate is: η(27.3 mm, 1.0 m 3 / s)=[∑W′(t:0~23)] / W=0.85;

[0046] Following this logic, we can calculate η(H=18.2mm, 27.3mm, 36.4mm, 45.5mm, 54.6mm, 74.6mm, 93.8mm, 112.3mm; Q′=0.7, 0.8, 0.9, 1.0, 1.1m). 3A total of 40 maximum flow capacities were used to determine the diversion rates corresponding to daily precipitation. A graph showing the relationship between daily precipitation, diversion scale, and diversion rate was plotted. Figure 1 ;

[0047] S3, Calculate the daily water diversion rate representing the design year:

[0048] S3-1, scaling the typical annual daily precipitation process according to the design annual precipitation, yields the design representative annual daily precipitation process:

[0049] Based on measured data, 2004 was selected as the typical year with P=75%, the typical annual precipitation was 1141.3 mm, and the designed annual precipitation was 1453 mm. The typical annual precipitation process was amplified using the same ratio amplification method to obtain the designed annual precipitation process, as shown in Table 3-1.

[0050] Table 3-1 Daily Precipitation Process for a Representative Design Year (Unit: mm):

[0051] date June July August September October November December January February March April May 1 0.1 1.9 7.9 19.7 2.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2 18.6 3.1 0.0 4.6 0.3 0.0 0.0 0.0 0.0 0.0 0.0 4.8 3 10.8 0.0 0.4 0.0 6.1 0.0 0.0 0.0 0.0 2.8 0.0 0.0 4 0.0 0.0 36.0 36.4 0.3 0.0 0.0 0.0 0.0 3.9 0.0 0.5 5 0.0 28.1 33.6 2.2 42.0 0.0 0.0 0.0 0.3 0.0 0.0 0.0 6 0.0 53.0 4.7 25.8 0.5 0.0 0.0 0.0 0.0 0.0 0.0 6.5 7 15.2 46.6 37.8 15.4 1.1 0.0 1.4 0.0 0.0 0.0 0.0 6.2 8 0.1 8.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 9 3.9 12.1 23.6 0.3 1.0 0.0 0.0 1.0 0.0 0.0 0.0 0.0 10 3.3 38.3 0.0 16.2 0.5 0.0 0.0 17.7 0.0 0.0 0.0 0.1 11 1.1 15.0 1.8 7.6 0.0 0.0 0.0 1.5 0.0 0.0 0.0 0.0 12 0.0 7.6 0.0 9.2 1.1 0.0 0.0 0.1 0.0 0.0 0.0 0.0 13 0.0 0.0 53.9 12.0 0.0 0.0 0.0 0.0 0.0 0.5 0.0 0.0 14 0.0 8.1 4.3 0.0 0.8 0.0 0.0 1.0 0.0 0.0 0.0 0.0 15 72.1 5.5 8.3 14.1 17.3 0.6 0.0 0.0 0.0 4.5 0.0 0.0 16 0.5 1.3 13.6 8.5 0.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 17 0.0 3.9 1.4 0.0 23.3 0.0 5.0 0.0 0.0 0.0 0.0 0.0 18 10.1 2.2 8.8 0.4 9.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 19 0.1 1.7 1.0 0.0 0.0 0.0 0.0 0.6 0.0 0.0 0.0 0.0 20 26.6 68.4 0.1 4.2 0.0 0.0 0.0 0.4 0.0 0.0 0.0 0.0 21 2.0 14.6 1.5 8.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 22 0.0 12.3 0.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 23 0.0 0.8 40.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 24 0.0 8.1 0.0 2.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 25 0.0 1.7 9.4 29.7 0.0 7.3 0.0 0.0 0.0 0.0 0.0 0.0 26 1.3 2.4 0.0 11.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 27 19.0 0.0 9.8 4.1 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.0 28 1.5 0.0 33.5 0.9 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 29 41.5 0.0 2.3 0.0 0.0 29.9 0.0 0.0 0.0 0.0 51.8 30 0.1 32.7 5.7 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 31 1.5 7.9 0.0 0.0 0.0 0.0 3.7

[0052] S3-2, combining the relationship between daily precipitation and water diversion rate, the daily water diversion rate for the design representative year is obtained:

[0053] Based on the daily precipitation process of the design representative year, and using η(H, Q′), the daily diversion rate corresponding to each maximum flow capacity Q′ is obtained by interpolation; for example, on July 20, 2004, the precipitation was 68.4 mm, and the maximum flow capacity Q′ = 1.0 m. 3 At a rate of / s, based on η(H, Q′), the water diversion rate is 0.23; the calculated daily water diversion rate for the design year is shown in Table 3-2;

[0054] Table 3-2 Maximum current carrying capacity Q′=1.0m 3 Daily water diversion rate per second:

[0055] date June July August September October November December January February March April May 1 1.00 1.00 1.00 0.97 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 2 0.99 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 3 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 4 1.00 1.00 0.66 0.65 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 5 1.00 0.83 0.71 1.00 0.53 1.00 1.00 1.00 1.00 1.00 1.00 1.00 6 1.00 0.37 1.00 0.87 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 7 1.00 0.44 0.62 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 8 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 9 1.00 1.00 0.91 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 10 1.00 0.61 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 11 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 12 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 13 1.00 1.00 0.36 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 14 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 15 0.19 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 16 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 17 1.00 1.00 1.00 1.00 0.91 1.00 1.00 1.00 1.00 1.00 1.00 1.00 18 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 19 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 20 0.86 0.23 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 21 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 22 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 23 1.00 1.00 0.56 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 24 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 25 1.00 1.00 1.00 0.80 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 26 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 27 0.99 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 28 1.00 1.00 0.71 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 29 0.54 1.00 1.00 1.00 1.00 0.79 1.00 1.00 1.00 1.00 1.00 0.38 30 1.00 0.73 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 31 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00

[0056] S4, Calculates the representative annual water diversion volume:

[0057] S4-1, Calculate the daily runoff of the design representative year: Based on the daily precipitation of the design year obtained in S3-1, subtract the baseflow from the runoff of the design representative year and distribute it to the day according to the precipitation, then add the baseflow back to obtain the daily runoff process of the design representative year.

[0058] The project's cross-section is designed for an annual runoff of 7.45 million cubic meters. 3 Considering a baseflow of 0.016m during the flood season 3 / (s·km 2 Dry season 0.004m 3 / (s·km 2 According to the daily precipitation process of the design representative year, the inflow process is obtained by allocating it to the day, as shown in Table 4-1;

[0059] Table 4-1 Daily Runoff Process for Representative Design Year (Unit: m³) 3 / s):

[0060] date June July August September October November December January February March April May 1 1.36 1.90 3.73 7.33 2.02 1.32 0.33 0.33 0.33 0.33 0.33 0.33 2 6.98 2.25 1.32 2.72 1.40 1.32 0.33 0.33 0.33 0.33 0.33 1.80 3 4.62 1.32 1.44 1.32 3.18 1.32 0.33 0.33 0.33 1.18 0.33 0.33 4 1.32 1.32 12.29 12.41 1.40 1.32 0.33 0.33 0.33 1.53 0.33 0.49 5 1.32 9.89 11.56 1.98 14.12 1.32 0.33 0.33 0.41 0.33 0.33 0.33 6 1.32 17.45 2.76 9.19 1.48 1.32 0.33 0.33 0.33 0.33 0.33 2.31 7 5.94 15.51 12.84 6.01 1.67 1.32 0.76 0.33 0.33 0.33 0.33 2.23 8 1.36 3.84 1.32 1.32 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.37 9 2.53 5.01 8.50 1.40 1.63 1.32 0.33 0.64 0.33 0.33 0.33 0.33 10 2.33 12.99 1.32 6.25 1.48 1.32 0.33 5.72 0.33 0.33 0.33 0.37 11 1.67 5.90 1.87 3.65 1.32 1.32 0.33 0.80 0.33 0.33 0.33 0.33 12 1.32 3.65 1.32 4.11 1.67 1.32 0.33 0.37 0.33 0.33 0.33 0.33 13 1.32 1.32 17.72 4.97 1.32 1.32 0.33 0.33 0.33 0.49 0.33 0.33 14 1.32 3.80 2.64 1.32 1.56 1.32 0.33 0.64 0.33 0.33 0.33 0.33 15 23.26 2.99 3.84 5.63 6.60 1.52 0.33 0.33 0.33 1.69 0.33 0.33 16 1.48 1.71 5.47 3.92 1.56 1.32 0.33 0.33 0.33 0.33 0.33 0.33 17 1.32 2.53 1.75 1.32 8.42 1.32 1.84 0.33 0.33 0.33 0.33 0.33 18 4.39 1.98 4.00 1.44 4.31 1.32 0.33 0.33 0.33 0.33 0.33 0.33 19 1.36 1.83 1.63 1.32 1.32 1.32 0.33 0.52 0.33 0.33 0.33 0.33 20 9.43 22.14 1.36 2.60 1.32 1.32 0.33 0.45 0.33 0.33 0.33 0.33 21 1.94 5.78 1.79 3.77 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 22 1.32 5.08 1.32 2.84 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 23 1.32 1.56 13.69 1.32 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 24 1.32 3.80 1.32 2.06 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 25 1.32 1.83 4.19 10.36 1.32 3.53 0.33 0.33 0.33 0.33 0.33 0.33 26 1.71 2.06 1.32 4.77 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 27 7.10 1.32 4.31 2.56 1.32 1.32 0.33 0.33 0.33 0.33 0.41 0.33 28 1.79 1.32 11.52 1.59 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 29 13.96 1.32 2.02 1.32 1.32 10.43 0.33 0.33 0.33 0.33 16.11 30 1.36 11.29 3.07 1.32 1.32 1.32 0.33 0.33 0.33 0.33 0.33 31 1.79 3.73 1.32 0.33 0.33 0.33 1.46

[0061] S4-2, Calculate the design representative year's annual water diversion rate: Multiply the daily runoff of the design representative year by the corresponding daily water diversion rate to obtain the daily water diversion volume, and sum them up to obtain the annual water diversion volume. The ratio of the annual water diversion volume to the design runoff volume is the design annual water diversion rate.

[0062] For example, current capacity 1.0m 3 At a rate of / s, the designed annual daily water diversion volume is shown in Table 4-2, with an annual water diversion volume of 6.11 million m³. 3 The water diversion rate is 82%.

[0063] Table 4-2 Design representative annual maximum flow capacity Q′=1.0m 3 Daily water diversion volume (unit: 10,000 m³) 3 ):

[0064] date June July August September October November December January February March April May 1 1.36 1.90 3.73 7.14 2.02 1.32 0.33 0.33 0.33 0.33 0.33 0.33 2 6.94 2.25 1.32 2.72 1.40 1.32 0.33 0.33 0.33 0.33 0.33 1.80 3 4.62 1.32 1.44 1.32 3.18 1.32 0.33 0.33 0.33 1.18 0.33 0.33 4 1.32 1.32 8.12 8.10 1.40 1.32 0.33 0.33 0.33 1.53 0.33 0.49 5 1.32 8.19 8.23 1.98 7.51 1.32 0.33 0.33 0.41 0.33 0.33 0.33 6 1.32 6.39 2.76 8.01 1.48 1.32 0.33 0.33 0.33 0.33 0.33 2.31 7 5.94 6.88 7.99 6.01 1.67 1.32 0.76 0.33 0.33 0.33 0.33 2.23 8 1.36 3.84 1.32 1.32 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.37 9 2.53 5.01 7.73 1.40 1.63 1.32 0.33 0.64 0.33 0.33 0.33 0.33 10 2.33 7.95 1.32 6.25 1.48 1.32 0.33 5.72 0.33 0.33 0.33 0.37 11 1.67 5.90 1.87 3.65 1.32 1.32 0.33 0.80 0.33 0.33 0.33 0.33 12 1.32 3.65 1.32 4.11 1.67 1.32 0.33 0.37 0.33 0.33 0.33 0.33 13 1.32 1.32 6.29 4.97 1.32 1.32 0.33 0.33 0.33 0.49 0.33 0.33 14 1.32 3.80 2.64 1.32 1.56 1.32 0.33 0.64 0.33 0.33 0.33 0.33 15 4.49 2.99 3.84 5.63 6.60 1.52 0.33 0.33 0.33 1.69 0.33 0.33 16 1.48 1.71 5.47 3.92 1.56 1.32 0.33 0.33 0.33 0.33 0.33 0.33 17 1.32 2.53 1.75 1.32 7.69 1.32 1.84 0.33 0.33 0.33 0.33 0.33 18 4.39 1.98 4.00 1.44 4.31 1.32 0.33 0.33 0.33 0.33 0.33 0.33 19 1.36 1.83 1.63 1.32 1.32 1.32 0.33 0.52 0.33 0.33 0.33 0.33 20 8.09 4.99 1.36 2.60 1.32 1.32 0.33 0.45 0.33 0.33 0.33 0.33 21 1.94 5.78 1.79 3.77 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 22 1.32 5.08 1.32 2.84 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 23 1.32 1.56 7.70 1.32 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 24 1.32 3.80 1.32 2.06 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 25 1.32 1.83 4.19 8.24 1.32 3.53 0.33 0.33 0.33 0.33 0.33 0.33 26 1.71 2.06 1.32 4.77 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 27 7.01 1.32 4.31 2.56 1.32 1.32 0.33 0.33 0.33 0.33 0.41 0.33 28 1.79 1.32 8.24 1.59 1.32 1.32 0.33 0.33 0.33 0.33 0.33 0.33 29 7.58 1.32 2.02 1.32 1.32 8.25 0.33 0.33 0.33 0.33 0.33 6.12 30 1.36 8.25 3.07 1.32 1.32 1.32 0.33 0.33 0.00 0.33 0.33 0.33 31 0.00 1.79 3.73 0.00 1.32 0.00 0.33 0.33 0.00 0.33 0.00 1.46

[0065] S5. Then, using the same method, we analyze the annual water diversion volume corresponding to different flow capacities and conduct economic and technical comparisons to determine the water diversion scale.

[0066] If the traditional calculation method is used, then based on the daily average flow data of the reference stations in typical years in Table 6-1, the design representative annual runoff (7.45 million m³) is calculated. 3 ) and the typical annual runoff of the reference station (72.6 million m³) 3 The average daily flow rate of the engineering cross-section design is obtained by scaling by the same factor, as shown in Table 6-2.

[0067] Table 6-1 Daily Average Flow Rate in a Typical Year (Unit: m³) 3 / s):

[0068] years day June July August September October November December January February March April May 2004 1 1.81 5.52 3.03 16.7 3.23 1.65 0.97 0.5 0.3 0.23 0.15 0.08 2 2.56 3.52 2.59 20.5 2.85 1.65 0.82 0.5 0.32 0.22 0.15 0.08 3 5.06 2.35 2.23 9.01 2.65 1.55 0.75 0.5 0.32 0.22 0.24 0.08 4 3.46 1.8 3.4 5.89 3.29 1.54 0.74 0.5 0.3 0.26 2.18 0.07 5 1.86 2.54 16.7 6.78 3.3 1.44 0.68 0.48 0.3 0.36 1.39 0.08 6 1.34 2.66 20.5 5.47 3.94 1.33 0.67 0.44 0.3 0.37 0.43 0.08 7 3.49 3.01 15.5 10.7 8.75 1.27 0.67 0.42 0.3 0.3 0.27 0.15 8 3.49 8.8 11.7 8.35 4.4 1.32 0.67 0.41 0.3 0.3 0.13 0.32 9 1.79 6.76 7.11 5.65 3.5 1.32 0.67 0.44 0.29 0.28 0.093 0.26 10 2.34 8.24 5.71 4.85 3.07 1.23 0.67 0.75 0.27 0.24 0.072 0.23 11 2.19 11.9 4.73 5.2 3.15 1.17 0.67 0.69 0.27 0.22 0.07 0.18 12 1.5 6.49 4.09 4.81 2.48 1.17 0.64 0.54 0.25 0.2 0.078 0.16 13 1.19 6.52 5.04 5.34 2.19 1.13 0.6 0.5 0.23 0.18 0.068 0.12 14 1.16 4.5 16.5 5.59 1.99 1.12 0.6 0.45 0.25 0.17 0.062 0.09 15 0.94 8.39 5.99 4.37 6.11 1.12 0.6 0.49 0.27 0.17 0.071 0.07 16 5.82 5.88 5 4.6 5.13 1.16 0.6 0.5 0.27 0.17 0.068 0.06 17 2.42 4.76 6.06 4.5 3.28 1.13 0.66 0.47 0.27 0.18 0.064 0.06 18 6.99 4.12 5 3.64 11.2 1.12 0.79 0.4 0.27 0.17 0.063 0.06 19 6.18 3.72 4.24 3.55 6.01 1.12 0.67 0.41 0.27 0.16 0.06 0.06 20 5.13 3.54 3.51 3.57 4.46 1.12 0.61 0.42 0.25 0.14 0.06 0.06 21 6.68 4.62 2.94 3.81 3.77 1.04 0.54 0.44 0.22 0.15 0.061 0.06 22 3.51 5.55 3.89 3.42 3.31 1.03 0.54 0.4 0.22 0.23 0.06 0.06 23 2.67 5.04 3.01 3.1 2.98 1.07 0.54 0.39 0.21 0.31 0.061 0.06 24 2.09 3.72 7.62 3.92 2.62 1.04 0.49 0.39 0.23 0.39 0.059 0.06 25 1.7 3.32 3.92 4.13 2.47 1.03 0.48 0.35 0.23 0.48 0.059 0.06 26 1.39 3.81 3.17 10 2.34 1.91 0.48 0.3 0.23 0.56 0.059 0.06 27 2.33 2.9 2.74 5.88 2.2 1.08 0.48 0.32 0.25 0.54 0.06 0.06 28 2.45 2.5 3.85 5.85 2.13 0.86 0.47 0.32 0.24 0.29 0.062 0.06 29 2.71 2.19 7.84 4.23 1.97 2.04 0.48 0.3 0.22 0.084 0.06 30 4.55 2.08 4.84 3.62 1.89 1.87 0.48 0.32 0.18 0.085 0.61 31 4.31 15.4 1.74 0.48 0.32 0.16 0.28

[0069] Table 6-2 Daily Average Flow Rate for Representative Design Year (Unit: m³) 3 / s):

[0070]

[0071]

[0072] The maximum flow capacity of several water diversion projects is determined to be Q′ = [0.7, 0.8, 0.9, 1.0, 1.1], and the water diversion volume is calculated by cutting the flow rate. For example, if the maximum flow capacity Q′ = 1.0 m³ / s... 3When the flow rate is / s, the inflow rate is the portion of the daily flow rate that is less than or equal to the maximum flow capacity, and the inflow rate that is greater than the maximum flow capacity is the maximum flow capacity. For example, the inflow rate on June 7th is 0.358m³ / s. 3 / s, less than the maximum overcurrent capacity Q′=1.0m 3 / s, the water diversion flow rate is the same as the inflow flow rate of 0.358m³. 3 / s; Inflow rate on July 11: 1.221m³ 3 / s, greater than the maximum overcurrent capacity Q′=1.0m 3 / s, the water diversion flow rate is the maximum flow capacity of 1.0m. 3 / s, maximum current capacity 1.0m 3 The water diversion volume corresponding to / s is shown in Table 6-3.

[0073] Table 6-3 shows the design representative annual maximum current capacity of 1.0m. 3 Daily water diversion volume (unit: 10,000 m³) 3 ):

[0074]

[0075]

[0076] Calculate the annual diversion rate corresponding to the ratio of annual diversion volume to design annual runoff for each maximum flow capacity. The diversion rates obtained from the calculations for the two methods are shown in the table below:

[0077] <![CDATA[Maximum overcurrent capacity (m 3 / s)]]> 0.70 0.80 0.90 1.0 1.1 This method calculates the water diversion rate. 0.75 0.78 0.80 0.82 0.84 Traditional methods for calculating water diversion rate 0.87 0.89 0.91 0.93 0.94

[0078] The water diversion rate calculated by this method is lower than that calculated by traditional methods. The main reason is that this method considers the impact of intraday runoff variation on the water diversion rate, more accurately reflecting the characteristics of small watershed flow processes; while traditional methods use daily average flow to represent intraday runoff processes, leading to a flattening of the runoff process and an overestimation of the water diversion rate. In conclusion, the water diversion rate calculated by this method is more realistic than that calculated by traditional methods.

Claims

1. A method for estimating the water diversion rate of small watershed water diversion projects based on daily precipitation, the specific steps of which are as follows: S1, using the composite unit hydrograph method to calculate the flood process corresponding to different daily precipitation: S1-1, Based on the collected daily precipitation data from the reference stations, determine the range of daily precipitation; S1-2. Based on the typical annual daily precipitation range of the reference stations, select a representative set of daily precipitation Hi. The selected Hi data should be able to represent the typical annual daily precipitation range, and the selected data intervals should be relatively uniform. The flow process Qit and the maximum 24-hour flood volume Wi corresponding to this daily precipitation are calculated using the integrated unit hydrograph method. Qit should be able to reflect the flood process and correspond to the maximum 24-hour flood volume. S2, Establish the relationship between daily precipitation and water diversion rate for different flow capacities: Determine a set of maximum flow capacities Q´j for the water diversion project, and calculate the water diversion volume by cutting the flow rate: Qit≤Q´j,Water diversion volume W´ijt=Qit×Δt; Qit>Q´j, water diversion volume W´ijt=Q´j×Δt; ； Water diversion rate ηij = W´ij / Wi; The relationship between daily precipitation Hi, maximum flow capacity Q´j, and water diversion rate ηij was obtained; S3, Calculate the daily water diversion rate representing the design year: S3-1, the typical annual daily precipitation process is scaled up and down according to the design representative annual precipitation to obtain the design representative annual daily precipitation process; S3-2, based on the daily precipitation process of the design representative year and the relationship between (Hi, Q´j, ηij), the daily water diversion rate of the design representative year is calculated by interpolation; S4, Calculates the representative annual water diversion volume: S4-1, Calculate the daily runoff of the design representative year: Based on the daily precipitation of the design representative year obtained in S3-1, subtract the baseflow from the design annual runoff and distribute it to the day according to the precipitation, then add the baseflow back to obtain the daily runoff process of the design representative year. S4-2, Calculate the design representative year's annual water diversion rate: Multiply the daily runoff of the design representative year by the corresponding daily water diversion rate to obtain the daily water diversion volume, and sum them up to obtain the annual water diversion volume. The ratio of the annual water diversion volume to the design runoff volume is the design annual water diversion rate. S5. Then, using the same method, we analyze the annual water diversion volume corresponding to different flow capacities and conduct technical and economic comparisons to determine the water diversion scale.

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