A method for determining the scale scheme of diversion ditches in small watersheds

Abstract

The present invention discloses a method for determining the scale scheme of diversion channels in small watersheds, including: preliminarily formulating the scale scheme of diversion channels, selecting the diversion outlet, and determining the maximum diversion flow rate of the scheme; determining the catchment area of the diversion outlet according to the diversion outlet, establishing a rainfall-runoff model for the small watershed and calculating the daily runoff of the diversion outlet based on this model; for the catchment area of the diversion outlet, constructing a storm flood model for the small watershed and using this model to calculate the peak-forming rainfall according to the maximum diversion flow rate; for the measured rainfall data, screening out all the excessive rainfall greater than the peak-forming rainfall; calculating the sum of the flows formed by all the excessive rainfall events at the diversion outlet, subtracting the water consumption of other water uses during the excessive rainfall and the maximum diversion flow rate to obtain the amount of water discarded; subtracting the water consumption of other water uses during water diversion and the amount of water discarded from the daily runoff to obtain the amount of water diverted; repeating the above steps, formulating different scale schemes of diversion channels, calculating the corresponding amounts of water diverted, conducting a technical and economic comparison, and determining the optimal scale scheme of diversion channels.

Description

Technical Field

[0001] The present invention belongs to the technical field of water conservancy projects, and particularly relates to a method for determining the scale scheme of diversion channels in small watersheds. Background Art

[0002] In China, the spatio-temporal distribution of water resources is uneven, and the water resources do not match the level of social and economic development. The contradiction between water supply and demand is prominent. In many regions, relying solely on tapping the water resource potential of the local area or basin cannot completely solve the problem of water shortage. The above problems are particularly prominent among small watersheds. Due to the small catchment area of small watersheds, the rivers are short and swift, and the water resource regulation capacity of the watershed itself is very small.

[0003] As a water resource allocation project, diversion channels have a wide range of applications in the field of water resource development and utilization. Its main function is to solve the spatio-temporal non-uniformity of water resources. Considering from the perspectives of optimizing the spatio-temporal allocation of water resources in the region, improving the degree of water resource development, utilization efficiency, and the water resource guarantee degree of water use objects, this type of project form of diversion channels is very common in the development and utilization of small watershed water resources. For example, there are construction requirements in aspects such as regional irrigation, water supply, power generation, and water ecological improvement. The scale of the diversion channel is comprehensively determined by factors such as the water diversion volume, maximum water diversion flow rate, and project investment. If the scale of the diversion channel is too large, the investment will increase significantly, but the water diversion volume does not necessarily increase correspondingly, resulting in a waste of project investment; if the scale is set too small, the water diversion volume is limited and cannot meet the water consumption demand of water use objects.

[0004] Currently, for the scale of the diversion channel, first, it is necessary to calculate the incoming water volume and water consumption volume at the cross-section of the water diversion inlet, then draw up the water diversion flow rate and water diversion volume schemes, and conduct runoff regulation calculations through the long series or representative year method. According to the calculation results, judge whether the water diversion flow rate and water diversion volume schemes will affect the original water use demand at the water diversion inlet; if the proposed scheme affects the original water use demand, it is necessary to redraw the water diversion flow rate and water diversion volume schemes and conduct runoff regulation calculations again until a reasonable water diversion flow rate and water diversion volume scheme are obtained; finally, determine the scale of the diversion channel according to the open channel hydraulic calculation method. The above method has a large amount of calculation work and high data requirements, and is less applicable to the calculation of the scale of small watershed diversion channels. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the embodiments of the present application is to provide a method for determining the scale scheme of diversion channels in small watersheds.

[0006] The embodiments of the present application provide a method for determining the scale scheme of diversion channels in small watersheds, including:

[0007] Step S1: Initially draw up a scale scheme for the diversion channel, select the location of the water diversion inlet, and determine the maximum water diversion flow rate of the scale scheme of the diversion channel according to the location of the water diversion inlet;

[0008] Step S2: Determine the water intake catchment area according to the location of the water intake, establish a small watershed rainfall-runoff model based on the hydrological cycle, and calculate the daily runoff of the water intake according to the small watershed rainfall-runoff model;

[0009] Step S3: For the water intake catchment area, construct a small watershed storm flood model based on the principle of runoff generation and concentration;

[0010] Step S4: According to the maximum water intake flow rate, use the small watershed storm flood model to calculate the peak rainfall duration and peak rainfall amount for generating the maximum water intake flow rate at the water intake in the water intake catchment area, that is, the peak rainfall;

[0011] Step S5: For the measured rainfall data, screen out all actual rainfall events greater than the peak rainfall, that is, the excess rainfall;

[0012] Step S6: Calculate the sum of the flow rates formed by all excess rainfall events at the water intake, subtract the water consumption of other water uses that must be deducted during excess rainfall, and then subtract the maximum water intake flow rate to obtain the water discharge to be discarded;

[0013] Step S7: Subtract the water consumption of other water uses that must be deducted during water intake from the daily runoff, and then subtract the water discharge to be discarded to obtain the water intake corresponding to the water diversion channel scale scheme determined in Step S1;

[0014] Step S8: Repeat Steps S1 to S7, formulate different water diversion channel scale schemes, calculate the corresponding water intakes, conduct technical and economic comparisons, and determine the optimal water diversion channel scale scheme.

[0015] Further, in Step S1, the water intake is selected according to the topography, geological conditions, river plane form, hydrological sediment characteristics, riverbed evolution law, construction conditions, target water intake volume, and catchment area of the water intake catchment area.

[0016] Further, in Step S1, the maximum water intake flow rate of the water diversion channel scale scheme is determined by the hydraulic calculation method of uniform open channel flow:

[0017]

[0018] where Q is the maximum water intake flow rate; A is the cross-sectional area; n is the roughness coefficient of the channel; R is the hydraulic radius; J 沟渠 is the channel slope, where the cross-sectional area and hydraulic radius are calculated according to the width and depth of the water diversion channel in the water diversion channel scale scheme, and the channel slope is determined according to the topographic changes at the water intake.

[0019] Further, the three-source Xin'anjiang model is adopted for the small watershed rainfall-runoff model.

[0020] Furthermore, the small watershed rainstorm flood model adopts the inference formula method and the instantaneous unit line method;

[0021] The inference formula method is applicable to the water intake catchment area of ​​50km 2 For small watersheds below 1000 m, the calculation formula is:

[0022]

[0023]

[0024] Where, τ is the confluence time; h t is the net rainfall; F is the catchment area of ​​the water intake; Q m is the peak flow; L is the length of the main stream of the river; m is the confluence parameter; J is the slope of the river;

[0025] The instantaneous unit line method is applicable to water intake catchment areas larger than 50km 2 The calculation formula for a small watershed is:

[0026]

[0027] Among them, u(t) is the instantaneous unit line vertical height at time t; k is a parameter reflecting the confluence time of the basin, that is, the regulation coefficient; n is the number of adjustments; Γ(n) is the nth order incomplete gamma function; t is time.

[0028] Furthermore, in step S4, the peak rainfall duration and peak rainfall intensity of the watershed catchment area, i.e., the peak rainfall, are reversely deduced through the small watershed rainstorm flood model, wherein the peak rainfall forms the maximum water diversion flow at the water diversion port.

[0029] Further, step S5 includes:

[0030] According to the spatial distribution of regional rainfall, the layout of hydrological stations and the age of data, a reasonable representative rainfall reference station in the catchment area upstream of the water intake determined in step S1 is selected, and all excess rainfall events with rainfall duration and rainfall intensity greater than the peak rainfall duration and rainfall intensity are extracted from the measured rainfall data.

[0031] Furthermore, the other water that must be deducted is the minimum guaranteed flow rate to meet the downstream living, production and ecological water needs of the water intake determined in step S1.

[0032] The technical solution provided by the embodiments of the present application may have the following beneficial effects:

[0033] As can be seen from the above embodiments, in view of the poor completeness of water use data in small watersheds, this application uses measured rainfall data and analyzes and calculates the scale scheme of diversion ditches in small watersheds through rainfall-runoff and storm flood models. This method is simple to calculate and has low data requirements, and can greatly improve the calculation efficiency of the scale scheme of diversion ditches.

[0034] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application.

[0036] Figure 1 is a flowchart of a method for determining the scale scheme of diversion ditches in a small watershed shown according to an exemplary embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] Here, the exemplary embodiments will be described in detail, and the examples are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0038] The terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a", "the", and "said" used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0039] It should be understood that although the terms first, second, third, etc. may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to determining".

[0040] Figure 1 is a flowchart of a method for determining the scale scheme of diversion ditches in a small watershed shown according to an exemplary embodiment, as Figure 1 shown, the method is applied to a terminal and may include the following steps:

[0041] Step S1: Initially propose a scale plan for the water diversion channel, select the location of the water intake, and determine the maximum water diversion flow rate of the water diversion channel scale plan based on the location of the water intake;

[0042] Step S2: Determine the water intake catchment area based on the location of the water intake, establish a small watershed rainfall-runoff model based on the hydrological cycle, and calculate the daily runoff of the water intake according to the small watershed rainfall-runoff model;

[0043] Step S3: For the water intake catchment area, construct a small watershed storm flood model based on the principle of runoff generation and concentration;

[0044] Step S4: According to the maximum water diversion flow rate, use the small watershed storm flood model to calculate the peak rainfall duration and peak rainfall amount, i.e., peak rainfall, for the water intake catchment area to form the maximum water diversion flow rate at the water intake;

[0045] Step S5: For the measured rainfall data, screen out all actual rainfall events greater than the peak rainfall, i.e., excess rainfall;

[0046] Step S6: Calculate the sum of the flow rates formed by all excess rainfall events at the water intake, subtract the water consumption of other water uses that must be deducted during excess rainfall, and then subtract the maximum water diversion flow rate to obtain the water discharge to be abandoned;

[0047] Step S7: Subtract the water consumption of other water uses that must be deducted during water diversion from the daily runoff, and then subtract the water discharge to be abandoned to obtain the water diversion volume corresponding to the water diversion channel scale plan determined in Step S1;

[0048] Step S8: Repeat Step S1 to Step S7, propose different water diversion channel scale plans, calculate the corresponding water diversion volumes, conduct a technical and economic comparison, and determine the optimal water diversion channel scale plan.

[0049] As can be seen from the above embodiments, in view of the poor completeness of water use data in small watersheds, this application uses measured rainfall data and analyzes and calculates the water diversion channel scale plan for small watersheds through rainfall-runoff and storm flood models. This method is simple to calculate, has low data requirements, and can greatly improve the calculation efficiency of the water diversion channel scale plan.

[0050] In the specific implementation of Step S1, initially propose a scale plan for the water diversion channel, select the location of the water intake, and determine the maximum water diversion flow rate of the water diversion channel scale plan based on the location of the water intake;

[0051] Specifically, the water intake needs to be selected according to the topographic and geological conditions of the water diversion catchment area, the planar form of the river, the hydrological and sediment characteristics, the law of riverbed evolution, construction conditions, and limiting conditions such as the target water diversion volume and catchment area.

[0052] Specifically, the maximum water diversion flow rate of the water diversion canal scale plan is determined by the hydraulic calculation method of uniform open channel flow. The hydraulic calculation method of uniform open channel flow combines the Chezy formula and the Manning formula:

[0053]

[0054] Among them, Q is the flow rate; A is the cross-sectional area; n is the roughness coefficient of the canal; R is the hydraulic radius; J 沟渠 is the slope of the canal. The cross-sectional area and the hydraulic radius are calculated based on the width and depth of the water diversion canal in the water diversion canal scale plan, and the slope of the canal is determined according to the topographic changes at the water intake.

[0055] Specifically, according to the width B and depth H of the water diversion canal in the proposed plan, the maximum water depth H' can be obtained after deducting the safety freeboard. Calculate the cross-sectional area A = B * H' and the hydraulic radius R = A / (B + 2 * H'). Determine the slope of the canal J (height difference / length of the water diversion canal, set manually based on experience) according to the topographic changes at the water intake location. The roughness coefficient n of the canal can be obtained from the "Hydraulic Calculation Manual" according to the lining material of the canal. After obtaining the above relevant parameters, the maximum water diversion flow rate Q can be calculated.

[0056] In the specific implementation of step S2, the catchment area of the water intake is determined according to the location of the water intake, a small watershed rainfall-runoff model based on the hydrological cycle is established, and the daily runoff of the water intake is calculated according to the small watershed rainfall-runoff model;

[0057] Specifically, the small watershed rainfall-runoff model can adopt models such as TOPMODEl, the Tank model, and the Sacramento model. In one embodiment, the three-source Xin'anjiang model is adopted because the Xin'anjiang model has a wide range of applications, there are a large number of application examples, and the calculation accuracy is high. The runoff generation calculation of the Xin'anjiang model adopts the concept of full storage runoff generation, and the confluence calculation is divided into two stages: hillslope confluence and river network confluence.

[0058] The input data required for the three-source Xin'anjiang model to calculate the daily runoff are the measured daily precipitation and daily evaporation of the catchment area of the water intake. After adjusting through the runoff generation and confluence parameters, the daily runoff results are calculated and output. Through this step, the daily runoff process can be calculated using the daily precipitation and daily evaporation, solving the actual situation of the lack of measured runoff data in small watersheds.

[0059] In the specific implementation of step S3, for the catchment area of the water intake determined in step S1, a small watershed storm flood model based on the runoff generation and confluence principle is constructed;

[0060] Specifically, the small watershed storm flood model adopts the rational formula method and the instantaneous unit hydrograph method;

[0061] Among them, the reasoning formula method is applicable to small basins with a catchment area of the water diversion inlet of 50 km 2 and below. Its calculation formula is as follows:

[0062]

[0063]

[0064] Among them, τ is the concentration time (h); h t is the net rainfall (mm); F is the catchment area of the water diversion inlet (km 2 ); Q m is the peak flood discharge (m 3 / s); L is the main stream length of the river where the water intake is located (km); m is the concentration parameter; J is the river bed slope (‰);

[0065] The instantaneous unit hydrograph method is mainly applicable to small basins with a catchment area of the water diversion inlet greater than 50 km 2 . The calculation formula is:

[0066]

[0067] Among them, u(t) is the vertical height of the instantaneous unit hydrograph at time t; k is the parameter reflecting the catchment concentration time of the basin, that is, the storage coefficient; n is the number of regulations; Γ(n) is the incomplete gamma function of order n; t is the time.

[0068] Select the corresponding calculation method according to the catchment area of the water diversion inlet, and then measure and calculate the main stream length and river bed slope of the river at the location of the water diversion inlet using topographic maps as the model input parameters; the parameters of the reasoning formula method and the instantaneous unit hydrograph method are simple and clear, and the data requirements are low, which is suitable for the calculation of storm floods in small basins.

[0069] In the specific implementation of step S4, according to the maximum water diversion flow rate, use the small basin storm flood model to calculate the peak rainfall duration and peak rainfall amount of the catchment area of the water diversion inlet to form the maximum water diversion flow rate at the water diversion inlet, that is, the peak rainfall;

[0070] Specifically, according to the maximum water diversion flow rate corresponding to the proposed water diversion canal scale plan, use the small basin storm flood model to inversely calculate the peak rainfall duration and peak rainfall intensity of the catchment area of the water diversion inlet, that is, the peak rainfall.

[0071] Using the storm flood model, input rainfall data and output the flow process. Through this step, the conversion between rainfall and flow can be realized, solving the problem of the lack of measured flood flow data in small basins.

[0072] In the specific implementation of step S5, for the measured rainfall data, screen out all actual rainfall events greater than the peak rainfall, that is, the excess rainfall;

[0073] Specifically, according to the spatial distribution law of regional rainfall, the layout of hydrological stations, and the data years, reasonable representative rainfall reference stations in the catchment area of the water diversion inlet determined in step S1 are selected, and all excessive rainfall events with rainfall duration and intensity greater than the peak-forming rainfall duration and intensity are extracted from the measured rainfall data (including the start and end times of precipitation and the corresponding precipitation).

[0074] Excessive rainfall is screened out according to the peak-forming rainfall. Subsequently, only the excessive rainfall needs to be used for the calculation of storm floods, avoiding the calculation of storms for all sites and saving calculation time.

[0075] In the specific implementation of step S6, the sum of the flows formed by all excessive rainfall events at the water diversion inlet is calculated, then the water consumption of other water uses that must be deducted during excessive rainfall is subtracted, and then the maximum water diversion flow is subtracted to obtain the water discharge.

[0076] Specifically, the other water uses that must be deducted are the minimum guaranteed flows to meet the domestic, production, and ecological water demand downstream of the water diversion inlet determined in step S1.

[0077] That is, the calculation formula for the water discharge is: Q 弃 = Q 超 - Q 生活超 - Q 生产超 - Q 生态超 - Q 引max , and the water discharge calculated in this step is used as an intermediate variable, which is a necessary process for the calculation of the water diversion volume. Among them, Q 超 is the sum of the flows formed by all excessive rainfall events at the water diversion inlet, and Q 生活超 , Q 生产超 , Q 生态超 are the water consumption of domestic water, production water, and ecological water during excessive rainfall respectively, and Q 引max is the maximum water diversion flow.

[0078] In the specific implementation of step S7, the daily runoff is subtracted by the water consumption of other water uses that must be deducted during water diversion, and then the water discharge is subtracted to obtain the water diversion volume corresponding to the water diversion channel scale scheme determined in step S1.

[0079] That is, the calculation formula for the water diversion volume of the water diversion channel scheme is: Q 引 = Q 径流 - Q 生活引 - Q 生产引 - Q 生态引 - Q 弃 , where Q 生活引 , Q 生产引 , Q 生态引 are the water consumption of domestic water, production water, and ecological water during each water diversion respectively. This step has a simple calculation and can greatly save the time for calculating the water diversion volume.

[0080] In the specific implementation of step S8, steps S1 to S7 are repeated to formulate different scale schemes of the diversion canal, calculate the corresponding water diversion volume, conduct a technical and economic comparison, and determine the optimal scale scheme of the diversion canal.

[0081] Specifically, steps S1 to S7 are repeated, that is, a new scale scheme of the diversion canal is formulated, and then the corresponding water diversion volume is calculated to form a scale - water diversion volume scheme group of the diversion canal. The selection principle of the optimal scheme is mainly that it is the most technically and economically reasonable on the basis of meeting the water diversion volume requirement.

[0082] After considering the specification and the content disclosed herein in practice, those skilled in the art will readily conceive of other embodiments of the present application. The present application is intended to cover any variations, uses, or adaptations of the present application, which follow the general principles of the present application and include the common general knowledge or conventional technical means in the technical field not disclosed in the present application.

[0083] It should be understood that the present application is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A method for determining the scale scheme of diversion channels in a small watershed, characterized in that, it includes: Step S1: Initially propose a scale scheme for the diversion channel, select the location of the diversion inlet, and determine the maximum diversion flow rate of the scale scheme of the diversion channel according to the location of the diversion inlet; Step S2: Determine the catchment area of the diversion inlet according to the location of the diversion inlet, establish a rainfall-runoff model for the small watershed based on the hydrological cycle, and calculate the daily runoff of the diversion inlet according to the rainfall-runoff model of the small watershed; Step S3: For the catchment area of the diversion inlet, construct a storm flood model for the small watershed based on the principle of runoff generation and concentration; Step S4: According to the maximum diversion flow rate, use the storm flood model of the small watershed to calculate the peak rainfall duration and peak rainfall amount for the catchment area of the diversion inlet to form the maximum diversion flow rate at the diversion inlet, that is, the peak rainfall; Step S5: For the measured rainfall data, screen out all actual rainfall events greater than the peak rainfall, that is, the excess rainfall; Step S6: Calculate the sum of the flow rates formed by all excess rainfall events at the diversion inlet, subtract the water consumption of other water uses that must be deducted during excess rainfall, and then subtract the maximum diversion flow rate to obtain the waste water volume; Step S7: Subtract the water consumption of other water uses that must be deducted during diversion from the daily runoff, and then subtract the waste water volume to obtain the diversion volume corresponding to the scale scheme of the diversion channel determined in Step S1; Step S8: Repeat Steps S1 to S7, propose different scale schemes for the diversion channel, calculate the corresponding diversion volumes, conduct a technical and economic comparison, and determine the optimal scale scheme for the diversion channel.

2. The method according to claim 1, characterized in that, in Step S1, the diversion inlet is selected according to the topography, geological conditions, river plane form, hydrological and sediment characteristics, riverbed evolution law, construction conditions, target diversion volume, and catchment area of the diversion catchment area.

3. The method according to claim 1, characterized in that, in Step S1, the maximum diversion flow rate of the scale scheme of the diversion channel is determined by the hydraulic calculation method of uniform flow in an open channel: Wherein, Q is the maximum diversion flow rate; A is the cross-sectional area; n is the roughness coefficient of the ditch; R is the hydraulic radius; J 沟渠 is the slope of the ditch, wherein the cross-sectional area and the hydraulic radius are calculated based on the width and depth of the diversion ditch in the diversion ditch scale plan, and the slope of the ditch is determined according to the topographic changes at the diversion inlet.

4. The method according to claim 1, characterized in that, the rainfall-runoff model of the small watershed adopts the three-source Xin'anjiang model.

5. The method according to claim 1, characterized in that, the storm flood model of the small watershed adopts the rational formula method and the instantaneous unit hydrograph method; Among them, the reasoning formula method is applicable to small watersheds with a catchment area of the water intake less than or equal to 50 km 2 and below, and its calculation formula is as follows: where τ is the concentration time; h t is the net rainfall; F is the catchment area of the diversion intake; Q m is the peak flood discharge; L is the main stream length of the river; m is the concentration parameter; J is the river slope; The instantaneous unit hydrograph method is applicable to small watersheds with a catchment area of the water intake greater than 50 km 2 , and the calculation formula is: wherein, u(t) is the longitudinal height of the instantaneous unit hydrograph at time t; k is a parameter reflecting the basin concentration time, that is, the storage coefficient; n is the number of regulations; Γ(n) is the incomplete gamma function of order n; t is the time.

6. The method according to claim 1, characterized in that, in Step S4, through the storm flood model of the small watershed, the peak rainfall duration and peak rainfall intensity of the catchment area of the diversion inlet are inversely derived, that is, the peak rainfall, and the peak rainfall forms the maximum diversion flow rate at the diversion inlet.

7. The method according to claim 1, characterized in that, Step S5 includes: According to the spatial distribution law of regional rainfall, the layout of hydrological stations, and the data duration, select reasonable representative rainfall reference stations in the upstream catchment area of the water diversion outlet determined in step S1, and extract all excess rainfall events from the measured rainfall data where both the rainfall duration and rainfall intensity are greater than the peak-forming rainfall duration and peak-forming rainfall intensity.

8. According to the method described in claim 1, characterized in that the other water consumption that must be deducted is the minimum guaranteed flow to meet the downstream domestic, production, and ecological water demand of the water diversion outlet determined in step S1.

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