BS ISO 1100-2-1998 Measurement of liquid flow in open channels - Determination of the stage-discharge relation《明渠液体流量测量 第2部分 水位流量关系测定》.pdf

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1、BRITISH STANDARD BS ISO 1100-2:1998 Incorporating corrigendum no. 1 Measurement of liquid flow in open channels Part 2: Determination of the stage-discharge relation ICS 17.120.20 BS ISO 1100-2:1998 This British Standard was published under the authority of the Standards Board and comes into effect

2、on 15 July 1998 BSI 2007 ISBN 978 0 580 60528 4 National foreword This British Standard is the UK implementation of ISO 1100-2:1998, incorporating corrigendum August 2000. It supersedes BS 3680-3C:1983 which is withdrawn. The start and finish of text introduced or altered by corrigendum is indicated

3、 in the text by tags . Text altered by ISO corrigendum August 2000 is indicated in the text by . The UK participation in its preparation was entrusted by Technical Committee CPI/113, Flow measurement of surface and ground water, to Subcommittee CPI/113/1, Velocity-area methods. A list of organizatio

4、ns represented on this subcommittee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligation

5、s. Amendments issued since publication Amd. No. Date Comments 17462 Corrigendum No. 1 31 October 2007 See national forewordBSISO1100-2:1998 ii Contents Page Foreword iii 1 Scope 1 2 Normative references 1 3 Definitions and symbols 1 4 Units of measurement 1 5 Principle of the stage-discharge relatio

6、n 1 6 Stage-discharge calibration of a gauging station 3 7 Methods of testing stage-discharge relations 16 8 Uncertainty in the stage-discharge relation 16 Annex A (informative) Uncertainty in stage-discharge relation and in continuous measurement of discharge 20 Annex B (informative) Bibliography 2

7、1 Figure 1 Arithmetic plot of stage-discharge relation 6 Figure 2 Relation of channel and control properties to rating curve shape 7 Figure 3 Logarithmic plot of stage-discharge relation 8 Table 1 Typical list of discharge measurements 4 Table 2 Tabulated values required to calculate s eand s mr 18

8、Table 3 Typical computation for the uncertainty in the daily mean discharge, using hourly values of discharge 19 Descriptors: Liquid, water flow, open channel flow, flow measurement, gauging stations. BSI 2007BSISO1100-2:1998 iii Foreword ISO (the International Organization for Standardization) is a

9、 worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represente

10、d on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards ad

11、opted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least75% of the member bodies casting a vote. International Standard ISO1100-2 was prepared by Technical Committee ISO/TC113, Hydrometric determinations,

12、 Subcommittee SC1, Velocity-area methods. This second edition cancels and replaces the first edition (ISO1100-2:1982), which has been technically revised. Annex A and Annex B of this part of ISO1100 are for information only. BSI 2007iv blankBSISO1100-2:1998 1 1 Scope This part of ISO1100 specifies m

13、ethods of determining the stage-discharge relation for a gauging station. A sufficient number of discharge measurements, complete with corresponding stage measurements, is required to define a stage-discharge relation to the accuracy required by this part of ISO1100. Stable and unstable channels are

14、 considered, including brief descriptions of the effects on the stage-discharge relation of ice and hysteresis. Methods for determining discharge for twin-gauge stations, ultrasonic velocity stations, electromagnetic velocity stations, and other complex ratings are not described in detail. These typ

15、es of rating are described in other International Standards and Technical Reports, namely ISO/TR9123, ISO6416 and ISO9213, as shown in clause 2. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO1100. At

16、the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO1100 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maint

17、ain registers of currently valid International Standards. ISO31:1992 (all parts), Quantities, units and symbols. ISO772:1996, Hydrometric determinations Vocabulary and symbols. ISO1000:1992, SI units and recommendations for the use of their multiples and of certain other units. ISO/TR5168: , Measure

18、ment of fluid flow Evaluation of uncertainties 1) . ISO6416:1992, Liquid flow measurement in open channels Measurement of discharge by the ultrasonic (acoustic) method. ISO/TR9123:1986, Liquid flow measurement in open channels Stage-fall-discharge relations. ISO9196:1992, Liquid flow measurement in

19、open channels Flow measurements under ice conditions. ISO9213:1992, Measurement of total discharge in open channels Electromagnetic method using a full-channel-width coil. 3 Definitions and symbols For the purpose of this part of ISO1100, the definitions and symbols given in ISO772 apply. Those that

20、 are not covered by ISO772 are given in the text of this part of ISO1100. The symbols used in this part of ISO1100 are given below: 4 Units of measurement The International System of Units (SI Units) is used in this part of ISO1100 in accordance with ISO31 and ISO1000. 5 Principle of the stage-disch

21、arge relation The stage-discharge relation is the relation at a gauging station between stage and discharge, and is sometimes referred to as a rating or rating curve. The principles of the establishment and operation of a gauging station are described in ISO1100-1. 1) To be published. (Revision of I

22、SO5168:1978) A cross-sectional area, C D a coefficient of discharge, C Chezys channel rugosity coefficient, h gauge height of the water surface, slope of the rating curve, Q total discharge, Q o steady-state discharge, r h hydraulic radius, equal to the effective cross-sectional area divided by the

23、wetted perimeter (A/P) S f friction slope, S o water surface slope corresponding to steady discharge, v w velocity of a flood wave, B cross-section width, e effective gauge height of zero flow, H total head (hydraulic head), n is Mannings channel rugosity coefficient, p is a constant that is numeric

24、ally equal to the discharge when the effective depth of flow (h e) is equal to1, t is time. BSI 2007BSISO1100-2:1998 2 5.1 Controls 5.1.1 General The stage-discharge relation for open-channel flow at a gauging station is governed by channel conditions downstream from the gauge, referred to as a cont

25、rol. Two types of control can exist, depending on channel and flow conditions. Low flows are usually controlled by a section control, whereas high flows are usually controlled by a channel control. Medium flows may be controlled by either type of control. At some stages, a combination of section and

26、 channel control may occur. These are general rules and exceptions can and do occur. Knowledge of the channel features that control the stage-discharge relation is important. The development of stage-discharge curves where more than one control is effective, where control features change, and where

27、the number of measurements is limited, usually requires judgement in interpolating between measurements and in extrapolating beyond the highest or lowest measurements. This is particularly true where the controls are not permanent and tend to shift from time to time, resulting in changes in the posi

28、tioning of segments of the stage-discharge relation. Controls and their governing equations are described in the following clauses. 5.1.2 Section control A section control is a specific cross-section of a stream channel, located downstream from a water-level gauge, that controls the relation between

29、 gauge height and discharge at the gauge. A section control can be a natural feature such as a rock ledge, a sand bar, a severe constriction in the channel, or an accumulation of debris. Likewise, a section control can be a manmade feature such as a small dam, a weir, a flume, or an overflow spillwa

30、y. Section controls can frequently be visually identified in the field by observing a riffle, or pronounced drop in the water surface, as the flow passes over the control. Frequently, as gauge height increases because of higher flows, the section control will become submerged to the extent that it n

31、o longer controls the relation between gauge height and discharge. At this point, the riffle is no longer observable, and flow is then regulated either by another section control further downstream, or by the hydraulic geometry and roughness of the channel downstream (i.e.channel control). 5.1.3 Cha

32、nnel control A channel control consists of a combination of features throughout a reach downstream from a gauge. These features include channel size, shape, curvature, slope, and rugosity. The length of channel reach that controls a stage-discharge relation varies. The stage-discharge relation for r

33、elatively steep channels may be controlled by a relatively short channel reach, whereas, the relation for a relatively flat channel may be controlled by a much longer channel reach. In addition, the length of a channel control will vary depending on the magnitude of flow. Precise definition of the l

34、ength of a channel-control reach is usually neither possible nor necessary. 5.1.4 Combination controls At some stages, the stage-discharge relation may be governed by a combination of section and channel controls. This usually occurs for a short range in stage between section-controlled and channel-

35、controlled segments of the rating. This part of the rating is commonly referred to as a transition zone of the rating, and represents the change from section control to channel control. In other instances, a combination control may consist of two section controls, where each has partial controlling

36、effect. More than two controls acting simultaneously is rare. In any case, combination controls, and/or transition zones, occur for very limited parts of a stage-discharge relation and can usually be defined by plotting procedures. Transition zones in particular represent changes in the slope or sha

37、pe of a stage-discharge relation. 5.2 Governing hydraulic equations Stage-discharge relations are hydraulic relations that can be defined according to the type of control that exists. Section controls, either natural or manmade, are governed by some form of the weir or flume equations. In a very gen

38、eral and basic form, these equations are expressed as: where Q = C D BH 1,5 (1) Q is discharge, in cubic metres per second(m 3 /s), C D is a coefficient of discharge and may include several factors, B is cross-section width, in metres (m), and H is hydraulic head, in metres. BSI 2007BSISO1100-2:1998

39、 3 Stage-discharge relations for channel controls with uniform flow are governed by the Manning or Chezy equation, as it applies to the reach of controlling channel downstream from a gauge. The Manning equation is: where The Chezy equation is: where C is the Chezy form of rugosity. The above equatio

40、ns are generally applicable for gradually varied, uniform flow. For highly varied, nonuniform flow, equations such as the Saint-Venant unsteady flow equations would be appropriate. However, these are seldom used in the development of stage-discharge relations, and are not described in this part of I

41、SO1100. 5.3 Complexities of stage-discharge relations Stage-discharge relations for stable controls such as a rock outcrop, and manmade structures such as weirs, flumes, and small dams usually present few problems in their calibration and maintenance. However, complexities can arise when controls ar

42、e not stable and/or when variable backwater occurs. For unstable controls, segments of a stage-discharge relation may change position occasionally, or even frequently. This is usually a temporary condition which can be accounted for through the use of the shifting-control method. Variable backwater

43、can affect a stage-discharge relation, both for stable and unstable channels. Sources of backwater can be downstream reservoirs, tributaries, tides, ice, dams and other obstructions that influence the flow at the gauging station control. Another complexity that exists for some streams is hysteresis,

44、 which results when the water surface slope changes due to either rapidly rising or rapidly falling water levels in a channel control reach. Hysteresis is sometimes referred to as loop ratings, and is most pronounced in relatively flat sloped streams. On rising stages the water surface slope is sign

45、ificantly steeper than for steady flow conditions, resulting in greater discharge than indicated by the steady flow rating. The reverse is true for falling stages. See6.8.4 for details on hysteresis ratings. The succeeding clauses of this part of ISO1100 will describe in more detail some of the tech

46、niques available for analyzing the various complexities that may arise. 6 Stage-discharge calibration of a gauging station 6.1 General The primary object of a stage-discharge gauging station is to provide a record of the discharge of the between two gauges, or rate-of-change in stage may also be use

47、d in rating calibrations. Stage-discharge relations are usually calibrated by measuring discharge and the corresponding gauge height. Theoretical computations may also be used to aid in the shaping and positioning of the rating curve. Stage-discharge relations from previous time periods should also

48、be considered as an aid in the shaping of the rating. 6.2 General preparation of a stage-discharge relation 6.2.1 General The relation between stage and discharge is defined by plotting measurements of discharge with corresponding observations of stage, taking into account whether the discharge is s

49、teady, increasing or decreasing, and also noting the rate of change in stage. This may be done manually by plotting on paper, or by using computerized plotting techniques. A choice of two types of plotting scale is available, either an arithmetic scale or a logarithmic scale. Each has certain advantages and disadvantages, as explained in subsequent clauses. It is customary to plot the stage as ordinate and the discharge as abscissa, although when using the st