1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 6421:2012Hydrometry Methodsfor assessment of reservoirsedimentationBS ISO 6421:2012 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO
2、6421:2012. The UK participation in its preparation was entrusted to TechnicalCommittee CPI/113, Hydrometry.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users
3、are responsible for its correct application. The British Standards Institution 2012. Published by BSI Standards Limited 2012ISBN 978 0 580 59639 1 ICS 17.120.20 Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the authority of
4、 the Standards Policy and Strategy Committee on 31 August 2012.Amendments issued since publicationDate T e x t a f f e c t e dBS ISO 6421:2012 ISO 2012Hydrometry Methods for assessment of reservoir sedimentationHydromtrie Mthodes dvaluation de la sdimentation dans les rservoirsINTERNATIONAL STANDARD
5、ISO6421First edition2012-08-01Reference numberISO 6421:2012(E)BS ISO 6421:2012ISO 6421:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, el
6、ectronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.org
7、Web www.iso.orgPublished in SwitzerlandBS ISO 6421:2012ISO 6421:2012(E) ISO 2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope 12 Normative references . 13 Terms and definitions . 14 General . 14.1 Origin of the sediment deposited in the reservoir . 14.2 Overview of reservoir-
8、sedimentation assessment methods 15 Sediment transport balance . 26 Topographic survey methods 36.1 General . 36.2 Reservoir sedimentation surveys . 36.3 Frequency 46.4 Survey equipment . 46.5 Density measurements and sediment samplers . 77 Topographic survey using the contour method 87.1 General .
9、87.2 Hydrographic survey 97.3 Topographic surveys 97.4 Computation of reservoir capacity .108 Topographic survey using a cross-sectional (range line) method 108.1 General .108.2 Reference frames/graphs 118.3 Calculation of reservoir capacity 159 Sub-bottom mapping 1910 Remote-sensing methods .2010.1
10、 General .2010.2 Advantages .2010.3 Limitations .2011 Light detection and ranging 2011.1 General .2011.2 Aerial applications of LiDAR 2111.3 Ground-based applications of LiDAR 2112 Aerial imagery methods .2212.1 General .2212.2 Photogrammetry methods 2212.3 Satellite imagery methods 2313 Uncertainty
11、 analysis .2313.1 General .2313.2 Principles .2313.3 Estimation of uncertainty 24Annex A (informative) Optimization of the arrangement of ranges.28Annex B (informative) Introduction to measurement uncertainty .32Bibliography .40BS ISO 6421:2012ISO 6421:2012(E)ForewordISO (the International Organizat
12、ion for Standardization) is a 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 h
13、as the right to be represented 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.Inte
14、rnational Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publicat
15、ion as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent right
16、s.ISO 6421 was prepared by Technical Committee ISO/TC 113, Hydrometry, Subcommittee SC 6, Sediment transport.iv ISO 2012 All rights reservedBS ISO 6421:2012ISO 6421:2012(E)IntroductionMost natural river reaches are approximately balanced with respect to sediment inflow and outflow. Dam construction
17、dramatically alters this balance, creating a reservoir which often results in substantially reduced velocities and relatively efficient sediment trapping. The reservoir accumulates sediment and loses storage capacity until a balance is again achieved; this normally occurs after the reservoir fills w
18、ith sediment. The rate and extent of sediment deposition depends on factors which influence sediment yield and sediment transport, as well as the reservoirs trapping efficiency. The distribution of sediment deposition in different reservoir regions is equally important. Depending upon the shape of t
19、he reservoir, mode of reservoir operation, sediment-inflow rates and grain-size distributions, the incoming sediment may settle in different areas of the reservoir. Declining storage reduces and eventually eliminates the capacity for flow regulation and concomitant benefits such as water supply, flo
20、od control, hydropower, navigation, recreation, and environmental aspects that depend on releases from storage. Water resource professionals are concerned with the prediction of sediment deposition rates and the probable time when the reservoir would be affected in serving its intended functions. Th
21、e estimation of sediment deposition is also important in the design and planning of storage reservoirs. However, it is difficult to estimate the volume and rate of sediment deposition accurately from the known criteria and available sediment transport equations. Reservoir capacity surveys indicate p
22、atterns and rates of sedimentation, which help in improving estimation of capacity-loss rates.This International Standard describes the following reservoir-sedimentation assessment methods: conventional topographic surveys (Clause 6) contour method (Clause 7) cross-sectional (range line) method (Cla
23、use 8) sub-bottom measurements (Clause 9) remote-sensing techniques (Clause 10) light detection and ranging (Clause 11) aerial applications ground-based applications aerial imagery (Clause 12) photogrammetry methods satellite imagery methods ISO 2012 All rights reserved vBS ISO 6421:2012BS ISO 6421:
24、2012Hydrometry Methods for assessment of reservoir sedimentation1 ScopeThis International Standard describes methods for the measurement of temporal and spatial changes in reservoir capacities due to sediment deposition.2 Normative referencesThe following referenced documents are indispensable for t
25、he application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any revisions) applies. ISO 772, Hydrometry Vocabulary and symbols3 Terms and definitionsFor the purposes of this document, the term
26、s and definitions given in ISO 772 apply.4 General4.1 Origin of the sediment deposited in the reservoirReservoirs are subjected to several types of sedimentation as a function of the geomorphology (geology, slope, topography and land use, drainage density, climate, etc.) of the watershed and the bio
27、logical cycles in the reservoir or the drainage basin, in the following order of importance.a) Erosion of the drainage basin produces dissolved substances and mineral particles with an assortment of sizes, shapes and types that are related to the rock type and slope of the drainage basin. In additio
28、n, landslides produce debris flows. Sediment is delivered to the reservoir both as suspended sediment load and as bed load.b) Sedimentation occurs due to plant debris from the drainage basin and from vascular plants and phytoplankton in the reservoir. The debris decomposes very slowly and often form
29、s alternating layers with mineral deposits. The mud resulting from this type of sedimentation is very fine and extremely fluid, often with a gelatinous texture. Accumulation of mud at a rate of several centimetres per year often causes problems when a reservoir is drawn down or drained. It has a ver
30、y high organic content resulting in heavy consumption of dissolved oxygen.The proportion of sedimentation caused by each type may be assessed by on-site visual observations and by analyses of the sediment deposit.4.2 Overview of reservoir-sedimentation assessment methods Two basic methods for assess
31、ment of reservoir sedimentation are described.1) Sediment transport balance: INTERNATIONAL STANDARD ISO 6421:2012(E) ISO 2012 All rights reserved 1BS ISO 6421:2012ISO 6421:2012(E)The sediment load (bed load and suspended load) is measured over all the watercourses flowing into the reservoir and then
32、 compared with the sediment load measured at the reservoir outlet. The difference between these two quantities is assumed to represent the sediment that has been deposited in the reservoir.The point of measurement should be sufficiently close to the reservoir periphery and particular care shall be t
33、aken to complete outflow sampling before it meets the erodible channel downstream.For further information, see Clause 5. 2) Capacity survey of the reservoir: Hydrographic surveys of the reservoir are carried out at regular intervals. They reveal the geographic distribution of sediment deposits in th
34、e reservoir and also help in determining lost storage capacity. A capacity survey of the reservoirs is carried out using topographic survey methods or remote-sensing techniques. Topographic bed surveying (i.e. bathymetry) involves measuring the depth at various locations in the reservoir, following
35、pre-determined profiles, cross sections or using a grid for contour determination. (See Clauses 6, 7, 8 and 9.) The remote-sensing technique uses images taken when the water level varies between near-empty and near-full, to define the shoreline contours at various water levels. (See Clauses 10, 11 a
36、nd 12.)5 Sediment transport balanceIn this method, the total sediment load (bed load and suspended load) is measured at suitable locations near the mouths of all the water courses flowing into the reservoir and at all the reservoir outlets. The difference in the incoming and outgoing total sediment
37、load is assumed to have been deposited in the reservoir. Data on water discharge and sediment discharge at each inflow and outflow location are required to be collected in order to arrive at the total sediment load.Generally, water discharge is calculated from stream gauge records (for which gauging
38、 stations should be set up as specified in ISO 1100-1), then calibrated in compliance with the standards describing the various stream gauging methods, e.g. ISO 748 for the velocity area method, ISO 9555 for dilution methods, etc.A number of traditional methods are available for computing sediment t
39、ransport, including an interpolation method for estimating suspended-sediment loads when measured loads are not available. When data are insufficient for the utilization of the interpolation method, sediment-transport curves may also be used to compute suspended-sediment loads. However, estimates of
40、 suspended-sediment transport from transport curves which are also used to compute bed load, and/or total loads may be subject to significant errors. The equations are predicated on the presence of specific relations among hydraulic variables, sedimentological parameters, and the rate at which bed l
41、oad or bed-material load is transported. The theory supporting the derivation of the equations tends to be incomplete, oversimplified, or non-existent. Additionally, even the most theoretically complete equations rely on experimental data to quantify coefficients of the equations. The availability o
42、f reliable environmental data to verify estimates from equations is often lacking, and the equations tend to ignore or underestimate the washload component, which can comprise a substantial fraction of the sediment depositing in a reservoir. Rainfall-runoff models based on watershed, meteorological,
43、 and hydrological characteristics may be useful, but tend to be time-intensive and, likewise, require reliable environmental data.Equipment and methods for sediment load measurements are detailed in various ISO standards, such as ISO/TS 3716, ISO 4363, ISO 4364, ISO 4365 and ISO/TR 9212.Presently, t
44、his method is not commonly used for assessment of reservoir sedimentation, because of the availability of improved techniques and because of a number of practical difficulties and limitations. These include:1) substantial costs and human resources involved for continuous, long-term measurements at s
45、everal locations;2 ISO 2012 All rights reservedBS ISO 6421:2012ISO 6421:2012(E)2) inadequacy of spatial and temporal representativeness of limited observations due to typically large variations of sediment load with time and discharge, and also in the cross section;3) change in masses, and in propor
46、tions of fine and coarse fractions of the transported sediment with time;4) limited accuracy of sediment measurements due to issues associated withi) sampler efficiencies and sampling techniques, andii) potential disturbances induced due to measuring equipment and procedures;5) large variations in e
47、stimates of the bed-load transport rates (in the absence of actual measurements), made using different sediment transport relations or calculated as a fraction of a measured suspended load.NOTE New surrogate technologies for monitoring sediment transport are being developed that may provide cost-eff
48、ective and quantifiably accurate sediment-discharge data at gauging stations. ISO 11657 (under development) describes a number of sediment-surrogate monitoring technologies, including the use of continuous turbidity and stream flow measurements to estimate suspended-sediment transport. Bulk-optic, l
49、aser-optic, digital-optic, pressure-difference, and acoustic techniques for metering suspended-sediment transport are being investigated. All of these techniques require in-stream calibrations to accepted standard monitoring instruments and techniques.6 Topographic survey methods6.1 GeneralIn topographic surveying, in order to assess the volume of sediment deposit along with its location in the reservoirs, direct measurements of the depths or elevations of the reservoir bed and the coordinates of the measurement points are periodi
