1、raising standards worldwide NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BSI Standards Publication BS ISO 6421:2012 Hydrometry Methods for assessment of reservoir sedimentationBS ISO 6421:2012 BRITISH STANDARD National foreword This British Standard is the UK implementation
2、 of ISO 6421:2012. The UK participation in its preparation was entrusted to Technical Committee 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 contr
3、act. Users are responsible for its correct application. The British Standards Institution 2012. Published by BSI Standards Limited 2012 ISBN 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
4、 authority of the Standards Policy and Strategy Committee on 31 August 2012. Amendments issued since publication Date T e x t a f f e c t e dBS ISO 6421:2012 ISO 2012 Hydrometry Methods for assessment of reservoir sedimentation Hydromtrie Mthodes dvaluation de la sdimentation dans les rservoirs INTE
5、RNATIONAL STANDARD ISO 6421 First edition 2012-08-01 Reference number ISO 6421:2012(E)BS ISO 6421:2012ISO 6421:2012(E) ii ISO 2012 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2012 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in a
6、ny form or by any means, electronic 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 office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 7
7、49 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandBS ISO 6421:2012ISO 6421:2012(E) ISO 2012 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope 1 2 Normative references . 1 3 T erms and definitions . 1 4 General . 1 4.1 Origin of the sediment deposited in
8、the reservoir . 1 4.2 Overview of reservoir-sedimentation assessment methods 1 5 Sediment transport balance . 2 6 Topographic survey methods 3 6.1 General . 3 6.2 Reservoir sedimentation surveys . 3 6.3 Frequency 4 6.4 Survey equipment . 4 6.5 Density measurements and sediment samplers . 7 7 Topogra
9、phic survey using the contour method 8 7.1 General . 8 7.2 Hydrographic survey 9 7.3 Topographic surveys 9 7.4 Computation of reservoir capacity .10 8 Topographic survey using a cross-sectional (range line) method 10 8.1 General .10 8.2 Reference frames/graphs 11 8.3 Calculation of reservoir capacit
10、y 15 9 Sub-bottom mapping 19 10 Remote-sensing methods .20 10.1 General .20 10.2 Advantages .20 10.3 Limitations .20 11 Light detection and ranging 20 11.1 General .20 11.2 Aerial applications of LiDAR 21 11.3 Ground-based applications of LiDAR 21 12 Aerial imagery methods .22 12.1 General .22 12.2
11、Photogrammetry methods 22 12.3 Satellite imagery methods 23 13 Uncertainty analysis .23 13.1 General .23 13.2 Principles .23 13.3 Estimation of uncertainty 24 Annex A (informative) Optimization of the arrangement of ranges.28 Annex B (informative) Introduction to measurement uncertainty .32 Bibliogr
12、aphy .40BS ISO 6421:2012ISO 6421:2012(E) Foreword ISO (the International Organization 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 b
13、ody interested in a subject for which a technical committee has been established has 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 Electro
14、technical Commission (IEC) on all matters of electrotechnical standardization. International 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
15、by the technical committees are circulated to the member bodies for voting. Publication 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 r
16、ights. ISO shall not be held responsible for identifying any or all such patent rights. 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) Introduction Most natural river reaches
17、are approximately balanced with respect to sediment inflow and outflow. Dam construction 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 cap
18、acity until a balance is again achieved; this normally occurs after the reservoir fills with 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 depo
19、sition in different reservoir regions is equally important. Depending upon the shape of the 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 elimi
20、nates the capacity for flow regulation and concomitant benefits such as water supply, flood 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
21、 probable time when the reservoir would be affected in serving its intended functions. The 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 c
22、riteria and available sediment transport equations. Reservoir capacity surveys indicate patterns and rates of sedimentation, which help in improving estimation of capacity-loss rates. This International Standard describes the following reservoir-sedimentation assessment methods: conventional topogra
23、phic surveys (Clause 6) contour method (Clause 7) cross-sectional (range line) method (Clause 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 me
24、thods satellite imagery methods ISO 2012 All rights reserved vBS ISO 6421:2012BS ISO 6421:2012Hydrometry Methods for assessment of reservoir sedimentation 1 Scope This International Standard describes methods for the measurement of temporal and spatial changes in reservoir capacities due to sediment
25、 deposition. 2 Normative references The following referenced documents are indispensable for the 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, Hydro
26、metry Vocabulary and symbols 3 T erms and definitio ns For the purposes of this document, the terms and definitions given in ISO 772 apply. 4 General 4.1 Origin of the sediment deposited in the reservoir Reservoirs are subjected to several types of sedimentation as a function of the geomorphology (g
27、eology, slope, topography and land use, drainage density, climate, etc.) of the watershed and the biological 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
28、 sizes, shapes and types that are related to the rock type and slope of the drainage basin. In addition, 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 fr
29、om vascular plants and phytoplankton in the reservoir. The debris decomposes very slowly and often forms 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 sev
30、eral centimetres per year often causes problems when a reservoir is drawn down or drained. It has a very 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
31、sediment deposit. 4.2 Overview of reservoir-sedimentation assessment methods Two basic methods for assessment 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 l
32、oad (bed load and suspended load) is measured over all the watercourses flowing into the reservoir and then 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
33、 point of measurement should be sufficiently close to the reservoir periphery and particular care shall be taken 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 reser
34、voir are carried out at regular intervals. They reveal the geographic distribution of sediment deposits in the 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 b
35、ed surveying (i.e. bathymetry) involves measuring the depth at various locations in the reservoir, following 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 betw
36、een near-empty and near-full, to define the shoreline contours at various water levels. (See Clauses 10, 11 and 12.) 5 Sediment transport balance In 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 i
37、nto the reservoir and at all the reservoir outlets. The difference in the incoming and outgoing total sediment 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 a
38、t the total sediment load. Generally, water discharge is calculated from stream gauge records (for which gauging 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 m
39、ethod, ISO 9555 for dilution methods, etc. A number of traditional methods are available for computing sediment transport, including an interpolation method for estimating suspended-sediment loads when measured loads are not available. When data are insufficient for the utilization of the interpolat
40、ion method, sediment-transport curves may also be used to compute suspended-sediment loads. However, estimates of 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 p
41、resence of specific relations among hydraulic variables, sedimentological parameters, and the rate at which bed load 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 theoret
42、ically complete equations rely on experimental data to quantify coefficients of the equations. The availability of 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 substanti
43、al fraction of the sediment depositing in a reservoir. Rainfall-runoff models based on watershed, meteorological, 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
44、 detailed in various ISO standards, such as ISO/TS 3716, ISO 4363, ISO 4364, ISO 4365 and ISO/TR 9212. Presently, this 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 limit
45、ations. These include: 1) substantial costs and human resources involved for continuous, long-term measurements at several 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
46、 variations of sediment load with time and discharge, and also in the cross section; 3) change in masses, and in proportions of fine and coarse fractions of the transported sediment with time; 4) limited accuracy of sediment measurements due to issues associated with i) sampler efficiencies and samp
47、ling techniques, and ii) potential disturbances induced due to measuring equipment and procedures; 5) large variations in estimates 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 sus
48、pended load. NOTE New surrogate technologies for monitoring sediment transport are being developed that may provide cost- effective and quantifiably accurate sediment-discharge data at gauging stations. ISO 11657 (under development) describes a number of sediment-surrogate monitoring technologies, i
49、ncluding the use of continuous turbidity and stream flow measurements to estimate suspended-sediment transport. Bulk-optic, laser-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 methods 6.1 General In topographic surveying, in order to assess the volume of sediment deposit along with its locatio
