1. the rate of movement of a contaminant through a river reach;
2. the rate of attenuation of the peak concentration of a conservative contaminant with time; and
3. the length of time required for the contaminant plume to pass a point in the river.

The report compiles the results of many of the US Geological Survey tracer studies and provides a method of making reasonable predictions quickly at locations where little data are available. Although the accuracy of the predictions can be greatly increased by performing time-of-travel studies on the river reach in question, the emphasis of this report is on providing methods for making estimates where few data are available. If a model is needed where neither travel time data or detailed cross-sectional measurements are available, the information in this report can be used to "calibrate" a model to provide at least reasonable results.

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Precipitation Estimation and Forecasting - by C.G. Collier (WMO No 887 OHR 46)

Over 97 per cent of the water in our world resides in the oceans, and only 0.001 per cent resides in the atmosphere. Indeed, only about 0.005 per cent of the total world water supply is in motion at any one time. However, this very small amount of water is associated with all weather and river flow, and has a profound impact upon the activities of mankind. The measurement of precipitation (rain, snow, hail, etc.) is of primary importance for hydrological calculations.

In this report, a wide range of techniques which have been developed worldwide for measuring and forecasting precipitation are discussed. Measurement techniques range from point gauge measurements to methods based upon the interpretation of, sometimes, very indirect data obtained from space-based instrumentation. However, all the techniques are complementary. Often one technique is used to calibrate or adjust another, and it is the purpose of this report to place the sometimes quite different performance characteristics of different methods into perspective. Likewise, forecasting techniques are wide-ranging, and aim to generate forecasts from a few hours ahead to days and even a month ahead. Mention is also made of prospects for seasonal forecasting.

The approach adopted in this report is to discuss measurement techniques from a technological point of view, reviewing levels of performance achieved, and, where possible, major limitations. While some techniques can be intercompared, for example the use of weather radar and satellite-based procedures, it is stressed that no one technique offers the optimum solution to precipitation measurement. Indeed, some techniques are used with others to achieve a level of improved performance. It is often not possible to recommend particular approaches, as any such recommendations will depend upon the specific applications to which the measurements are put.

The first half of this report outlines point measurements of precipitation using collectors, weighing devices and hailpads. Areal measurements of precipitation using interpolated point values, radar and satellite techniques and combinations of different approaches are discussed. The degree to which current technology and algorithms can satisfy the hydrological requirements for precipitation is considered briefly.

The second half of this report deals with precipitation forecasting over temporal scales from minutes to seasons. Such a wide range of forecast lead times makes it necessary to consider the use of simple extrapolation, artificial intelligence, simple to complex numerical modelling and statistical-dynamical procedures.

Finally, input to hydrological models of both measurements and forecasts of precipitation is not necessarily straightforward. The specific error characteristics of each type of measurement and forecast have different implications for the range of hydrological model types used. An outline description of these model types is followed by consideration of the impact of particular types of input data on the flow forecasts so-generated. The development of real-time error correction procedures is noted, and the importance of further work to understand the interrelationship between input data quality and model output is considered.

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Manual on sediment management and measurement (abstract) – by Yang Xiaoqin (WMO No 948 OHR 47)

This report covers a wide range of issues related to sedimentation. Its objectives are to present to readers a basic understanding of operational methods of sediment transport measurement, and serve as a practical reference in dealing with sedimentation engineering.

Ecological and environmental concerns are increasingly affecting the sustainable development of human societies worldwide. In Chapter 1, the impacts of soil erosion and river and reservoir sedimentation on ecologies and environments are discussed, as are potential benefits of sediment as a resource.

Chapter 2 presents soil erosion in detail, including its basic characteristics, monitoring and prediction of erosion and sediment yield in a basin, soil and water conservation, and watershed management. Finally, an overview of the global issue of soil erosion is presented.

In Chapter 3, the contents of sediment transport in rivers are discussed. The basic concepts of patterns of river sediment transport form the basis on which to deal with river sediment. They are elucidated concisely and thoroughly. Following this is a discussion on bed load, suspended load and total sediment load, using authoritative papers. Based on a large amount of data and papers, mainly developed in China, hyperconcentrated flow is discussed briefly at the end of this chapter.

Chapter 4 elaborates on fluvial processes. The main points include classification of patterns of alluvial rivers, fluvial processes of each basic river pattern, and stabilization and rectification of river channels. In this report, the alluvial rivers are classified into four basic patterns: meandering, wandering, branched and straight. In many literatures, three basic river patterns are differentiated: meandering, braided and straight. Such a difference may be induced by the large amount of sediment load transported by some Chinese rivers.

Reservoirs play a significant role in human society, including flood control, water supply, power generation, irrigation, navigation improvement, recreation, etc. With the passage of time, many reservoirs, particularly those built on sediment-laden rivers, lose a certain percentage of their storage capacity due to sedimentation. In Chapter 5, the subject of reservoir sedimentation and its impacts on river processes are expanded upon. Deposition processes in reservoirs are presented first. Then, methods of estimation of long-term deposition in reservoirs, both empirical and numerical, are briefly discussed. A discussion of reservoir management follows, emphasizing the possibility of preserving long-term reservoir capacity for permanent usage. Six case studies show the reality of reservoir sedimentation problems.

Accurate sediment data are the basis of every aspect of sediment management and numerical (computer) modelling of sedimentation. In Chapter 6, operational methods of sediment measurement, including measurements of suspended sediment, bed load and total sediment load, are discussed. Also, laboratory procedures, data processing and assessment of accuracy and reliability in sediment measurement are presented. Finally, some recommendations for sediment measurement are given.

Water pollution is an increasingly important issue in many places, particularly in developing countries. In Chapter 7, water quality related to the transport of sediment and toxic materials, the main source of water pollution, is elucidated briefly. To quantify such impact, a water quality model is introduced.

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Hydrological data management: present state and trends – by A. Terakawa (WMO No 964 OHR 48)

The key to providing accurate, timely and often life-saving information and forecasts on flooding and drought lie in hydrological data management. With the expansion of computerization and global information networks, recent years have witnessed a consequent increase in the scope and forms of data management undertaken. Geographical information systems (GIS) have evolved since their introduction in the 1960s, to become sophisticated analytical tools, enabling detailed consideration of the many factors affecting river basins and their management. In this application, GIS rely on strong hydrological databases.

The importance of hydrological databases, their basic characteristics and how they are exploited in operational hydrology cannot be underestimated. Forecasting and managing flood and drought events, as well as day-to-day river basin management would be impossible without both real-time and historical databases and the tools, such as Geographical Information Systems (GIS), to analyse them.

This report, prepared for the World Meteorological Organization’s Commission on Hydrology (CHy) Working Group on Basic Systems details the present state and trends in constructing databases for hydrological data, the real-time utilization of the data and the application of GIS to operational hydrology in various countries.

Following a brief Introduction, Chapter 2 catalogues the relationship between real-time and historical data. The essential characteristics of a range of countries’ hydrological databases are given. Constructing a database involves a number of stages and these are outlined. An effective database also requires making provision for maintenance and updating. The issue of public access is explored, and finally, Chapter 2, describes examples of working hydrological databases from Australia, Japan and the United States.

In Chapter 3 GIS — its development and current trends —are described. The importance of GIS to operational hydrology is outlined and its practical application in various situations, from management of the Rhine River to assessing and disseminating data on water quality in South Africa, is presented.

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Guidelines on the Role Operation and Management of National Hydrological Services (WMO No 1003 OHR 49)

Recent years have seen a worldwide trend towards a widening of the mandate of National Hydrological Services (NHSs), beyond their traditional operational hydrology responsibilities. The scope of the responsibilities of NHSs now encompasses issues relating to environmental aspects and contributes to the integrated management of water resources, as a necessary step towards sustainable development. All of this comes with a backdrop where public organizations are typically requested to reduce their operational costs and their spendings. It is no longer good enough to claim that an NHS should be the exception to the rule in view of the uniqueness of its activities and the long-term benefits provided to the society through its public services. Numerous examples demonstrate that the political establishments are not inclined to accept this line of thought.

Under the situation described above, even the best trained managers would be under stress to meet the expectations from their services. Realizing that in most cases, managers of NHSs are technical people (that is, hydrologists) promoted to a managerial responsibility on the strength of their brilliant technical career, but with little or no managerial training, it is evident why an increasing number of NHSs have requested the World Meteorological Organization to issue some guidance material to assist senior officials in managerial capacities to fulfill their responsibilities.

The main objective of these guidelines is to provide guidance to the senior managers of Hydrological Services, on the key issues that they might face, as they lead, manage and administer their Services.

Chapter 1 sets the scene, as it summarizes recent trends in hydrology and water resources management and makes the point that, even though in most cases NHS are public organizations, they still must be run in a business-like manner in order to be effective.

This is followed by an overview of the responsibilities and functions of NHSs, which, while recognizing the different institutional arrangements that may be encountered in different regions, tries to defi ne typical products and services as well as the activities normally undertaken by NHSs. Several possible arrangements for the legal framework and institutional arrangements are mentioned.

Chapters 3 to 9 review in more detail the different aspects of management, such as strategic planning human resources management, financial management, marketing, asset management, process and quality management, and relationships with other institutions. Without being prescriptive, emphasis is made on the issues that must be taken into consideration in each particular case.

Finally, in the Annexes a variety of material is presented as examples for some of the concepts described in the main text. In Annex 1, the organizational arrangements of two NHS is examined, only in as much as they represent typical cases, and not trying at all to have a geographical balance, as they are not representative of any region in particular. Annex 2 gives an example of an Interview Form, which could be used to compare candidates for a job position, while Annex 3 provides a sample employment contract which could be used as the basis for preparing contractual arrangements for NHSs that need to do so, and Annex 4 contains a form that could be used in a performance appraisal exercise.

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