Technical Papers in 24

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Technical Papers in Hydrology 24

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In this series:

1. Perennial ice and snow masses. A guide for compilation and assemblage of data for a world inventory.

2. Seasonal snow cover. A guide for measurement, compilation and assemblage of data.

3 . Variations of existing glaciers. A guide to international practices for their measurement.

4. Antarctic glaciology in the International Hydrological Decade.

5. Combined heat, ice and water balances at selected glacier basins. A guide for compilation and assemblage of data for glacier mass balance measurements.

6. Textbooks on hydrology—analyses and synoptic tables of contents of selected textbooks.

7. Scientific framework of world water balance.

8. Flood studies-an international guide for collection and processing of data.

9. Guide to world inventory of sea, lake, and river ice.

10. Curricula and syllabi in hydrology.

11. Teaching aids in hydrology.

12. Ecology of water weeds in the netropics.

13. The teaching of hydrology.

14. Legends for geohydrochemical maps.

15. Research on urban hydrology, vol. 1.

16. Research on urban hydrology, vol 2.

17. Hydrological problems arising from the development of energy.

18. Urban hydrological modelling and catchment research, international summary.

19. Remote sensing of snow and ice.

20. Predicting effects of power plant once-through cooling on aquatic systems.

21. Research on urban hydrology, Vol. 3 . 22. Curricula and syllabi in hydrology.

23. Dispersion and self-purification of pollutants in surface water systems.

24. Experimental facilities in water resources education.

25. Teaching the systems approach to water resources development.

26. Study of the relationship between water quality and sediment transport.

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A contribution to the International Hydrological P r o g r a m m e

Experimental facilities

in water resources education

Report by a team of authors on IHP-II Project B.2.1.4,

"Experimental facilities in water resources education"

Unesco

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T h e designations employed and the presentation of the material do not imply the expression of any opinion whatsoever on the part of Unesco concerning the legal status of any country or territory, or of its authorities, or concerning the frontiers of any country or territory.

Published in 1983 by the

United Nations Educational, Scientific and Cultural Organization

7, place de Fontcnoy, 75700 Paris

Printed by Imprimerie de la Manutention, Mayenne ISBN 92-3-102107-9

© U n e s c o 1983 Printed in France

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Preface

Although the total amount of water on earth is generally assumed to have remained virtually constant, the rapid growth of population, together with the extension of irrigated agriculture and industrial development, are stressing the quantity and quality aspects of the natural system. Because of the increasing problems, m a n has begun to realize that he can no longer follow a "use and discard" philosophy—either with water resources or any other natural resource. A s a result, the need for a consistent policy of rational management of water resources has become evident.

Rational water management, however, should be founded upon a thorough understanding of water «availability and movement. Thus, as a contribution to the solution of the world's water problems, Unesco, in 1965, began the first world-wide programme of studies of the hydrological cycle—the International Hydrological Decade (I H D ) . T h e research p r o g r a m m e was complemented by a major effort in the field of hydrological education and training. The activities undertaken during the Decade proved to be of great interest and value to M e m b e r States. By the end ofthat period, a majority of Unesco 's M e m b e r States had formed I H D National Committees to carry out relevant national activities and to participate in regional and inter- national co-operation within the I H D programme. The knowledge of the world's water resources had substantially improved.

Hydrology became widely recognized as an independent professional option and facilities for the training of hydrologists had been developed.

Conscious of the need to expand upon the efforts initiated during the International Hydrological Decade and, following the recommendations of M e m b e r States, Unesco, in 1975, launched a n e w long-term intergovernmental programme, the International Hydrological Programme (IHP), to follow the Decade.

Although the I H P is basically a scientific and educational programme, Unesco has been aware from the beginning of a need to direct its activities toward the practical solutions of the world's very real water resources problems. Accordingly,, and in line with the recommendations of the 1977 United Nations Water Conference, the objectives of the International H y d r o - logical P r o g r a m m e have been gradually expanded in order to cover not only hydrological processes considered in interrela- tionship with the environment and h u m a n activities, but also the scientific aspects of multi-purpose utilization and conservation of water resources to meet the needs of economic and social development. Thus, while maintaining IHP's scientific concept, the objectives have shifted perceptibly towards a multidisciplinary approach to the assessment, planning, and rational m a n a - gement of water resources.

A s part of Unesco 's contribution to the objectives of the I H P , two publication series are issued: "Studies and Reports in Hydrology" and "Technical Papers in Hydrology". In addition to these publications, and in order to expedite exchange of information in the areas in which it is most needed, works of a preliminary nature are issued in the form of Technical Documents.

The "Technical Papers in hydrology" series, to which this volume belongs, is intended to provide a means for the exchange of information on hydrological techniques and for the coordination of research and data collection. Unesco uses this series as a means of bringing together and making k n o w n the experience accumulated by hydrologists throughout the world.

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List of illustrations

1.1 Main processes and storage states composing the hydrologie cycle

1.2 The five reservoirs in the land phase of the hydrologie cycle and their related flux functions

3.1 Pitot-Prandtl tube

3.2 Venturi meter for pipe flow

3.3 Rehbock weir for design discharge of 50 l.s 3.4 Vertical Reynolds tube experiment

3.5 Piezometric measurements at an abrupt expansion 3.6 Hydraulic jump in a rectangular flume

3.7 Model of a spillway in a fixed bed flume 3.8 Surface flow pattern visualization 4.1 Hydrologie cycle

4.2 A Hele-Shaw ground water analog model showing interface between intruding sea water and fresh water in a coastal aquifer with impervious layers 4.3 Schematic drawing of a weighable lysimeter

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Foreword

The educational programme of the International Hydrological Programme is a follow-up of the activities carried out by the International Hydrological Decade (1965-1974) but the scope has been broadened to include the various applications of hydrology to the development and management of water resources.

The Intergovernmental Council for the IHP established a programme of publications in the field of hydrological and water resources education, partially to replace older IHD publications issued around 1972 or to treat fields which so far had not yet been covered. The Council established a working group on Teaching Aids which met in Padova, Italy (March 1 9 7 6 ) , Paris (October 1979) and Paris (September 1981) with the main aim of preparing four reports to be published by Unesco.

(a) Teaching the systems approach to water resources development (b) Teaching the use of computers in water resources development (c) Experimental facilities in water resources education

(d) Teaching aids in hydrology

The Council entrusted Mr. R. A. Lopardo (Argentina) with the task of compiling the present publication. He was assisted by a Team of Authors, consisting of Messrs. L. de Backer

(Belgium), M. H. Diskin (Israel) and J. M. Wiggert (USA). The team held three meetings:

Koblenz (FRG) in May 1979, Graz (Austria) in November 1980 and Koblenz (FRG) in September 1981.

The Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA greatly assisted in the preparation of the final manuscript and Unesco is much indebted.

This publication is intended to serve students but particularly teachers and those who are involved in the planning and design of experimental facilities related to water resources education. It is conceived as a teaching and planning aid for undergraduate and post-graduate studies.

The four publications mentioned above are closely inter-related and the reader of this publication is particularly advised to consult the report on teaching aids in hydrology.

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1. Introduction

1.1. THE IMPORTANCE OF THE EXPERIMENTAL EXPERIENCE IN WATER RESOURCES EDUCATION

Everybody understands an idea, a fact or a problem much better when he has experienced it.

Then one can talk about it, explain the situation or discuss possible solutions. In the field of water resources, the problem of one is the problem of all because water resources have no borders. Therefore, problems of water resources concern all of us, not only the specialists.

Exchange of information about water resources eases the problem and leads to more efficient solutions than when people fight each other because of lack of knowledge. Let us not forget that the word rival comes from the same root as the word river. The."right for water" still leads to good or bad experiences at all levels of survival, individual, regional, national and international, sometimes simply due to the degree of understanding. Water resources are of vital importance for the world population which is going to increase by about two billion souls by the year 1990. A level of understanding on the proper use of water resources can be reached without conflict by taking advantage of previous experience.

The field of water resources is very complex and requires the cooperation of different types of specialists to bring water of the right quality to the right place and at the right moment. Much has still to be learned scientifically about water resources. Fortunately, much has been learned by experience and can be transmitted through education (IWRA, 1975). It is

the main purpose of this publication to show that experimental facilities can help greatly in the training of water resources practitioners. Broadly speaking, the idea of "experimental experience" is that of an educational process which consists in repeating time after time through the handling of materials and equipment the experiences which lead to a desirable level of knowledge. This in turn will lead to increase the amount of information and data necessary to improve our understanding in the field of water resources. The experimental educational process is particularly important because it brings the student into a simulated situation which allows him to make mistakes and to correct them before he is confronted with the real problem.

1.1.1. Understanding the Hydrologie Cycle

The role of water in our universe does not need to be demonstrated here. However, the water needs of mankind and the desire to improve man's quality of life make it compulsory to understand the water cycle or hydrologie cycle in order to evaluate the available water resources necessary to meet these goals without harmfully disturbing the natural process.

The hydrologie cycle is an expression of the ideas that the quantity of water on earth is constant and that this quantity of water takes part in a number of natural processes which transfer* it from one state of storage to another. The primary states of storage are those in the oceans, in ice, in the atmosphere and on or in the land. The main transfer processes are evaporation, precipitation and runoff (Figure 1.1).

Early in their schooling, people are taught about the basic concepts of evaporation, E, (from sea and bare land) and évapotranspiration, ET, (from vegetated land) under the sun's action on these surfaces as well as of precipitation, P, from the clouds due to the effect of water vapour condensation in atmosphere. This domain of "hydrometeorology" involves the atmosphere and is limited to the earth's surface.

From there, the various paths followed by the precipitated water reaching the oceans or returning to the atmosphere are complex and not easily separated. Indeed, it is sometimes hard to visualise the various parts; for example the runoff, R, which feeds the river and the

infiltration, I, covering the behaviour of the part of the water infiltrating the soil profile.

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EVAPOTRANSPIRATION EVAPORATION

Fig. 1.1 - Main processes and storage states composing the hydrologie cycle

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The runoff process is the domain of the "Surface Hydrology" and the infiltration process is that of "Agrohydrology".

The soil is a temporary water reservoir from which the plants feed. The water of the soil reservoir that is not returned back to the atmosphere by évapotranspiration nor retained in the soil by capillary forces percolates through the subsoil to the aquifers. These are groundwater reservoirs where water fills up all the cavities and pores within the geological formations.

This is the domain of "Hydrogeology".

In an unconfined aquifer the level of the water surface is called the "piezometric level".

In a confined aquifer the piezometric level is the sum of pressure head and water elevation.

Where the piezometric level is the same as that of the ground or higher, a "spring" appears and where it is in contact with a river, groundwater flow contributes to the "base flow" of the river on its way to the sea.

As fresh water is continuously replenished in the land phase of the hydrologie cycle, man not only catches it, either at the earth's surface in springs, rivers, ponds, lakes and man- made reservoirs or below the surface in aquifers with the help of pumps, but also returns most of what he uses back as waste water either in the rivers, in the ground or in the sea. The bypassing of the natural cycle created by agricultural, industrial and domestic activities has generated two major water resources problems of supply and pollution. The complexity of these problems results from the conflicting combinations of the quantity and the quality of the water needs and uses as functions of time and space.

The first and most important quality of water resources is their quantity. Quantitative aspects of water resources have traditionally formed the basis of water resources education.

This publication concerns only the experimental facilities for the study of these quantitative aspects. A book on water quality surveys has already been published by UNESCO and WHO in 1978.

The total amount of water in vapour, liquid and solid phases is essentially constant around the earth. Most of the water is in the ocean, but water resources available to man are

unequally distributed in time and space over the land surfaces.

With the symbols introduced above, a water balance equation for a given catchment and during a given period of time can be presented as follows:

• P = ET + R + I +_ AS (1.1) where AS represents with the plus sign the increase of storage and with the minus sign the loss

of storage in the catchment.

The terms of this equation are commonly expressed in units of water depth and must be determined with maximum accuracy. The difficulties encountered with this equation are due to the fact that the methods used for the determination of the terms in it seldom involve the same time period and that it often occurs that more than one term remains unknown. Besides, direct measurements are not always possible, so the terms of the equation are often estimates obtained through calculations of other data.

Another approach showing the relations between the flux'(or process) functions and the natural water reservoirs of a region for the water cycle over land surfaces is illustrated in Figure 1.2. This approach allows for the explication of the variations of the water storage during a given period of time At in the hydrologie cycle according to the following equation:

ASm = AS, + AS„ + AS„ + AS "+AS„ ' (1.2)

T A P S G R

where AS is the total water storage variation, and

AS is the storage variation of the soil surface subjected to the flux functions P, E, R, I

AS is the storage variation of the soil profile subjected to the flux functions E, I, L, D

AS is the storage variation in the subsoil subjected to the flux functions D and A AS is the storage variation in the groundwater reservoirs subjected to the flux

functions A, B, W

AS is the storage variation in the rivers and lakes subjected to the flux functions R, L, B, Q

This change in water storage is related to the flux functions by

A ST = P - (E + Q + W) (1.3)

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FLUX FUNCTIONS:

E. EVAPOTRANSPIRATION P. PRECIPITATION I. INFILTRATION R. RAPID RUNOFF L. SLOW RUNOFF

D.DRAINAGE OF THE SOIL PROFILE RESERVOIR A. AQUIFER INPUT FLUX

B.BASE FLOW

W.WATER LOSSES FROM THE AQUIFER Q.RIVER DISCHARGE

2 - The five reservoirs in the land phase of the hydrologie cycle and their related flux functions

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The time period At to be considered still raises problems due to the fact that the hydrological terms (P, E, R, I, L, D, A, B, W and Q) which link the water reservoirs depend upon natural phenomena involving different time scales, e.g., from minutes for P to months and years for W

(De Backer, 1978).

From Figure 1.2., it can also be seen that over a long time period, for which AS equals zero, the total flow discharge of a river Q is given by the sum of the rapid runoff R, delayed runoff L, and the base flow B

Q = R + L + B (1.4) It should be pointed out that the precipitation P and the flow discharge Q are the only two

hydrological terms commonly measured.

It is tempting to use the simple Rainfall-Runoff relationship frequently considered in modelling when one realizes the intricacy of the natural ways followed by water. Such simple models are based on the idea that surface runoff R and delayed runoff L contribute most to the total flow discharge. However, studies based on measurements show that the base flow B can contribute up to two-thirds of the total flow discharge Q of the river over a year.

Fortunately, the terms in Equation (1.2) can be studied separately according to the

specific water resources objectives and could possibly be measured by means of actual, advanced or new methodologies and technologies.

These very schematic and brief considerations about the hydrologie cycle and its relations with water resources emphasize the need for more hydrological data of different types and more studies. This implies in turn the development of more experimental facilities for water resources education.

1.1.2. Study of Hydraulics and Hydrological Processes

Today it appears that most of the plentiful catchments have been tapped or no longer meet our needs and that waste water pollutes our environment. We thus have to find new ways to supply more water and to manage our effluents. Hydraulics is used to solve problems with well-defined boundary conditions, but hydrological processes are considered when natural conditions must be taken into account. Hydrological study is thus used for such projects as the development of new catchments, artificial recharge of aquifers, waste water disposal, etc.

One has to determine the location and the size of watersheds large enough to fill new reservoirs and supply the amount of water required, of wells either for groundwater supply or for artificial recharge or for wastewater disposal by selecting the adequate aquifers, of infiltration sites for artificial recharge or waste water disposal, etc. All these determinations ' imply knowledge of the hydrological processes involved in the water cycle as they are affected by man's activities. With the development of multipurpose water works, the complexity of the problems and the amount of information necessary to study the projects increase drastically.

What was some time ago a one-man project now becomes a team project involving many more' specialized people.

A long historical series of hydraulic and hydrological data is needed before the project starts, and after the completion of the entire work more data must be collected regularly in order to follow its behaviour and to insure its maintenance as well as to verify the various hypotheses and models made during the establishment of the project. The improvement of our knowledge about hydraulics and hydrological processes depends upon these continuing studies through guided experience.

1.1.3. Role in the Educational Process

A harmony in the teaching of geoscientific knowledge is established through books, laboratory work and field trips. In natural sciences, the process is basically descriptive. In engineering sciences, a high level of abstraction is necessary in order to define the system in which a given phenomenon occurs.

While natural phenomena and mechanisms are often not yet fully understood, engineers have physical laws and technical tools which allow them to work with systems well defined by

boundary conditions. It is then obvious that the transfer of knowledge through demonstrations and practice are far better developed in engineering than in natural sciences and experimental facilities in engineering education are readily available where technological development requires experimental skill due to the degree of sophistication. Yet, experimental experience plays a more important role in natural sciences because the amount of knowledge still to be acquired is overwhelmingly greater than in engineering sciences.

Water resources sciences proceed with the combination of both types of experiences; the sophistication found in engineering and the understanding of hydrological processes which belong to natural sciences. The part devoted to experimental experience for water resources

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education is thus of prime importance and must be developed at all levels of education through- exercises, laboratory, field trips and reports.

1.2. THE NECESSITY OF EXPERIMENTAL PRACTICE

In addition to the motivation described above about the importance of experimental experience in water resources education, experimental practice is a necessity in the understanding of theory, in the training of practitioners, in the gathering of data and its improvement for water resources design needs and for operation and management of water resources projects.

1.2.1. Understanding of Theory

Deep in the nature of man, curiosity acts as one of life's driving forces: the desire to know. Several steps mixed with reasoning are involved in the process of acquiring knowledge.

Observation and description, analysis and interpretation, separation and relation, induction and deduction, experimentation and verification all converge with intuition toward principles or laws. Together with rules, and conventions they form the basis of what is called theory. It is transmitted from generation to 'generation, and whenever necessary, modified, improved or rejected.

No matter how ambitious one man can be, he will never be able to rediscover in one life all the heritage of knowledge. In his field of activities he will pick up whatever is .useful to him. Even such selection is time consuming and therefore educational programs have been set up, for example, by UNESCO in the Technical Papers in Hydrology, N° 10 and N° 13.

In water resources education, the theoretical part involves the principles, laws, rules and conventions of hydraulics and hydrology. By means of carefully selected demonstrations and experiments, the students can go concisely through the steps that lead to their establishment and so satisfy their curiosity by rediscovering the theory. They should also understand the field of application and limitations of the theory. Through experience, they can also develop inventiveness and appreciate the quality of data.

Another very important reason for experimental practice is the improvement of theory.

Many applications of theory are made possible by analogy between some phenomena. Theory also gives rise to models either physical, analog or digital (UNESCO, Technical Paper in Hydrology, N° 11). Practical experience with models helps greatly in understanding not only the theory on which they are based and the phenomena-simulated by the models, but also their limitations in giving a true picture of the phenomena.

Both laboratory and field facilities are described for hydraulics and hydrology in Chapters 3 and 4.

1.2.2. Training of Practitioners

A practitioner is one who practices a. profession. Do such professions as those of hydraulician and hydrologist exist? Yes, despite the fact that the domains of knowledge

required to be fully qualified are so large that even if one could understand all the theories, it is impossible for him to put them all in practice. Therefore, one speaks usually of technicians, engineers or researchers in some specialized fields of hydraulics or of hydrology.

Thus there exist some training levels that depend mostly upon the amount of theory which -the practitioner wants or is able to understand as well as his ability to put them into practice.

All educational programs include experimental practice for these reasons. This is particularly true in hydraulics and in hydrology because the sophistication of most theories and equipment requires a great deal of intellectual as well as manual ability, not only in the laboratories but also in the field (WMO, Guide to Hydrological Practices, 3rd Edition, 1974).

The practitioner cannot always repeat exactly the same experiment, especially in natural phenomena, and must constantly demonstrate the reliability of his results. Moreover, the water resources managerial decision on which often- depends the well being of the population and/or the preservation of the environment depends, in turn, on the conclusions drawn by the practitioner.

The teaching of experimental practice in water resources obviously does not include all the situations .which the practitioner will encounter but should give him the background necessary to adapt his knowledge to real situations. To be a,good practitioner implies more than repeating exactly what he has learned at school. Self teaching and self training char- acterise the efficient practitioner. However diligent in his profession, he cannot be aware of all the new developments that occur in this: growing science of water resources. Continuing education programs with organized field trips and laboratory visits are presented in each specialisation and contribute largely to the training of the active practitioner.

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1.2.3. The Gathering of Data and its Improvement for Water Resources Design Needs

Water is in perpetual movement. The only way to evaluate the amount of water available for a given purpose is to measure regularly and/or predict the water fluxes that cross at any moment the input and output boundaries, first according to natural conditions, second within the design structures, and third according to the disturbed natural conditions. The comparison between the undisturbed condition and the new situations shows the feasibility of the design to meet the required needs and to define the consequences that the future design structures will bring to the local water balance. Most water problems occur because these precautions are not taken rigorously.

Hydrological measurements (see Chapter 4) might seem expensive at a time when water

resources are not yet needed. However, prediction is impossible without a historical recording of hydrological measurements. The longer the record, the better the prediction.

Hydraulics measurements (see Chapter 3) are usually taken only when a model of some • structure is required. The running and/or maintenance of such models might involve a period of time exceeding the time of the study in order to verify the results obtained by the model with those of the prototype.

Special procedures must be set in order to give enough reliability to the measurements before any treatment, interpretation and use., Chapter 2 is devoted to these considerations.

The results of measurements are therefore only part of all the data needed for water resources design (see Section 1.3).

Data gathering is expected to be a well organised activity in which a great deal of responsibility is involved. Many users of these data need them for various purposes either directly related to the concerned water resources design or for later development of activities involving the same water resources (see Section 1.2.4).

Educational programs in water resources must give the student an opportunity not only to perform some measurements but also to present the data in a way that will allow him and others to use them later on. This presentation varies from one service to the other but all information must be at hand to guarantee the meaning of the data. As it was mentioned above, water resources design needs might develop anywhere and at any moment. This means that water resources data gathering over long periods of time is of utmost importance everywhere. This . might have seemed impossible some years ago but since the development of remote sensing tech- nology water resources investigation can be made almost anywhere provided enough ground truth data are available to establish the relationship with the remote sensed data. Today, the amount of information obtained from remote sensing by far outnumbers the availability of corresponding ground truth information. Experimental practice in the gathering of data in these new fields will therefore lead to meeting the needs required in water resources designs of water works.

1.2.4. The Gathering of Data for Operation and Management of Water Resources Projects The development of water resources projects requires several years and as many data as possible. The data should cover not only periods before the projects are initiated but also complementary data during development. Once a project has been executed its operation requires the gathering of data necessary to meet requirements of operation. Sophisticated equipment is developed to guarantee measurements on a "real time" basis. At such levels of operation the computer is a necessity. The control of all the elements of the project can thus be maintained and their behaviour followed according to the predictions as well as to the models developed during the study of the project. Modifications can then be brought forth and accidents pre- vented.

Students in water resources education also should be aware of data gathering expressly for water resources management. These data involve not only:all the data necessary for water resources design and project elaboration and operation but also data pertaining to the eval- • uation and prediction of water resources needs within the project, and even those of other projects if the resources are not completely available within the project.

As the level at which one studies water resources increases, the degree of complexity of data gathering increases along with the degree of reliability of the measurements. This emphasizes the importance of experimental experience in the training at all levels in water resources. Special attention should'be drawn to the use of models in the operation and the management of water resources projects:

Data gathering must not only be well organized but also well understood by all parties.

On one side, those who perform the measurements and prepare the data necessary for the running of the models must receive a general outline of the models and have a good understanding of the scope of the project. The instructor's readiness to learn and answer the students' questions about situations where "their" data are used contributes highly to improve their motivation for the work, their integration into the project and, as a consequence, the reliability of the

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data. On the other side, those who elaborate and/or work with the models/ besides the general scope of the project, need training in measurements in order to understand both the field conditions and especially the work as well as the limits involved in obtaining the data.

A common language thus develops among all partners of the project and leads to a mutual understanding between those who produce and those who use the data, and therefore to the efficiency of operation and management of the project.

1.3. WATER RESOURCES DATA

The collection of data is essential to analysis, design and management of water resources projects. In this section the nature of data for water resources development uses is discussed, along with the purpose and usefulness of data.

1.3.1. Definition

Water resources data are understood to be numerical values of the measurements of those hydrological and meteorological phenomena which change with time and which can be measured directly or by a direct consequence of their occurrence, and other, more general information which does not change with time, needed in water resources development. Hydrological and meteorological data result from the measurement of physical phenomena such as velocity, discharge, groundwater levels, sediment carried by stream flow, evaporation quantities, precipitation, wind speed, temperature, specific humidity, cloud cover and insolation. Some data result from simple, single measurements, such as wind speed, water stage, precipitation, stream flow velocity at a point and groundwater levels. Other data.are derived from one or more simple measurements, such as stream discharge, évapotranspiration, groundwater flow, and dewpoint. In any case, all data of this sort are directly applicable to water resources management.

Some data are records of time-varying phenomena; examples are wind speed, precipitation and discharge. Others are records of phenomena which are relatively constant with time and normally do not need repeated measurements to establish a time function. Examples of non- varying information are catchment size, stream slope and soil structure. These data are often available from sources other than measurement by the water resources data gathering team. They can be obtained from topographic maps, soil survey maps and the like.

Some data are used in water resources work but are not essentially hydrological in nature.

Such factors as land use, demographic figures and water requirements for industry are examples.

Collection of data of this sort is outside the scope of this work. This monograph is concerned only with measurements of a hydrological and meteorological nature.

1.3.2. Purpose of Data

The collection of data serves a primary purpose in water resources management and development; as an information source for analysis, design and operation of facilities. Often measurement and data collection are directed to a specific purpose or project, and have utility only to meet that particular need. Despite the limited utility however, this purpose of data is, of course, extremely important. Data collection can be performed for purposes other than design, for example, a measurement and data collection network might be developed for a flood- forecasting program. . .

. Data are gathered and stored in order to build up an information base for future, unspecified uses. This may be the most important function of water resources data collection.

It has already been noted that the planning and design of water resources systems depends heavily on an inventory of accurate and relevant data. These data are very often time dependent, so historical records are often essential for. many projects. In many cases the value of the information gained from the data is a function of the length of record. For example, stream flow records provide more accurate estimates and permit more types of analysis if the records are long and.unbroken. It is apparent that data collection networks must be designed with the idea that future uses may have needs presently unrecognized, that long, continuous records may be necessary, and that fairly broad areal coverage by data is desirable.

Obviously, it is extremely difficult to plan data collection networks to meet future, unspecified needs for the data. Nevertheless, the difficulty does not lessen the importance of this purpose, but rather makes it imperative that careful, serious work be done in collecting and preparing data for these kinds of data bases. The opportunity to take the measurements and record the data will pass and will not be present in the future. It is better to err on the side of taking more data than to find that insufficient data were taken.

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1.3.3. Quality of Data

Data quality can refer to several aspects of data. One feature of data quality is continuity. Continuity is that unique property that time series of measurements have. The quality of data which describes time-dependent variables is impaired if there are breaks or gaps in the record. Records can be of high quality in other ways, but if they are not continuous the data may be useless for many purposes.

Data should also be consistent in the statistical sense, they should be a record of measurements of variables of the same population. Sometimes this feature of data is destroyed by moving a gauge,, or by changing environmental factors in the area of the measuring site. It is quite possible, of course, that this aspect of data is outside of the control of the manager of the data collection scheme. It is therefore important to place on record information, other than the data recorded, that will give future users an evaluation of the extent of changes in environmental factors. Consistency of data includes consistency of its precision and accuracy.

The collection of data should be undertaken with a good understanding of the requirement of completeness. Data should be complete, sufficient to the purpose, whether the purpose is operation and management of a-project or economic design of a major water resources system.

Completeness can have a statistical context, but the meaning goes beyond that to meeting the technical and engineering needs. The burden of designing an information and data system for future needs rests heavily on the data gathering office and its administrators.

1.4. THE OBJECTIVES OF THE MONOGRAPH

This monograph is intended as a guide to the teacher of water resources technicians and university students, to aid the teacher in establishing physical facilities which can introduce the learner to methods, techniques and instruments used in water resources management and assessment. It is not intended to be an exhaustive list of equipment and their descriptions or a laboratory manual, rather it is to be a form of rough blueprint to aid in the planning of the laboratory experience and to aid the teacher in the selection of equipment and experiments.

The facilities described are limited to hydrological and hydraulic aspects of water resources design and management. Specifically excluded are matters directly related to water quality.

1.4.1. Scope of Hydraulics and Hydrology Facilities

The facilities described in this monograph are classified into two types, hydraulic and hydrological. The hydraulic facilities are representative of a quite traditional hydraulic or fluid mechanics laboratory. The activities in the hydraulic facilities are intended to present demonstrations and experiments that illustrate and amplify on principles of fluid mechanics.

Experiments requiring calibration and use of standard laboratory instruments are envisioned along with operation of equipment such as pumps, valves, gates, etc. Descriptions of basic and desirable equipment and instruments are provided, along with some suggestions on sizes and capabilities. Emphasis is given to equipment found in hydraulics laboratories, such as open- channel flumes, both with and without sediment flows.

Hydrological teaching facilities is a term used to describe equipment and instruments—and places to use them—that are normally associated with field work in hydrology. The placé of instruments for measuring meteorological variables, precipitation, evaporation, stream velocity and stage, discharge and soil moisture is described. Specialised equipment and its need is described—some examples are groundwater analogies, photographic interpretation and data handling equipment. A section is devoted to description of outdoor, or field work, and some attention is paid to the details of that aspect of hydrological facilities, an area that the authors believe is extremely important.

1.4.2. . Educational Level of Facilities

The water resources experts who would be the subject of training given in the facilities described here are intended to be senior-level technicians and university students. Senior- level technicians can be expected to be field party chiefs or others in responsible charge of data collection in the field and storage of data. Of course, it is apparent that such technicians need good training and -experience in measurement techniques". In all the teaching facilities described here there are devices for measuring properties of fluids and materials and calibration equipment as well as instruments and equipment more specifically directed to hydraulics and hydrology. This has been done because the authors believe that senior technicians need a practical understanding of basic fluid flow concepts, so that the senior technician can make good judgements when faced with new experiences in the field. The senior technician must be trained to be able to manage without close supervision. University

students, too, need training in measurement techniques, and although their expertise in the use

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of instruments and techniques need not be as high as that of senior technicians, their understanding of the purpose, techniques, and strengths and limitations of measurements is

essential. Obviously, university students of engineering in hydraulics, hydrology and water resources need a sound foundation in the properties of water and in the basic concepts of fluid flow, as well as some understanding of practical or applied hydraulics and hydrology. In the authors' thinking, the needs of senior practitioners and university students are parallel enough to permit the use of common facilities. The teacher will have to determine the specific direction of experiments and projects for the two groups. The facilities described in this monograph are not intended for research per se, but it is recognised that some of the equipment could be used for basic or applied research. Normally, research activities require consider- ably more free space and flexibility of space and equipment than is proposed to the teacher in this monograph.

1.4.3. Suggestions for Teachers

The chapters that follow have been planned to be suggestions for teachers that represent, in the authors' opinion, a minimum facility for training in the measurement and collecting of water resources data. These are recommendations for equipment and instruments for both hydraulic and hydrological teaching facilities, and descriptions of possible physical arrange- ments. Also included are suggestions for outdoor facilities and activities. The authors believe experience in realistic situations to be an essential part of the training program for water resources data gathering practitioners.

The individual teacher developing and using a water resources training facility will likely find it necessary to modify the recommendations and suggestions found in this monograph.

Restrictions imposed by funding, class size, climate, level of trainee, objectives of training program, etc., are all factors which must be considered, and can possibly lead to differences in selection of alternatives in facility size and equipment. Nevertheless, this monograph should provide a ready source of information to aid the training of water resources practitioners.

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2. General concepts of measurements

2.1. GENERAL

In this chapter definitions and meanings of some of the terms used are established, and the general importance of measurement is discussed, along with its relationship to data and variables. The treatment is not intended to be a guide to statistical and probabilistic foundations for designing a program of experimental measurement, rather it is planned to provide a general background in terminology and to be a reminder of some of the important considerations in data collections.

2.1.1. Definition and Characteristics of Measurements; Dimensions and Units

Measurement is the name given to the value or amount of length, capacity, velocity, or some other property of a quantifiable, physical entity. Measurement is obtained through the act of measuring. The values of the measurement of the physical entity serve to describe it.

Measurements are expressed by the concepts of dimensions and units.

Dimensions are the names given to those singular attributes of physical entities that describe their relation to other physical entities. Examples of dimensions are the qualities of mass, length, time, temperature and electrical charge. Many of those singular attributes are recognized in applied fluid mechanics and hydrology. Some, such as temperature, are important in defining properties of the fluid, like density and viscosity. Other attributes are quite directly part of the phenomena of fluid flow. This is particularly true of mass, length and time. For example, velocity and acceleration can.be expressed as combinations of length and time, and pressure is a combination of mass,^ length and time. In fluid mechanics practice force can be expressed through the empirical relationship of Newton's First Law, force equals mass times acceleration, where acceleration is expressed dimensionally as length divided by time squared. It should be stressed that because dimensions are descriptions of the

singular attributes they cannot be reduced further, although they can be stated alternatively through essentially empirical relationships as described above...

Units are arbitrary measures of dimensions and combinations of dimensions because measurements are essentially artificial and arbitrary. Although the measurement is artificial and the unit is arbitrary, the properties of the physical entity-being measured is neither artificial nor arbitrary. For example, the area of a lake is a physical reality regardless of the dimensions and units used to describe it. The dimension of area is usually expressed as length squared. The units of area are arbitrary, however; they can be hectares, square metres., etc.' Similarly, the time interval between discharge measurements can be expressed in minutes, hours, days, etc., and although our concept of time is that it is physically real, the. unit is arbitrary even though it may be based on an observation of a physical phenomenon (the rotation of the earth).

There are many systems of units, but the metric Systeme International (SI) and the English are probably the most widely used. The Systeme International is the only recommended one. All systems have been developed for many years and contain units that are constructed to describe measurements of combinations of dimensions. For example, discharge can be expressed in cubic metres per second, but it is a combination of the dimensions of length cubed divided by time.

The relationship of units to dimensions is valuable in conversion from one system of units to another.

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2.1.2. Simple and Derived Measurements

Simple measurements are those taken of entities or the phenomena directly, for example, flow velocity or rainfall depth. Many water- resources data are records of measurements of this kind. The data representing these measurements are very important since they are the bases for a great part of the water resources information.

Derived measurements is the name given to values of variables which are computed from other measurements, but are still values representing a fundamental variable. For example, infiltration is estimated by observing rainfall and runoff, and essentially taking the differ- ence. Similarly, discharge in a stream can be determined by measuring velocity at a number of points and combining these with measurements of the area of the cross-section of flow.

2.2. ACCURACY

Accuracy is a description of the closeness of a measurement to the true value of a •

physical entity. The concepts of accuracy of data are important in any data collection effort.

In water resources data there are problems of matching the accuracy of one set of data to another. Involved in the definition of accuracy are precision of instruments and problems of systematic and casual errors. In this section the topics named above are treated in a general fashion, and some aspects peculiar to the accuracy of water resources data are discussed.

2.2.1. Precision of Instruments

Precision is the ability to discriminate between different values of the same variable.

It largely is a function of the instrument used. As an example of instrument precision, some rain gauges are precise to 0.1 mm. The capabilities of instruments used in water resources data collection are generally well known, and information on the precision of most is generally available from the manufacturer. When planning data collection networks and management

practices it is essential that consideration of the precision of the instruments be included.

Such considerations can limit the general accuracy of the data being collected, or it can affect the selection of the instruments or the method of data reduction.

2.2.2. Sources of Error

Errors lead to an erosion of the accuracy of data. The operator or the instrument can contribute to the magnitude of errors which may be casual errors or systematic errors. Casual errors are relatively small positive or negative random variations from the true value due to various sources. They are usually described in statistical terms. Systematic errors con- sistently tend to either overestimate or underestimate the measurement. For example, a staff gauge may have an erroneous reference elevation, or a current meter may have a faulty bearing, causing drag which slows down the propeller's revolution count. Some systematic errors can be corrected if the nature of the change in the data can be ascertained. Sometimes systematic errors are present in data which are used in turn for further computation, or which are reduced in some other way, and the reduced data are all that is kept in archives. In such a case the reduced data are in error, and the correction for systematic error would have to go back to the data where the error was introduced.

Errors due to the operator's.mistakes sometimes enter into data. These are random in nature and may be sometimes positive and sometimes negative. They typically occur through human error; misreading a gauge, or writing down an incorrect number. It is also possible that a malfunctioning instrument can introduce these errors. It is virtually impossible to correct such errors unless they are noticed at the -time of measurement. Since these errors generally affect only one item of data, they are not subject to correction as are systematic errors.

2.2.3. Total Accuracy

The total accuracy is a function of the combination of instrument precision, casual and systematic errors. Instrument precision can be expressed in a statistical fashion, as a unit of precision plus or minus a number. That number usually is the standard deviation, which, if a normal distribution describes the instrument's Variation in precision, means that approxi- mately 68 percent of the measurements made will be within the range. ^ Of course, the magnitude of systematic errors and mistakes cannot be expressed in a probabilistic manner, although their occurrence can be anticipated in a.statistical sense.

The aspect of matching the accuracy of water resources measurement and data gathering to their purpose is extremely important. It is essential to consider the ways in which the data are to be used, so that the accuracy of the data is appropriate to their purpose. If un- necessary accuracy is attained, the cost of acquiring data will be higher than necessary, and

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alternative uses for the money allocated to data collection will be lost. If the accuracy of the data is insufficient, the loss of information can never be recovered in many cases, and further losses may be incurred through poor design, faulty operation or some other, similar consequence of poor information. However, since the future use of water resources data is not known, it is considered better to err by having too much accuracy rather than too little. The senior water resources practitioner should be aware of the problem of matching accuracy, and he should understand the role the practitioner plays in matching objectives and data gathering.

Generally speaking, the accuracy of measurement should be that of the precision of the instrument. Only through techniques such as replication can accuracy greater than instrument precision be attained. However, since variables measured in water resources work are nearly always time varying, space varying or both, replication of many commonly made measurements is impossible. A measurement of less precision than that of the instrument may take just as long to perform, and so it will not represent a cost saving. The problem of matching the need for accuracy in data collection to the purpose is more severe in water resources applications since the future use is often unknown, and the requirement of the level of accuracy cannot be determined. In this regard, it is important for.the water resources practitioner to record his estimates of accuracy: of the data he collects so a future user can make an assessment of its importance.

2.2.4. Temporal and Spatial Variability of Water Resources Data

Most useful water resources information is highly variable in space and time. As an example, rainfall rates vary widely during a storm, as is seen from looking at a trace of a recording rain gage. Rainfall distribution varies widely spatially, too. Similar examples can be given of nearly all water resources variables. The planners and managers of a data collection system must be aware of this variability and take it into account. The selection of locations for measurements and the sampling intervals must be carefully considered in relation to the purpose of the measurement. There are approaches to optimization of gauging networks that have been successfully applied, and offer valuable examples of the optimization technique.

The use of "benchmark" stations, which are stations that are established for acquiring long- term records, and a program to correlate short-term records at other nearby stations might prove to be valuable and productive, and better than an attempt to establish a very large number of long-term stations.

Experimental basins are often used to help establish the nature of hydrological regimes, so that the knowledge .of the regimes can be extended to operational use and for development of water resources generally. The data collection networks for experimental basins will be much more extensive than those networks intended to establish a general data base for water resources systems. Too, the experimental basins will often have special requirements that need to be met. Much like benchmark stations, special care must be taken in the selection, location and operation of the data collection system on these experimental basins. The accuracy

expected for measurements taken in experimental basins is higher than that usually attainable in field measurements.

2.3. WATER RESOURCES VARIABLES

Measurements and data collection and storage are means to obtain values of water resources variables. The variables themselves are the things of interest and importance in the analysis, design and operation of water resources systems and in the science of hydrology. The hydro- logic cycle is studied through measurements which provide data. These data in turn serve to describe the water.resources variables, and finally our understanding of the hydrologie cycle is increased by the study of the nature of the variables.

2.3.1. The Nature of Water Resources Variables

Most water resources variables can be considered state variables of a dynamic system.

State variables are called that because they describe the state of the system at any particular time. The name comes from the literature of dynamic programming. The system is usually the catchment or some part of it, and the state variables describe its conditions. Since the system is dynamic, state variables are time dependent. In hydrological systems these state variables also have a space dependency. The time and space dependency is, of course, the reason for on-going data collections of water resources variable measurement. The very nature of time and space dependency is what the hydrologist and water resources analyst wants to determine. State variables may be exemplified by precipitation, stream discharge, soil moisture and groundwater levels.

Related-to state variables are parameters, those entities that describe the catchment itself. Examples might be stream length, basin area and a trace of the watershed. While state

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variables are functions of time and space, parameters are considered to be invariant in analysis. Of course some, if not all, parameters change with time when time is measured on a very long scale, and sometimes man's activities change parameters through construction (a dredging and channel straightening project) or through land use. It is useful to think of water resources data collection in this sense because it parallels the newer ways of describing

the response of catchments through numerical simulation.

One can also describe the characteristics of water resources variables in the same general way that measurements were described in Section 2.1.1., in terms of their dimensions and units.

As with the measurements, some state variables and parameters have simple dimensional description, others are expressed as combinations of dimensions. Units, of course, are arbitrary and conversion from one system of units to another is a simple process.

2.3.2. Measurements and Instruments for Water Resources Variables • Instruments used to measure water resources variables are as varied as^ the variables

themselves. Some instruments are available to measure the state variables directly. In fact, the concept of the utility of a specific variable and the development of an instrument to measure it are parallel and mutually dependent. Other instruments measure variables from which the water resources variables of interest are computed. Many instruments are standard devices in engineering and science practice. Devices for measuring length, time, mass and temperature, for example are not particularly unique to the water resources field. Other instruments are unique to hydrology, hydraulics and water resources. This list would include apparatus for measuring evaporation, precipitation and soil moisture content.

New instruments and techniques are constantly being introduced for the measurement of- water resources variables. Examples are radar for measurement of precipitation, radioactive tracers for diffusion studies, ultrasound for flow, etc. One can expect these new instruments to trigger the development of new ideas about water resources variables and their management.

2.4. DATA HANDLING

Central to the problem of producing useful data for water resources planning, management and operation is the handling of the data after the measurements are taken. A program of variable measurement and data collection is not complete unless care is given to the handling and storage of the data. The quality of the data handling and storage should be at least equivalent to the quality of measurement.

2.4.1. Data Collecting, Reliability and Reduction

Data collection should be systematic, with methods of data handling standardized as is the measurement process. Data handling includes transmission, reduction, recording, storage, and recovery, and each operation should be given attention.

Transmission of data is sometimes the simple act of delivering a notebook, but it can also include electronic transmission of signals in some way. Remote rain and snow gauges have been in common use for some time, as an example, and the information that they acquire is often sent by wire. Transmission of data can also include delivery of information to a user from the storage location or archives. Sometimes that delivery can be through electronic means. The data transmitted can be in the form of printed or written tables but it can also be on magnetic tapes or punched cards.

Data reduction refers to the transformation of the values of the measurements themselves to the values to be stored; which are the variables of interest. Reduction is sometimes done by hand, but it can be done by a computer. Care must be exercised in the reduction of data', because systematic and casual errors can arise here as easily as they do in the field. The accuracy of the information after reduction should not be less than that of the data brought in for reduction. In some cases, again using rain gauges as an example, the sensor can transmit data electronically to a central computer where the measurements are transformed or reduced to the desired variable form and then stored for future use by the computer. In such instances, no intervention by man is necessary in the flow of information. . • •

Recording,, storage and recovery of data refer to the processes of creating and using a data bank. Data are stored in the data bank; those stored data are called a data base. As implied earlier, a data bank can be a computer memory device, with electronic connections to the sensors of measurements, or terminals for entering data, and with connections to users through electronic displays, printers or some other device. Data banks can be less elaborate, too, and may simply be files, decks of punched cards, magnetic tapes, or similar storage equipment.

Whatever methods of data handling are used, the same level of care in development and operation of them should be exercised as done in the collection of measurement data. The

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accessibility and reliability of the results of a data collection program is as important as any other factor in water resources development.

2.4.2. Verification and Correlation of Measurements

Independent checks of the data collected in field measurements make it possible to verify their correctness. This can be done in several ways, one of which is repetition of the measurement in the field, sometimes with a different instrument. For some time varying measurements it will not be possible to replicate, of course. In some cases an additional measurement may be too costly, or otherwise impossible. Often, verification in a rough way can be achieved in the data reduction stage through comparisons. Values which are significantly different from those of previously taken measurements may be suspected of error.

Several types of correlation, consistency and statistical analyses are available as checks on the correctness of data. In some cases it may be possible to establish the correctness of the data, or rather the lack of gross errors and mistakes, by computing the correlation coefficients between the observed data and other data collected at the same site or at nearby sites.

Techniques such as double mass curves may be useful in this respect. Some stochastic variables may be checked by computing auto-correlation coefficients of the series of values as they are being collected or reduced.

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3. Hydraulics laboratories

3.1. GENERAL

As Stelczer writes in the 1972 UNESCO publication, "Teaching Aids in Hydrology", (Tech- nical Paper in Hydrology, N° 11): "For a proper understanding of hydrological phenomena, an understanding of the related hydraulics and the relevant relationships are essential. No up-to-date teaching of hydraulics is possible without demonstrating the hydraulic processes, and it is inevitably necessary for the students not only to observe the phenomena but to perform measurements personally in order to determine the characteristic values, get an idea of the nature of relationships and discern the roles of variables."

Experimental techniques in fluid mechanics have been used since the earliest efforts in this science, but the hydraulics laboratory as an educational or research tool was not developed until the introduction of physical models for the study of hydraulic problems. Only at the beginning of this century, after the early research work on hydraulic models, has the hydraulics laboratory become universally required for experimental research and education.

3.1.1. The Purpose of Experimental Hydraulics Teaching

j •-

In many disciplines, rational theories are sufficient to account for the various phenomena which comprise their fields. In fluid mechanics, too, the application of the conservation principle to mass, energy and momentum together with the fluid state equation should be enough

to solve any problem, taking proper account of the boundary conditions of the case under study.

However, even within the framework of the relatively simple Newtonian mechanics, where the general equations that describe fluid movement are well known, many problems still require experimental treatment. This is mainly due to approximations in describing the boundary conditions or simplifications introduced in the equations.

Considering the importance of experimentation in the field of hydraulics it is thus

imperative to introduce it during the educational stages of professionals and technicians. In addition to its role in solving real problems, the experimental observation permits the student to clearly understand the fundamental principles which cannot be easily explained by the

teacher. The student will be able to come into contact with the fundamental laws and verify their validity.

It is possible to demonstrate the fundamental laws through experiments using simple equipment, which can be constructed locally. A complex and very precise system is not always the most suitable for educational purposes. The student must be able to observe and understand all the equipment which is used in the experiment and at the same time, he must keep in mind the purpose of the experiment.

The hydraulics laboratory facilities should offer the possibility of performing classic experiments, and the demonstration of fundamental laws. Generally, the hydraulics laboratory should have facilities for scientific and technological research in addition to those specifically for educational purposes.

The dimensions of the laboratory will depend on educational requirements, the available means, and the laboratory's expected use in research. Naturally, the design of the laboratory is an important task because it will impose conditions on the equipment to be installed, it will also determine its characteristics in relation to the aim, whether educational only, or educational and basic and/or technological research. Generally it will be worthwhile to combine the purposes, but too many technological uses will compete with the educational