Data collection systems and their impact on the future development of hydrology, by J. Rodda

Data collection systems and their impact on the future development of hydrology, by J. Rodda

Introduction

Hydrologists are aware that considerable advances have been made in recent years in hydrological forecasting, especially during IHD ( W O , 1969; W O , 1974).A range of methods has been devised for river flow forecasting, particularly through the use of mathematical models (Clarke, 1973; IAHS, 1974)'and a number of methods are now used operationally.

The situation is completely different as far as forecasting hydrology is concerned.

Few advances have been made in recent years and only a rudimentary methodology exists for forecasting the future of the subject.

any science, or trying to determine when major breakthroughs in technology are likely to occur, are not easy tasks at any time.In the current climate of economic uncertainty, however, and because of changes in relation- ships that have hitherto seemed unchanging, such fgrecasting is becoming increasingly difficult.Even if the trends with which we have lately been familiar continue into the future, there are those prophets of doom (Meadows et al, 1972) who interpret these trends to show that the collapse of our

expansionist civilization is imminent.In these circumstances it seems likely that attempts to foretell the impact of one facet of modern technology on the future of hydrology can have only a small chance of approaching what will really happen in the years ahead.

the future, this paper first considers the past and the attitudes towards instrument systems that have existed.Then examples of presently operating'advanced' systems are described.Finally some ideas are put forward about the likely trends in hydrology in the years to come, using these advanced systems as a guide to the future.

It is recognized that this threefold division is rather artificial and that in practice it is not possible to separate past, present and future.The 'past' phase of

instrumentation may be the 'present' in some countries, particularly (but not exclusively) the developing ones.In others, the traditional system may have been supplanted by a more modern network in certain areas.This raises problems of how to integrate the two components of a national network which are at different

technological levels, and, in the case of In fact, forecasting the advancement of

In common with other attempts to see into

developing countries, of how to plan the advancement of the countrywide network.

Should the traditional countrywide network be replaced or supplemented by the most advanced system currently available, or should some intermediate stage of instrument- ation be aimed at, which may equate more readily to the infrastructure of the country and the skills available7

Like most other scientists concerned with observing changes in the environment,

the hydrologist has been faced with an enor- mous problem.This problem was, and still is to a large extent, how to collect sufficient data to represent realistically the spatial and temporal variations in the phenomena that are scientifically important, in this case the hydrological phenomena.Faced with a lack of techniques for observing certain variables, the limited applicability of other

techniques, a reliance on observer-read

instruments and the need to integrate the date from them over large areas, it is not sur- prising that the hydrologist made slow prog- ress.0nly one medium existed for recording data and this made the system for collating, archiving and analysing very laborious and inflexible.When instruments were designed, they were usually not thought of as the 'front end' of a complete system, which also comprised data processing and storage modes, as well as those for data analysis and application.

trated from the field of precipitation,There is still the lack of a technique for

routine registration o € snowfall.There are still difficulties in measuring rainfall to any degree of precision, particularly where sites are over-exposed such as in mountainous areas, just the conditions where radar is most handicapped.There is still the fact that the majority of rain- fall measurements are obtained from gauges that are sited so that they minimize problems of access, rather than maximize the value of the information they produce.The various types of rain recorder mostly give chart records which are represented by back logs of unanalysed charts in a considerable number of archives.Indeed in one country where the archives contain a mass of rain- fall data, much going back for 100 years or more, only a few per cent of the value of these data has been realized by manual Some of these problems are well illus-

f. Rod&

methods ( W O , 1971).The same state must apply in a number of other countries and to other hydrological data.Automatic scanning techniques are now being applied to rain recorder charts; a similar device is needed to transform the manuscript rainfall data sheets into a form suitable for machine processing.

The present

Today the concept of the integrated data collection system is gaining acceptance and more and more examples of these systems are coming into use.They range enormously in their complexity,Some consist of a single device which continuously gathers and stores measurements of one variable on site, for later removal of the record to and pro- cessing at base.0ther systems regularly obtain enormous amounts of information from vast areas and transmit it to one or more base stations.There the information passes through various stages: quality control, processing, analysis, publication and application before finally reaching the archives (Fig.l).Preceding these stages are those of network design and network operation ( W O , 1974b).

The practice of publishing hydrological data in year books is widespread:some

national year books contain long series o f daily observations of discharge, rest water level,precipitation, water temperature and like phenomena.For example, the Hydrological Year Book for Hungary dates back to 1876.

Now more countries are publishing references to libraries of material available on tape and microfilm and increasing use is being made of the hydrological map as a vehicle for publication.Canada is an example of a

country where hydrological maps are being exploited to a considerable degree.

not be solely concerned with station-type time series observations .More and more information is being obtained by surveys and question- naires and by regular returns of census-type data.The latter are particularly important where information on water use and costs is assembled annually for analysis, for example by the government department concerned with the national water manage- ment programme.Information about recreation

Of course, data collection systems need

and amenity aspects of water is becoming increasingly important i n those countries where there is competition between different

leisure users of the water space, for inst- ance between water skiers and anglers.

Improved knowledge of the visual and environ- mental aspects of the riverscape (Leopold

& Marchandm 1968) is being sought for environmental protection and planning purposes, as well as for water management:

the physical and chemical characteristics of a river and the immediate surroundings, its ecological features and its features important to man are significant in this context (Langbein, 1972a).

During the course of the Decade considerable progress has been achieved in the development and use of innovative data collection systems.The status of systems employed in representative and experimental basins has been carefully catalogued by Toebes and Ouryvaev (1970), while the WMO Working Group on Instruments and Methods of Observation gave examples of automatic equipment for observing and transmitting data ( W O , 1973a).This paper now examines several examples of data

collection systems that are the likely fore- runners of systems that will come into widespread use in the future.

a) The Thetford Project: an on-site data This project is designed to establish the detail of the evaporative characteristics of Scots pine through the use of a computer- controlled data acquisition system and the development of a simulation model of the processes involved (Institute of Hydrology, 19711.A stand near the centre of the largest British forest in a flat area was chosen for this project, two 30 m high towers were erected (Fig. 2) together with two smaller ones and housing for the computer, equip- ment and staff.

aspirated quartz crystal wet and dry bulb thermometers at various levels (Institute of Hydrology, 1973) and the other aupports lightweight anemometers and wind vanes (Oliver and Oliver, 1973).The smaller towers carry net radiometers and upwards and downwards facing solarimeters above the canopy, while more of these instruments are mounted below the canopy and there are

collection and processing system

One of the 30 m towers carries pairs of

FIGURE

Schematic chart of the major elements of hydrological data acquisition, transmission and processing systems.

COMMUNICATION

MICROWAVE RADIO TELEPHONE TELEGRAPH MAIL MESSENGER

I I I I OBSERVING

MEASURING I I I

I I STOR IN G c-

V

DISSEMINATING

INTERNAL AND EXTERNAL TO THE COLLECTING AGENCY

-

I

DECISION MAKING

RESOURCE EVALUATION RESOURCE DEVELOPMENT RESOURCE MANAGEMENT

I I I I

A

REDUCTION SYNTHESIS COMPUTATION MANIPULATION

A I I I

----J

EXPLANATION

DATA FLOW

ICOMMUNICATION)

-

PLANNING AND

PROGRAMMING ^~

- - -

AREA OF MUTUAL INTERESTTO THE DATA PROCESSING AND DATA ACQUISITION ACTIVITIES

DISSEMINATION

PUBLICATION MICROFORM PRINTOUT MANUAL OUTPUT MACHINE COMPATIBLE

FROM Whststone G W. and Gwriw y J. 1972 ïi@roiogi Information Systems”

UNESCO/WMOSîudesand Reporisin Hydrology 14 72p

FIG. 3 Flow Chart for data co!lection arid analysis for the experiment in Thetford Forest, United Kingdom.

EVAPORATION FROM FORESTS

MLTEOROLOGICAL INSTRUMENT4TIf2N

FIRST STAGE ANALYSIS BOWEN RATIO & EVAPORATION

CALCULATIONS

.

I t

BASIC EVAPORATION RESUITS FROM

I

1 I I

SECOND STAGE ANALYSIS RESISTANCES AERODYNAMIC VALUES etc BOTANICAL

c I ^I

EVAPORATION & TRANSPIRATION

DATA FROM OTHER SITES

M E T E O R O L O G I C A L A N D BIOLOGICAL

i

FIG. 2 Instruments Towers in Thetford Forest, United Kingdom

PREDICTIVE MODELS FOR EVAPORATION & TRANSPIRATION

FOR FORESTS & OTHER AREAS

J. Rodda

soil heat flux plates in the litter layer.

The thermometers are divided into two sets, one on either side of the mast: data are selected once a minute from the upwind set.

Wind run is registered each hour and radiation every 15 seconds.

The computer collects observations from a total of 110 sensors, applies calibration factors and outputs five-minute averages on paper tape for later verification (Fig.3).

Hourly averages are listed and profiles drawn automatically so that faults become apparent and can be rectified.The system is usually operated for periods of 48 hours or longer and the data used to compute 20- minute averages of available energy, the Bowen ratio and evaporation (Stewart and Thom, 1973).

b) Snow survey by satellites: use of remote Information about snow, its extent, depth and water equivalent is usually very difficult to obtain by conventional methods.Because

satellites seemed to offer a unique means of obtaining at least some of this information

through the use of photographs and sensors of various kinds, WMO launched a cooperative study of this topic in 1968.After a preliminary survey of Members, seven countries agreed to participate in the study which was largely based on the United States satellites of the Tiros, Nimbus and Essa series and the U.S.S.R.'s Meteor satelliteS.Both the United States and U.S.S.R. satellites carry television cameras and infra-red sensors, the ground resolution of the television pictures being from 3 to 4 Km and between 1 and 2 Km respectively

(WM0,1973b).

taken in several contrasting areas to determine how precisely the limits of the snow cover could be 1ocated.It was found that the presence of clouds, vegetation contracts and a n u m b e r of other factors caused complications in interpreting the phot0graphs.h flat terrain, the edge of continuous snow cover could be located to within 20 Km of the true ground positi0n.h mountainous regions the position of the snow line could be fixed to within 150- 200 m of the ground truth.Severa1 countries supplied information on the use of densito- meters for analysing the photographs and on processes used to convert photographs into a digital form.The use of infra-red sensors was

sensing

Using these pictures, studies were under-

mainly to determine snow surface temperatures and to detect the presence of melting snow.

c) The Dee PPoject: a computer-controlled data acquisition

and

The operation of reservoirs for flood allevi- ation on the one hand and water supply on the other can be diametrically opposed:

management strategies have to be carefully planned for a basin where river regulation is practised.In the case of the Dee a regulating reservoir, a regulated lake and a direct supply reservoir are being used to control the flow of 5he river at Erbistock (Fig.4).

Some 1040 JSm of the basin lies upstream of Erbistock and it contains a network which transmits rainfall, water level and evapora- tion measurements to the control centre.There a computer interrogates each station at half- hour intervals (Water Resources Board,1972).

A long-term control strategy is required for water supply purposes: a short-term strategy is needed for flood alleviation.

The latter defines the optimal releases from the reservoirs during critical periods (Jamieson, 1972) : the operation of the sluices depends on forecasts of future flow sequences derived by a similation model (Jamieson and WilkinsonYl972).This model employs the telemetered water levels to define initial conditions; it acts on rainfall amounts to forecast flows in the tributaries, routes and flows through the reservoirs and down the main river channel.

the operation of the sluice gates froms the on-line processor for the data input from the instrument network to the computer.

The existing manual operation of the sluice gages could ultimately be replaced by on- line control by the computer.

In order to prove the use of radar for operational areal rainfall assessment and improve the input to the simulation model, a radar has been installed on high ground at the downstream end of the basin (Harrold et a1,1973).In the real time system being installed in 1974 the radar data will be processed by an on-line computer.The radar will be calibrated in real time against one telemetering raingauge in the centre of the basin and compared with a network of 60 magnetic tape recording gauges installed flush with the ground.In comparing the two

The short-term control strategy deciding

FIGURE

Phase 1 and proposed phase 2 of the telemetry scheme.

rainfall measurements

e

^'

o

\z

-

O 5 10 15 o+O P H A S E 2 potential evaporation measurements

1 ,

O 5 10 -*..** L A N D LINE

MILES

RADIO LINK

FIGURE

Location of U.S. Geological Survey water-quality monitor sites in the Delaware River basin.

Water-quality monitor sites:

1 Delaware River near 7 Schuylkill River at 2 Delaware River at 8 Delaware River at 3 Lehgh River at 9 Delaware Rwer at 4 Delaware River at 1 O Delaware River at 5 Delaware RNer at 1 1 Delaware River at 6 Delaware River at

Philadelphia, Pa.

East Stroudsburg, Pa.

Easton. Pa. Chester, Pa.

Easton. Pa Delaware Memorial Bridge

Bristol, Pa.

Torresdale. Philadelphia, Pa.

Benjamin Franklin Bridge

Reedy Island Jetty, Del.

Ship John Shoal Lighthouse

25 50 MILES

O 40 io KILOMETRES

85

J. Rodda

estimates of rainfall so far, it has been found that in 326 separate comparisons of 3 hourly totals only 22 have differed by more than 20% and 1 mm.Flow forecasts for one sub-catchment employing the two sets of estimates show that a considerable degree of reliance can be placed on the radar- derived measurements of rainfall.

d) The Delaware Basin

-

Because this time lag i s unacceptable to the agencies managing the basin, two of the stations were equipped with line telemetry.

To provide ip more complete picture of the state of the basin all eleven water quality stations (Fig, 5) and other hydrometric stations, a maximum of 20 in all, were equipped with radio telemetry.Besides the information on quantity of water, observa-

tions of dissolved oxygen, temperature, conductivity and pH are transmitted to ERTS-A during the period when the stations,

the satellite and the acquisition site (Greenbelt Md) are mutually visible (Paul- son,1971) .Such a period exists for 10 minutes once every 12 hours when between 4 and 7 data messages can be transmitted and received.These data are processed at Greenbelt and forwarded by teletype to the local office on the Delaware River for screening and dissemination.

ground stations worked satisfactorily and for most of the time at least one message was received from each station per 12 hours

(Paulson,l973).The data relayed to Delaware office are processed remotely on a large computer i n Washington.For operational fore- casting of quantity and quality an on-line dedicated computer would be necessary.

of data collection system that are becoming more widely used in hydrology.0ther systems could be added to the list, for example considerable use is made of advanced methods of data collection i n the Soviet Union and particular attention has been given to the automated processing of data (Grigor'ev and

collection system

When the network commenced operation the

These are just four examples of the types

Lesnikova,l971).A number of countries have developed telemetering systems which are employed on a routine basis.The Hungarian Hydra II is one such system;it has been developed to collect information from up to 32 observing stations within a radius of 50 Km of the central station (Puskas and Karsai ,1973).

from the attributes of these systems?What special features are indicative of forth- coming trends in hydrology?One obvious characteristic of all these systems is their complexity: increasing sophisitication implies greater capital costs and greater maintenance costs.More time and skill will have to be devoted to their upkeep which will in turn require more technicians: more attention will have to be given to determining the value of the information these systems produce.Coct/

benefit techniques will help to show how much automation is needed as well as how much can be afforded.High costs also point to the need for international collaborazion so that countries may share facilities.

hydrological processes, it is very likely that systems will be required similar to that set up in Thetford Forest.Such systems will incorporate improved sensors, especially

for water quality monitoring, and on-line computers to control data acquisition and for data processing.To improve the use of operational methods, it is probable that ground-based telemetering systems and systems employing satellites will become more numerous in the future.Greater reliance for operational purposes will be placed upon techniques which can integrate areally such as radar.

a widening range of data:for their collection computers and satellites are becoming increasingly important.Five ,

aspects of the quality of these data ise assuming considerable significance:

amassing a large quantity of data is no longer seen as an end in itself.Reliability concerns the degree to which the measurement approaches the true value.Representativeness involves the adequacy of the relationship between point and areaalvalues.Impartiality

(LangbeinYl972b) relates to the bias that may be introduced unknowingly by the agency collecting the data, a bias towards the

What clues to the future can be detected

To improve the basic knowledge of

Hydrology is currently concerned with

J. Rodda

agency's own responsibility.Relevance

concerns the balance between data collected Íor currently urgent problems and data

collected for future as yet unknown problems, the former at the expense of the latter.

Continuity hinges on the fact that most hydrological data are time series; as such they are at risk at times of stress, for example during war, natural disaster, financial stringency and organizational change.

The future

Measurement of the progress of a science is not an easy task; advancement is never continuous but rather a series of break- throughs and periods of consolidation.

Sherman's work on the unit hydrograph was probably the breakthrough in the 1930s, followed by Gumbel's application of the extreme value theory and the studies of evaporation of Thornthwaite and Penman a decade or so 1ater.It is likely that the 1950s was a period of consolidation, a period which terminated when computers came into widespread use in hydrology, a little before the start o f the Decade.Perhaps the 'computer revolution' and the application of satellites will be classed by future historians as the breakthrough of the century as far as hydrol~ogy, meteorology and like sciences are concerned.

The likelihood is that hydrology will consolidate these gains during the next 20 to 30 years and that data collection systems similar to those described will come into widespread use.During this period much of

the progress of the science seems likely to hinge on the improvements made to instru- ments and methods of data collection.This probably applies to both the furtherance of

the understanding of hydrological processes and to advancement of operational models used for forecasting purposeS.In fact,methods of forecasting seem to be presently limited more by the quality of the data employed in them than the lack of verisimilitude in the models employed.The use made of satellites

and other vehicles for remote sensing will depend very largely on these improved instruments producing the ground truth for the different images.Geostationary satellites (Flanders and Schiels,1972) will come into

routine use for relaying data to central forecast offices for real time modelling, There will be a need for information services to provide listings of hydrological data banks and resumes of what they hold, as well as details of simulation models and other methodological matters.

More data will be sought of a type that can be employed for planning and management decisionS.This applies not only to data o n river flows, evaporation and so on, but also to data on water costs and water use,

Information o n the damage costs of floods, droughts, erosion and pollution also comes into this category as does information o n the merits and demerits of proposed water resources schemes, such as a major dam in an area of natural beauty.

wider than the confines of science and engineering.What part has the hydrologist to play in determining the future of

civilization?Is the present perood of rapid growth of population and industrialization an ephemeral feature

-

These are long-term problems and the author is not brave enough to predict their outcome.

Hydrology exists in a world that is

Aeknow Zedqements

The author wishes to express his gratitude for the assistance he has received in the preparation of this paper to Mr. A. Flanders, U.S.Nationa1 Weather Service, Messrs.M.Hackett and A.I.Johnson,U.S.Geological Survey,

Dr.D. Harding,University College,Swansea, Dr.T.Harrold,Meteorological Office,Bracknell, Mr.D.Newsome,Water Resources Board,Reading, Dr. J.S.G.McCulloch,Dr.R.B.Painter,Mr.J.B.

Stewart,Mr.I.Strangeways,Institute of

Hydrology, and his colleagues in the Depart- ment of the Environment.

References

Clarke,R.T. 1973,Mathematical models in hydrology. FAO Irrigation

&

J. Rodda

Flanders,A.F., Schies1,J.W. 1972. Hydrologic data collection via geostationary

satellite. IEEE !?'ratzsactions on Gsoscience EZectronics,vol.GE-10, p.47-51

Grigor'ev,V.I., Lesnikova,G.V. 1971. Methods of automated control and processing of hydrological observations.Report of meeting of bads of water resource

management bodies of CHEA member countries,

M08COW, 1970.

1973. The Dee Weather Radar Project, the measurement of area precipitation using rada. Weather, v01.28, p.332-338.

IAHS, 1974. Proceedings of the symposium on mathematical models in hydrology. Gent- brugge, IAHS (Pub. no. 100).

Institute of Hydrology. 1971.Research 1970-71.

Wallingford.

Institute of Hydrology. 1973.Research 1972-73.

Jamieson,D.G. 1972. River Dee Research Program Harrold,T.W., English,E.J., Nicho1ass.C.A.

1.ûperating multi-purpose reservoir

systems for water supply and flood allevia- tion.Water Res.Research,vo1.8,p.899-903.

Jamieson,D.G.,Wilkinson,J.C. 1972. River Dee Research Programme 3.A short term control strategy for multipurpose reservoir systems.Water Res.Research,vo1.8,p.911- 920.

Langbein,W.B. 1972a. Riverscape inventory and river environmental surveys.In:

Langbein

,

Langbein,W.B. 1972b. Water data today and in prospect .Hydmlogäoal Sdencee Bulletin, Leopold,L.B.,Marchand,M.L. 1968. On the quanti-

vo1.17,p.369-385.

tative inventory of riverscape. Water Res.

Research,vo1.4,p.709-717.

Meadows,D.H.,Behrens,W.W. 1972.Meadats D.L., Landers J, and The Limits to Growth, New York,Universe Books.

Oliver,S.A.,Oliver,H.R. 1973. A computer method for automatic acquisition of wind speed data. Physics, E6 ,p .401-403.

Paulson,R.W. 1971. The role of remotely sensed and relayed data in the Delaware Basin.U.S.Geotogica1 Survey Prof. Paper 7 5 0 - ~ , ~ . ~ 1 9 6 - C 2 0 1

Paulson,R.W., 1973. Preliminary analysis of ERTS

-

Puskas,T.,Karsai,H, 1973. Hydra I 1 . h automa- tic digital telemetering system.IASH/

UNESCOh3íO symposium on hydrometry, Coblena 1970,vol. 2,p. 717-721.Pari8,

Unesco.(Studies and Reports in Hydrology, No. 13).

Stewart, J.B., Thom,A.S. 1973. Energy budgets in Pineforest.Quart. J.Roya1 Met.Soc., v01.99,p.154-170

tive and experimental basins

-

national guide for research and practice.

Paris,Unesco. (Studies and reports in hydrology ,4.)

Water Resources Board.1972.The Dee Research Programme .Appendix E,Eighth annual report of the Water Resources Board for the year ending 30 September 1971.

H.M.S.O.,London.

325p.(Tech.note.no.92).

logical data,Geneva,WM0,79p.(Tech,note no.115).

WM0.1973a.Automatic collection and trans- mission of hydrological observations.

Geneva,WM0,69p.(Operational hydrology report no. 2).

WM0.1973b.Snow survey from earth satellites.

WMO/IRD Project Report No.l9,42p.

WMO.1974a.Hydrological forecasting.A report prepared for the End of Decade Conference- WM0.1974b .Hydrological data acquisition,

transmission and processing systems. A report prepared for the End of Decade Conference.

Toebes,C.,Ouryvaev,V.(ed.) 1970.Reprseenta-

WMO

.

J. Rodah

Data collection systems and their impact on the future development of hydrology.

by J. Rodda Abstract

In the past the concept of systems for data collection was largely foreign to hydro1ogy:an instrument was not regarded as the "front end" of a system for collecting,processing,storing,analysing and applying data.Too little attention was given to the value of the information produced by the instrument and too much to the analysis of that information.Errors resulting from the instruments themselves, faults in their distribution and in the processing and storage of data were rarely taken into account in the various methods of analysis.

integrated data collection systems is becoming accepted.More and more examples of such systems are coming into use in hydrology They range enormously in compiexity.Some systems collect,store and sometimes process one variable on s1te:e.g.automatic weather stations,automatic water quality stations,and some transmit to a control base by land Ifne or radio.Satell1te-based sensors regularly transmit images of various types to ground stations for processing and analysis.As more and more systems of this sort come into use more and more real time data will become available for analysis.Examples of the following types of systems are descr1bed.a) an automatic weather station and its use;b) a basin instrumented and operated from real tims collection of data on rainfalls (using radar),water levels,evaporation;c) satellite- based systems such as ERTs and G0Es;d) a basin instrumented and operated for collection and processing of water quality data.

them that will come into more widespread use in the future.

analysis and methods of data collection will be narrowed.More flexible and more reliable instrument systems will come into use,to provide a wider range of data,more frequently and from moro sites than hitherto for its use in real time.More use will be made of imaging systems and various types of data obtained from surveys and questionnaires.More data will be sought of the type from which management decisions can be made.5pecific reference is made to needs for new data on:water equivalent of snow,actual transpiration, water quality,including the chemical and biological characteristics of riverS.The need to collect data on an economic nature is also referred to,particularly information about water costs and water use.Although not necessarily dependent on instruments for its collection,reference is made to the need for data on the amenity and leisure use of water,particularly those where decisions have to be made about alternative uses.

The situation at present is rather d1fferent:the concept of

Such systems are given as the forerunners of the systems like In the future the gap that now exists between the methods of

Les systèmes de collecte de données et leur incidence sur l'avenir de l'hydrologie, par J. Rodda

R L;szmd

Autrefois,le concept de "systèmes de rassemblement de données"

était largement ignoré des hydro1ogistes:un instrument n'était pas considéré comme le premier maillon d'un système de rassemblement,de traitement,d'archivage,d'analyse et

d'application de donnécs.0n n'accordait pas assez d'attention à la valeur des informations produites par cet instrument, et on en donnait trop à l'analyse de ces informationS.Les erreurs résultant des instruments eux-mêmes,les lacunes dans leur répartition et dans le traitement et l'archivage des données n'étaient que rarement prises en considération dans les diverses méthodes d'analyse.

La situation actuelle est quelque peu différente:le concept da "systèmes intégrés de rassemblement de c o n d e s " commence à être accepté.Des exemples de plus en plus nombreux de ces systèmes sont maintenant utilisés en hydrologie.Leur complexité est extrêment variable.Certains d'entre eux rassemblent,emmagasinent et parfois

traitent sur place une seule variab1e:par exemple,les stations météorologiques automatiques,les stations automatiques de surveillance de la qualité des eaux,et certains les transmettent à une base centrale par fil ou par radio.Les capteurs installés

sur satellites transmettent régulièrement divers types d'images à des stations au so1,en vue de leur traitement et de leur analyse.Au fur et à mesure de la mise en service de nouveaux systèmes de ce genre,on dispose de plus en plus de données "en temps réel" pour 1'analyse.Quelques exemples de ce genre de systèmes sont décrits: 1) une station automatique météorologique et son utilisaion;2) un bassin équipé et exploité pour rassembler

"en temps réel" des données sur la pluie (en utilisant le radar), les hauteurs d'eau et l'évaporation;3) des systèmes installés sur satellites,tels que les ERTS et les GOES;4) un bassin équipé et exploité pour le rassemblement et le traitment des données sur la qualité de 1'eau.Les systèmes indiqués ci-dessus ne sont que les précurseurs d'autres systèmes analogues dont l'emploi tendra à se répandre de plus en plous dans l'avenir.

La lacune qui existe actuellement entre les méthodes d'analyse et les méthodes de rassemblement des données se comblera dans l'avenir.

Des systzmes comportant des instruments plus souples et plus sûrs seront mis en exploitation,pourfournir,plus fréquemment et en provenance d'un plus grand nombre de stations que jusq'à maintenant.une gamme plus étendue de donnéeS.en vue de leur utilisation immédiate.0n fera davantage usage de systèmes de transmission d'images et de divers types de données obtenues à partir d'enquêtes et de questionnaires.

On cherchera à obtenir de plus nombreuses données du type permettant aux organes de gestion de prendre des décisions.L'auteur examine particulièrement les besoins en nouvelles données sur:l'équivalent en eau de la neige,l'évapotranspiration réelle,la qualité de l'eau, y compris les caractéristiques chimiques et biologiques des cours d'eau.11 traite également de la nécessité de. rassembler des données de natureéconomique,et en particulier des informations sur le coût et l'utilisation de l'eau.11 examine ensuite,bien qu'il ne faille pas nécessairement des instruments pour les rassembler, les besoins en données concernant les utilisations de l'eau pour les activités d'agrément et les loisirs,et surtout lorsqu'il s'agit de prendre des décisions impliquant un choix entre diverses utilisations.

LOS sisteinas de acopio de datos y En el pasado el concepto de sistemas de concentracion de datos sus repercusiones en el futuro era en gran parte ajeno a la hidro1ogia:un instrumento no se desarrollo de la hidrología. consideraba como la "entrada" de un sistema de concentracion, por J. Rodda procesamlento,archivo,an~lisis y aplicación de datos.se prestaba

escasa atenci6n al valor de la información presentada por el instrumento y demasiada,al analisis de esa 1nformación.Era

R ~ > S U I I I P I I poco corriente que los errores debidos a los propios instrumentos

y a fallas de su distribuciôn se tuvieran en cuenta en los diversos métodos de análisis.

el concepto de sistemas integrados de concentración de datos y cada vez hay mas ejemplos de la utilizaciÓn de esos sistemas en hidrologfa.El grado de su complejidad varia enormemente.Algunos sistemas reunen,almacenan y a veces elaboran una variable sobre el terreno como por ejemplo,las estaciones meteorológicas automáticas ,las estaciones automáticas para determinar la calidad del agua,y algunas transmiten información a una central por radio o líneas de comunicacion terrestres .Los aparatos de percepción instalados en satélites transmiten regularmente imageries de diversos tipos a estaciones terrestres para que éstas las procesen analicen.Conforme se vayan empleando m'as sistemas de este tipo,se obtendrán y podrán analizar más datos de tiempo real.Se describen ejemplos de los siguientes tipos de s1stemas:a)una estación meteorológica automática y su uso;

b) una cuenca dotada de instrumentos y explotada para concentrar datos en tiempo real sobre la precipitecion (con empleo de radar), los niveles del agua y la evaporaci6n;c) sistemas instalados en satélites.como los de ERTS y G0ES;d) una cuenca dotada de instrumentos

La situación actual es completamente dist1nta:se va aceptando

J. Rodda

y explotada para concentrar y procesar datos sobre calidad del agua.

análogos que se utilizarán mas ampliamente en el futuro.

entre los métodos de analisis y los métodos de concentracion de datos.de podran emplear sistemas con instrumentos mas flexibles y fiables para obtener una gama mas amplia de datos em tiempo rea1,con más frecuencia y a partir de mas emplazamientos que hasta ahoramSe hará mas uso de los sistemas de reproducción de imágenes y de diversos tipos de datos obtenidos a partir de encuestas y cuestionarios.Se procurara conseguir datos de los que permiten adoptar decisiones.de hace una referencia concreta a la necesidad de nuevos datos sobre el equivalente en agua de la nieve,la transpiración real y la calidad del agua,

incluidas las Características quimicas y biologicas de los rios.Tambien se hace alusión a la necisidad de reunir datos de caracter econÓmico,y en particular de información sobre

los costos del agua y el empleo del agua.Se hace asimismo referencia a la necesidad de datos sobre la utilización del agua para fines de recreo y esparcimient0,bien que su concentración no depende forzosamente del uso de instrumentos,sobre todo cuando hay que optar entre diferentes usos posible.

Esos sistemas se presentan como los precursores de los sistemas En el futuro se reducirá la diferencia que existe actualmente

J. Rodda

M M c M 3 0 6 p a x e ~ M f f ~ ~ , n namine p a s a n s ~ o r o X a p m T e p a , n o a m a e -

M Y noncica 60~1bmero KoanrlecTBa A a H H H x T a K o r o X a p a m e p a , H a M u e H a O C H O B e o6sopa M B O I Q O C H M K O B . B y A y T IIPHMBHffTbCff CYICTe- O C H O B B K O T O P H X M O X H O 6 y A e T B H H O C H T b p e m e H H a IiO BOlTpOCaM YIlpâBJIeHMñ H 3KClIJIyaTâqMH. K O H K p e T H a f f CCHJIKâ AeJIâeTCff H a H m B H O B H X A a H H H X , a M W B H H O : BOAHhlfi 3 K B M B a H e H T C H e r a , @a- KTHrleCKaff 3BaIlOTpaHCnMpaqMff, KC89eCTBO BOAH, B K P P 9 a R X L W M 4 e C - K a H a H e 0 6 X O A K K O C T b B cóope A a H H H X 06 3KOHOM4rleCKHX aCìTeicTaX,

B 9 a C T H O C T M , H a MH@OpMaIJLID OTHOCMTeJIbHO C T O M W O C T M BOAbI M MC- lIOJIb30BâHMff B O A H . neJIaeTCSI CCHJIKB , XOTff L4 He06ff3BTeJIbH0, B 3aBMCM)AOCTM OT IipM60pOB AJIff c6opa AaHHblX, H a H W Y B d a H H H X OTHOCMTeJibHO MCIIOJIb30BaHMSI B O U AJiff MepOIlpHffTML?, 3Bff3âHHhlX C O T W X O M W BpeMffllpOBOXAeHMeM H a BOAe, B P B C T H O C T M , B T B X CJIyYaffX, K O r A a JlOJIXHH BHHOCLITbCff peDieHMff 06 a J l b T e p H a T W B a X MCiiOJIb3OBâHMff B O A H .

~ y p 5 n 6~0~1ornrlec~yp3 x a p a r e T e p n c T m n p e K . T a x e AesaeTcff cem-