Hydrology - A look back and a look forward, by S. Dumitrescu and J. N e m e c
This year the international scientific community is celebrating the Tercentenary of Scientific Hydro1ogy.Perhaps the date is chosen somewhat arbitrarily,for in the historical development of hydrology the year
1674
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in which Pierre Perrault published his book De l'origine des fontaines-
represents neither the very origin of hydrology nor the time of a comprehensive formulation of its basic conceptions.
conference recall the long history of the study of water resources and the many theoretical and practical contributions which finally led to the emergence of hydrology as a specific science.In this historical perspective Perrault's work, together with subsequent contributions by Mariotte and Halley,nevertheless constitute a milestone indicating the beginning of quantitative assessments of the water cycle which were essential for the further
development of hydrology.
the event we are now celebrating to assemble all the basic constitutive elements of
modern hydrological science.In fact,those related in particular to river and
groundwater hydraulics became available only towards the middle of the nineteenth century.From then on,an unprecedented development of water resources created a strong impulse for the progress of hydrology.
It was only during the last century that hydrology achieved definite recognition as an independent discipline.This gradual process was marked by several important advances :
landscape factors which determine the hydrological regime;
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abandonment of the empirical approach, which prevailed at the end of the nineteenth and beginning of the twentieth centuries and brought about a multitude of formulae through which engineers thought they could easily determine all the basic hydrological parameters required for various waterprojects
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progress in hydrometeorology,river and groundwater hydraulics which made i t possible to give a deterministic explanation of the various aspects of the hydrological regime;
Some of the papers presented to this
It still took about two centuries after
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better knowledge of climatic and-
development of multi-purpose schemes of water resources development within a river basin entailing the need.for a general hydrological background of the given basin, regardless of a specific use of water, thus separating the organization of hydrological investigations from the immediate needs of a specific project; development of hydro- logical services responsible for data collection and processing,warnings and forecasts of the hydrological regime;-
the application to hydrology of statistical methods,acceptance of the concepts of risk and uncertainties,which created a clear distinction between hydrology and traditional hydraulics and water engineering;-
development of experimental methods in hydrology which led to a more profound knowledge of the hydrological process.The consolidation of hydrology as a separate discipline was accompanied by the publication during the last five or six decades of a series of manuals of hydrology, thus recording the scientific progress which was being made,by the appearance of
specialized journals,and by the creation of hydrological research centres and .
institutes.
Analysing the present status of hydrology and forthcoming needs,one can identify a number of problems,both theoretical and practica1,which will influence its further development.
Firstly,the increase in empirical knowledge and in theoretical foundations, while contributing to the progress of a
science,always generates new problems and marks important crossroads,raising questions which are difficult to answer straight-
forwardly.Hydrology continues to develop as a geophysical as well as an engineering science.It is not easy,and perhaps not even desirable,to draw a line between the two, but solid bridges must be built between
them.The entry of pure mathematics and of systems analysis in stochastic or
deterministic approaches and the ease of finding numerical solutions by computer for theoretically formulated equations may lead either to the sterility of ivory tower, ''pure science'' theoretical exercises or to an enlightened,scientifically-founded and rapid advance for both earth and engineering scientists in the field of hydrology.
S. Dumitrescu and J. Nemec
This is not just a hypothetical development but a fact of 1ife.In many instances a dangerous gap is already being noticed between hydrological research and practice,both at the national and the international 1evels.Those who have attended some of the recent hydrological symposia,during which one part of the audience has lost communication with the other,can corroborate this.
On the other handythe most spectacular advances in hydrology during the last two decades were precisely due to the
introduction of stochastic concepts and mathematical models in genera1,which necessarily leads to a high degree of
"mathematization" of the hydrological scienceS.This is certainly nowadays a common feature of most sciences,but in the case of "natural" science like hydrology,a number of problems of principle have evolved.
Thus,a serious clash developed at a certain time between deterministic and stochastic interpretation of hydrological processes.
Although there are still disputes,for instance over the legitimacy of considering river flow sequences as a stochastic
process,hydrologists agree today on the need to integrate deterministic and stochastical approaches in hydrological investigations.
While the usefulness of further refinement of mathematical models used in hydrological calculation can no more be questioned,one should be aware of a danger inherent in mathematical abstraction,namely the loss
of physical meaning or ignorance of confidence limits.Physica1 research of hydrological processes should therefore necessarily accompany and guide development of any mathematical model used in hydrology.
specialized manp0wer.B~ extending to hydrology the well-known definition that
science is the activity performed by scientists,we must realize that we cannot talk about hydrological science until the specific profession of "hydrologist." is recognized.At present there are still very few universities in which hydrology is
taught as a separate field of specialization.
Therefore specialized hydrologists come mainly from neighbouring fields such as
civil or agricultural engineering,geology, other geophysical branches,geography,etc.
While a pluridisciplinary approach to hydrological phenomena is highly desirable,
Another critical problem is that of
it often occurs that people trained in other disciplines introduce certain
misconceptions to hydrology due to lack of comprehensive understanding of its specificity.
Still another crucial problem refers to the availability of hydrological data.
As mentioned above,there are no miraculous formulae to calculate the various hydro- logical parameters without a serious backgrour:d of direct measurements.Methods of artificial data generation have been developed especially during the last
10-15 years,but the pattern chosen for such generation can truly be established only on the basis of actual obseïvational data.The extension of water use,as well as the introduction of more sophisticated methods of hydrological calculations, require more and more observational data, while developing countries find it
difficult to develop even their basic hydrological networks in pace with the increasing needs.
logy as a science dealing with the natural hydrological cycle need to be radically revised,in the presence of increasing changes in water resources induced by human activities.Hydrology should
contribute to the solution of the crucial problems brought out by the present energy crisis and by the growing concern for the protection of the environment.
The hydrology of natural rivers becomes more and more a hydrology of water
systems as modified by man's intervention.
Influences of agriculture,urbanization and industrialization on the hydrological cycle should be taken into consideration, and not only as correctives to the natural water balancesbut also from the viewpoint of the creation of new hydrological environmentS.These changes in the water regime have implications for all aspects of hydrological investigations,including the structure and operation of hydrometric networks.In genera1,the role of hydrology is no longer limited to serve only as an initial input for water resources
deve1opment;without losing its individual- ity,hydrology becomes more and more
involved with water management.A particular case of the above-mentioned developments is the growing interdependence between water quantity and water quality.Without necessarily entering the technological
Traditional representations of hydro-
S. Dumitrescu and J. Memec
aspects of water pollution abatement, . hydrology has a major role to play in the studies of diffusion of pollutants in water media and of self-purification capacity of water systems,and in establishing the scientific basis for monitoring the quality of the water environment.
But here again a certain caution is necessary.The role of hydrology in the larger context of environmental protection and solutions to the energy crisis should not lead to a loss of its identity and detract attention from basic hydrological problems.The monitoring of pollution by sampling polluted water without any concern for the actual river flow,the development of new energy sources without taking into account the possibility of radical improvement of the operation of existing hydropower developments by means of real-time hydrological and meteorological forecasts,represent only two random
examples of losing sight of the forest because of the trees.
The growing gap between progress in the developing countries and in the rest of the world is perhaps the most important problem facing the world today.It is felt particularly acutely in the assessment and management of natural resources,and has thus special significance for hydro- logy and water resources.While the solution to this problem is still not in sight,hydrologists all over the world should constantly bear it in mind and, at least in their restricted field,work
together towards the solution of those relevant technical aspects which are within their reach and possibilities.
Fifty years ago the International Association of Scientific Hydrology was established as a first recognition of the need to develop international co-operation in this field.The need has increased greatly,especially during the last two decadeS.Several circumstances have combined to bring about this development:
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the water cycle,which is the main concern of hydrology,is itself a large-scale process and therefore its study requires an international effort;
techniques
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based among others on-
the refinement of measurementthe application of electronics and nuclear techniques,the use of remote sensing,as well as the introduction of new investigation tools such as models and the use of computers
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made necessary a better exchange of information between countries in order to generalize the most
promising procedures and to confront various methods and the results ob t ained
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after achieving independence,most developing countries were faced with the need to make better use of their natural resources,among which water played a major ro1e;water resources development in these countries was hindered by lack of hydrological data, due to absence or inadequacy of observational networks,ofinstitutional infrastructure and the necessary specialists.Internationa1 co-operation made a significant contribution towards overcoming these difficulties.
The above circumstances fostered international co-operative actions which were taken at intergovernmental level and resulted in the International Hydrological Decade sponsored by Unesco and the
Operational Hydrology Programme developed by the World Meteorological Organization.
The International Hydrological Decade contributed to the realization that hydro-
logy is a prerequisite for water resources development and to the diffusion of
hydrological knowledge throughout the
world.It also favoured a major international effort for the training of hydrologists which primarily benefited the developing countries.The basic objectives of the IHD will be pursued by the Unesco long-term
International Hydrological Programme to start in 1975.
WMO concentrates on the development of hydrological networkssthe improvement of data collection and processing,the
standardization of instruments and methods of observation,and on ensuring the supply of hydrological data for design purposes and the development of hydrological forecasting services.
wider perspective may also prove of some The Operational Hydrology Programe of
A
look back and a look forward in aS. Dumitrescu and J. Xemec
value in planning the international
programmes of the UN organizations and the international scientific community.The International Hydrological Programe of Unesco and the Operational Hydrology Programe of WMO were conceived on the basis of needs expressed by national authorities involved in international Co-operation.It is,however,obvious that such comprehensive programmes should represent something more than a mere collection of wishes expressed at the national 1evel.The character of the ad hoc actions taken in the past by different international organizations has responded perhaps to some of these wishes;nevertheless, a concerted effort by the international cornunity is required to achieve a
qualitative step forward that will enable balanced progress in the main directions outlined above. It is obvious that this effort basically coincides with national interests sinceyin the end,all international programmes are here to serve national
interests,but it is clear that all interests may not be accommodated in all instances by anyone programme which
operates necessarily with limited financial and human resources.The question remains as to how to prepare the scientific background of such programmes and to establish,on the basis of expressed national needs,the possible alternatives and the best ways of solving the problems.
Perhaps a small international group of specialists,both from scientific and operational backgrounds,organized in what may become an international institute for
hydroìogy,simi-lar C O centres already in existence for severak'important fields of natura1,social and economic sciences, could undertake such a task and permit the international programes in hydrology to be scientifically planned and documented.
The decisions on the contents of programmes do and will belong to governments and to bodies elected by them.It is,however,the duty of the scientists to help the
governments in the analysis and synthesis of all knowledge necessary for such decisions.
In the forthcoming years Unesco and WMO
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within the International Hydrological Programe and the Operational Hydrology Programme respectively-
as well as other international organizations inside and outside the United Nations systemswill continue to promote hydrology as a science, as an object of teaching and as a practical cictivity in the service of economicdevelopment,Technical assistance to developing countries will remain one of their basic components.
It is hoped that the celebration of the Tercentenary of Hydrology will inspire some fruitful meditation on the history,present status and future trends of this sckence.Holding it in conjunction with the International Conference on the Results of the International Hydrological Decade and on Future Programmes in
Hydrology will ensure that some of the conclusions will be used to extend and improve international co-operation in the field of hydrology.
Hydrology
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look back and a look forward, by''
DumitreSc" and J.Abstract
The reasons for celebrating the Tercentenary of Hydrology are recal1ed.A number of problems are identified,both theoretical and practica1,which may influence the further development of hydrology.The first and major problem is the development of a communication gap between hydrological research and practice.
The need to use physical research simultaneously with mathematical models is stressed.Another problem is that of
specialized manpower and of the recognition of the profession of "hydrologist". Still another crucial problem is the
unavailability of hydrological data;in particular,developing countries find it difficult to develop even their basic networks .
On the other hand,hydrology should contribute to the solution of the crucial problems brought to light by the present energy crisis and by the growing concern for the protection of the environment.The hydrology of natural rivers becomes more and more the hydrology of water systems as
modified by man.However,in this connexion,the need for maintainin&
S. Dumitrescu and J. Nemec
the identity of hydrology is stressed.But perhaps the most important problem remains the imbalance between progress in developing countries and progress in the rest of the world.
These problems and other circumstances have fostered internationa1,co-operative action in hydrology,initiated half a century ago by the establishment of the L4HS and later resulting,at the intergovernmental leve1,in the International Hydrological Decade sponsored by Unesco and the Operational Hydrology Programme of WM0.A concerted effort by the international community is needed to achieve a qualitative step forward in the planning and implementation of
international programmeS.This effort should basically coincide with national interestS.The scientific preparation of international programes in hydrology may be assisted by a centre similar to the international institutes already in existence for other sciences.It is hoped that the celebration of the Tercentenary of Hydrology will inspire meditation,and th t the conclusions drawn will lead to improved international c o k e r a t i o n in hydrology.
Hydrologie
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Bilan et perspectives, par S. Dumitrescu et J. Nemec RésuméLes raisons de la célébration du Tricentenaire de l'hydrologie sont rappelées ici.Un certain nombre de problèmes,à la fois théoriques et pratiques,susceptibles d'avoir une influence sur le développement futur de l'hydrologie sont évoquéS.Le premier problème très important est l'absence croissante de communi- cations entre la recherche hydrologique et ses applications.
La nécessité d'utiliser simultanément les recherches physiques et les modèles mathématiques est soulignée.Un autre problème est celui de la main-d'oeuvre spécialisée et de la reconnaissance de la profession d"'hydrologue".Le manque de données hydrologiques est également menti0nné;dan.s les pays en voie de développement en particulier on rencontre même des difficultés pour développer les réseaux de base.
de problèmes cruciaux mis en lumière par la présente crise de l'énergie et par l'inquiétude grandissante ressentie de protéger 1'environnement.L'hydrologie des cours d'eau naturels devient de plus en plus l'hydrologie de systèmes hydriques modifiés par 1 'homme.
de l'hydrologie est souligné.Mais le problème le plus important est sans doute le déséquilibre entre les progrès réalisés dans les pays en voie de développement et ceux réalisés dans le reste du monde.
Ces problèmes et d'autres circonstances ont favorisé le développement de la coopération internationale dans le domaine de l'hydrologie,qui a débuté il y a un demi-siècle par la création de 1'A.I.S.H. et qui a entraîné plus tard,sur un plan intergouvernementa1,la Décennie hydrologique internationale patronnée par l'Unesco et le Programme d'hydrologie opérationnelle de 1'OMM.Un effort concerté de la communauté internationale est nécessaire pour améliorer de façon substantielle la planification et la mise en oeuvre des programmes internationaux.Cet effort devrait coïncider fondamentalement avec les intérêts nationaux.
La préparation scientifique des programes internationaux en hydrologie peut être facilitée par la création d'un centre similaire aux instituts internationaux déjà existants pour d'autres sciences.11 faut espérer que la célébration du Tricentenaire de l'hydrologie portera à réflexion et que les conclusions tirées conduiront à améliorer la coopération dans le domaine de l'hydrologie.
D'un autre cÔté,l'hydrologie devrait contribuer à la solution
Cependant,dans ce contexte,le besoin de maintenir l'identité
S. Durnitrescu and J. ,Vernec
Hidrología
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Pasado y futuro, por S. Dumitrescu y J. NemecSe recuerdan las razones que justifican la conmemoración del Tricentenario de la Hidrologca Científica. Se determina una serie de problemas,teÓricos y prácticos a la vez,que pueden influir en el desarrollo aún mayor de esta ciencia.El primero y principal es la aparición de una brecha en la comunicación entre la investigación y la práctica de la hidrología.Ce insiste en la necesidad de utilizar simultáneamente la investigación física y los modelos matemáticos.
Plantean otro problema importante la mano de obra especializada y el reconocimiento de la profesión de "hidrÓlogo".También plantea un problema decisivo la falta de datos hidro1ogicos;en particular,los países en vías de desarrollo tienen dificultades en mejorar siquiera sus redes básicas.
problemas angustiosos que plantean la crisis actual de energía y la creciente preocupacion por la protección del medio.La hidrología de los ríos naturales se convierte cada vez más en hidrología de los sistemas hídricos modificados por el hombre. Sin embargo,a ese respecto,
s e hace hincapié en la necesidad de mantener la identidad de la
hidrología.Con todo,el problema más importante tal vez sea el del desequilibrio entre el progreso registrado en los paises en vias de desarrollo y el progreso en el resto del mundo.
Estos problemas y otras circunstancias han estimulado las
actividades cooperativas internacionales en hidrolog;a,que se iniciaron hace medio siglo al establecerse la AICH y más adelante dieron por resultado en el plano intergubernamenta1,el Decenio Hidrologico Internacional patrocinado por la Unesco y el Programa de Hidro1og;a Operacional de la 0MM.Se necesita un esfuerzo concertado de la comunidad internacional para dar un gran paso adelante en el planeamiento y la aplicacion de los programas internacionales.Esos esfuerzos deberían coincidir en lo fundamental con los intereses nacionales. Se confía en que la conmemoració'n del Tricentenario de la Hidrologia Científica haga reflexionar al respecto y que las conclusiones a que se llegue,
contribuyen a mejorar la cooperaci8n hidrológica internacional.
Resumen
Por otra parte,la hidrología debería contribuir a resolver los
S. Dirmitrescu and J. ivemec
