Reconciling hydrology with engineering (Openning lecture)

Hydrology has played an important role in the birth of Science in the antiquity. Indeed, the first scientific problems, put and studied as such, were about hydrological phenomena. Yet practical hydrological knowledge existed before the development of natural philosophy and science. This knowledge had its roots in human needs related to water storage, transfer and management. The term “hydrology” did not exist in the ancient literature and appeared only in the end of the eighteenth century to describe a body of knowledge related to water, on the one hand, and meteorological, climatological and health issues, on the other hand. However, it was the close relationship of hydrology with engineering that advanced it in a modern quantitative scientific discipline. This relationship is testified even in the first books bearing the name “hydrology” in their cover. These books, published in the second half of the 19th century, contained hydrological observational information along with hydraulic formulae and tables. It was only in the 1960s that, owing to UNESCO, hydrology acquired a clear, elegant and practically unquestionable until today, definition as a science. This definition places it among the geosciences and does not explicitly recognize a link with engineering. Nonetheless, hydrology continued its interaction with engineering and its development was related to the needs of the design and management of water infrastructures. In the 1980s this interaction was questioned and it was emphatically supported that cutting the umbilical cord between hydrology and engineering would be beneficial for both. Thereafter, hydrology, instead of becoming an autonomous science, it developed new umbilical cords, becoming a subservient to politically driven agendas, including green and, particularly, climate-related politics. This change of direction was dictated by the research funding opportunities, which disfavoured the autonomous character of hydrology and narrowed its role, for example in studying hypothetical or projected climate-related threats. Several negative experiences from the developments in the last years may make us think that reconciling hydrology with engineering could help hydrology to land again from the virtual reality into the real world, where data and facts are more important than models and predictions are tested against empirical evidence. Engineering experience may help hydrology to appreciate that parsimonious macroscopic descriptions are more powerful than inflationary detailed ones and that holistic approaches are more effective than reductionist ones. A fertilizing field of mutual integration of hydrology and engineering could be the study of change and the implied uncertainty and risk, which we cannot eliminate yet we can live with and cope with, in a manner that can be, and needs to be, quantitative and rigorous.