Although Leonardo da Vinci is commonly considered as one of the greatest geniuses of our times, few people realize that his achievements went well beyond his outstanding paintings, his anatomical descriptions of the human body, or the development of new weapons and innovative concepts of warfare. His work covers a tremendous field of interest, indicating that he was guided by a strong desire to continuously push back the limits of our knowledge (White, 2000).
The past century, in particular, has seen considerable progress in hydrological sciences. In spite of this, hydrology is still a very young field of science. This is part of the reason why recently hydrologists have looked back and evaluated the most important progress that has been made over the past decades. These efforts may well be an expression of a desire to better understand where we stand today, and to redefine the strategies to tackle the challenges that lie ahead.
Recently, the IAHS launched a series of benchmark papers in hydrology under the editorship of Jeff McDonnell. The first issue in the series was compiled by Keith Beven and deals with benchmark papers on streamflow generation processes, essentially starting with the papers by Horton (Beven, 2006). In the light of this publication, it is interesting to look at hydrological literature that far predates the scientific journals of modern times. In this regard, the work of Leonardo da Vinci should be considered a benchmark in hydrology as well.
Indeed, while assessing where we have come from, we should not forget the work of Leonardo da Vinci, who may be considered one of the founding fathers of hydrology. This sets the origin of modern hydrology back to the sixteenth century. There are two good reasons to do so. Firstly, da Vinci's legacy contains a large number of writings that document his efforts to describe and understand the water cycle, the basis of hydrology. Secondly, he is an exponent of the Renaissance, a period where a clear paradigm shift took place from the dominant religion-centred paradigm of the Middle Ages to science centred paradigm, based on empiricism and deduction.
Leonardo da Vinci spent a lot of time trying to figure out what makes water circulate around our planet. His approach was clear and simple, as he himself stated, saying that 'whenever speaking about water, you have to keep in mind that you first have to invoke experience, before reasoning' (McCurdy, 1942). The experience could only be gained through the identification of relevant