Ecohydrology — seeking consensus on interpretation of the notion

The terms ecohydrology and hydro-ecology (also written as eco-hydrology and hydroecology) are now in common usage. A search on the Internet comes up with a plethora of related entries. There are university units, study courses, research projects, scientific conferences, and journal papers devoted to ecohydrology. There are several books with ecohydrology (or hydro-ecology) in the title and even a dedicated periodical: the International Journal on Ecohydrology and Hydrobiology, launched in 2001 (edited by Zalewski and Harper). Yet, despite dynamic recent activity in the area of ecohydrology, the notion does not necessarily mean the same thing to everyone. A number of competing definitions raise sensitivity and controversy among scientists and practitioners alike. This situation may confuse many a layman. Therefore, it seems worthwhile to extend the base of the consensus as to the interpretation of the notion "ecohydrology", and to strive towards more clarification and order (without detriment to creativity). As Editor of Hydrological Sciences Journal (HSJ), I took the initiative to promote an exchange of thoughts among experts actively involved in ecohydrol-ogy research, who may not necessarily agree as to the interpretation of the term. I circulated a draft background paper early in 2002 among a dozen or so scientists involved in ecohydrology research, with an invitation to react in the form of commentaries or short stand-alone articles. Positive reactions from most respondents to the idea of such a discussion endorsed my willingness to accommodate a Special Section on Ecohydrology in a regular HSJ issue. This Special Section contains five elements. After my background paper "Ecohydrology— seeking consensus on the interpretation of the notion", there are two discussions: "Is eco-hydrology one idea or many?" (Nuttle) and "Ecohydrology—a completely new idea? (Bonell). These are followed by two independent papers: "Ecohydrology: a challenging multidisciplinary research perspective" (Porporato & Rodriguez-Iturbe) and "Ecohydrology—the use of ecological and hydrological processes for sustainable management of water resources" (Zalewski). These articles, which I was delighted to read, were prepared simultaneously and contain no cross-references to each other. Even if experts do not necessarily agree on the details of the interpretation of the notion of ecohydrology, they seem to agree that the interface between hydrological and ecological sciences is a major research challenge. A question of much theoretical and practical importance is: How do hydrological systems control (and how are they controlled by) ecological systems? Ecohydrology, understood broadly as the science of bilateral interactions between water resources and …