Abstract: This article offers a historical review of (cognitive) scientific research that demonstrates the development of key concepts relating to the hydrological and hydro-climatic cycle as well as balances, with these in turn offering a basis for the quantitative and qualitative assessment of renewable water resources. Work referred to here produced results revealing the direction knowledge took as it developed through successive cognitive and applied stages. Emphasised in particular are global and regional hydrological conditioning underpinning integrated concepts for the management of water resources. The primary aim of this article has nevertheless been to describe the main achievements, approaches and scientific initiatives, along with their theoretical underpinnings, in the hop that both application and further appreciation will be encouraged. Attention is thus paid to milestones along the road to global development, as manifested in the (at-times abruptly changing) effort to better assess and understand the use of water resources in different economic, social and ecological activity. And here again, the aim is first and foremost to encourage the achievement of sustainable development as humankind’s main hope for the future. A further focus is on important and justified initiatives, as well as scientific issues and concepts, that have been espoused by international organisations and denote the more and more essential harmonious use of water resources at the local, regional, continental and planetary levels. The suitability of current assessments of water resources is indicated, and reference made to ecologically-integrated answers like the so-called Nature-based Solutions (NbS), as backed by the UN and UNESCO (2018); in combination with principles set out in the EU’s Water Framework Directive (2000/60/EC).