The influence of hydro-climatological balances and Nature-based solutions (NBS) in the management of water resources

. This article offers a historical review of (cognitive) scientific research that demonstrates the development of key concepts relating to balances in the hydrological and hydro-climatic cycles, thereby supplying a basis for quantitative and qualitative assessment of renewable water resources. The review reveals the direction knowledge took as it developed through successive cognitive and applied stages. The emphases are on how global and regional hydrological conditioning underpin integrated concepts for the management of water resources. The primary aim of this article is to describe the main achievements, approaches and scientific initiatives, along with their theoretical underpinnings, in the hope of encouraging application and further appreciation. 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 various economic, social and ecological activities. 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 initiatives, scientific issues, and concepts that have been espoused by international organisations and illustrate the increasingly essential harmonious use of water resources at local, regional, continental, and planetary scales. Relevant global conferences have demonstrated wide readiness to adopt declarations, or to issue appeals and resolutions, in support of fuller assessment of renewable water resources. Examples of excessive use have been identified, and efforts have been made to counteract both floods and deficits, and hence avoid crises. These deliberations have also stimulated long-term forecasting, for periods up to 2030 or even 2050. Also stressed here are the challenges, inspirations, and achievements of pure and applied science when it comes assessing the risk that the Earth’s potential to supply water resources will be exceeded. The suitability of current assessments of water resources is evaluated, and reference made to ecologically-integrated answers such as 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).