Disruption of the hydrological cycle

Disruption of natural water systems

Nature

Human activities may change various aspects of the hydrological cycle. Among other consequences this may contribute to climate modification over large areas of the Earth. Direct changes in in surface hydrology over large areas may occur as a result of changes in the vegetative cover or in the area covered by irrigation systems. Tropical deforestation results in significant modifications to surface hydrology, since any disruption in vegetative cover effects the water-storage capacity of the land and modifies the water supply. To the extent that runoff is increased, evapotranspiration is decreased, modifying the time and spatial characteristics of rainfall.

Background

The global significance of hydrological cycle disruption emerged in the mid-20th century, as large-scale dam construction, deforestation, and urbanization visibly altered rainfall patterns and river flows. Scientific concern intensified in the 1970s with evidence linking human activities to declining groundwater, increased flooding, and regional droughts. International research initiatives, such as UNESCO’s International Hydrological Programme, have since deepened understanding of the complex, far-reaching consequences of disturbing Earth’s water balance.

Claim

The world water cycle seems unlikely to be able to cope with the demands that will be made of it in the coming decades. Severe water shortages already hamper development in many parts of the world, and the situation is deteriorating.