Author(s): Roberto Ranzi
Linked Author(s): Roberto Ranzi
Keywords: Climate change; Hydrology; Red River; Afforestation; World population
Abstract: The hydrological cycle is far from being a stationary process and always experienced changes in the past. In recent years it seems that both climate and anthropogenic factors are accelerating the variability of meteorological and also hydrological processes. Starting from examples and long-term data on processes influencing coastal dynamics in the Red River (China-Vietnam), it will be shown first how anthropogenic factors, as reservoir impoundment, can dramatically reduce up to 80% , on average, of suspended sediment load downstream. Another anthropogenic factor, as land-use change may increase suspended sediment load up to 28% Considering climatic projections, instead, downstream in the Red River delta it can be expected that by the year 2050, with a projected decrease of rainfall by 3-5% in the dry season and an increase of temperature of about 1. 2-1. 5 °C, water deficit severity would increase by 7-8% and its intensity by 2. 5-3. 0% , relative to actual conditions, thus influencing potential saline intrusion from the sea. But a major factor influencing the water demand in the red-river delta is the socio-economic development in this area. These results will be compared with similar evidences collected worldwide on climate- and human-induced changes in the hydrological cycle, water management and engineering. Two type of feedbacks which are being observed at the global scale are discussed: the first is the reduced speed of global deforestation and the natural afforestation in the Northern Emishphere occurring over the last two decades and the second are the projections of future global populations showing a global homogeneisation of fertility and life expectancy standards which will influence the future water demand.