Role of hydrological forecasts and river flow modelling in rational agricultural water management in the perspective of a climate change — A case study of the Rivers Upper Nile and Niger
Abstract An international scientific conference under the auspices of WMO, UNEP and ICSU on the role of CO 2 and other greenhouse gases in climate variation made a statement that, if the concentration of CO 2 in the atmosphere doubles in the near future as present trends indicate, the global mean surface temperature would increase by 1.5–4.5°C. The paper discusses the impact such a climate change may have on water resources and on their management in agriculture. It stresses the importance of the possible increase in variance and frequency of extreme climatic events and subsequent water yield. It further outlines the ways of exploring the consequences of such development by using hydrological and water management models. It also proposes that real-time hydrological forecasting systems, able to produce forecasts with long, medium and short lead times, are one of the most effective measures to offset possible negative effects of the climate change, by increasing the effectiveness of storage management. These propositions are documented by means of case studies from developing countries using models on the River Nile, in particular in the basin of Lake Victoria, and of a hydrological forecasting system on the River Niger. It is proposed that it is important to develop a simulation model of the whole River Nile, together with a real-time forecasting system on the river in order to operate efficiently existing and future storages. Modelling of climate change impact on the water yields of River Niger is also discussed.
Sensitivity of water resource systems to climate variation
ABSTRACT The problem of the response of water resource systems to climate variations is stated. The importance of the sensitivity of the systems to such variations is demonstrated with respect to the stationarity of the mean and the extremes. A definition of moderate climate variation is adopted. Results of deterministic modelling of the influence of such a variation on streamflow are reported, in extreme conditions of arid and humid basins. The results are used in modelling the influence of climate variations on reservoir storage systems. The model indicates a considerable amplification of the effect of climate change on runoff and storage and emphasizes the importance of studies of sensitivity of water resource systems to climate variation.
On the Distribution of Climate Change Resulting from an Increase in CO2 Content of the Atmosphere
Abstract A study of the climatic effect of doubling or quadrupling of CO2 in the atmosphere has been continued by the use of a simple general circulation model with a limited computational domain, highly idealized geography, no seasonal variation of insolation, and a simplified interaction between cloud and radiative transfer. The results from the numerical experiments reveal that the response of the model climate to an increase of CO2 content in air is far from uniform geographically. For example, one can identify the high-latitude region of the continent where the runoff rate increases markedly, a zonal belt of decreasing soil moisture around 42° latitude, and a zone of enhanced wetness along the east coast of the subtropical portion of the model continent. The general warming and the increase of moisture content of air, which results from a CO2 increase, contributes to the large reduction of the meridional temperature gradient in the lower model troposphere because of 1) poleward retreat of highly refl...