Great rivers in the tropical climate zones are likely to die. Great rivers in the temperate climate zones are not likely to. This is due to the effect of global warming as a result of man’s activities that include deforestation and pollution. Global warming is gradually changing the world’s climates and this will greatly affect the water bodies and water catchments areas.
As the human population increases, there is a need for settlement areas, development of farms and industries to absorb skilled labor produced by education systems. This implies trees are going to be cut down and natural forests are going to be affected. This will encourage desertification (gradual encroaching of desert-like features). Trees act as wind breaks and their absence means the affected areas will receive low and unreliable rainfall. Where is the river going to get its water from if it is fed by dry tributaries? Eventually, a river is going to have a low water volume and consequently its size will continue to decrease. In the end, many rivers are going to become seasonal (able to have water only when a rainy season prevails).
Global warming contributes greatly to this problem. Temperatures are increasing and this will cause glaciers to thaw. This has the effect of increasing the volume of ocean water. Therefore the oceans will claim more land. This in turn affects the direction of winds and ocean currents. The monsoon winds are likely to blow parallel to the coastline. More rain would fall in the ocean itself and establish cold deserts in the neighboring lands. Many rivers that rely on rain bearing winds would dry up. The reliability of rainfall would become unpredictable. This will cause great rivers in tropical areas to cease from having any economic value and would in the end dry up.
The scenario would be different in temperate areas. With melting of glaciers, the great rivers in these areas would have higher water volumes. The amount of rainfall experienced would be very high such that it would be destructive to property and life. The great rivers that originate from lakes in temperate climates are likely to cause more floods due to increased water volume. This would occur during summer seasons when the melting of glaciers is likely to be more. This has an effect of transforming summers not just into rainy season but periods when heavy flooding is likely to occur. The ocean currents may also lead into water waves that may cause untold destruction once they spill into the land. In terms of providing reliable water, global warming is only affecting the tropical climates where the seasons of La Nina are more of a threat than any episode of El Nino. Therefore, countries in the tropical zones need to be prepared for the disasters associated with drought.