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Changing availability of water due to variations in precipitation
Occurrence of floods due to excessive rainfall and droughts due to lack of rainfall over a prolonged period of time.
View the video on a flash flood which affected Singapore on 17 April 2021
What is the cause of the flash flood?
Flash floods are caused by exceptionally heavy rainfall over a short period of time. This often occur in urbanised areas where the land is mainly concrete and cannot absorb the excess water. As water cannot infiltrate into the ground, most of the rainwater that falls onto the ground becomes surface runoff which quickly floods low-lying areas.
Can you relate this to a water surplus in a water catchment?
View the video on a flash flood which affected Singapore on 23 June 2020.
View the video on thunderstorms and flash floods which affected Singapore on 2 Nov 2020.
What is the cause of the river flood?
River floods can be caused by intense rain or increase in melt water.
The flood in Australia was caused by intense rainfall whereas the one in Russia by increase in melt water in April, 2024.
The rivers could not accommodate the sudden increase in water and this resulted in water overflowing the river banks and river flooding occurs on the low-lying land.
Watch this video how flood and drought affected countries in Africa due to variation in precipitation.
In Somalia, hundreds of thousands have been driven from their homes by severe flooding in 2019. South Sudan, parts of northern Kenya and Ethiopia have also been hit by extreme rainfall. But Somalia has been particularly affected with more than 300 thousand people have been made homeless. This is said to be some of the worst flooding the country has experienced in years, maybe decades.
It's a different story in southern Africa where many parts of the region have been hit with a devastating drought. In Zimbabwe, animals have been affected the most as the lack of rain dries up water holes and grazing areas. More than 100 elephants have died in Zimbabwe's wildlife reserves since September 2019.
Look at the drought experienced in Vietnam 2024.
What caused the drought?
What are the impacts of the drought?
Support river ecosystems
Precipitation provides regular supply of water to river.
The water in the river supports the river ecosystem in which the plants and animals in the river interacts with one another.
The zooplankton feed on the phytoplankton. Insects , which feed on the zooplankton, are eaten by fish. Fishes are eaten by human which is at the top of the food chain.
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