Water Cycle (or hydrological cycle) is the continuous transfer of
water between the sea, the land and the atmosphere. It is a continuous
cycle with no beginning or end.
A basic description of the Water Cycle:
Precipitation (rain, snow, sleet or hail) falls to the ground.
This is either:
INTERCEPTED by vegetation or buildings
INFILTRATES into the ground
the surface of the ground (as a river or stream).
Energy from the sun evaporates the water. If the air cools it
causes condensation (clouds), then precipitation.
river basin is an area of land drained by a river and its tributaries.
River basins have typical features, these include:
Tributaries - smaller rivers flowing into a larger river.
A Watershed - an area of highland surrounding the river basin.
A confluence - where a river joins another river.
Source - The start of a river.
Mouth - Where a river meets the sea or an ocean.
erode in four ways:
or corrasion - This is when large pieces of bedload material wear
away the river banks and bed.
Attrition - This is when the bed load itself is eroded when sediment
particles knock against the bed or each other and break, becoming
more rounded and smaller.
Hydraulic Action - This is when the force of water erodes softer
Solution or corrosion - This is when acidic water erodes rock.
can bring both advantages and disadvantages to an area. Floods can
deposite rich, fertile alluvium on agricultural areas. Also, flood
water can replenish irrigation channels. On the other hand floods
can destroy food supplies, homes and transport infrastructures.
Deforestation - Cutting down trees causes increased run-off
(water flowing over the surface of the earth). Rain water reaches
rivers faster. Flooding becomes more likely.
Urbanisation - Man-made surfaces such as concrete result
in greater run-off. Rain water reaches rivers faster and can cause
- Planting more trees reduces run-off and increases interception.
Dams - Although very expensive, dams can significantly
reduce the risk of flooding downstream
Study - Ganges/Brahmaputra River Basin
is a significant problem in the Ganges/Brahmaputra river basin.
They cause large scale problems in the low lying country of Bangladesh.
There are both human and natural causes of flooding in this area.
Deforestation - Population increase in Nepal means there
is a greater demand for food, fuel and building materials. As
a result deforestation has increased significantly. This reduces
interception and increases run-off. This leads to soil erosion.
River channels fill with soil, the capicity of the River Ganges
and Brahmaputra is reduced and flooding occurs.
Tectonic Activity - The Indian Plate is moving towards
the Eurasian Plate. The land where they meet (Himalayas) is getting
higher and steeper every year (fold mountains). As a result soil
is becoming loose and is susceptable to erosion. This causes more
soil and silt in rivers. This leads to flooding in Bangladesh.