What explains how water moves through the environment?
-Inputs, stores and outputs
What are blue water flows?
What are green water flows?
Three factors that are inked to water supply
How is climate linked to water supply?
How are river systems linked to water supply?
River flow generally increases downstream as tributaries feed into the main river, though high temperatures can lead to considerable water loss by evaporation
-Seasonal changes in climate can also create significant variations in discharge and produce distinctive river regimes
How is geology linked to water supply?
What is water stress?
Water stress occurs when demand for water exceeds the amount available during a certain period, or when poor quality restricts its use.
-Therefore when a country’s water consumption is more than 10% of its renewable freshwater rate it is said to be water stressed.
Why has 20th century water consumption increased?
due to population growth and
economic development:
Farming uses 70% of all water and in LEDCs this is up to 90%
Industrial and domestic use has to compete with farming needs as a country develops
Daily domestic water use on average is 47 litres per person in Africa, compared with 578
litres in the USA
What are the consequences increased water stress?
This has lead to the development of a world water gap with 1.4 billion lacking clean drinking water and
12% of the world’s population consuming 85% of the world’s water.
How has agriculture led to water stress?
How has industry led to water stress?
How does domestic water use lead to water stress?
Two types of water sources
- Aquifers
Why is surface water a store of water?
-Rivers, lakes and reservoirs provide large amount of surface water for a wide variety of uses
‘mega-dams’ found in the world’s major rivers.
-Half of all the worlds dams are in China, USA and Japan and account for 25% of global freshwater supply
_Bring short-term economic gains in terms of water supply and HEP, must be measured against longer term environemtnal impacts
Why aquifers a store of water?
What is physical water scarcity?
-shortages occur because demand exceeds supply
What is economic scarcity?
-people cannot afford water, even when it is readily available
Human factors that affect water availbility
How does sewage disposal affect water availability?
Sewage disposal in developing countries is expected to cause 135 million deaths by 2020.
How do chemical fertilisers affect the availability of water?
Chemical fertilisers contaminate groundwater as well as river and water supplies.
-These add
nutrients to the water leading to an increase in the growth of algae downstream.
-In Yucatan, Mexico, the level of nitrate in the groundwater is 45mg-1, increase growth of algae which removes oxygen along the shores of the Gulf of Mexico-Eutrophication
How does industrial waste affect the availability of water?
How does dams affect the availability of water?
-Trap sediment in reservoirs which reduces floodplain fertility and the flow of nutrient
from rivers into seas.
How does abstraction affect water availability?
removing water from rivers and groundwater sources can cause issues that in some arid areas rainfall can never recharge these underground stores and the removal of freshwater from aquifers in coastal locations can lead to salt water incursion.