461806
Description
Mind Map by Jodie Goodacre, updated more than 1 year ago
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Created by Jodie Goodacre
over 10 years ago
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Human impacts on water availability
- Human activity can have a negative effect on the water environment
- Pollution caused by human activity and excessive abstraction
of water supplies can further increase water stress.
- Pollution of groundwater is much less obvious than surface-water pollution, but is no less a problem:
- Sewage disposal in developing countries is expected to cause 135 million deaths by 2020 (World Health
Organization). Diseases such as hepatitis, typhoid and cholera are common in areas with polluted water. In the
UK we add 1,400 million litres of sewage to our rivers daily, though most of it has been treated.
- Chemical fertilisers used by farmers contaminate groundwater as well as rivers and water supplies. In Yucatan, Mexico, the
level of nitrate in the groundwater is 45 mg l-1. Sewage and fertilisers add nutrients to the water and increase the growth
of algae downstream. The algae remove oxygen from the water, for example along the shores of the Gulf of Mexico.
- Each year the world generates 400 billion
tonnes of industrial waste, much of which is
pumped untreated into rivers, oceans and other
waterways. Heavy metals such as lead, cadmium
and mercury also become concentrated in rivers.
Chemical waste includes toxic and widely
banned polychlorinated biphenyls (PCBs).
- Big dams trap sediment in reservoirs, which reduces floodplain fertility
and the flow of nutrients from rivers into seas. This may damage
coastal fish stocks and prevent beach formation, which in turn can
expose coasts to greater erosion. Sediment disturbance during dam
construction can also block the gills of river fish and suffocate them.
- Sewage disposal in developing countries is expected to cause 135 million deaths by 2020 (World Health
Organization). Diseases such as hepatitis, typhoid and cholera are common in areas with polluted water. In the
UK we add 1,400 million litres of sewage to our rivers daily, though most of it has been treated.
- Abstraction
- Removing water from rivers and groundwater sources, whether for
drinking water or for irrigation, can have unintended consequences:
- Worldwide, water is being extracted from aquifers faster than it is being replaced. In arid areas, rainfall
can never recharge these underground stores.
- The removal of freshwater from aquifers in coastal locations can upset the natural balance of saline and fresh
groundwater and lead to salt water incursion and salinisation of wells, boreholes and wetlands.
- Worldwide, water is being extracted from aquifers faster than it is being replaced. In arid areas, rainfall
can never recharge these underground stores.
- Removing water from rivers and groundwater sources, whether for
drinking water or for irrigation, can have unintended consequences:
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