Water World

The Hydrological Cycle

The water cycle

The Earth's water is always on the move around the Hydrological Cycle.

Surface Flow

Rain falls onto the ground and flows on the surface into rivers and lakes.

Through Flow

Rainwater is soaked into the soil (infiltration) and flows slowly to rivers.

Groundwater Flow

Rain water is soaked into rocks below the soil. It moves slowly through cracks and joints or airspaces (pores)

Hydrological Processes

There are three hydrological processes you need to know...

Evaporation when water warms up and returns to the atmosphere as water vapour.
Condensation when water vapour cools and forms tiny water droplets, sometimes forming visible clouds
Precipitation when the tiny water droplets previously formed collide and grow until they fall to the ground as rain or snow.

Climate and water supplies

Unreliable water supplies and their impacts

Here are the three main reasons why water supplies may be unreliable:

Case Study - South West USA

Effect of Climate Change on Asia

Threats to the Hydrological Cycle

There are many things which us humans are doing which is impacting on the hydrological cycle.

Causes of River Pollution Managing River Pollution
Untreated sewage pumped into rivers can lead to serious diseases such as Cholera and typhoid. Sewage is treated before it can be pumped into rivers
Intensive agriculture which releases fertilisers, pesticides and herbicides into the local water systems can poison wildlife and affect water quality. Farmers and land-owners regulate their use of fertilisers and chemicals to reduce pollution and damage
Waste chemicals which are leaked from factories can poison wildlife and affect water quality Factories dispose of their chemical waste before returning water to the river. In the UK, the Environment Agency imposes heavy fines on any factory which releases chemical waste into the environment.
Contain basaltic magma which is very hot with low silica and gas content Made up of layers of thick lava and ash
Plastic bags and other non-biodegradable waste can kill wildlife, clog up water ways and affect water quality. Plastic and all other recycable waste is sent to recycling centres to be recycled rather than being dumped in rivers.

Large scale water management

Water management schemes try to deal with the water supply problems a place might face. These large scale water management schemes:

Developed world case study - The Colorado River, USA

Benefits Disadvantages
Reduces flooding that would normally occur in the summer, and reduces drought that would normally occur in the winter Land is lost to flooding when making the dams.
Electricity is produced by the dam for local towns, farms and factories Sediment has built up behind the dams which affects the workings of the Hydroelectric Power (HEP) generation.
Water is stored behind the dam which can be used for irrigation and for supplying growing cities such as Las Vegas. Less sediment flowing down the river has disrupted the habitat for native fish.
There is year-round supply of clean water for US cities. Also, the lack of sediment means sandbanks have shrunk which is also impacting animals and their habitats.
Less water downstream in Mexico

Developing world case study - The Three Gorges Dam, China

Benefits Disadvantages
Reduced risk of flooding for homes, farms and factories along the Yangtze River Good farmland has been lost because of the dam.
Water stored behind the dam is available for irrigation Over 1 .3 million people were forced to move their homes as towns and villages disappeared under water.
Hydroelectric power (HEP) is generated by turbines in the dam. It's the world's largest capacity HEP station.
The electricity it produces means China saves 31 million tonnes of coal each year and thier overall greenhouse gas emissions has reduced
The project was very expensive, $US 22.5 billion, but some people estimate the actual cost to be as high as $US 50bn.
The river is deeper and more navigable for ships, so it has improved transport and trading in China. There is an increased risk of landslides in some places.
Important cultural and archaeological sites were lost.
Sediment is building up behind the dam.
There is no sediment to maintain river banks resulting in downstream areas becoming more at risk to flooding.
Important wetland areas have been destroyed.

Small Scale Water Management

In the developing world, you are more likely to find small scale, intermediate technology solutions to any unreliable water problems. These solutions are relatively cheap to build and maintain, cover small areas, are organised by the local people in conjunction with charities and local organisations, and help local people access clean water and increase water storage safely.

Wells Wells are dug to reach underground water supplies. They are lined with concrete and have a concrete lid to prevent pollution by sewage.
Hand Pumps A more efficient way of reaching underground water where there is less chance of water becoming contaminated.
Rain Barrel Water barrels collect rainwater from gutters and roofs can can be stored and used in times of droughts. This is called water harvesting. The water stays clean in the covered barrel.