Factors affecting water availability
There are several reasons why global water supply is not even.
Factors affecting water supply
Access to a fresh water supply is affected by the following factors:
- Climate. Low levels of rainfall and high temperatures lead to water deficitA place that has less water than required.. When rainfall is low, there is less water available. When temperatures are high, water evaporates and so there is less available to use. water surplusA location that has more water than required. are common where rainfall is high and temperatures are lower.
- Geology. Rainfall flows down to the rocks beneath the ground. Some rocks are permeable rockA type of rock which allows water to pass through its joints and cracks, eg limestone. and allow water to flow through them. Permeable rocks can lead to less surface water. For example, limestone landscapes often have dry rivers - the rivers only exist when rain has just fallen. Permeable rocks form aquiferNaturally occurring underground water stores., which means they are stores of water. 70% of the water supply in the south east of England comes from the chalk aquifer beneath the surface. Other rocks are impermeableA substance which fluids are unable to pass through.. These rocks do not hold water, but they can trap it in the layers above.
- Pollution. Some places have plenty of water, but pollution has made it unsafe to use. Untreated sewageWaste organic matter that sometimes pollutes water systems, eg faeces. and waste water from factories cause problems. groundwaterWhere water is stored in rocks beneath the ground. is usually cleaner, although pollutants can travel down into the ground. Gold mining near Johannesburg, South Africa, has led to uranium, arsenic and sulphuric acid polluting streams and rivers.
- Over-abstraction. When water is taken from aquifers, groundwater levels fall. If the amount of water taken is greater than the amount of water falling as rain, it is called over-abstractionThe process of extracting too much water.. The Sonoran desert in Arizona has experienced over-abstraction as water is taken for irrigation and urbanisation. The land here is subsidenceA fall in land levels. and water is becoming scarcer.
- LimitedinfrastructureThe basic structures needed for an area to function, for example roads and communications. . Pipelines are needed to safely move water from place to place. Sealed pipes reduce the potential for leaks and pollution. Some places do not have these pipes in place. They can be expensive to lay as they need to be buried underground. Water pumps also form part of the water infrastructure. Water pumps in villages across Kenya were recently fitted with transmitterAn electronic device that produces radio waves. that send text messages if the devices break down.
- Poverty. Nearly 1 billion people in Africa do not have access to clean, safe water. This locks them in a cycle of cycle of povertyA set of factors which keeps someone in poverty, without hope of an escape. - they cannot afford water so they become ill and when they become ill then cannot work and earn money.