Reasonable access to safe drinking water is defined as the availability of at least 20 litres per person per day from an improved source within 1 kilometre of the user's dwelling.
The figure above demonstrates the percentage of countries population who do NOT have access to potable water. It also shows clearly that access to potable water is not related to environmental and climatologic conditions but with other aspects, such as water management structures or peoples way of living; pastoralist cannot – per definitions – have access to potable water, because of their migrations. Wars play an extraordinary role to water management, since infrastructure and governmental structures (regulatory authorities) are often destroyed and dismissed.
Developing countries show a wide variety of water supply systems for its population. The following pictures from the African continent demonstrate several, but not all possibilities of water supply systems.