\r\nIn Target 10 of Goal 7 of Millennium Development Goal, "access" to an improved water source mean?

Propoion (%) of population with sustainable access to an improved water source, rural (G7.710.130) : "improved" water sources means household connection, public standpipe, borehole, protected dug well, protected spring, rainwater collection. "Access" means the availability of at least 20 litres water per person per day from a source within one kilometre of the user's dwelling. Ref: Park's textbook of Preventive and Social Medicine, 21st edition, page-831