Drinking water service coverage, World

Total population using a given drinking water source. At least basic drinking water represents an improved source within 30 minutes’ round trip to collect water; 'limited'constitutes an improved water source more than a 30 minute round-trip away; 'unimproved' is one that by the nature of its construction does not adequately protect thesource from outside contamination; and 'surface' is that from surface water sources.