The United Nations says, "In some makeshift sites around Bangladesh’s Cox’s Bazar area, humanitarian agencies have built tube wells that provide a much-needed source of drinking water for undocumented Rohingya living outside the official camps. ©UNHCR/Saiful Huq Omi"
Up to 400,000 Rohingyas have fled the state of Rakhine in Myanmar/Burma for neighbouring Bangladesh since August 25. That's in addition to the 400,000 Rohingya refugees who had fled earlier from Myanmar to Bangladesh.
The Independent explains, "Rohingya Muslims face widespread persecution in Buddhist-majority Burma, where the recent violence has driven hundreds of thousands to seek refuge overseas. ...Members of the ethnic group are commonly referred to as 'Bengalis' by many in Burma who insist they migrated illegally from Bangladesh."