Wastelander Water Request

 refers to an unmarked quest in the Fallout 3 add-on Broken Steel.

Walkthrough
This quest becomes available after Broken Steel has been downloaded and holy water has been completed. In front of the town, where the normal caravans are some Megaton settlers will try to take the aqua pura from the Brotherhood of Steel escorted scavenger.

Should the player do nothing, The Brotherhood escorts will fight back, and in the ensuing fight the settlers, Deputy Weld, and Stockholm will all likely be killed. The Brotherhood escorts will then say that the settlers attacked first, comment that the mission was all normal, and then continue on their way. If the settlers manage to defeat the Brotherhood entourage (an almost impossible outcome without player intervention), each of them will take a bottle of aqua pura from the corpse of the brahmin caravan.

Passing a speech check with one of the Brotherhood of Steel caravan guards will give the settlers the water, at the expense of Big Town's ration, thereby preventing the shootout. Alternatively, a speech check can be used with the settlers to convince them to back off, preventing the shootout and allowing the caravan to be on its way.

Reward
Good Karma or loot off the bodies.

Bugs

 * If the Brotherhood is convinced to give up Big Town's share of water, the fight may still take place.