In Diamonds Are Forever, James Bond is in America, and is again escorted by Felix Leiter for a time and given lessons in the native food and drink.
He walked home with the crowds, had a shower and some sleep, and then found his way to a restaurant near the sales ring and spent an hour drinking the drink that Leiter had told him was fashionable in racing circles – Bourbon and branch water. Bond guessed that in fact the water was from the tap behind the bar, but Leiter had said that real Bourbon drinkers insist on having their whisky in the traditional style, with water from high up in the branch of the local river where it will be purest. The barman didn’t seem surprised when he asked for it, and Bond was amused at the conceit.
Branch water is preferable if it has been limestone-filtered, which removes the iron from the water. Iron would discolor the bourbon. Bourbon is made with limestone-filtered water, and as part of the state of Kentucky sits on an ancient limestone aquifer, it is the bourbon capital of the world. Limestone-filtered water is also very smooth on the palette, and thus is the perfect mixer for the bourbon.
At least five times in the novel Bond has this drink. When he is in Las Vegas, he orders the drink again, and tests the bartender, as Leiter had told him Vegas was a desert and there were no river branches to get the water out of.
He walked over to the bar and ordered himself a Bourbon and branch water to celebrate the five thousand dollars in his pocket.
The barman produced a corked bottle of water and put it beside Bond’s ‘Old Grandad’.
‘Where’s this come from? ‘ asked Bond, remembering what Felix Leiter had said.
‘Over by Boulder Dam,’ said the barman, seriously. ‘Comes in by truck every day. Don’t worry,’ he added “it’s the real stuff.”
When he is being held by Spang in Spectreville, Bond also demands a bourbon and branch water “half and half” before talking. Nowadays, Branch is simply a term that many bourbon drinkers use for water.