It is not really difficult to do this calculation: In general it is assumed that between 15,000 and 20,000 liters of water are required to produce one kilogram of beef – depending on its type and on the way the animals are kept.
The term ‘burger’ here only refers to its actual content of meat, which amounts to about 200 g.
3,000 liters of water are needed for 200 g of beef (15,000 : 5).
One shower consumes 30 l of water on average.
The enormous consumption of water in meat production is primarily due to the watering of the plants which livestock animals feed on. Formerly cattle and sheep etc. basically ate grass, which cannot be made use of by man. Nowadays, however, they are mostly fattened with corn or soy beans produced on huge plantations. But also the water which these animals need to drink and the amounts of water that are needed for cleaning the fattening units must be included in the calculation.
In most industrial nations the question of water shortage is not relevant. 2025, worldwide every third human is suffering from the consequences of the lack of water according to a survey of UNICEF and the World Health Organisation (WHO). http://www.zmescience.com/science/water-scarcity-2025-23032016/
Due to the continuously rising world population and due to climate change, the consumption of water will keep on increasing in the years to come.
Consequently, we should be more aware of the valuable resource of water, which means to do without meat more often in the first place.
In view of this fact it seems like beginning on the wrong end when children are already taught at primary school that they should prefer a shower to a bath. Eating just one steak less would allow us to have twenty baths.