In the early twentieth century, the British Army allowed 1 imperial gallon (4.5 litres) per man for daily drinking and cooking (General Staff Regulations 1911). An experimental march in Roman equipment and in hot conditions during the 1980s revealed that the men had to drink at least 0.5 gallons (2.27 litres) a day when marching to prevent medical issues. The British allowance, with its cooking component, would consequently seem a reasonable estimate for Roman troop consumption during the siege of Numantia 134/133 BC, especially with its hot summer temperatures.
The British allowed 10 gallons (45.5 litres) per horse per day when in camp. This may have been generous, as normally horses drink 23 litres, but it varies depending on the weather and their fodder, so could range up to as much as 38–45 litres.
