Stock Water Requirements Calculator NZ
This calculator works out how much drinking water your stock need each day, how much storage that implies, and what flow rate a trough has to deliver, all in litres rather than the US gallons the tools currently ranking for this question in New Zealand use. You enter your stock by class and the litres each animal drinks a day, choose how many days of storage you want to hold, and it returns daily demand, total storage, the tank size that represents and the peak hourly flow. Two things matter more than the daily total. The first is that stock drink in bursts rather than steadily, usually after milking or in the evening, so a trough fed by an undersized pipe runs dry exactly when the mob arrives, and a big tank behind a slow line still gives you thirsty animals. Size the pipe to the peak hourly draw, not to the daily figure. The second is that demand is highly seasonal: a lactating dairy cow needs more than 100 litres a day in summer and much less in winter, so a system sized on an annual average will fail in February. Where a class of stock has no default rate here, that is deliberate. Rates for dairy cattle and dairy goats come from New Zealand sources; rates for beef cattle and sheep were not found on a New Zealand authority, and filling that gap with an American or Australian figure would be exactly the mistake this page exists to correct. Enter your own and the calculator will use it.
| Class of stock | Head | Litres each per day | Litres a day |
|---|---|---|---|
| Lactating dairy cows | 18,000 | ||
| Beef cattle | 0 | ||
| Sheep | 0 | ||
| Dairy goats | 0 | ||
| Other stock | 0 |
A summer figure, not a year-round average. Size the pipe to the peak hourly draw rather than the daily total, because stock drink in bursts and a trough on a slow line runs dry exactly when the mob arrives.
How it works
Daily demand is each class multiplied by its litres per head per day, added together. Storage is that daily figure multiplied by the days you want to hold, and the tank size is the same number expressed in cubic metres, since a cubic metre is a thousand litres. Peak flow takes the share of the day's water you expect to be drunk in the busiest window, divides it by the hours that window lasts, and gives litres an hour, which is the figure a pipe and pump have to meet. The sustained figure spreads the whole day evenly for comparison, and the gap between the two is the point: a system built to the sustained number will not keep up at the peak. A class with no rate entered contributes nothing and is named below the result rather than being quietly counted as zero.
Worked example
A herd of 180 lactating dairy cows at 100 litres a day each needs 18,000 litres a day. Holding three days of storage means 54,000 litres, or a 54 cubic metre tank, which in practice is likely to be two or three tanks plumbed together. If 60 percent of that daily water is drunk in a four hour window after milking, the peak draw is 10,800 litres over four hours, which is 2,700 litres an hour. Spread evenly across the day the same herd would only need 750 litres an hour, so a system designed to that figure would be about a third of what the peak actually asks for, and the troughs would be empty every afternoon.
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