# Managing water for all your dairy needs; milk matters Richard Davies.

WITH increasing dairy herd sizes across Wales and the UK, water is not usually a priority when it comes to upgrading farm infrastructure.

But water is obviously a necessity. By calculating the water demand and the supply required, you can plan a system to cater for current and future water needs.

On average a cow will drink between 65 and 100 litres a day, more in hot weather. Drinking speed is 14 litres per minute, with 30 to 50% of the daily intake required within three hours of milking.

Therefore the system must provide a reservoir (tank size) large enough to satisfy this demand.

For example, the requirement for 200 cows can be calculated as follows: 200 cows x 100 litres = 20,000 litres/day + young stock + other farm use.

Tank size in paddocks - should be 9 litres per cow x 200 = 1800 litre tanks.

Remember that 50% of the water intake is required within three hours of milking.

Therefore calculate the supply as follows: 100 litres x 50% /3 hours = 17 litres/cow/hour 200 cows x 17 litres = 3,400 litres per hour = a supply requirement of 56 litres per minute.

To check your supply, mark the level of water in one of the tanks, tie up the ballcock and empty 50 litres from the tank.

Then release the ballcock and hold it down until the water returns to the mark.

Note how long this took and calculate the flow rate per minute.

Most problems are due to the size of pipe being used. A 50mm pipe will have four times the cross sectional area of a 25mm pipe.

Also, if the farm is on a bore hole or a spring, the supply is often not adequate to meet the spike in demand.

Solve this by having a reservoir or tank and then pump the water as required around the farm.

Alleviate pressure loss by using a mains loop.

The tank will draw from the least resistance, which will almost double the flow rate. High capacity ballcocks are also available that will allow the desired flow rate.

For more information look at the DairyCo Dairy Housing a best practice guide at www.dairyco.org.uk | Richard Davies is the exten-sion officer in North Wales for DairyCo. He can be contacted on 01824 790214 / 07966 237841 or by email richard. davies@dairyco.ahdb.org.uk