Make The Most Of Rain With Water Harvesting

Rainwater collection from roofs or other clean areas can make a significant contribution to water supply according to DairyCo extension officer Chris Coxon.

The average cost of water supply to a dairy farm is 31 per cow per year, says Mr Coxon. And with the average farmer getting through 10,000 litres per cow per year for just washing parlour walls and floors, the use of harvested rainwater can prove highly efficient.

Higher rainfall areas or large catchment areas obviously have more potential, but small volumes can contribute to vehicle, yard and parlour wall wash-down as this water needs minimal filtering. If you are collecting larger volumes you will need to use it for stock drinking, and in that case the water must be filtered and treated to avoid contamination. It is also very important to remember that dairy hygiene regulations require that any water used for hand, udder or dairy plant washing must be from a potable source.

Filtering and storage can have a significant cost, continues Mr Coxon, but if you have, or can get, inexpensive water storage such as a pond or storage tank, this will make water harvesting a much more cost effective option. There are other advantages to investing in your own storage facility, including having the security of your own supply, and a relatively predictable volume of water which will enable you to plan for a known payback period.

Check your local rainfall data so you can see how valuable it might be. You will also need to calculate your roof area to get an idea of what is available for collection. On average the amount that falls reduces by 10-20% when collected due mostly to evaporation, so one cubic metre of rain will become 0.80-0.90 cubic metre once collected.

Work out just how much you can really afford to spend, continues Mr Coxon, then consider aspects such as potential contamination from birds or vermin and the need for filtration or UV treatment systems, which Id strongly recommend for drinking water. Youll also need to take into account running costs, and remember that this water still isnt free once you have paid off the capital investment as the cost of disposing of dirty water ranges from 0.50-1.50 per cubic metre.

For more information DairyCos revised booklet Effective use of water on the dairy farm takes you through the processes you need to go through. Order a copy from publications@dairyco.org.uk or by calling 02476 478695