Water – Waste not, want not!

Even before we entered the driest six month period since 1984 this summer, water use on farms was starting to be mentioned as one of the assessment criteria to be potentially added to farm audits. Making the most efficient use of water is becoming more important from a financial and environmental viewpoint.

SOURCES

Mains supply
This offers a reliable and safe supply of water. Meters and invoices can provide accurate measurement of water used. Like other utilities, it is possible to shop around for the best price. When doing this, it is important to look at daily standing charges as well as rate per cubic metre. These can vary for a number of reasons, including the diameter of the pipe at the meter.

Boreholes
This gives a huge reduction in the cost of water used. However, both quality and supply are not guaranteed. A connection to the mains supply may be necessary as a back up, for example, in case of pump failure. Although the long-term cost of using a borehole is less than a mains supply, the initial capital cost is higher.

To construct a borehole, permission should be sought from SEPA. One of a number of licenses is also required depending on the volume of water to be abstracted. Less than 10m3 a day, which is enough drinking water for up to 110 lactating cows (depending on yield), requires no licence or registration. The details of requirements for different levels of abstraction are detailed in the table below.

Source : SEPA (Figures correct at 13/07/2018).

This also applies to abstraction from watercourses for irrigation. There have been cases recently of umbilical slurry systems being used to irrigate grassland using river water. The equivalent of 1 inch of water per acre will require over 1000m3. SEPA will take a hard line on unauthorised abstractions of this amount.

Rainwater harvesting
Collecting rain that falls on roofs is a good way to reduce the amount of mains water used, but has limitations in dry spells. Limiting factors are area of roof, size of collecting tank and, occasionally, amount of rainfall. If building a new shed, it is important to remember gutters and downpipes that are part of a rainwater harvesting system can be claimed against tax as an “integral feature”.

As with borehole water, harvested rainwater needs to be filtered and treated, if necessary. Red Tractor Dairy Standards require that non mains supplies are tested for quality and test results must be available for inspection.

REDUCING USE

Some of the best ways to reduce water use are the simplest. Making sure taps are switched off when not in use and water troughs are not overflowing can make a significant difference. Using a pressure washer, where practical, instead of a volume washer can also help. Identifying and sorting leaks can reduce metered water use. A leak or dripping tap that loses 1 ml per second will increase water use by 31m3, or nearly 7000 gallons in a year. Even if coming from an unmetered source, this water will then go on to fill slurry stores or use up bedding. This will add further costs to the business.

Although reducing water use is important, making sure that cows have access to adequate, fresh water is vital. There should be enough trough space for 10% of the herd to drink at any one time and a recommended 10cm of trough space per cow for all cows at all times. Ideally, troughs should not all be in one location to avoid dominant animals stopping other animals from using the trough.

Water pressure should be high enough to ensure adequate flow at times of peak demand. If this isn’t provided straight from supply, header tanks should be used. The table below shows the recommended daily water requirement for dairy cows.

alasdair.scott@sac.co.uk