Rainwater Harvesting for Agricultural Irrigation

Rainwater harvesting for agricultural irrigation help conserves our most valuable resource – water.  Water is a valuable and finite resource – and it is becoming scarcer. The costs of your mains water are rising, and it will get more expensive as time goes on. So, it makes sense to use rainwater – or does it?

During recent years there has been a great deal of interest and research into the climatic effects and feasibility of rainwater harvesting – and still more urgently needs to be done. Agricultural irrigation needs large quantities of water, so is water harvesting worth investigating for you?

In this article, we look at the types of rainwater harvesting for irrigation systems and explain how you can calculate the approximate savings you can make. But first –

What is rainwater harvesting for farms?

Rainwater harvesting is the collection of rainwater for use elsewhere. It extends from the water butt in your garden to complex systems involving underground storage in large tanks, water management and treatment depending on the final use.

A typical system for farming use will utilise roof water that drains into a tank through a filter to remove debris.  Calming inlets are fitted to prevent the sediment from disturbance, and oxygenation of the water is provided to prevent the growth of algae.

You must decide which roofs are suitable to collect water, how large a tank you require and where to put it. We can help you choose a rainwater harvesting solution and the best filter system for your circumstances.

Domestic rainwater harvesting systems can be used as a cost-effective way to reduce drinking water use using water for;

• Washing machines
• Toilet flushing and washing
• Irrigation
• Car washing

How much can you save from barn roofs?

This formula will give you an initial idea – is it worth it?

• Roof area in square metres x annual rainfall in cubic metres
• If you divide this by 12, you will find your average monthly collection.
• Compare this with your mains water rates.

Not all months are equal, and we recommend that your store three months of rainwater cover drier spells. You also must factor in the initial cost of setting up the system – how long will it take to recover the cost – and are there maintenance costs?

Despite these costs, it is often possible to halve your water bill with these popular sized tanks – 1,000 Litre | 1,500 Litre | 2,000 Litre | 5,000 Litre | 10,000 Litre | 15,000 Litre | 20,000 Litre | 25,000 Litre | 30,000 LItre

Different types of rainwater harvesting

There are various methods of collecting rainwater, but three main methods use gravity (usually together with a water pump), direct pumps and indirect pumps.

Gravity Only

Sometimes a gravity only system might work. Rainwater is collected from areas above the filter and storage tank. These are above the outlets. This is energy ultra-efficient, but most systems do require a pump at some point.

Direct pumps

The pumps can be situated either outside the tank or within it, which is the most common. When the pump is outside, it gives you some measure of control. If the tank with an internal pump is in danger of running dry, a small amount of mains water is fed into it, and a dual pump arrangement is often installed for commercial uses.

Indirect pumps

Sometimes pumps will be used to pump the rainwater up to a tank at a higher level, and then gravity will take over. It only must work when the top tanks need refilling.

Booster pumps can be used to supply the outlets, and then it does not matter what level the tank is and offers greater flexibility. This indirect pump suits underground storage tanks.

We can help you choose the system most suited to your requirements. Very often, for irrigation on a farm, an indirect gravity, pump assisted method will be the best option.

Rainwater Tanks with Mains Water Backup

Sometimes mains water back up is required for rainwater harvesting tanks. This helps ensure there is water in the tank during spells of warmer weather when more water is used, and there may be less rain. These mains water backup systems often come under WRAS Guidelines in the Water Regulations Advisory Scheme (WRAS) for rainwater harvesting under the Water Supply (Water Fittings) Regulations 1999.

Category 5 includes the letterbox style air gap to prevent cross-contamination of the mains water supply where a rainwater harvesting system or water from another source is connected. Enduramaxx header tanks/break tanks and mains water backup tanks are designed to comply with the Water Supply (Water Fittings) Regulations 1999.

Are there finance & grant opportunities for rainwater harvesting?

Yes, there are grants available in some parts of the country in the Countryside Stewardship schemes. More details are available here.

The quality of the rainwater

Rainwater can be contaminated with dust, particles of suspended mud, microbes, and leaves. It may need to be treated to make it suitable for crop irrigation. The filtering is the first step in this treatment process, and this may be sufficient for non-potable use.

There are farming rules for water quality here.

Enduramaxx rainwater harvesting tanks

We have a huge collection of tanks suitable for rainwater harvesting. They vary from the elegant slimline tanks or water butt holding just 150 litres to large tanks with 30,000-litre capacity. You can see our collection of above-ground tanks here and our below ground tanks here.

For farmers requiring larger quantities of water storage, interlinking tanks with a flanged pipe or spiral hose linking kit can give you a storage capacity of over 100,000 litres.

Our tanks are of rotationally moulded, non-reactive plastic manufacture. They are sturdy and durable. We can provide all the necessary fittings and filters – and help you choose the best rainwater harvesting system for your situation to reduce water bills. Call us today on 01778 562810.