Every Roof is a Reservoir: Making More of Rainwater on the Farm

2 days ago
3 min read

After the summer we’ve just had, water availability has understandably been a recurring conversation across the Cluster. For many farms, the challenge is not simply having enough water, but having it where it is actually needed.

Getting water to outlying fields can mean long runs of pipe or regular trips with a bowser. Meanwhile, significant volumes of rainwater fall onto farm buildings each year and can simply disappear into the drainage system.

So, could we make better use of the roofs we already have?

how much water could you collect?

As a simple illustration, based on 600mm of rainfall:

a 1,000m² roof receives around 600,000 litres of rainwater
a 300m² field barn receives around 180,000 litres.

Actual collection will vary according to rainfall, roof area, system design and losses, but the figures demonstrate the potential of existing farm buildings as part of a wider approach to water management.

And it is worth looking beyond the main yard.

Rainwater harvesting is often considered around the buildings we use every day, but the real opportunity on some farms could be the satellite buildings – field barns, outlying sheds and shelters dotted across the holding.

Adding guttering, suitable storage and a trough could turn these buildings into useful water collection points, reducing reliance on bowsers or long pipe runs and providing water closer to where livestock need it during prolonged dry periods.

Strategically located stored water could potentially have other benefits too, including providing an additional water source during periods of heightened fire risk.

Think about where , and when, you need water

This summer has provided a useful opportunity to identify where water availability creates the biggest challenges across a holding.

Which fields became difficult to graze? Where were bowsers repeatedly needed? Which satellite buildings have useful roof areas that aren't currently collecting water?

Storage capacity also matters. It is worth designing a system around when and where the water will be needed, rather than simply how much rain falls over the course of a year. A tank that fills readily through the winter but runs dry halfway through a prolonged dry spell will have limited value when it is needed most.

Could Capital Grants help?

Capital Grants have supported a number of items that can form part of rainwater management infrastructure. Current published rates include:

Rainwater goods (RP16) – £11.55/m
Above-ground tanks (RP18) – £73.34/m³
First-flush rainwater diverters and downpipe filters (RP19) – £174.59/unit
Livestock troughs (LV7) – £152.92/unit.

Eligibility and conditions vary between items, with some rainwater management options requiring support from Catchment Sensitive Farming (CSF) and only being available in areas targeted for reducing agricultural water pollution.

Although the 2026 Capital Grants window remains open nationally, the CSF involvement and application preparation required means it is now too late for us to develop these opportunities for this year's round.

However, with the challenges of this summer still fresh in our minds, now is a good time to start looking ahead. Identifying where better water capture and storage could make a practical difference gives us time to explore suitable options and prepare for future funding opportunities.

Future grant items, eligibility and payment rates may change, so the current figures should be treated as a guide rather than an indication of what will necessarily be available in future rounds.

Planning ahead

Rainwater harvesting won't be the answer everywhere, but it is one practical option worth considering as part of building greater resilience to increasingly variable weather.

Take a look at the buildings across your holding, particularly those away from the main yard and consider where a relatively simple combination of roof + guttering + storage + trough could make a difference.

If this summer has highlighted areas of your holding where water availability is limiting grazing or creating other challenges, please speak to Tom or Oli. We can start looking at the options now and help you prepare for future funding opportunities.

Tom: tom@cotswoldfarmers.org

Oli: oli@cotswoldfarmers.org