When we construct artificial surfaces on our farms, such as farm roads, yards, paved areas, or shed roofs, we inadvertently create zones where rainwater cannot naturally seep into the soil.

Instead, water flows swiftly across these hard surfaces, gaining momentum and carrying sediment and other potential contaminants along with it.

While soiled water must be directed to storage tanks, one option for improving the quality of rainwater runoff is to create ‘wetland planted buffer zones’. These simple, nature based systems work by ‘slowing the flow’ of water, which in turn allows sediment to settle and excess nutrients to be naturally absorbed by wetland vegetation before reaching nearby watercourses.

Moreover, when these buffer zones are populated with native wetland plants, they can serve as valuable wildlife habitats.

Water quality measures

Footprint Farmer Martin Crowe has carried out a wide range of wetland and water-quality related measures on his 353ac dairy farm in Co Limerick in recent years.

Actions he has undertaken include creating a substantial wildlife pond and buffering the pond area with a two-hectare riparian zone under ACRES.

He has also recently constructed a wetland planted buffer zone to help to filter any contaminants out of clean water runoff from his farmyard.

Constructing a wetland planted buffer zone

To construct this system, Martin excavated three collecting pools; each divided by an earthen dam and interconnected by overflow pipes.

The three collecting pools serve to decelerate the water flow, enabling the heavier sediment to settle.

Féidhlim explained that the sediment pools in Martin’s system were slightly deeper than they needed to be, which made planting more of a challenge. Shallower pools of six inches in depth are best in order to allow for planting and to promote strong growth of wetland plants.

The overflow pipes then transport the cleaner surface water to the subsequent collecting pool, where this process is repeated.

This week, wetlands expert Féidhlim Harty (www.wetlandsystems.ie) paid a visit to Martin’s farm to help him to put the finishing touches on his filtration system.

Féidhlim Harty planting native Irish wetland species, including bulrush, common reed, branched bur reed, yellow flag iris and reed sweet grass, to create a natural filtration system that both improves water quality and supports our native wildlife.

Martin and Féidhlim were joined by Footprint Farmer Barry Powell, who milks 400 cows on his 420ac dairy farm in Co Tipperary.

Like Martin, Barry is keen to explore simple, nature-friendly solutions to mitigating the risks of water pollution from farmyard runoff.

The focus on the day was on populating the collecting pools in Martin’s new system with native wetland plants.

These plants play a dual role by both further slowing and filtering the water as it progresses through the system and by aiding in the absorption of any surplus nutrients.

Martin chose to plant a variety of native species, including bulrush, common reed, branched bur reed, yellow flag iris, and reed sweet grass.

Additionally, watercress and brooklime have already naturally established themselves in the area.

Since these plants are native species, they will also provide an excellent habitat for our native wetland wildlife, including many species of insects, birds and mammals.

Over the coming weeks, we’ll be checking in on Martin’s progress with his newly planted filtration system.

Wetland-planted buffer zones can ‘slow the flow’ of farm runoff, allowing sediment to settle and excess nutrients to be absorbed by wetland vegetation.

We’ll also be reporting from Barry’s farm, where he’ll be working with Féidhlim to explore how a similar filtration system to Martin’s could help to improve water quality in his own farming system.

Top tips for creating and maintaining a wetland filtration system

  • Targeted location: every farm is different – seek advice or take some time to consider where a filtration system will offer the most value in terms of water quality on your farm.
  • Level base: ensure that the area you dig out is level from the inlet to the outlet and from left to right. This means that the entire area you dig will be effective.
  • Shallow depth: aim for a depth of six inches. If it’s too deep, plants tend to grow only along the edges or to fall over and create a floating mat. Shallow planting, which leads to a thick, dense mat of vegetation, is best.
  • Outflow control: when designing the system, ensure you have the capacity to adjust the water level at the outflow. This flexibility allows you to maintain a lower water level while plants are establishing and gradually raise it as they mature.
  • Small actions: simple actions like widening, damming and planting your existing farm drains can be as effective as creating a new filtration system.
  • Take care: digging and moving earth near watercourses can lead to substantial pollution from escaped sediment: the work described here is for seasonal farm drains – any works on streams need permission from Inland Fisheries Ireland.
  • Preserve existing habitats: avoid destroying one habitat to create another. If species-rich wet grasslands or wide, slow-flowing drains are already effectively filtering your farm runoff, preserve them.
  • Buffer wetland systems: allow for a buffer zone around your filtration system; avoid tilling, spreading, spraying or allowing livestock to graze the buffer zone.
  • Farm safety: fence the buffer zone to prevent access by children.
  • It’s important to distinguish between the wetland system on Martin’s farm, known as a ‘wetland planted buffer zone,’ and an ‘integrated constructed wetland’ (ICW). An ICW is a larger-scale project that necessitates 200% of the yard area, planning permission and a discharge licence. In contrast, wetland planted buffer zones are far simpler to install, and typically do not require planning permission or a discharge licence. For more on ICWs scan the QR code, below.
  • Explore Ireland’s wetlands: if you’re interested in learning more about Ireland’s stunning network of wetlands and waterways and the wildlife that calls them home, consider checking out Richard Nairn’s latest book, Wild Waters.