The dry weather is offering ideal conditions for watercourse maintenance. Rivers and drains on many farms have not been maintained for a number of years and, as result, have become clogged up with silt, overgrown with vegetation or their banks have collapsed and blocked the water flow.

There is often a lack of understanding about what is and is not allowed when it comes to maintenance work if required.

Inland Fisheries Ireland (IFI) and Teagasc have produced a useful publication of the main points to consider. Catherine Keena, environmental specialist with Teagasc, says farmers should be mindful that all watercourses are important for biodiversity in their own right, even small drains that don’t contain fish, but are also important for their influence on larger watercourses.

Cleaning

July and August are the best months to avoid harming spawning ground or fish habitats. According to Catherine, the best approach to take when planning to carry out work on an existing watercourse is to consult IFI first. The rules for cleaning drains are:

  • Do not disturb the non-working bank slope.
  • Do retain vegetation at water’s edge.
  • Do leave working bank slope intact.
  • Do remove vegetation and silt material from the open channel only.
  • Do not remove stone or gravel.
  • Do place spoil along the bank outside the bank-full line, spreading thinly.
  • Do leave a buffer of 20m at the downstream end of a drain to act as a silt trap.
  • River crossings by bridge or box culvert are preferred fisheries solutions. Pipe culverts and fords can block the fish passage. Machinery in the channel can damage eggs of salmon, trout and lamprey.

    IFI says the non-working banking (bank opposite where the drainage digger is working) of the slope should be left untouched to ensure its stability. They say vegetation helps to stabilise the banks and is also good for biodiversity.

    This is an example of what is not allowed. According to IFI vegetation helps to stabilise the banks and is also good for biodiversity.

    Any superficial silt and vegetation can be removed from the open channel. The objective, however, should not be to deepen the watercourse to lower than its natural level, according to IFI.

    Removing gravel and stones from a river bed can do serious harm to salmon and trout spawning areas, by either uprooting current spawning areas or having a negative effect downstream.

    Farmers argue for the need to deepen watercourses to improve drain capacity and effectiveness but IFI says this is not only bad practice but often has little benefit in terms of draining the field.

    They say a drain is only as good as its outlet. If a drain is lowered below the level of the outlet, there will be no drainage benefits.

    Fencing watercourses

    Catherine Keena says watercourses are valuable habitats for fish but also for plants, invertebrates, otters, frogs, newts, kingfisher and other riparian flora and fauna. She says the value of smaller streams and drains is often underestimated. Leaving unrestricted access of cattle to these watercourses can cause significant damage. It can:

  • Damage the bank and bed of rivers.
  • Cause a significant decline in water quality.
  • Cause erosion and possibly flooding.
  • Result in loss of productive land.
  • Fencing off watercourses and providing an alternative source of water is a good way to avoid damage to the river bank and bed.

    “By fencing off the river you can prevent silt entering and building up in the water,” she explained. In GLAS, many farmers have chosen the protection of watercourses from bovines action. Catherine says this action was included in GLAS to prevent pollution and prevent the breakdown of vegetation on the banks of rivers. Drinking points are not allowed in the scheme and farmers need to use an alternative source of drinking water for their livestock.

    Fish habitat

    Watercourses provide a habitat for different fish species. It is best to make contact with the IFI before carrying out work to ensure there is no issue with the proposed maintenance. To find one of the regional offices, check the website www.fisheriesireland.ie or call 01-884 2600. As mentioned previously, July and August are the best months to carry out this work. Fish are active at different times of the year and in different types of watercourse depending on the species and their life stage:

  • Salmon and trout spawn on gravels in winter. Lamprey spawn on gravels in late spring/summer.
  • Coarse fish lay their eggs in weedy parts of the channel in spring/early summer.
  • Salmon and trout use riffles in the first year and move to deeper water as they grow larger.
  • Minnow and stickleback like slow-flowing habitat in rivers big and small.
  • Coarse fish and larger trout and pike will be found in deeper pool areas.
  • Juvenile lamprey live buried in silty margins of watercourses.
  • When cleaning drains be aware of potential damage to fish and their habitats, including impacts downstream.
  • Fish and their spawning grounds are protected under fisheries acts.
  • Consult Inland Fisheries Ireland www.fisheriesireland.ie.
  • Allowable drainage works are least disruptive to fish and their habitats when carried out from July and August.