A study has demonstrated that the correct farm advice can deliver a threefold improvement in water quality over a 30-year period.
A pilot agri-environmental scheme and associated community engagement and education programme resulted in a 24% reduction in the herbicide MCPA concentration in the raw river water abstracted for drinking water treatment.
MCPA is the most frequently used pesticide throughout Ireland for grassland and fodder crops by both spray area and weight.
It is highly soluble and does not bind well to soil, and is easily lost to water bodies following rainfall, especially when applied to poorly drained soil.
Source to Tap and water quality
The study’s findings arise from the Source to Tap project, which is a €4.9 million cross-border partnership project aimed at improving water quality in rivers and lakes in the Derg and Erne catchments.
The EU-funded, Source to Tap project partners are: Northern Ireland Water; Irish Water; the Agri-Food and Bioscience Institute (AFBI); The Rivers Trust; Ulster University; and East Border Region.
This agri-environmental scheme also awarded €1.16 million in grants to farmers to adopt more sustainable land management practices in the 38km2 River Derg drinking water catchment.
As a result of the scheme, the quantity of MCPA lost from land to the River Derg was reduced by 41%, to 26.6kg in 2021, from what would have been expected in the absence of intervention.
The majority of cost savings resulting from this major project were achieved because regulatory breaches in MCPA trigger substantial capital and operational spends for water treatment that could be avoided with effective catchment management.
Reducing pollution
The agri-environmental scheme aimed to enhance raw water quality by reducing pollution from herbicides, sediment-run off and erosion and was implemented by three catchment officers, working in partnership with local farmers.
There are approximately 340 farms in the catchment of which 236 were surveyed, identifying 1,700 pressures and resulting in €1.16 million in grants being awarded to 118 farmers.
Although weed-wiping with glyphosate and pesticide storage cabinets were the second and third most popular measures (62% and 64% of applicants respectively), they account for just 7.4% (weed-wiping) and 2.9% (pesticide store) of funding awarded.
Only 3% of the agricultural land area was weed-wiped during the project, but this was sufficient to contribute to the improvement in water quality that was observed.
The most popular intervention was fencing, with 66% of applicants choosing this measure, which accounted for 49% of the cost of the scheme.
The River Derg Water Treatment Works is permitted to abstract 26.6 million litres of water per day to supply drinking water to a population of 41,681 in west Co. Tyrone.
As part of the annual review of the Northern Ireland Water Drinking Water Safety Plan for the Derg catchment, MCPA was identified in 2018 as the most pressing threat to drinking water quality.
The monitoring of raw water in the Derg river during the Source to Tap project demonstrated that high levels of MCPA were present, which increase the cost of the raw water treatment process.