The average concentration of phosphorus in NI waterways has dropped and is at its lowest level since 2015, according to new data published by DAERA.

Phosphorus in local rivers is the main water quality issue in NI and long-term build-up of the nutrient was a factor behind algal blooms in Lough Neagh last year.

However, the latest official data shows that average phosphorus levels in 2023 stood at 0.062mg/l, down from 0.073mg/l the year before.

Phosphorus levels in NI waterways peaked in 2005 at 0.083mg/l, then moved on a downward trend after rules around slurry storage and spreading were introduced under the first nitrates action programme.

A low point of 0.047mg/l was seen in 2012, but phosphorus levels generally followed an upward trend over the next 10 years.

Last year’s improvement in water quality is significant given that 2023 was a wet year and there was more risk of nutrients leaching into rivers from farmland.

The new DAERA figures also show that nitrates levels in NI waterways improved slightly last year with 78.9% of rivers falling in the lowest bracket for nitrate concentrations, compared to 78.5% in 2022.

There has been an increase in the number of water pollution incidents caused by NI farms, with 249 incidents occurring in 2023. However, the rise follows on from a record low seen in 2022 when 194 farm pollution incidents occurred.

Last year, agriculture was deemed the source of 30% of water pollution incidents in NI, with 31% of cases categorised by DAERA as “other”. Transport and industry were each responsible for 13% of pollution cases and 10% of incidents were the fault of NI Water.

EFS and trees

Details of the area of land under agri environment agreements are contained in the latest statistics published by DAERA, with 62,000 hectares (ha) under the Environmental Farming Scheme last year.

The figure is down from 64,000ha the year previous and pales in significance to the peak seen in 2010 when 470,000ha were under agri environment schemes in NI.

The publication states that there were 433 ha of new trees planted in NI during 2023-2024, made up from 392ha of broadleaf trees and 41ha of conifers.

Last year’s forestation total is down from 451ha the year before and 540ha in 2021-2022, although it remains well ahead of the 10-year average of 283ha.