River Taf water testing results-September 2026

This report provides an analysis of the water quality data collected across the River Taf in September 2026 at Llandowror, the Water monitoring station, Whitland Church, Login, and Glogue, with comparisons to results from August 2026 and previous months.

Water temperatures decreased across the river network in September, reflecting the seasonal transition into early autumn. Downstream temperatures along the lower stretch were recorded at 16.5°C at Llandowror, 15.7°C at the Water monitoring station, and 15.6°C at Whitland Church, representing a reduction of roughly 4.3°C to 4.7°C from August. Upstream locations also cooled, with Login measuring 14.5°C (down from 18.4°C) and Glogue measuring 13.7°C (down from 16.3°C).

Corresponding with the lower water temperatures, dissolved oxygen levels increased across all five monitoring locations. Dissolved oxygen along the downstream stretches ranged between 9.3 mg/L at Whitland Church, 9.9 mg/L at Llandowror, and 10.1 mg/L at the Water monitoring station. Upstream

readings were similarly high, recorded at 10.0 mg/L at Login and 9.6 mg/L at Glogue, remaining within healthy parameters for aquatic life across the catchment.

pH readings moved slightly lower across all sites in September. Along the lower stretch, values were measured at 7.0 at the Water monitoring station, 6.4 at Llandowror, and 5.6 at Whitland Church.

Upstream, pH values were recorded at 6.2 at Login and 6.2 at Glogue. Glogue continued to stabilize following its initial reading of 10.1 in July.

Nutrient parameters generally reduced across the river system during September. Phosphate levels along the downstream locations decreased to 0.30 mg/L at Llandowror and 0.29 mg/L at the Water monitoring station (down from 0.60 mg/L and 0.50 mg/L in August respectively), while Whitland Church

measured 0.28 mg/L. Upstream phosphate levels measured 0.19 mg/L at Login and 0.04 mg/L at Glogue. Low/normal 0-0.06ppm, Medium 0.06-0.3ppm, High 0.3-1.15. Above 0.3 reduces oxygen levels, causes algae blooms

Nitrate levels also decreased across all monitoring stations. Downstream readings were measured at 0.9 mg/L at Llandowror, 0.8 mg/L at the Water monitoring station, and 0.6 mg/L at Whitland Church.

Upstream nitrate levels dropped to 0.7 mg/L at Login and 1.0 mg/L at Glogue (down from 1.9 mg/L in August). All nitrate values remain well below the excessive guidance threshold of 5.0 mg/L.

Ammonia readings remained low across all sites, ranging from 0.00 mg/L to 0.04 mg/L across four stations, with Llandowror recording a minor increase to 0.22 mg/L. All readings remain within the target threshold of less than 0.3 mg/L.