River Taf Water Quality Report: November 2026

Monthly Water Quality Assessment & Incident Review (Glogue Catchment)Laugharne Citizen Science Group

1. Monthly Summary & Incident Review

This report provides a review and comparative assessment of the water quality data gathered across the River Taf in November 2026 at Glogue, Login, Whitland Church, the Water monitoring station, and Llandowror. Testing was conducted Testing was conducted yesterday and we had a local report indicating that a tanker of agricultural slurry had entered the Taf in the vicinity of Glogue several days prior to sampling.

Analysis of the chemical data confirms strong circumstantial evidence consistent with an agricultural or organic run-off event in the upper catchment. Notably, Electrical Conductivity (EC) at Glogue spiked to 530.0 µS/cm, exceeding the 500 µS/cm pollution indicator threshold and marking the highest reading recorded across the catchment all year. In addition, Glogue registered elevated salinity (0.32 PSU), elevated nitrates (2.6 mg/L), and an acute increase in phosphate to 0.70 mg/L. Further downstream at Whitland Church, phosphate reached 0.98 mg/L and ammonia climbed to 0.13 mg/L, while water conditions were recorded as 'Murky' along the main channel.

Reassuringly, colder winter temperatures (9.1°C to 10.2°C) and strong autumn water flows preserved robust dissolved oxygen levels (10.2 to 14.6 mg/L) across all monitoring points, preventing acute in-river suffocation. However, the distinct chemical signature warrants logging with Natural Resources Wales (NRW) for appropriate follow-up regarding local farm slurry management and storage.

2. Detailed Chemical Parameter Analysis.

Evidence of Agricultural Ingress at Glogue

• Electrical Conductivity & Salinity: Standard monitoring guidelines define healthy freshwater conductivity between 100 and 250 µS/cm, while a spike of 500 µS/cm or above serves as a primary indicator of agricultural run-off or sewage ingress. The reading of 530.0 µS/cm at Glogue (up from 360.0 µS/cm in October) represents an acute ionic spike. This was corroborated by salinity rising to 0.32 PSU (compared to the typical freshwater baseline of 0.02–0.04 PSU).

• Phosphate Surge: Agricultural slurry is exceptionally rich in phosphorus. Glogue recorded a phosphate level of 0.70 mg/L, a substantial rise from 0.04 mg/L in September and 0.20 mg/L in October. Downstream at Whitland Church, phosphate surged to 0.98 mg/L. Both readings sit well within the Water Framework Directive (WFD) 'poor' ecological status region (>0.306 mg/L).

• Nitrate Dynamics: Nitrate at Glogue climbed to 2.6 mg/L (compared to 1.0 mg/L in October), recording the highest nitrate concentration across the catchment this month.

• Ammonia Progression: Because sampling took place several days after the reported discharge, the acute pulse of volatile ammonia had largely passed or oxidised in the aerated upstream waters, returning Glogue to 0.00 mg/L on test day. However, a downstream pulse of 0.13 mg/L was detected at Whitland Church, along with 0.09 mg/L at Llandowror, both remaining below the detrimental threshold of 0.3 mg/L.

Wider Catchment Seasonal Trends

Water temperatures dropped sharply into seasonal early-winter boundaries across the catchment, ranging between 9.1°C at Login and 10.2°C at Llandowror (down from 13.7°C–14.7°C in October). Colder water inherently holds more dissolved gas, resulting in excellent dissolved oxygen readings ranging from 10.2 mg/L at Whitland Church up to 14.6 mg/L at Login. Catchment pH values remained stable and slightly alkaline, measuring between 8.1 and 8.6, well within the safe ecological range of 6.0 to 9.0.

3. Data Summary Table: November 2026 (with October Comparisons)

Monitoring Station	Temp (°C)	pH	DO (mg/L)	Phosphate (mg/L)	Nitrate (mg/L)	Ammonia (mg/L)	Salinity	EC (µS/cm)	Condition
Glogue (Upstream)	9.4 (13.7)	8.6 (8.5)	11.8 (9.8)	0.70 (0.20)	2.6 (1.0)	0.00 (0.07)	0.32 (0.19)	530.0 (360.0)	Not logged
Login (Upstream)	9.1 (14.3)	8.4 (8.5)	14.6 (9.8)	0.28 (0.33)	2.0 (0.8)	0.02 (0.01)	0.17 (0.04)	290.0 (190.0)	Clear
Whitland Church	9.5 (14.4)	8.3 (8.3)	10.2 (9.2)	0.98 (0.22)	1.0 (1.5)	0.13 (0.04)	0.11 (0.06)	260.0 (260.0)	Murky
Water Monitoring Stn	9.4 (N/A)	8.2 (N/A)	12.1 (N/A)	0.29 (N/A)	2.0 (N/A)	0.01 (N/A)	0.06 (N/A)	220.0 (N/A)	Murky
Llandowror (Downstream)	10.2 (14.7)	8.1 (8.3)	13.3 (9.5)	0.55 (0.50)	1.2 (2.0)	0.09 (0.02)	0.11 (0.07)	280.0 (280.0)	Clear

*Note: Values in brackets indicate preceding October 2026 figures for direct monthly comparison.

4. Conclusions & Recommended Actions

1. Incident Logging with NRW: Share the November chemical findings with Natural Resources Wales (NRW), highlighting the specific EC spike (530 µS/cm) and phosphate surge (0.70 mg/L) at Glogue as evidence corroborating the reported local slurry tanker discharge.

2. Continued Upstream Monitoring: Maintain focused sampling at Glogue and Login in December to verify whether ionic conductivity, salinity, and phosphate return to baseline levels following dilution by winter rainfall.