Phosphate Monitoring on the Rothay
The aim of this citizen science project is to collect data to demonstrate the extent to which the Ambleside Waste Water Treatment Works (WwTW) outflows are affecting phosphate levels in the River Rothay, which, together with its tributary Stock Ghyll, runs through Ambleside before discharging into Windermere just after receiving the treated effluent from the works. The Rothay comprises 34% of the flow into Windermere’s North Basin, with the Brathay a further 39% and hence are Windermere's principal water sources. The study developed a methodology that can be expanded to establish a baseline of data on the broader health of the Rothay and Brathay, potentially identifying other problem areas such as hotspots of pollution from drains, farming and septic tanks which can then be highlighted to the appropriate authorities and tackled.
A sampling methodology was constructed to examine all potential local sources of phosphate - sewage works, farming fields, drains and off-grid sites. Weekly samples were taken from the River Rothay and Stock Ghyll, both above and below the WwTW, and phosphate levels analysed using a commercially-available, low-cost tester. Urban and rural drains discharging into the river were also tested to determine whether they contained rainwater or were contaminated with phosphate, the latter though either sewer misconnections or leakage of phosphate-dosed tap water.
The testing period lasted from March until September 2023, covering the tourist peaks of Easter, Bank and school holidays as well as the 32-day drought from late-May to mid-June. The results were striking as shown below – clear peaks in phosphate levels flowing into the lake were identified during both the drought and August holidays, the maximum of 120ppb breaking the Rothay’s Good Quality Water Framework Directive targets and being directly attributable to sewage outflow. Furthermore, a series of contaminated drains were reported to the Environment Agency for investigation into misconnections or water-main leaks. No evidence of farming-based phosphate pollution was found.
To analyse the potential impact on Windermere of this phosphate load, a hydrometric model was constructed and compared to satellite-based phosphate measurements. The conclusions from this analysis can be found in the presentation and report produced for this first year's activities.
Tim Boden
A sampling methodology was constructed to examine all potential local sources of phosphate - sewage works, farming fields, drains and off-grid sites. Weekly samples were taken from the River Rothay and Stock Ghyll, both above and below the WwTW, and phosphate levels analysed using a commercially-available, low-cost tester. Urban and rural drains discharging into the river were also tested to determine whether they contained rainwater or were contaminated with phosphate, the latter though either sewer misconnections or leakage of phosphate-dosed tap water.
The testing period lasted from March until September 2023, covering the tourist peaks of Easter, Bank and school holidays as well as the 32-day drought from late-May to mid-June. The results were striking as shown below – clear peaks in phosphate levels flowing into the lake were identified during both the drought and August holidays, the maximum of 120ppb breaking the Rothay’s Good Quality Water Framework Directive targets and being directly attributable to sewage outflow. Furthermore, a series of contaminated drains were reported to the Environment Agency for investigation into misconnections or water-main leaks. No evidence of farming-based phosphate pollution was found.
To analyse the potential impact on Windermere of this phosphate load, a hydrometric model was constructed and compared to satellite-based phosphate measurements. The conclusions from this analysis can be found in the presentation and report produced for this first year's activities.
Tim Boden
Page last updated 07.12.23 . Copyright 2023 Ambleside Action for a Future . All Rights Reserved.