| River Blakewater at Lancaster Street Road Bridge | River Blakewater | 19 km | Last sampled 6 Dec 2017, before the imported period | |
| River Darwen at Feniscliffe Bridge | River Darwen | 18 km | 24 Jun 2026 · 3 months ago | Oxygen 113.8%Temp 18.2 °CpH 8.52Ammonia below 0.03 mg/l |
| River Blakewater above the confluence with River Darwen | River Blakewater | 18 km | 24 Jun 2026 · 3 months ago | Oxygen 91.5%Temp 18.8 °CpH 8.05Ammonia 0.11 mg/l |
| River Roddlesworth at SD 646 227 | River Roddlesworth | 18 km | Last sampled 10 Mar 2020, before the imported period | |
| River Darwen at Plessington Fields | River Darwen | 17 km | Last sampled 14 Jan 2020, before the imported period | |
| River Darwen upstream of Butler's Bridge | River Darwen | 16 km | 10 Dec 2024 · 22 months ago | Oxygen 98.9%Temp 6.4 °CpH 8.14Ammonia 0.041 mg/l Nov 2024 |
| Finnington Brook above the confluence with River Roddlesworth | Finnington Brook | 14 km | Last sampled 7 Jun 2007, before the imported period | |
| River Roddlesworth above the confluence with River Darwen | River Roddlesworth | 14 km | 12 Mar 2025 · 19 months ago | Oxygen 103.3%Temp 5.8 °CpH 8.3Ammonia 0.037 mg/l |
| River Darwen at Hoghton Bottoms | River Darwen | 11 km | Last sampled 3 Mar 2020, before the imported period | |
| River Darwen at Samlesbury Mill Bridge | River Darwen | 8.2 km | Last sampled 9 Mar 2005, before the imported period | |
| Hole Brook above the confluence with River Darwen | Hole Brook | 6.1 km | Last sampled 23 May 2018, before the imported period | |
| River Darwen at Roach Bridge | River Darwen | 4.8 km | 7 Sep 2026 · 31 days ago | Oxygen 101% Mar 2025Temp 8 °C Mar 2025pH 8.35Ammonia 0.035 mg/l Mar 2025 |
| Fowler Brook above the confluence with River Darwen | Fowler Brook | 2.8 km | Last sampled 3 Mar 2020, before the imported period | |
| Many Brooks above the confluence with River Darwen | Many Brooks | 1.5 km | 10 Mar 2025 · 19 months ago | Oxygen 110.8%Temp 7.4 °CpH 8.41Ammonia 0.077 mg/l |