A scour test involves slowly opening and closing the outlet valve, which causes the release of water into the stream. This is likely to cause increased turbulence and deterioration of water quality immediately downstream for the duration of the test and for a short while after.
On the day, tests generally commence between 7-10am and may last for up to 4 hours in total, with a release at full flow rate for about half an hour. If you might be affected by a particular test, please check a week beforehand as there is a small chance for test dates to be moved to a later date or for additional tests to be required.
Aire
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| STUBDEN/IRE | 06/01/2026 | Stubden Beck |
| THORNTON MOOR/IRE | 06/01/2026 | Stubden beck |
| LOWER LAITHE/IRE | 13/01/2026 | Sladen Beck |
| LEEMING/IRE | 22/01/2026 | Leeming Water |
| LEESHAW/IRE | 22/01/2026 | Dunkirk Beck |
| BARDEN LOWER/IRE | 03/02/2026 | Embsay Beck |
| ELDWICK/IRE | 12/02/2026 | Eldwick Beck |
| GRAINCLIFFE/IRE | 12/02/2026 | Eldwick Beck |
| EMBSAY/IRE | 26/02/2026 | Embsay Beck |
| SILSDEN/IRE | 26/02/2026 | Silsden Beck |
| REVA/IRE | 03/03/2026 | Jum Beck |
| WEECHER/IRE | 03/03/2026 | Gill Beck |
| PONDEN/IRE | 05/03/2026 | River Woorth |
| HEWENDEN/IRE | 19/03/2026 | Hewenden Beck |
| GILSTEAD/ESR | 24/03/2026 | Little Beck |
| ELSLACK/IRE | 21/04/2026 | Elslack Beck |
| WHINNY GILL/IRE | 21/04/2026 | Little Brook |
| DOE PARK/IRE | 07/05/2026 | Denholme Beck |
| EMBSAY/IRE | 16/06/2026 | Embsay Beck |
| WATER SHEDDLES/IRE | 18/06/2026 | River Worth |
| LOWER LAITHE/IRE | 07/07/2026 | Sladen Beck |
| LEEMING/IRE | 21/07/2026 | Leeming Water |
| LEESHAW/IRE | 21/07/2026 | Dunkirk Beck |
| KEIGHLEY MOOR/IRE | 23/07/2026 | Morkin Beck |
| SILSDEN/IRE | 13/08/2026 | Silsden Beck |
| THORNTON MOOR/IRE | 01/09/2026 | Stubden beck |
| STUBDEN/IRE | 03/09/2026 | Stubden Beck |
| HEWENDEN/IRE | 24/09/2026 | Hewenden Beck |
| ELDWICK/IRE | 29/09/2026 | Eldwick Beck |
| GRAINCLIFFE/IRE | 29/09/2026 | Eldwick Beck |
| ELSLACK/IRE | 01/10/2026 | Elslack Beck |
| WHINNY GILL/IRE | 01/10/2026 | Little Brook |
| REVA/IRE | 06/10/2026 | Jum Beck |
| WEECHER/IRE | 06/10/2026 | Gill Beck |
| DOE PARK/IRE | 08/10/2026 | Denholme Beck |
| GILSTEAD/ESR | 22/10/2026 | Little Beck |
| PONDEN/IRE | 03/11/2026 | River Woorth |
| WATER SHEDDLES/IRE | 03/12/2026 | River Worth |
| KEIGHLEY MOOR/IRE | 08/12/2026 | Morkin Beck |
| FARNLEY STORM/SLK | 22/04/2026 | Wortley Beck |
| FARNLEY STORM/SLK | 04/11/2026 | Wortley Beck |
Calder
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| GORPLE LOWER/IRE | 20/01/2026 | Hebden Stream |
| GORPLE UPPER/IRE | 20/01/2026 | Gorple lower |
| MIXENDEN/IRE | 27/01/2026 | Hebble Brook |
| OGDEN/IRE | 27/01/2026 | Hebble Brook |
| WALSHAW DEAN MIDDLE/IRE | 29/01/2026 | Walshaw lower |
| RYBURN/IRE | 05/02/2026 | River Ryburn |
| WALSHAW DEAN UPPER/IRE | 19/02/2026 | Walshaw middle |
| WHITLEY/ESR | 10/03/2026 | Whitley wood |
| GORPLEY/IRE | 02/04/2026 | Gorpley Clough |
| BAITINGS/IRE | 07/04/2026 | River Ryburn |
| WITHENS CLOUGH/IRE | 09/04/2026 | Turvin Clough |
| ALBERT/ESR | 21/04/2026 | To Sewer |
| RAMSDEN WOOD/ESR | 21/04/2026 | BrownHill IRE |
| BOOTH WOOD/IRE | 23/04/2026 | Booth Dean Clough |
| DEANHEAD/IRE | 02/06/2026 | Black Burne Brook |
| SCAMMONDEN/IRE | 02/06/2026 | Black Brook |
| RINGSTONE/IRE | 04/06/2026 | Butts Clough |
| GREEN WITHENS/IRE | 09/06/2026 | Booth Dean Clough |
| SPA CLOUGH/ESR | 09/06/2026 | Booth Dean Upper IRE |
| ARDSLEY/ESR | 11/06/2026 | Haigh moor beck |
| WALSHAW DEAN LOWER/IRE | 18/06/2026 | Hebden Stream |
| DEAN HEAD LOWER/IRE | 23/06/2026 | Luddenden Dean |
| DEAN HEAD UPPER/IRE | 23/06/2026 | Luddenden Dean |
| WARLEY MOOR/IRE | 23/06/2026 | Deanhead upper |
| WIDDOP/IRE | 25/06/2026 | Hebden Stream |
| RYBURN/IRE | 16/07/2026 | River Ryburn |
| MIXENDEN/IRE | 21/07/2026 | Hebble Brook |
| OGDEN/IRE | 21/07/2026 | Hebble Brook |
| GORPLE LOWER/IRE | 25/08/2026 | Hebden Stream |
| GORPLE UPPER/IRE | 25/08/2026 | Gorple lower |
| WALSHAW DEAN MIDDLE/IRE | 27/08/2026 | Walshaw lower |
| WALSHAW DEAN UPPER/IRE | 27/08/2026 | Walshaw middle |
| BOOTH WOOD/IRE | 03/09/2026 | Booth Dean Clough |
| WHITLEY/ESR | 08/09/2026 | Whitley wood |
| BAITINGS/IRE | 10/09/2026 | River Ryburn |
| ARDSLEY/ESR | 29/09/2026 | Haigh moor beck |
| GORPLEY/IRE | 01/10/2026 | Gorpley Clough |
| DEANHEAD/IRE | 13/10/2026 | Black Burne Brook |
| SCAMMONDEN/IRE | 13/10/2026 | Black Brook |
| ALBERT/ESR | 15/10/2026 | To Sewer |
| RAMSDEN WOOD/ESR | 15/10/2026 | BrownHill IRE |
| WITHENS CLOUGH/IRE | 29/10/2026 | Turvin Clough |
| RINGSTONE/IRE | 19/11/2026 | Butts Clough |
| DEAN HEAD LOWER/IRE | 03/12/2026 | Luddenden Dean |
| DEAN HEAD UPPER/IRE | 03/12/2026 | Luddenden Dean |
| WARLEY MOOR/IRE | 03/12/2026 | Deanhead upper |
| WIDDOP/IRE | 08/12/2026 | Hebden Stream |
| GREEN WITHENS/IRE | 10/12/2026 | Booth Dean Clough |
| SPA CLOUGH/ESR | 10/12/2026 | Booth Dean Upper IRE |
| WALSHAW DEAN LOWER/IRE | 15/12/2026 | Hebden Stream |
Colne & Holme
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| BLAKELEY/IRE | 08/01/2026 | Butterely IRE |
| BOSHAW WHAMS/IRE | 29/01/2026 | Upper house dyke |
| HOLMESTYES/IRE | 29/01/2026 | River Ribble |
| BILBERRY/IRE | 03/02/2026 | Digley Reservoir |
| DIGLEY/IRE | 03/02/2026 | Digley Brook |
| BUTTERLEY/IRE | 10/02/2026 | Wessenden Brook |
| WESSENDEN HEAD/IRE | 12/02/2026 | Wessenden Brook |
| WESSENDEN OLD/IRE | 12/02/2026 | None |
| LONGWOOD COMP/IRE | 17/02/2026 | Longwood Brook |
| LONGWOOD/ESR | 17/02/2026 | Longwood Brook |
| RIDING WOOD/IRE | 19/02/2026 | Ramsden IRE |
| YATEHOLME/IRE | 19/02/2026 | Netherley Clough |
| BROWNHILL/IRE | 17/03/2026 | River Holme |
| RAMSDEN/IRE | 17/03/2026 | To Sewer |
| BLACKMOORFOOT/IRE (NORTH) | 17/03/2026 | Brow Grains Dyke |
| BLACKMOORFOOT/IRE (SOUTH) | 17/03/2026 | Hoyle House Clough |
| DEERHILL/IRE | 24/03/2026 | Bradley Brook |
| SNAILSDEN/IRE | 11/06/2026 | Harden Dike |
| BLAKELEY/IRE | 16/06/2026 | Butterely IRE |
| BUTTERLEY/IRE | 16/06/2026 | Wessenden Brook |
| RIDING WOOD/IRE | 06/08/2026 | Ramsden IRE |
| YATEHOLME/IRE | 06/08/2026 | Netherley Clough |
| WESSENDEN HEAD/IRE | 13/08/2026 | Wessenden Brook |
| WESSENDEN OLD/IRE | 13/08/2026 | None |
| BOSHAW WHAMS/IRE | 18/08/2026 | Upper house dyke |
| HOLMESTYES/IRE | 18/08/2026 | River Ribble |
| BILBERRY/IRE | 17/09/2026 | Digley Reservoir |
| DIGLEY/IRE | 17/09/2026 | Digley Brook |
| LONGWOOD COMP/IRE | 22/10/2026 | Longwood Brook |
| LONGWOOD/ESR | 22/10/2026 | Longwood Brook |
| BLACKMOORFOOT/IRE (NORTH) | 03/11/2026 | Brow Grains Dyke |
| BLACKMOORFOOT/IRE (SOUTH) | 03/11/2026 | Hoyle House Clough |
| DEERHILL/IRE | 03/11/2026 | Bradley Brook |
| BROWNHILL/IRE | 12/11/2026 | River Holme |
| RAMSDEN/IRE | 12/11/2026 | To Sewer |
| SNAILSDEN/IRE | 10/12/2026 | Harden Dike |
Derwent
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| ELVINGTON/NO 1 ESR | 09/03/2026 | Pumping Station |
| ELVINGTON/NO 2 ESR | 09/03/2026 | 0 |
| ELVINGTON/NO 3 ESR | 09/03/2026 | 0 |
| LOFTSOME BRIDGE/ESR | 12/03/2026 | River Derwent |
| TOPHILL LOW/NO 1 ESR | 19/05/2026 | Barmsten Drain |
| TOPHILL LOW/NO 2 ESR | 19/05/2026 | Barmsten Drain |
| ELVINGTON/NO 1 ESR | 15/09/2026 | Pumping Station |
| ELVINGTON/NO 2 ESR | 15/09/2026 | 0 |
| ELVINGTON/NO 3 ESR | 15/09/2026 | 0 |
| LOFTSOME BRIDGE/ESR | 06/10/2026 | River Derwent |
| TOPHILL LOW/NO 1 ESR | 17/11/2026 | Barmsten Drain |
| TOPHILL LOW/NO 2 ESR | 17/11/2026 | Barmsten Drain |
Don
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| BROADSTONES/ESR | 06/01/2026 | Broastones Dike |
| MIDHOPE/IRE | 27/01/2026 | Hagg Brook |
| WINDLEDEN LOWER/IRE | 03/02/2026 | Clough Beck |
| WINDLEDEN UPPER/IRE | 03/02/2026 | Windleden Lower |
| RIVELIN UPPER/IRE | 05/02/2026 | Rivelin Lower IRE |
| RIVELIN/DEP POND IRE | 05/02/2026 | River Rivelin |
| REDMIRES MIDDLE/IRE | 10/02/2026 | None |
| REDMIRES UPPER/IRE | 10/02/2026 | None |
| REDMIRES LOWER/IRE | 12/02/2026 | None |
| INGBIRCHWORTH/IRE | 26/02/2026 | Ingbirchworth Dike |
| MOREHALL/IRE | 03/03/2026 | Ewden Beck |
| DALE DIKE/IRE | 10/03/2026 | River Loxley |
| DAMFLASK/IRE | 17/03/2026 | River Loxley |
| ROYD MOOR/IRE | 24/03/2026 | River Don |
| SCOUT DIKE/IRE | 26/03/2026 | River Don |
| STRINES/IRE | 02/04/2026 | Dale Dike IRE |
| WINSCAR/IRE | 12/05/2026 | River Don |
| UNDERBANK/IRE | 20/05/2026 | Little Don River |
| LANGSETT/IRE | 21/05/2026 | Little Don River |
| BROADSTONES/ESR | 21/05/2026 | Broastones Dike |
| AGDEN/IRE | 26/05/2026 | Agden beck |
| RIVELIN LOWER/IRE | 04/06/2026 | River Rivelin |
| HARDEN/IRE | 11/06/2026 | Winscar IRE |
| INGBIRCHWORTH/IRE | 18/06/2026 | Ingbirchworth Dike |
| BROOMHEAD/IRE | 25/06/2026 | Morehall IRE |
| MIDHOPE/IRE | 21/07/2026 | Hagg Brook |
| RIVELIN UPPER/IRE | 04/08/2026 | Rivelin Lower IRE |
| RIVELIN/DEP POND IRE | 04/08/2026 | River Rivelin |
| REDMIRES LOWER/IRE | 11/08/2026 | None |
| REDMIRES MIDDLE/IRE | 11/08/2026 | None |
| REDMIRES UPPER/IRE | 11/08/2026 | None |
| WINDLEDEN LOWER/IRE | 27/08/2026 | Clough Beck |
| WINDLEDEN UPPER/IRE | 27/08/2026 | Windleden Lower |
| MOREHALL/IRE | 03/09/2026 | Ewden Beck |
| DAMFLASK/IRE | 22/09/2026 | River Loxley |
| DALE DIKE/IRE | 24/09/2026 | River Loxley |
| SCOUT DIKE/IRE | 29/09/2026 | River Don |
| STRINES/IRE | 01/10/2026 | Dale Dike IRE |
| WINSCAR/IRE | 08/10/2026 | River Don |
| UNDERBANK/IRE | 15/10/2026 | Little Don River |
| ROYD MOOR/IRE | 29/10/2026 | River Don |
| AGDEN/IRE | 05/11/2026 | Agden beck |
| RIVELIN LOWER/IRE | 24/11/2026 | River Rivelin |
| BROOMHEAD/IRE | 03/12/2026 | Morehall IRE |
| LANGSETT/IRE | 08/12/2026 | Little Don River |
| HARDEN/IRE | 10/12/2026 | Winscar IRE |
Esk
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| RANDYMERE/ESR | 06/01/2026 | 0 |
| RANDYMERE/ESR | 14/07/2026 | 0 |
Hull
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| BRANSHOLME/SLK | 23/01/2026 | To Sewer |
| BRANSHOLME/SLK | 23/07/2026 | To Sewer |
Nidd
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| ANGRAM/IRE | 05/02/2026 | NONE |
| SCAR HOUSE/IRE | 05/02/2026 | River Nidd |
| GOUTHWAITE/IRE | 10/03/2026 | River Nidd |
| JOHN O GAUNTS/IRE | 07/04/2026 | Oakdale Beck |
| SCARGILL/IRE | 07/04/2026 | Oakdale Beck |
| GOUTHWAITE/IRE | 08/09/2026 | River Nidd |
| ANGRAM/IRE | 15/09/2026 | NONE |
| SCAR HOUSE/IRE | 15/09/2026 | River Nidd |
| JOHN O GAUNTS/IRE | 22/10/2026 | Oakdale Beck |
| SCARGILL/IRE | 22/10/2026 | Oakdale Beck |
Ouse
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| CLIFTON LAKE/SLK | 26/03/2026 | Blue Beck |
| CLIFTON LAKE/SLK | 24/09/2026 | Blue Beck |
Swale
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| THORNTON STEWARD/ESR | 10/03/2026 | Finghall Beck |
| COD BECK/IRE | 14/05/2026 | Cod Beck |
| THORNTON STEWARD/ESR | 27/10/2026 | Finghall Beck |
| COD BECK/IRE | 29/10/2026 | Cod Beck |
Ure
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| LEIGHTON/IRE | 26/03/2026 | River Burn |
| LUMLEY MOOR/IRE | 23/04/2026 | Holborn Beck |
| ROUNDHILL/IRE | 04/06/2026 | LEIGHTON IRE |
| LUMLEY MOOR/IRE | 12/11/2026 | Holborn Beck |
| LEIGHTON/IRE | 01/12/2026 | River Burn |
| ROUNDHILL/IRE | 01/12/2026 | LEIGHTON IRE |
Wharfe & Washburn
| RESERVOIR | DATE | NAME OF WATERCOURSE AFFECTED |
|---|---|---|
| FEWSTON/IRE | 06/01/2026 | SWINSTY IRE |
| CHELKER/IRE | 08/01/2026 | Bank Gill Beck |
| MARCH GHYLL/IRE | 20/01/2026 | Bow Beck |
| GRIMWITH/IRE | 24/02/2026 | River Dibb/Wharfe |
| ECCUP/ESR | 26/02/2026 | Eccup Beck |
| CARR BOTTOM/IRE | 10/03/2026 | WOODHEAD BECK |
| PANORAMA/IRE | 10/03/2026 | Black Beck |
| LINDLEY WOOD/IRE | 12/03/2026 | River Washburn |
| THRUSCROSS/IRE | 07/05/2026 | River Washburn |
| SWINSTY/IRE | 21/05/2026 | River Washburn |
| FEWSTON/IRE | 21/05/2026 | SWINSTY IRE |
| CHELKER/IRE | 16/06/2026 | Bank Gill Beck |
| BARDEN UPPER/IRE | 23/06/2026 | Barden Beck |
| MARCH GHYLL/IRE | 16/07/2026 | Bow Beck |
| BARDEN LOWER/IRE | 18/08/2026 | Barden Beck |
| LINDLEY WOOD/IRE | 08/09/2026 | River Washburn |
| CARR BOTTOM/IRE | 17/09/2026 | WOODHEAD BECK |
| PANORAMA/IRE | 17/09/2026 | Black Beck |
| GRIMWITH/IRE | 22/09/2026 | River Dibb/Wharfe |
| ECCUP/ESR | 10/11/2026 | Eccup Beck |
| BARDEN UPPER/IRE | 10/12/2026 | Barden Beck |
| THRUSCROSS/IRE | 10/12/2026 | River Washburn |
| SWINSTY/IRE | 15/12/2026 | River Washburn |