Catchment area 15.8km2, length 8.6km. Not designated artificial or heavily modified.


Waterbody description

The Derry Brook rises south-west of Minety on rural land supplied largely by field drains. It initially flows in an easterly direction then heads north before passing the boundary of the Ashton Keynes and Leigh Parishes before joining Swill Brook. It has been consistently failing for both ecology and water quality (except 2013 Cycle 2), with the ecological status determined by macrophyte (moderate) and invertebrate data (poor). The brook has high levels of Phosphates and very low oxygen levels. The reasons for these failures are thought to be diffuse pollution and physical modification.

The river habitat was surveyed in February 2015(1)) and found to run as a field boundary with significant scrub and is very shaded. Water quality looked poor with the water being very muddy and turbid. Where it was visible the base was a mix of fine gravels sand and silt. Surrounding farmland is largely semi-improved pasture for cattle and horses and some arable crops. A significant section is owned on alternate banks by the Wiltshire Wildlife Trust and Distillery Meadows Nature Reserve. The villages of Ashton Keynes and Minety are under no real risk of flooding.



Some section with Pendulous sedge growing.


Few fish noted – No evidence of otter or water vole. The brook is likely to be too small to provide otter holt habitat although they might potentially use the brook to forage for food. Mallard ducks and species more typical of pasture, hedgerows and woodland were more commonly noted including Robin, Long-tailed tit, Blue tit, Great tit and Wood Pigeon.


Main conclusions from the WILD parish reports

Overall the brook is too small and shaded to have significant value as an aquatic habitat, but the surrounding scrub has value particularly for birds. In the summer it is likely that brook has very little water flow however it may provide habitat for smaller fish species. Any potential enhancement to the brook’s morphology is unlikely to be cost effective. Turbidity is worthy of further investigation if the water quality of the brook is to be improved

  1. Water with Integrated Local Delivery (WILD) Project, River Thames Management Plan, Ashton Keynes Parish, March 2016. Also, Leigh Parish (March 2016) Mintey Parish (February 2016)


Water Framework Directive

WFD 2016 (Cycle 2) Bad overall status (Bad for Invertebrates, Bad for Dissolved Oxygen and Ammonia, Poor Phosphates, Moderate for Macrophytes and Phytobenthos.


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