The Cholsey Brook rises from a number of chalk springs, the primary one of which is close to the old Anchor Inn in South Moreton, South Oxfordshire. It flows in a generally southerly direction until it reaches West End where it turns north east passing under the Great Western main railway line. It then continues in the same direction past Cholsey to Brook House where it turns in a south easterly direction passing under the A329 Reading Road to enter the River Thames at Bow Bridge to the north east of Cholsey a total distance of 6.4km (4 miles).
The Environment Agency has designated most of the catchment as a Surface Water Nitrate Vulnerable Zone (NVZ). They have two monitoring points along the length of the Brook, the results of which show the greatest load from nitrogen compounds is the Cholsey Sewage Treatment Works.
The system is classified by the Environment Agency as a river and designated Hydromorphologically as not being an artificial or highly modified water body.
Environment Agency Classification for the Cholsey Brook
|2009 Cycle 1||2016 Cycle 2||Objectives|
|Water body status overall||Poor||Moderate||Good by 2015*|
|Ecological Status||Poor||Moderate||Good by 2015*|
|Chemical Status||Good||Good||Good by 2015*|
*As reported in Environment Agency's WFD Classification Status Cycle 2 v3 data set published 18th May 2017.
As can be seen from the table above, in 2016 the Environment Agency classified the Cholsey Brook and its tributaries as having Moderate Ecological Status and Good Chemical Status giving an overall classification for 2016 of Moderate. The Ecological Status of Moderate was based on its Invertebrate and Macrophyte elements being classified as Moderate. The Chemical Status is classified as Good, rather than High, arising from a slightly reduced Dissolved Oxygen concentration and the presence of trace levels of Priority Chamical Substances. Both the Ecological and Chemical Status of the Cholsey Brook are predicted to remain Good.
You can find out more about the classification of rivers in our catchment by using the Environment Agency’s Catchment Data Explorer.