Ewelme Stream (Source to Thames)


© Crown copyright and database rights 2017 Ordnance survey

The village of Ewelme is situated at the western end of the Chilterns, on the eastern slopes of the Thames valley in an area of outstanding natural beauty (AONB). Its name derives from a spring just to the north which forms the “King's Pool”, an attractive pond that empties into the chalk stream called the Ewelme Brook or Stream, Ae-whylme is Anglo-Saxon for “waters whelming”. The Ewelme Stream, fed by this Chiltern spring, once supported a water mill in the village and another two (or perhaps three) in Benson before flowing into the River Thames at Benson 3.7 km (2.3 miles) away.

The Ewelme Brook was at one time used extensively for the cultivation of watercress. Although the watercress beds are recorded as being present in the 1880’s, they are believed to have been in the village for centuries. The stream was dammed and widened to provide large beds of shallow slow-running water, under which the cress was planted, fed all the year around by water from the spring that flows at a constant temperature of 10oC. However, during the last quarter of the 1900s, regulations prevented the sale of watercress from Ewelme and this, together with greater competition, led to the industry's demise, production ceasing in 1988.

For four years the 6.5 acre site was left to nature until 1992 when it was purchased by the Chiltern Society. The Ewelme water cress beds are now owned and managed by the Chiltern Society as a local nature reserve. The beds run the whole length of the village and are accessible from the road in several places. There are water voles and a variety of plants and invertebrates to be found on site.

The Ewelme Brook is classified by the Environment Agency as a river and designated Hydromorphologically as not being an artificial or a heavily modified water body. The total catchment area is 15.1 km2 (5.8 miles2).

The Environment Agency has designated all of the catchment as the Ewelme Stream (Source to Thames) Surface Water Nitrate Vulnerable Zone (NVZ). They have one monitoring point along the length of the system the results of which show that the greatest pollution load from nitrogen compounds is of agricultural origin.

Environment Agency Classification for the Ewelme Stream (Source to the River Thames)

  2009 Cycle 1 2016 Cycle 2 Objectives
Water body status overall Moderate Moderate Moderate by 2015*
Ecological Status Moderate Moderate Moderate by 2015*
Chemical Status Does not require assessment 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 Ewelme Stream and its tributaries as having Moderate Ecological Status and Good Chemical Status, giving an overall classification for 2016 of Moderate. The Moderate Ecological classification of Good, rather than High, is primarily due to phosphate that is suspected to be of agricultural and land management origin. The overall status of the water body is expected to remain Moderate due to the phosphate issue.

You can find out more about the classification of rivers in our catchment by using the Environment Agency’s Catchment Data Explorer.

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