Results - Wellhams Brook



WellhamsWellhams Brook in Martock takes the form of two watercourses, Hurst Brook (centre in front of buldings) and Mill Brook just in front of the Church, flowing right to left.

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Wellhams Brook at Martock
Wellhams Brook is the name given by the Environment Agency to the network of watercourses that drain the Yeovil scarplands from Ham Hill in the south, the Yeovil boundary in the east and Tintinhull in the north. The main watercourse flows under the A303 near Cargate where it is called Hurst Brook. It splits before the village, the noirthern course being a Mill Race called Mill Brook and the two rejoin just before joining the Parrett at Gawbridge. A network of rhynes flow into both.

Martock Sewage Treatment Plant is built adjacent to Hurst Brook (at this point called Hinton Meads Brook) a little downstream from Martock but the outflow is now piped to the river Parrett just downstream from Gawbridge.

The Hills-to-Levels scheme
Wellhams Brook is the source of all Martock Floods which happen when it is unable to drain adequately into the Parrett at times of high rainfall and high tide in the Bristol Channel. The Hills to Levels scheme is promoted by the Somerset River Authority and FWAG South West as a flood prevention scheme involving slowing the flow through the village by means of a series of dams, big and small, upstream. These not only slow the flow but also provide the right conditions for lowering phospahe concentrations on the watercourses. They do this by ensuring good oxygenation through small waterfalls and well developed riparian and pond planting.


Main observations
These observations may refer to a sample number in brackets. To locate this, follow the link to the maps showing observations..

1 The phosphate levels in the Wellhams system were moderate to poor
All the watercourses tested showed moderate or poor phosphate levels–with two exceptions noted below. All sources are agricultural. Levels were notably higher than recorded by the Environmant Agency who stopped recording in 2017

2 The origin of phosphate in this system is almost all agricultural
There are no Sewage Treatment Works (STW) discharging into this system. Although Martock STW is located next to Hinton Meads Brook downstem of the village, its outflow was moved soem time ago to the River Parrett just downstream of Gawbridge. There are some septc tank outflows in the area and one phosphate-rich tributary has its origins now in a new housing estate near Yeovil.

2 The exansion of fields into previously wide margins.
We have seen increasingly over recent years the gradual narrowing of field margins as farmers seek to replace the Basic Support grant with income, particularly to supply fodder for Witcombe dairy. A number of fields that have previously been grass meadows, often annually flooded, have recently been ploughed to grow fast-growing grass. DEFRA guidelines on farming near water are being increasingly stretched.

4 The Hills-to-Levels Scheme contributes to reducing phophate levels in the system.
This was particularly noticable
where the water is retained for any lentgth of time in ponds. See the Cartgate Case Study below and note the reading (W21) of the newly estabished retention pond at Montacute. This requires a more detailed assessment. Whether this can be scaled up to be of wider applicability is uncertain.

5 Small field margins lead to higher levels of phosphate pollution.
There is evidence that small field margins lead to higher levels of pollution particularly where there was a gradient to the ditch. This can be seen above the confluence of Ball's water and its tributary from Lufton. The Balls Water phosphate reading (W23) field margins above this confluence are shown in the photograph (right)

6 Mill Brook is markedly more polluted than Hinton Meads Brook
Of the two parts of this system, Mill Brook is fed by a greater volume of water downstream of the village. Hinton Meads Brook (Hurst Brook) is normally maintained low, filling at times of flood. Two substantial rhynes drain the valley into Mill Brook, both fed only by field run-off. One of these, the more polluted, currently drains a building site.

7 Bower Hinton Brook–temporary agricultural run-off
Bower Hinton Brook drains the higher land south of Bower Hinton. On occasions the stream fills rapidly with run-off from newly ploughed land that is normally contained but occasionally overflows. All the streams feeding this were in a poor state for short periods in mid March and in mid May after heavy storms. The phophate level of this ditch under normal conditions has not yet been measured.



Environment Agency Sampling
The Environment Agency sample the System in two places monthly at Hills Farm, Martock. Their results are here and show a roughly repeated annual pattern with phosphate levels varying from around 0.1 to 0.3 ppm.

Download the full data here, xlsx file

Survey scale used


<0.04 ppm
0.04-0.07 ppm
0.08-0.19 ppm
0.20-1.00 ppm
>1.00 ppm

This scale is adapted from recommendations of the UK Technical Advisory Group of the Water Framework Directive (Phosphorus Standards for Rivers, 2013)

Data map
A data map showing the location of all measurements is here








Balls HillHills to Levels. Balls Water showing wide field margins on the right but none on the left. This stream had a high phosphate concentration

Cartgate feed Cartgate pond

Case Study - Cartgate Pond
The picture on the left shows Cartgate pond input and output. It has a phosphate level of 0.20 ppm (poor) and a significant growth of blanket algee. The pond itself, shown on the right, is fed only by this stream and is only 10m away from the photograph. At the time this picture was taken it showed no sign of blanket algae and had an undetectable level of phosphate.

The pond itself, shown above, is particularly rich, both in the water and around the edges, in oxygenating plants and the algae is generally unable n to out-compete for resources. The pond is also rich in amphibia, small fish and invertebrate larvae. The key lesson here is that the amount of phosphate entering a pond such as this must not exceed the amount the pond vegetation can contol. This was shown very clearly three yeas ago after dredging removed a lot of the oxygenating plants resulting in the alga covering the whole surface.