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Living Rivers - A Team Effort part 1

Posted: Thursday 22nd October 2015 by Living Rivers

River LeaRiver Lea

The Trust's Living Rivers Officer, David, talks about the team effort needed to make the Living Rivers a success and we hear from some of the volunteers involved.

Working on catchment scale projects you quickly realise this is not a task one person can accomplish alone. This is no different for the Living Rivers Project and since beginning my role as project officer back in May I have been fortunate to meet and get to know a wide network of people who give up their time in dedication to conserving and improving their local rivers and ultimately making Living Rivers a success. With such a vast amount of work being delivered by volunteers throughout the Lea Catchment it seemed almost necessary to invite some of the people engaged with Living Rivers to talk about their rivers, the projects they have worked on and their experiences within the Living Rivers project.  

River Lea – Patrick McNeil

As HMWT champion for part of the Upper Lea, “my” stretch is from a short distance upstream from Leasey Bridge to Lemsford. The river meanders naturally through most of this stretch, resulting in a good variety of runs, riffles and pools and many lengths of good gravel bed.

This stretch is not officially classified as a chalk stream because a large proportion of the flow consists of treated effluent from the sewage treatment plant at East Hyde, resulting in high levels of phosphates and nitrates. It nevertheless supports a wide range of flora and fauna. Even a total amateur like me can see that the river is rich in vegetation, including water crowfoot, fool’s watercress, yellow flag, purple loosestrife, water mint, water plantain, bulrush, common reed, and several other varieties of rush and sedge. There is also, of course, the dreaded Himalayan Balsam but regular pulling, including by many riparian owners, means that it is under control for most of this stretch. I haven’t identified any other invasive vegetation.

The Environment Agency does an annual survey of fish stocks in the river at a location in Wheathampstead. In August 2014, biomass was high compared with other rivers in the area and had increased dramatically since 2004. Density had increased by 120% since 2013 and was the second highest ever recorded at this site. Chub and roach were the most abundant species, followed by dace and gudgeon. Local anglers know that barbel are common in deeper parts of the river. The EA re-stocked the river with grayling in 2012 and a private fly-fishing consortium re-introduced brown trout in 2014 and 2015.

Bird life is excellent, including kingfishers (with at least three nesting sites), grey wagtails, little egrets, snipe, reed bunting, reed warbler, sedge warbler, grey herons, mute swans, and, of course, scores of mallards, coots and moorhens.

Working with the Riverfly Monitoring Initiative, we have found satisfactory numbers of key indicator species such as freshwater shrimps, olives and caddis flies, though not in the large numbers that live in purer chalk streams such as the Ver and the Chess.

The River Mimram – Robin Cole

The River Mimram is one of the best Chalk streams in the country, supporting a wide variety of birds and mammals, invertebrates and aquatic plants characteristic of this special habitat.

However, as with many other chalk streams, there are many pressures on it including; water abstraction from the chalk aquifer which supplies it through many springs, pollution from surface drainage and sewage spills, and modification of its natural channel shape by dredging and straightening, weirs which cause sediment to accumulate on the gravel beds upstream, and over-shading of the river, discouraging aquatic plant growth.

The Living Rivers project was set up to address these problems throughout the upper Lea Catchment and the situation on the Mimram has been greatly improved recently. Restoration projects have included the removal of a weir (Sherrards Wood), replacement of silt by gravel (Singlers Marsh), and removal of over-shading trees. It has also been fortunate in having the water abstraction licences revoked on two pumping stations, with the prospect of significantly reduced abstractions and restoration of natural flows. In addition, following some serious pollution incidents in 2013, when a river of untreated sewage was released from the Bessemer Road Sewage Pumping station, a total of 18 Riverfly sampling sites were selected for monthly monitoring of pollution levels, in order to detect if, and where, pollution incidents might have occurred.

Finally, there is a project to protect the river Mimram and associated wetland habitats, by designation as a SSSI (Site of Special Scientific Interest). There are 13 such chalk stream SSSIs in the country, and the Mimram is regarded as the one with the longest stretch of completely natural, undisturbed chalk stream channel in the country – through Panshanger Park. A good deal of surveying work is needed to collect the evidence for this designation, and is underway.

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