Dave Rumble, CEO of Wessex Rivers Trust (WRT) spoke to one of our largest audiences in recent memory when 56 people came along to the first meeting of the new season to hear about water quality in the River Nadder, why it matters, and what can be done about it.
He explained that the Wessex Rivers Trust works with landowners and others to conserve rivers in a wide area covering the catchments of the Dorset Stour, the Hampshire Avon, the Test and the Itchen, as well as rivers in the New Forest, East Hampshire and the Isle of Wight. These include most of the chalk streams that are one of the UK’s most distinctive ecological habitats and make up 85% of all the chalk streams on the planet. Of these, The Avon, with its tributary the Nadder, is arguably the most important of them all.
What makes chalk streams distinctive are that their source, the underlying chalk aquifer, favours a range of plants, such as the distinctive ranunculus (water crowfoot), the range of invertebrate species such as river flies that feed on these plants and the fish that live there. Dave described the way different invertebrates fulfil different roles, complimenting one another in living off the plant life and help keep the river clean, and made the point that their presence, or absence, are good indicators of a river’s health. And he drew particular attention to the presence in the Avon catchment – in addition to the grayling and trout that chalk streams are commonly known for – of a genetically distinct salmon sub-species that returns from the ocean to spawn here. It is this unique salmon and its vulnerability that makes conserving the Avon, and the Nadder, so particularly important from an ecological perspective. Together these are the reasons why the Nadder and the Avon catchment are considered a Special Area of Conservation.
He described the ‘Trinity of Health’, or ‘three-legged stool’, that a healthy chalk stream and its ecology depend on, as Sufficient Flow or volume of water, Sufficiently Clean, and a Natural Habitat, and he went on to discuss the threats to each of these. The first point he made is that legacy issues take a long time to become apparent; because it may take years or decades for rainwater to percolate through the chalk aquifer, problems may only become apparent long after they were caused. He characterised the principle sources and causes of issues as; pressure from increasing population, climate change, agricultural practices, highways, the underinvestment in sewage treatment infrastructure, and septic tanks. Before talking about each of these and what can be done about them, he described the quality of water in the Nadder along its length.
The Environment Agency analysis (using methodology that dates back to the relevant EU regulation) shows the Headwaters of the Nadder - above Wardour Lake - are Poor in quality. The Upper Nadder, from Wardour down to Tisbury, together with the River Sem, is Moderate, as is the stretch from Tisbury to Wilton. From Lower Wilton to Salisbury the river’s quality improves to Good.
Dave explained that the presence of Phosphates probably arising from septic tanks and agricultural practices, are the most likely largest contributors to the Poor rating in the Headwaters and the Moderate rating in the Upper and Middle stretches. But in addition to the these there are signs of mercury and PBDE (a family of man-made flame retardant compounds used in a wide range of applications) that may come from highways or industrial sources and that are persistent pollutants. Quality improves further down the river, partly at least, as a result of settlement further upstream, and as the river flow increases.
He drew attention to the fact that even treated effluent can cause serious pollution harm, in particular due to the emerging problem that pharmaceutical residues that are toxic to wildlife are not removed during treatment. In this context he also drew attention to the harm that can be caused to invertebrates by traces of insecticides used to treat dogs for fleas, and appealed to dog-owners to be alert to this and not let their pets swim in the river for several days following treatment.
Turning to the issue of effluent treatment, Dave homed in on the issue of storm water overflows of raw sewage into the Nadder at Tisbury, Fovant and Barford St Martin, drawing attention to recently reported data showing that between them the three largest water companies, Thames, Southern and Wessex had spilled raw sewage during dry weather for 3,572 hours in 2022, a problem that will take huge investment to rectify. He went on to discuss the issue of broken or poorly functioning septic tanks, a problem that is largely hidden and that the government has attempted to address with new regulations introduced in 2020 requiring an upgrade, with installation of what is effectively a mini-effluent treatment plant, if you want to sell a house with a septic tank. And he explained the significance of the overturning a day previously in the House of Lords of Government plans to remove a requirement to safeguard river health by ensuring the nutrient neutrality of new developments.
Dave gave examples of Wessex River Trust’s work to address some of the other problems he had mentioned, including changes to drainage to reduce the build-up of silt incorporating tyre residues and other pollutants resulting from run-off from roads. And he showed pictures of work to revive the river Test by reintroducing meanders, and the major project currently underway at Amesbury to revive the Avon’s ecology by reintroducing meanders that had been removed when the river was canalised to permit building of the roundabout at the junction of the A303 with the A345.
And, in comments on the need to reduce fresh water consumption so as to preserve the flow of these valuable natural river systems, Dave emphasised the Trust’s work in education and engagement, involving children in exploring the diverse natural world of chalk streams and explaining to them how important this is.
In a closing summary he stressed that a healthy chalk stream is self-cleaning and suggested anyone interested in pursuing the topic further should read a ‘Guide To River Restoration Techniques’ (on the Wessex Rivers Trust website) and ‘Rivers’ a book describing the natural and man-made changes that have affected British rivers since the last ice written by two river ecologists, Nigel Holmes and Paul Raven.
In response to a question from the audience, Dave remarked that usually the best way to manage a risk of flooding was not to carry out dredging, but to increase the river’s capacity by restoring natural meanders and the flood plain, so as to hold back the flow, and mentioned that DEFRA are about to launch a £35million scheme to support flood management schemes. In response to a question about the impact of watercress, Dave said that, as with other forms of horticulture and agriculture, watercress growers using excess fertilizer could lead to nitrogen and phosphate run-off that would pollute the river. And in response to a question regarding water meadows, like the ones at Harnham above Salisbury Cathedral, he said these are amongst the most abundant wildlife habitats, although entirely artificial, having been created by farmers in the Middle Ages to provide early grazing for sheep.
There are spaces available for our September Field Trip, organised by Julia Willcock, your editor. Guests are very welcome for £2 per ticket. Members and under 21s are free. If you'd like to join us, please use the Contact form or the new email address which Andrew (controller of the lists) and other members of the committee can access, as requested in the monthly TDNHS newsletters. Unfortunately we can no longer publish that email address in our blogs because we're attracting Spam!
Keith Lea is guiding us around a section of Savernake Forest and we shall be learning about the veteran trees and biodiversity of this Special Site of Scientific Interest (SSSI) which boasts more than a thousand years of history as a forest.
Keith has over 30 years' consultancy experience in woodland management, with the overall aim of his work being to improve woodland biodiversity. He is the Vice-Chairman of The Salisbury and District Natural History Society and says "I have been a birdwatcher for over 40 years and have a keen interest in butterflies and native flora. I enjoy leading natural history walks and sharing my knowledge with others."
Special instructions: No dogs. Please note that the forest is grazed by cattle which may be near us at times on our outing. Bring binoculars if you have them.
Meet at the Nadder Centre car park at 9:00am on Sat 30 Sept or roughly one hour later at the Burbage petrol station, SN8 3AR at the junction of the A338/A346/B3087. There are parking bays at the garage or by the side of the B3087. We shall gather there and Keith will lead us in convoy to the parking area on the Grand Avenue, within the forest.
Distance, Difficulty and Footwear - Under 3 miles with plenty of stops before lunch and there will be a short (5 minutes) drive after lunch for the optional afternoon walk of under 2 miles. The terrain is generally flat with gravel or hard tracks. Some minor pathways can be muddy and slippery underfoot. There are a few inclines, but they are relatively short. Hiking boots should be fine, rather than wellies, although it always worth packing them. Bring a packed lunch and refreshments.
We look forward to seeing you on Thursday 14 September at the Victoria Hall, Tisbury High Street. Doors open at 7:00pm for the bar and the talk starts at 7:30pm.
Dave Rumble, CEO of Wessex Rivers Trust will give our first talk of the Autumn/Winter series on "Water quality and Biodiversity of the River Nadder and the Avon Basin".
The Wessex Rivers Trust is dedicated to the conservation of chalk streams and rivers throughout the region, looking for ways to improve them and work with partners to make them healthy for both wildlife and people. Dave Rumble has had a love of rivers since his boyhood in Hampshire; before joining the Wessex Rivers Trust three years ago, he had sixteen years’ experience in leading roles with the Hampshire & Isle of Wight Wildlife Trust. In this talk he aims to cover the things that make the Nadder and the Avon catchment special, the threats they face from pollution, and what we should be doing about them.
No need to book. Members and those under 21 have free entry. Guests £2 on the door or please contact us for our BACs information as we do prefer online payments.
In the late 60s and early 70s, Dutch Elm Disease wiped out millions of trees throughout the country changing the landscape for ever. A promotional campaign at the time encouraged us to “plant a tree in ‘73” and then “plant one more in ‘74” to fill at least some of the gaps.
Today, there is much talk about tree planting to lock up carbon and combat climate change. But currently this seems to assume planting will be on a relatively large scale with the expectation on rural landowners to take the initiative. However, we can all play a part.
Significant trees have a tremendous impact on how our villages look. Imagine the view up and down Tisbury High Street without the cedar at the bottom of the hill or the Christmas tree outside the Benett. Or what the Avenue would look like without the line of limes along it. But even the longest living trees will die eventually and if others have not been planted during their lifetime as replacements, their loss is a shock and leaves us all worse off.
As well as old age, we lose trees, or parts of them for numerous reasons. Ash Die Back Disease means that we are likely to lose huge numbers of ash trees in the years ahead. Will they be replaced? Trees are lost to development, while others just get too big for their location. Felling is not always necessary though as a good tree surgeon can bring the tree back to an acceptable size and shape to flourish for many more years.
Unfortunately, it is easy to have double standards on trees. We like to see them in the view but don’t want them to block our view. We like to see blossom, berries, and autumn leaf colour (ideally on someone else’s land or garden) but might not want seeds, dead flowers and leaves on our cars and gardens or noisy birds disturbing our sleep in spring.
Planting a tree is a vote of confidence in the future. The people who planted the largest trees we see around us never lived to see them in their prime as we do. By the time trees planted today reach maturity our successors may find their shade particularly welcome in a warming world.
So as autumn approaches, is there scope to plant more trees around the village? Plant a tree in ’23? Or can we find room in our gardens? Some species never grow to a great size and can be controlled but still have a contribution to make. If we already have trees around us, let’s look after them for everyone’s benefit now and in the future. Trimming, lopping, and felling without adequate replacement will inevitably leave future generations the poorer for their loss.
Photo: Avocets (Izzy Fry)
The headers display photos taken by our members. Do get in touch via the Contact Form if you'd like to submit a photo for selection.