Protecting chalk rivers
The team poddle down the River Cam to their first stop on the trip. Captain Peter tells the Naked Scientists of J. R. R. Tolkien's favourite pub in Cambridge, The Green Dragon. Supposedly, the freehold makes its own apperance in the novel and iconic films too. Iain Webb, Community Communication Officer at The Wildlife Trust Cambridge, has the boat steered over to a quiet river mouth entering the Cam. Iain and colleagues are putting in efforts to protect the rare chalk rivers and wildlife they harbour...
James - Well, I'm not sure how you've wangled this, Harry. I can see we're approaching our vessel here. It looks pretty plush.
Harry - It does look pretty plush, the 'Princess Charlotte'.
James - The Princess Charlotte of 'Eco Cam Trips'. And we're about to be introduced to our skipper, Pete, and Ian Webb from Cambridgeshire Wildlife Trust.
Harry - Well, let's go say hello, shall we?
James - Hello, Peter.
Peter - Good morning.
James - Nice to meet you. Thanks for having us on your boat.
Peter - It's a pleasure.
Harry - Morning, Peter. And what a vessel as well.
Peter - Yeah. The Princess Charlotte is a lovely eco boat powered by solar panels on the roof and what a better day to get it out and about on the river with you.
James - Absolutely. So that's where the 'eco' in Eco Cam Trips comes from.
Peter - Yes. Yeah. Absolutely. We're trying to do our bit for the environment and especially with Ian here today, need to make sure that everything's done properly in a clean way that preserves the wildlife and the integrity of the river.
James - Well, that segues us on very nicely to Ian. Nice to meet you, Ian.
Ian - Nice to meet you.
James - And what might we see today?
Ian - Well, who knows? It's always an adventure going on the river because you never know what you're gonna see. But, you know, Moorhens, ducks, swans, the usual fair. But, we might see a kingfisher; might see a grass snake swimming along the edge; water voles; maybe we've got some dragonflies or damselflies; fish leaping out the water. But it's always wonderful being on the river and it's always a surprise, what we're gonna see.
James - I'm chuffed, I'm really excited. Pete, are we ready?
Peter - We are, yeah, we'll cast off in a moment if you'd like to get yourselves on board.
James- Thank you very much.
Peter - All right, gentlemen, here we go. As you can hear the boat is lovely and quiet. Just a little hum from the electric motor.
Harry - And there we go. It's official, we've weighed anchor. We've been out this morning, James and I, in the water ourselves. And obviously we're sort of preserving that by, on our trip today, being on your electric boat, as you've said. I mean, do you see many of these actually on the water and what's going on? What's this bit of tech, is it half decent?
Peter - Yeah. we believe it to be a unique boat in the UK. It's an electric catamaran and then we converted it to solar panels in the last couple of years. So yeah, we think it's a very special boat because it doesn't use any fossil fuels, it's virtually silent and, at the end of the boat's life, the boat's built of aluminium and it can be recycled completely itself. We'll quite happily power the boat all day, top the batteries up as well, and that would give us about four or five hours of evening cruising, even when the sunlight disappeared.
Harry - How much power do you need to get this thing going?
Peter - Currently, we are using about one kilowatt and the solar panels are generating about two and a half kilowatt.
Harry - Oh, fantastic. And for the rest of the day, where are we off to? What's this journey gonna look like?
Peter - Well, we started off at our main moorings at The Plough at Fen Ditton, just on the Northern edge of Cambridge and we're currently traveling upstream in towards the city center. We're just coming around Ditton corner and, if you draw an imaginary line across the river, this is the city boundary. So we're leaving, Fen Ditton behind and here is Cambridge in front of us, but it doesn't look like it because there's cows in the meadow, there's ducks and ducklings directly in front of us, there's people wandering around. This could be somewhere out in the East Anglian Fens, not a mile and a half from the city center. Looking over the side of the river, the water looks quite clear and you can see down towards the river bed, but that is a slight problem that the river's not flowing that much at the moment. When we get down to Jesus Lock in town, you'll see that the weir is hardly flowing at all. That means the river is stationary and there's lots of weeds growing up through the river, which is good in some ways, but it does make navigation a bit tricky sometimes. During the winter, it's a completely different story. The river turns brown with all the sediment that gets washed out from the fields. And, at that stage, the river's flowing very fast. We're currently about three or four inches below the normal river level because it's not being topped up with fresh water all the time.
James - So Ian, following on from what Harry was talking about with Pete, the stillness of the water is one of the things that strikes us as we are gliding down it. What can we take from how that will impact the environment?
Ian - So yeah, the lack of rainfall we've had this spring has really had an impact on the flow of the fresh water into the river. That impacts on not just the quality of the water, as Pete mentioned, it's really quite still, there's not much flow going on. The fresh, regular fresh water from showers and storms, et cetera, throughout the year helps dilute any pollutants that are found in the water and the, runoff from farming, which inadvertently happens. Oh, sorry, it's just a grey heron just heading our way.
James - Oh, amazing. That's coming right for us.
Ian - It is. It's gonna go through the middle. <laugh> Nearly.
James - That is beautiful.
Ian - Very nice. And with the lack of flow means the build up of water plants. We can see there's curled pondweed in there. I saw some water milfoil all growing in the bed of the channel, which is great, but when there's a low flow, it really does get quite thick and can clog up the river. And it's not just the lack of rainfall in the spring that's the issue, it's the over abstraction of water. So yeah, a lot of the river Cam water comes from chalk streams of which England has an international responsibility. It's a very scarce habitat in the globe. We'll be seeing one in a bit actually along Stourbridge Common, those water bodies are fed by chalk water that rises from the chalk aquifers that are beneath South Cambridgeshire, which is quite a unique habitat. The aquifer, you know what an aquifer is, is a sort of subterranean reservoir of water that is charged by rainfall.
Ian - So when the rain falls on the ground, some of it runs off into rivers and streams et cetera, but a lot of it percolates into the ground and it sort of collects in a big underground reservoir in the chalk. At certain points, at a certain level where the chalk surface is broken, that water bubbles up - it 'spring heads'. So there's quite a few in south Cambridge, 'Nine Wells' just south of Cambridge is a good example. Where we'll be looking at Coldham's Brook that rises in Cherry Kinton, which is in Cambridge as well. So that water flows from those spring heads and, as all water does want to do, goes downhill. So eventually it created these habitats, these streams, these water features that are really quite unique and, because of the nature of the water, it being very clean because there's very little pollutants, it has come straight from the ground, it's a very constant temperature as well, about 10 degrees throughout the year.
Ian - It has created quite a unique habitat. Some of the features have been lost over the years of over-engineering, over -dredging of these chalk streams. So one of the major features is graveled bottomed chalk streams. Nice, not very deep and quite wide, providing great habitat for aquatic plants, such as 'water crowfoots', which in turn provide really good habitat for lots of invertebrates, which in turn provides food for fish, brown trout are a good example of a species found in chalk streams. And from that, if you talk about food webs from a good, healthy base of plant life, you get a very complex and very diverse and very secure food web going all the way up to otters. And we have otters coming through the city all the time.
James - I find that amazing that the temperature of the water stays so consistent all year round.
Ian - Because it's coming straight from the ground and it's been, obviously now there's lots of water coming off roads and the arable land et cetera. It is sped up, you know, the actions of people draining the land, et cetera, building lots of houses causing lots of hard services means the water flows off very quickly. It doesn't have time to percolate in and that's why you have issues with flooding with lots of hard impermeable land. When it rains in something, as we have more experience of stochastic rainfalls, a really heavy downpour, that water's got nowhere to go. So it just flows into the drains and flows into the rivers. And that causes either localized flooding, if the drainage isn't sufficient to remove that water, or it causes flooding in the river when all the water joins and sort of adds to what's already there. We're getting to where Coldham's Brook, a chalk stream, now enters the Cam on the edge of Stourbridge Common.
Harry - It's quite picturesque, isn't it?
Ian - It is very nice. Nature is wonderful when it gets an opportunity to show off itself.
Harry - What have we got there on the riverbank? There's a bit of pink sprouting out and there's draping green.
Ian - I can see branched bur-reed. You've got a greater willow herb. You've got a moorhen chick sitting on the rock. You've got some water mint. There's some gypsy wort.
Harry - I know you said that these types of habitat are quite rare and England has a real duty to protect them. Firstly, what do they bring about that we need to protect? And secondly, are you working with the wildlife trust to help look after them?
Ian - There's about 200 chalk streams or chalk fed streams and rivers in the world. And we have about 85% of them in England. So, as a habitat, which is really quite special, it is really quite rich for invertebrate and plant life and is indicative of good quality habitat. We have a great responsibility to make sure we're looking after it as well as we can. And that is difficult because yes, we can change the sort of physical nature of these streams and rivers. But it's the amount and the quality of the water that is key that makes the habitat so special. And that is a lot harder to manage. My colleague Ruth Hawksley is an amazingly active person working to enhance these chalk streams, and where possible engaging with the landowner, to introduce features that would've been present in a natural chalk stream, but have been lost due to overengineering. So putting in gravel beds, putting in more meandering, The nature of how rivers and streams have been managed over the years is to get rid of the water as quickly as possible, powering water mills, et cetera.
Harry - And agriculture, I suppose as well.
Ian - Oh yeah. Wanting to drain the land so we can grow food to feed our population, which is an important thing to do.
Harry - And so Ruth's just putting some of these features back in, like you said. Meanders, gravel pits, what else is she doing?
Ian - She's putting in big lumps of wood, which is quite exciting, just to help the water move more within the channel, let it become more natural. And one of the issues with chalk streams is there isn't that much flow because they're spring fed. It's not like a raging torrent up in the Yorkshire Dales or something with a large amount of energy in the water to do a lot of movement of gravels, et cetera. These rivers are quite gentle. And so once a feature is lost, it's very difficult for that volume of water to actually make an effect. That's why we have to introduce these gravels, because a lot of the gravels would have been scooped out when they were straightened or deepened to allow the passage of water to be quicker, et cetera.
Harry - And as Peter now pootles us away from Coldham's Brook, are there any particular success stories from the local area where Ruth's gone in and changed the dynamic flow of the river?
Ian - There's this work starting to look at Coldham's Brook. Hobson's Conduit is another one. And outside of the city, there's Hoffer Brook, there's Mel river. There's actually places within the river Cam itself where these features being put in. And also one of the things working with mentioning other organizations is partnership work, working to help remove barriers within the rivers and streams, that hinder migration of fish. So weirs to control water flow, et cetera, or if they can't be removed, putting in features to allow fish to pass through. So if you go to Byron's pool in south Cambridge, there's a bypass channel, which bypasses, as they suggests, the weir at Byron's pool, but allows fish to migrate upstream.
Harry - What fish are we talking?
Ian - Oh, there's about 18 species of fish.
Harry - Here in the river Cam?
Ian - Yeah. They're all under the water, you see, that's the thing. You can't really see them. It's a challenge. So with a lot of the things, looking at the health of rivers.
Harry - And what are a few of those?
Ian - Eel, brown trout, pike, perch, dace, rudd, chub, pike. Yeah.
Harry - I think you've nearly got the whole 18.
Ian - Possibly <laugh>. Yeah. So there is a really rich fish fauna within the river, which is great, but it could be so much better and you just need to create those habitats within the river channel to allow them to find those places to live, but also making sure that water is there constantly flowing, clean and healthy.
Peter - So just to give you a description of where we are on the river at the moment, we've just come under the Green Dragon footbridge. It's proper name is the Stourbridge footbridge, but the Green Dragon pub is just at the end of the bridge. And as we come along this little stretch with all the liveaboard boats, just off in front of us, got a small herd of cattle. You were off the boat a little earlier on looking at Stourbridge Common. We're just coming to the tail end of it and Ian was talking about the cattle that come and graze the meadow. Well, here they are standing underneath one of the trees. There's a horse trough fed by the water point, just here. So the cattle come and have a drink here. So it's quite natural for people to come across them, just standing around milling around, not doing a lot. And off in front of us, the tall chimney of the old waterworks building, the old technology museum just here on Riverside.
Harry - And little does James know I've got a bit of a surprise for him because we're actually visiting that. So we'll be pulling in, in just a couple seconds.