Author: rangeley

I’ve known this bit of river since I circled the entry in John Wilson’s Fishing in Norfolk. Definitely since before I could drive. I would cadge a lift there when my parents went to the open-air market in Fakenham. Early 1980s then, maybe even late 1970s. The river in those days, according to memory, was broad, tidy and fishless. My fly-angling skills were not that developed but I was handy with an upstream worm. And yet I never caught much more than a few dace. The trout Wilson had promised were very few and far between. Not so in more recent years: trout have been far more numerous.

There will be a number of correlations: water quality, no doubt, which will be generally better now that the Wensum is a Special Area of Conservation (SAC) and privileged by reasonably high standards of sewage processing. But the most significant correlation, I am certain, will relate to that word “tidy”. The river isn’t tidy anymore and therefore the trout have been allowed to thrive.

Back in those darker days of the late 1970s, with the Common Agricultural Policy at its economic height, the Wensum was dredged to destruction. And every time it reared its almost lifeless head off the canvas, it was dredged some more. To be honest, I was amazed the Wensum was ever designated an SAC, as a more physically ruined chalk stream you will not find. Trout find it hard to get along in a dredged, straightened and impounded river that is razed to its silty bed once a year.

But an SAC the Wensum became and perhaps partly for that reason, but mostly because the flood defence teams of the NRA/EA/IDB, have been far less zealous in the last couple of decades, the gentle-natured Wensum has been clambering back slowly, at least onto its knees, if not yet its feet. Trees have been left in the stream. Reeds have been allowed to encroach. The process of self-repair has started.

In fact, that process had contrasted intriguingly with the accelerated “repair” enacted in the name of river restoration on other parts of the stream. I have been watching, for example, the startling difference between the reach 100 yards below the sewage outfall in Fakenham (left-hand image below), where the riparian reeds have encroached on a gravel bar and recreated a natural, meandering channel, with the reach 200 yards below the old railway viaduct (right-hand image below), where a “riffle” (aka weir) made of outsized flints has been installed, impounding the river drastically, causing a massive drop-out of silt and bank to bank accumulation of burr-reed.

The lesson being, nature knows best.

Rather the reason why the likes of David Sear and others have been questioning so hard exactly what we mean by “river restoration”, especially when it comes to chalk streams. They are such gentle rivers: what we do to them stays done for many years. We ought to make sure we get it right, therefore. I certainly made sure we used the CaBA Chalk stream strategy to broadcast that message loud and clear: chalk stream restoration should be about the restoration or facilitation of natural process and not the imposition of arbitrary anthropogenic concepts of riverine form (many of which actually stall those processes as the pictures above show all too clearly).

That self-repair that I was talking about: it had all been happening in the reach between Fakenham Mill and the railway viaduct. The river, as I have suggested, was four decades or so along a successional journey that, in my best estimate, was due to take at least a century, if not longer. But it was at least on that journey.

The Wensum here has been – like all chalk streams – diverted away from its natural course, impounded (in the two spots where the railway crossed it), and very heavily dredged and incised. The picture above shows the existing course in red and the natural course in blue. A chalk stream stuck in this kind of physical prison (red course) will take many, many years to break free. But break free it must … eventually. It would be intriguing to find out exactly how long “eventually” takes. I had been watching the Wensum in this rural but municipal reach, hoping its public ownership (it is council water) meant that it might be left alone long enough, and that I might live long enough, to find out.

Trees help and gradient help. Luckily for the Wensum, in the upper half, where there are not that many riparian trees, the stream is quite steep and in the lower half, where it is incised and impounded, there are lots of trees. So, it had the keys to its jail.

To recover the river must either:

a) recreate a meandering form within its current course (as in the picture on the left in the sequence above), which it will do a bit more quickly if the gravel bed is reasonably intact and if there is gradient, or much more more slowly if it first has to restore the gravel bed that was removed or if there is very little gradient (gradient equals energy and energy determines speed of recovery). In truth, this side of another Ice-Age, a chalk stream will not truly recover a gravel bed on the channel pathway from which the gravel has been removed: the best the stream can do in situ is blow out its banks and throw more gravel into the system, or fill up with silts and fine sands.

or it can

b) break out of its channelised, impounded and dredged course and carve a new pathway across the flood-plain, where there will be gravel that hasn’t been removed by dredging or find its way back to the original channel, which may not have been damaged.

It will only do either of these two things successfully if trees are allowed to fall in and create energy hot-spots, or fall in and sink to the bottom and set a new bed level with the silts and sands filling the spaces between, or so block the stream that the river is forced out of its banks and can find its way over-time to its original course, or maybe carve a new one. Or all the above.

Trees kind of matter therefore. They are critical to the process.

Amazingly, on the River Wensum in this reach, they had been falling in and falling and falling in and no-one had come along all tidy-minded to remove them. And bit by bit the stream was doing amazing things. I walked it in the high flows of the 2020/21 winter and took a load of photographs to record the process.

The top left image shows the river breaking out across the floodplain. The rest of the images are all taken in the woods to the north of the existing channel, and show the start of the process whereby a river starts to reclaim its former, natural pathways … so long as fallen trees are left in the existing channel.

The gallery below shows trees across the main channel which were facilitating this escape. The KEY difference between trees blocking a channel in this way and a flint weir of the type so often installed in well-intentioned “restoration” projects, is that the trees enhance the energy processes of the flowing stream, by creating pinch-points and blow-outs, whereas the gravel bar kills the energy processes by effectively impounding long tracts of the stream: the small energy release that occurs over the installed riffle looks good in photos, but is like lead face-paint to the ecology of the stream.

With all this process-driven self-restoration occurring on an SAC chalk stream, I had hoped the river was being left alone deliberately. I may have been wrong.

Last autumn I noticed works were in progress but was barred from taking a look by Heras fencing and Keep-Off signs. The little I could see through the barriers did not look encouraging. It seemed that the work was driven by the need to repair the footpath, but I could see that a lot of trees were being taken down and stashed untidily on the floodplain beside the raised path.

I went back this morning. The footpath is still “out of bounds” but given that a much more significant crime than trespass was clearly occurring along the river bank – and that lots of other people were also ignoring the injunctions – I walked down to take a look. I could see that some effort had been made to pin a few branches here and there into the edge of the stream. But set beside what had been taken out and – more than that – what could have been done with all the trees now felled and bulldozed out of the way, these efforts were pretty unimpressive. Large tracts of the stream are now wide open and tidy again.

This was mostly ecological vandalism with only a nod in the direction of river restoration or habitat mitigation. The process of self repair has been set back 20 years, sadly. I was a bit heart-bropken, to be honest.

What a missed opportunity! And more than that … what was the point? Did the footpath have to be repaired with enormous machines cutting a swathe through the place and tidying it up like Mrs Mop Transformer?

You say all this stuff about river restoration and everyone nods and sometimes you wonder if anyone really gets it. It’s about PROCESS. So, don’t do stuff that kills process. Least of all on an SAC! FFS.

Whose the beneficiary here … bats and fish, or people?

Sort of trying, in that one limb has been left over the stream … but why remove the lower limb, the one doing all the work?

What purpose was served by the removal of that?

Or that?

Nice and tidy, at least, with none of that messy stuff in the way.

Meanwhile, that flint weir continues its work robbing gradient from hundreds of yards, to spend it all on ten.

So … here’s an idea. Why not do what the Wensum wants to do if only we would let it. Let’s put it back into the blue channel, and for public access create a suspended board-walk that intersects the stream, but doesn’t snuff the life out of it.

(Pictured above: a scarp-face chalk stream in Oxfordshire)

The South East Rivers Trust has issued a call for help in identifying chalk streams in their region. Please have a look at the link HERE.

For other areas, it’s worth noting that Natural England has welcomed this work from SERT, as it specifically works off and feeds into the new, updated NE map that we worked on last year. If you suspect that there are unidentified chalk streams in your region, then take a look at the SERT project or get in touch with them to study how they have run through the process of identifying, checking and notifying.

As SERT points out, while all the “classic”chalk streams are recorded, along the spring-line of the scarp slopes (ie what tends to be the north-east face of the chalk, where it sits on older layers of flint and greensand) there are currently numerous unrecorded chalk springs and rills.

These may even be nameless but are nevertheless ecologically very special. We need to think less in terms of chalk stream catchments here, as chalk spring-lines and their associated habitats.

Apologies for the delay in publishing this … an oversight. This is the collective Chalk Streams First response to the Thames Water WRMP. It will be quite involved for the lay reader, so read my jargon-busting blog if it helps.

The key point, I feel, is that although abstraction reductions are now on the agenda, they are very much back-loaded towards 24040 / 2050 and beyond: take a look at the chart I have made up on the second page of the letter.

They don’t need to be. We have transfer schemes and ideas like Chalk Streams First that, with political backing, could be unrolled in a much tighter timeframe.

Chalk streams have waited far too long. If you can get your hands on the latest copy of Classic Angling, there is a very moving piece on the River Darent, once a mecca for London’s fly anglers: it makes you realise what we have lost … and what we have so long to wait for to return.

It is true that groundwater abstraction is empirically lower now than in the late 1980s. But we’ve reduced abstraction from such very high peaks, the gains are barely discernible when abstraction still remains far too high.

I’ve recieved a friendly moan from an old friend that our letters to Water Resources South East (WRSE) and Affinity Water are unintelligible and therefore difficult to support.

As someone who is passionate about using plain English and trying to write simple, accessible prose I feel a bit embarrassed to receive this fair complaint. The submissions were to specialist audiences at WRSE and Affinity and they will be more than familiar with all the contents. But the average chalk stream fan won’t be. So, while I don’t intend to change the letters, a bit more content and explanation may well help you to endorse them.

Water Resources South East (WRSE) is one of several regional groups tasked by Ofwat (the government appointed watchdog of the water industry) with developing plans to build resilience of supply (making sure we don’t run out of water) and environmental protection into our national water-resources infrastructure (the abstractions and pipelines and reservoirs that bring water to your tap) over the next 50+ years.

This is the best opportunity we’ve ever had to ease pressure on chalk stream abstraction.

WRSE has developed a draft regional plan which is out for consultation with the general public: this is where you get a say in the priorities and thinking behind the plan. The deadline for responding to this consultation is the 20th February. LINK HERE.

In addition there are the water company WRMPs (water resource management plans) which deal with the application of the WRSE work in each given water company area. Again, the deadline for responding to the Affinity Water WRMP is the 20th February. LINK HERE.

I won’t deal with everything in these plans, but specific to chalk streams and especially Chalk Streams First (CSF being a proposal to reduce groundwater abstraction in the chalk stream tributaries of the Colne and Lea and take the water from the lower river instead after it has flowed down the chalk streams) the following should help you understand what we have said:

Prioritisation (where abstraction reductions will happen)

The WRSE plan has taken on board our ideas of prioritising abstraction reduction in the chalk stream tributaries. This is good news and we support it.

However, the WRSE “environmental deficits”(ie. the amount of water we should cease taking from the environment) in the most ambitious versions of the planning, are massive: so large it is difficult to envisage where all the replacement water will come from. These deficits have been arrived at through the application of Environment Agency flow targets on every single water body without, thus far, any published detail to draw distinctions between places where the ecological need is urgent and places where it isn’t.

Given that all water comes from the environment somewhere, the problem with this lack of prioritisation is that we could easily end up creating environmental problems in one place whilst trying to fix them in another, or we could end up not fixing them in a place of great ecological importance by protecting a place of lesser ecological importance.

We think this prioritisation has been slow to develop because it is a very difficult decision-making process. It must be done, however, or we will not achieve value for money, or even the right outcomes, in our attempts to restore and protect the environment.

Demand reduction (each of using less water)

Using less water is a really obvious way to ease pressure on the environment. Currently we use at least 33% more per head than we should: 150 litres per person per day versus a target of 100 – 110 litres per person per day. It’s easy to use too much water when you have no idea how much you are using: you just get complacent. On the other hand, incentivising people to use less water is very tricky: you rely on the full time application of a conscientious approach, which is tough to keep up.

Evidentially, by far the best way to get people to use less water is to fit a smart meter to the house: if people can have sight of how much they are using and how much it is costing them, and how much they could save by using less, they will use less. Simple as.

The government has now allowed for the designation of any chalk stream area as “water stressed”: this means water companies can roll-out compulsory smart metering.

We think they should get on with it as fast as possible.

New sources (finding new water)

The WRSE region is especially stressed because there are just too many people versus too few raindrops in south east England.

Whilst smart meters and leak reduction can help address a large chunk of the deficits, the results from both of these programmes are uncertain.

To ease pressure on the environment and address these flow deficits (as above) we also need to find new water from somewhere, ideally without creating another environmental problem in that other place.

Therefore, we believe the best and most certain way to ease the burden on the chalk streams in the WRSE region is to transfer new water into the region. And the best way to do this without creating a flow problem somewhere else is to transfer water that is “going spare”, so to speak.

GUC (Grand Union Canal)

The most obvious and massive source of water that is going spare is the 400 Ml/d (millions of litres per day) that comes from the Minworth sewage works outside Birmingham. Water that currently swells the flows of the Tame well beyond anything that would have flowed down it naturally, because this water ultimately comes from Wales (through Birmingham), where it rains a lot more than in the south east (and where there are fewer people).

There is also an easy way to get some of that water in to our region, via the Grand Union canal, which for Phase 1 (50 Ml/d by 2030) requires only a modest amount of extra work. This is a no-brainer. Everyone agrees it is. And so we support this transfer fully.

We would also like to see Phase 2 brought forward, so that there is less reliance on the uncertain leak and demand reductions. Not that these aren’t important measures, but they are at best, uncertain.

T2AT (Thames to Affinity Transfer)

Another component of these water transfer schemes that could help ease the burden for chalk streams is a pipeline called the Thames to Affinity Transfer, T2AT (aka Supply 2050). This pipeline would allow any recovered flow that comes from a result of dialling down chalk stream abstraction to be captured in the lower catchments and used to supply the places formerly supplied by groundwater abstraction.

Supply 2050 was once called Supply 2040. When we launched the Chalk Streams First idea we asked for it to be brought forward and called Supply 2030. So, moving it back is the WRONG DIRECTION OF TRAVEL and threatens to delay the recovery of the chalk streams by decades.

Therefore we have objected to this and asked for the Thames to Affinity Transfer to be brought forward.

The delay appears to be based on an Affinity Water estimate that the flow recovery from the chalk stream abstraction reduction (how much of the water you leave in the ground which comes back as surface flow) will be only 17% at low flows and during droughts. Therefore, they appear to be saying that we need a large SRO “strategic resource option” like Abingdon reservoir, or the Severn to Thames transfer, to underwrite the abstraction reductions.

Thames to Affinity transfer, therefore, is currently linked to the construction of Abingdon / Severn to Thames.

Chalk Streams First has no problem with either of these schemes, but strongly objects to the idea of linking chalk stream abstraction reduction to them, as it will delay everything.

We don’t agree with the overly precautionary 17% flow recovery estimate. Our own research suggests the flow recovery will be much more like 50%, as it was during the average flow percentiles that existed for the duration of the two worst droughts in the past 100 years (1921 and 1933/34) (these drought are used as benchmarks for planning).

That’s why we have asked for T2AT to be brought forward.

Groundwater Insurance Scheme

Although we don’t agree with the 17% figure, we do accept that there is uncertainty. No one knows for sure how much flow comes back at given times. The best way to insure against this uncertainty is a groundwater insurance scheme.

This is a tried and tested idea: there is one in existence called the West Berkshire Groundwater Scheme. It is used very occasionally (designed for use every 25 years or so) to pump water from the deep storage of the chalk aquifers of Berkshire into streams like the Pang, where it flows down to the Thames and feeds the London reservoirs during droughts, when they are running out of water. It adds 90 Ml/d to London’s supplies. That’s a lot.

But it is a counter-intuitive idea because it involves abstracting from the chalk in a drought!

Huh?!?!

For reasons that I have tried to explain HERE that actually doesn’t take water from the flow at the time, but instead creates a debt to future flows. This is because there is a time-lag between the abstraction and the impact. By the time the impact hits the winter flows would aid recovery.

Besides, you use the chalk streams to deliver the water.

So, the net impact is actually enhanced flows during the drought and lower flows than natural the following year. However, even through the flows would be lower the following year, they would still be much higher than if we carried on with the current abstraction regimes.

In other words the scheme allows you to dial down abstraction to a minimum most of the time, knowing that you have an insurance fall-back to help water supplies in a drought.

Its a total no-brainer in our opinion and we have asked for an urgent investigation into the viability of the scheme in the Colne and Lea catchments if it means we can get on with dialling down groundwater abstraction to the minimum level as soon as possible.

What does rheophilic mean?

rheo = flow / philic = loving.

Salmon, trout, ranunculus, blue-winged olives etc. are all rheophilic. Natural chalk streams have rheophilic ecologies.

But George Orwell would have always written flow-loving in the first place!

I hope all the above helps. Any more questions … just ask!

Here is the Chalk Streams First coalition response to the Affinity Water WRMP consultation. It has been put together in consultation with all the groups in the coalition.

We are publishing our response ahead of the deadline (20th Feb) so that any individual or group can adapt or quote our collective position in their own response.

Some of the recent posts on this blog help to contextualise the content of our response: see, for example “Something We Should All Agree On”, “The Green Elephant in the Room” and “Flow Recovery Following Abstraction Reduction”.

Find out more about the Affinity Water WRMP on this link HERE

The CSF report into flow recovery following abstraction reduction referred to in our response is available via a link on THIS PAGE or directly HERE

Here is the Chalk Streams First coalition response to the WRSE draft regional plan. It has been put together in consultation with all the groups in the coalition.

We are publishing our response ahead of the deadline (20th Feb) so that any individual or group can adapt or quote our collective position in their own response.

Some of the recent posts on this blog help to contextualise the content of our response: see, for example “Something We Should All Agree On”, “The Green Elephant in the Room” and “Flow Recovery Following Abstraction Reduction”.

Find out more about the WRSE regional plan on this link HERE.

The CSF report into flow recovery following abstraction reduction referred to in our response is available via a link on THIS PAGE or directly HERE

Pictured above: the flow gauge at Redbourne on the River Ver. It may not look like it sometimes but following a significant abstraction reduction in 1993 at Friar’s Wash on the upper river, an average of approx 80% of the water returned as surface flow. The River Ver, however, is still heavily over-abstracted.

The Chalk Streams First coalition has CSF has commissioned an independent investigation (CLICK HERE) into flow recovery following abstraction reductions in the Colne and Lea chalk streams.

This is an important piece of work because currently overly precautionary and unrealistically low estimates of flow recovery are shaping WRSE and Affinity Water plans.

Everyone acknowledges that if you switch off groundwater abstraction a lot of that water comes back as river flow. Not all: some stays under the ground as aquifer throughflow. But about 80% on average comes back as river flow: known as flow recovery.

The flow recovery is not evenly distributed through the year, however. You get a much higher % back at high flows than low flows (see my post “something we should all agree on”). The return at low flows becomes critical, because this is the time when London’s supplies are most threatened and under stress.

Therefore, it is useful if we can find extra water to underwrite the lower returns you get at low flows. And of course, quite how much you get back makes a big difference to cost.

We need about 150 Ml/d to re-naturalise flows in the Colne and Lea chalk streams. And that has been recognised in WRSE plans. So far, so good.

Currently the Grand Union Canal transfer is set to underwrite about 50Ml/d of reductions by 2030-ish. Also, so far, so good.

BUT … the majority of the proposed reductions are not scheduled until after 2040 and are framed as being dependent upon a large strategic resource option such as either the Abingdon Reservoir or the Severn to Thames transfer.

This would push the ecological recovery of the chalk streams decades down the line. We think that is a really bad idea. And unnecessary.

The contingency / delay appears to be based on an estimate of 17% flow recovery from chalk stream abstraction reduction at very low flows, Q95 – Q100, meaning the strategic resource is necessary to underwrite the abstraction reductions. The 17% figure derives from a triangulated process of analysis conducted by Affinity Water and consultants, summarised in Technical Appendix 5.6 “Deployable Output Benefits from Abstraction Reduction”.

Our independent investigation into flow recovery from abstraction reductions suggest that the 17% figure is unjustifiably conservative and that average flow recoveries at the relevant percentiles are considerably higher: in the region of 50% to 60% of upper catchment reductions translates into increased deployable output in downstream reservoirs at the average percentiles through the 1921 and 1933/34 droughts.

The delay in implementing the reductions is therefore unnecessarily precautionary.

It’s a long report, so maybe just read the summary. Once again, it is really important that as many of us as possible get our heads around the nitty gritty of all this, so we can be well informed in our discussions with the water companies, WRSE, the EA and government.

Picture above: The “River” Beane. For much of the time it is not imaginarily dry. It is actually dry.

Just before Christmas I published a long post that few people will have chewed through: my responses to some of the points Rob Soley, technical director at WSP, made in a webinar about abstraction reductions and his view that it is unwise for the UK to “abandon” groundwater abstraction.

Rob has followed up that webinar with a feature in CIWEM magazine entitled “Enormous Cuts to Groundwater Abstraction in England are Unwise”. Rob is an eminent hydrogeologist. His arguments will be taken seriously. Some of what he says I fully agree with, certainly the need to prioritise abstraction reductions so that we get the best ecologic outcomes for the investments.

But as with the webinar, we have to unpick the reasonable arguments from parts that are hyperbolic and alarmist, arguing against the most extreme interpretations of the new ideas. No one is about to turn all these pumps off. There is a reasonable debate now – and not before time – about how to realign water resources and ease the pressure on the environment. As is the nature of debate, there are various points of view. We need to find common ground. Common ground is not the status quo.

The water industry and its army of hydrogeologists must accept that groundwater abstraction has caused and is continuing to cause significant ecological damage to precious habitats in chalk streams around London, into Kent, Cambridgeshire and Bedfordshire. This are where the environmental pressures are at their apex and they are massive.

The NGOs, and river groups need to accept that the public needs water, Water Cos have to supply it, that it has to come from somewhere and that therefore we do need to engage in a pragmatic discussion about compromise and priority.

Rob’s argument is essentially that through a laudable but deluded greenwashing project we are in danger of losing sight of a formerly more rounded definition of “sustainable” water resources, which should include a consideration of fact that we currently enjoy relatively inexpensive and clean chalk groundwater with tolerable ecological impact, versus the costs to society of developing alternative sources (should we do that), the carbon impact of transporting water, and the disappointing ecological outcomes that are likely to follow all that (unnecessary) investment. He characterises this project as the green elephant in the room.

This is a somewhat polarised way of seeing things and I suggest that the problem at the heart of this polarisation is the sheer size of the abstraction reductions which have been put to the regional groups without much attempt, thus far, to really distinguish between them in terms of priority. The deficits were calculated using the EA’s EFI methodology, and applied to every single water-body, without distinguishing between whether the water-body was a vulnerable, headwater chalk stream, or the navigated, impounded and discharge-supported lower reaches of a large, urban river.

This is ringing alarm bells for water companies and their consultants. But Rob is taking arms against a straw man.

At least Chalk Streams First is not arguing for the scale of abstraction reduction Rob takes issue with. But we are arguing for the restoration of flows to streams like the Ivel, Ver, Chess, Beane, Misbourne, Rib, Darent, etc. In our submissions to WRSE and WRE we have argued for a transparent prioritisation process. And indeed the EA has taken note of this and some work is being done in the area.

That work needs to be made urgent now. Otherwise the debate will entrench and become this all or nothing dichotomy in which I am certain the environment will lose out. After all money trumps ecology every single time and if the bill can be characterised as foolhardy and massive, it won’t get paid.

One example: the total deficits for the whole Colne system down to the Thames amount to 270Ml/d. That’s a lot of water. Two Abingdon reservoirs of deployable output. The total deficits on the chalk stream tributaries, however, amount to about 80 Ml/d. Factoring in a reasonable expectation of 50% flow recovery (see my previous post) at low flows, that leaves a net deficit of 40 Ml/d. This can be cheaply provided via the Grand Union Canal transfer.

If you add to this the idea of a groundwater insurance scheme, the net deployable output to London actually goes up.

The lower Colne, which makes up the bulk of that enormous 270 Ml/d deficit, is highly modified, embedded in a stable water-table, much supported by discharges and would benefit from the all the chalk stream flow recovery anyway.

There are intelligent ways to do this, in other words. Ways that are not all or nothing, but consist of pragmatic and measured improvements that are well worth paying for.

Pic above: The River Ver in the drought of 2022. And the million dollar question: how much flow do we get back if we turn off abstraction?

Making Chalk Streams First a reality: how do we overcome the uncertainties?

A few months ago the Chalk Streams First group commissioned a follow-on report from John Lawson, to investigate and collate evidence of flow recoveries following abstraction reductions in the Chilterns and Herts chalk streams. The report is now finished and we will publish it soon. 

The blog post below introduces some of the complex discussions in the report. It leads to an important proposal for a type of scheme which traditionally the conservation community has been wary of, but which is well worth considering in the light of the debate over flow recovery. 

It could help to address water-supply resilience and ecological restoration and thus allow the full delivery of Chalk Streams First within a few years as opposed to a few decades.

PART 1.

If I was to say “abstraction has a much smaller impact on chalk stream flows at low flows and in times of drought, than it does at high flows and in winter” you’d probably furrow your brow. 

Everyone does.

The explanation is actually found in simple physics. But it’s counter-intuitive and so not easily understood, and because of that, not generally known.

But it is really important that we get our heads around the idea, because otherwise we’re in danger of allowing the Chalk Streams First project, and especially the potential pace at which it could be realised, to be derailed. And we’re in danger of missing the clear benefits of a groundwater scheme that could bring all parties together.

With a surface abstraction from a river, it’s easy to see the link between abstraction and flow. The river is flowing at X Ml/d. You insert a pump into the river and pump at a rate of Y Ml/d and the flow d’stream of the pump will become X – Y Ml/d. 

As the flow in the stream diminishes through the summer, Y will become a larger and larger proportion of that flow. And vice versa, it will become a smaller and smaller proportion of that flow through the winter. Therefore constant surface water abstraction has a BIGGER impact on low flows than high flows.

And yet most groundwater abstractions – and certainly groundwater abstractions at a catchment scale – seem to have the opposite impact: a smaller impact on low flows than high flows.

How?

The reason is bound up with the fact that once you abstract water from the ground and not directly from the river, the impact on flows is no longer direct either, but occurs via the impact on groundwater level. Thus the impact is bound to the relationship between groundwater level and flow, because it is groundwater level – the head of the groundwater level above the bed of the river – that drives flows into chalk streams.

Just as the rate of flow out of a hole at the bottom of a bucket increases as the level of water in the bucket rises, so the rate of flow from an aquifer into a chalk stream rises as the groundwater level rises. The force that drives the flow is gravity or hydraulic head.

But it’s not just hydraulic head that places a cog in the link between groundwater level and flow. There are the properties of the rock matrix of the aquifer – how much water it holds and where and how quickly that water can move – as well as the topographical shape of the valley. And there’s time too. 

All of these combine to create a non-linear relationship between groundwater level and flow. Which means that for each unit rise in groundwater level, you get an exponential increase in flow. The aquifer, its topographic features and time provide gearing, if you like. 

So, if a rise in groundwater level from, say, 98 to 99 AOD gives a much greater increase in flow than a rise from 95 to 96 AOD, it stands to reason that a reduction in groundwater level from 99 to 98 AOD, will cause a much greater reduction in flow than a reduction in groundwater level from 96 to 95 AOD. 

Same unit rise or fall, but a bigger or smaller net reduction in flow.

Abstraction has an overall lowering effect on groundwater level. Therefore, one can see that the overall effect will have a bigger impact on flow when groundwater levels and flows are high, than when they are low.

The implications of this, when combined with water resource considerations, are significant.

We’ve always said, when pushing the case for Chalk Streams First, that if you switch off abstraction you get, on average, about 80% of the water back as surface flow. We’ve also always said that % flow recovery varies through the year, with over 100% in winter and as low as 30% or so in late summer (when groundwater levels are lower). In very low flows (Q99) this recovery might drop to only 20%.

This is where TIME comes in. The abstraction rate was constant, but because of aquifer gearing, the “less” you get back in the summer, actually comes back as “more” in the winter and you have to take a long view to see that over the full year the amount of water you get back is about 80% of that former abstraction rate (the remaining 20% passes through the aquifer under the ground).

Obviously these figures vary stream to stream.

It is the figure at low flows that is key, because it is low flows and especially 18-month droughts, that threaten water supplies in and around London. 

In the current drafts of Affinity Water’s & Thames Water’s water resource management plans, and the WRSE national framework plan, the estimate of flow recovery at low flows is a conservative 17%, where we think the figure should be over 50%.

The critical droughts used for planning purposes are the 1921 and 1933/34 droughts. The WRMPs are built around the basis that flows in these droughts averaged at the 98^th percentile. In fact, from the beginning to the ends of these droughts flow averaged the 95^th and 89^th percentiles respectively, a combined average of the 92^nd percentile, at which flow recovery from the Chilterns chalk streams – in our estimation – would be over 50% of the abstraction reduction.

The knock-on effect of planning according to that – in our view – irrationally low figure of 17% is that the lion’s share of the Colne / Lea chalk-stream abstraction reductions have to wait for a very large strategic resource option such as Severn-to-Thames Transfer or Abingdon reservoir. That pushes them back until after 2040. 

Can we really wait two more decades – and probably longer – for the full restoration of flows to our beleaguered chalk streams? In our view we could see most of the very much needed abstraction reductions far sooner. 

Part 2. The way round this which we could all agree on and act now.

Despite our differences of opinion over flow recovery, we can probably all agree that there is indeed uncertainty over the % flow recovery we will see at low flows. 

Therefore, from all points of view it is surely best to investigate ideas that overcome this uncertainty, ideas that might ensure the resilience of public water supply – as that is the issue of greatest concern to Affinity and their primary statutory duty – and also fully re-naturalise flows in the chalk streams, within a reasonable time-frame, not 20+ years.

The original Chalk Streams First idea was designed as a pragmatic solution to the formerly irreconcilable tension between public water supply and the ecological health of chalk streams near London. It always depended on storage because of the differing levels of flow recovery you get through the year. Now, with flow recovery at the very lowest of flows identified by planning constraints as the limiting factor, it is surely worth exploring additional ways to insure against these uncertainties.

Minworth – GUC transfer.

Water transfer from the Minworth sewage outfall via the Grand Union Canal is one such idea that has been universally accepted as worthwhile: it is in the WRSE and WRMP plans and of itself covers off a proportion of the abstraction reductions needed to restore natural flows to the Chilterns and Herts chalk streams. But it isn’t enough.

Licence Relocation

Rolling the groundwater abstractions down the catchment is another such idea: this came from Affinity and is a version of the Chalk Stream First concept. If the abstractions are sited down-catchment, where there is always perennial flow that vastly exceeds the pumping rate, much supported by discharges, then it is likely that stream-side groundwater abstractions will have an almost 1:1 impact in the same way surface abstractions do.

Groundwater Insurance Scheme.

In spite of both ideas above being no-brainers and enjoying universal support, the full-fat version of the Chalk Streams First proposal is presented as dependent on another large strategic scheme, such as Abingdon Reservoir or the Severn-to-Thames transfer. The Chalk Streams First group sees both as potentially important components to help ensure resilient water-supplies, but we would be extremely and justifiably disappointed if the full realisation of Chalk Streams First was made contingent on these either or both of these schemes. It would push the ecological recovery of these chalk streams decades down the line.

Therefore a third idea, tried and tested elsewhere, and worth exploring in the context of the Colne and Lea, would be a version of the West Berkshire Groundwater scheme (WBGWS).

Once it is understood that abstraction at low flows has a much smaller proportional impact at the time*, then it can be understood that something like the WBGWS has the potential to guarantee drought supply with a minimal ecological impact. This guarantee then underwrites the whole Chalk Streams First concept because the limiting low-flow recovery is underwritten.

(*Important to contextualise this “smaller” impact: where abstraction runs at 25 – 50% of recharge, as it does in the chalk streams around London, this “smaller” difference can still be the difference between flow and a dry river).

The West Berkshire Groundwater Scheme (WBGWS) was constructed in the 1970s to augment London’s water supplies during severe droughts – its planned use is about once in 25 years. The scheme abstracts water from boreholes in the chalk aquifer in the upper Lambourn, Pang, Enbourne and Loddon valleys, discharging water into those rivers from where it flows down into the River Thames for later abstraction to fill London’s reservoirs. It contributes about 90 Ml/d to London’s deployable output. 

The WBGWS concept could be used in the Colne and Lea chalk tributaries, in combination with current proposal for reduced abstractions for day-to-day supplies. Replacement supplies would be transferred from the London supply system using the Thames to Affinity transfer and the ‘Connect 2050’ pipe network. 

Our initial assessment of the WBGWS concept in the Chilterns chalk streams has shown that on the River Ver a reduction of abstraction from the current 28 Ml/d to about 8 Ml/d, combined with WBGWS-type drought support of up to 25 Ml/d, would almost re-naturalise River Ver flows and also give a net increase in London supplies of about 9 Ml/d. 

If the concept was adopted in all the Colne and Lea chalk streams, abstraction could be reduced by 150 Ml/d to meet EFIs throughout the catchment. The 50 Ml/d first phase of the GUC transfer is a no-brainer, so only 100 Ml/d of replacement needs to come from the connection to London’s supplies. 

If the deployable output recovery of London’s supplies from the 150 Ml/d reduction is the 50+% that we predict, the concept gives a 50-60 Ml/d gain in London’s supplies. If the DO recovery is only 17%, the concept would still allow the 150 Ml/d chalk stream reductions to take place without impacting London’s supplies.

The drought support would only be needed about once in 25 years. Drought flows in the chalk streams would be increased by the WBGWS-type releases and would be slightly less in the following year but importantly, they would still much more than with abstraction at recent levels. 

This would remove much of the doubt that currently exists over the amount of flow recovery from abstraction reductions. A net gain in deployable output of 55-60 Ml/d could make this a significant new water resource in its own right. 

Why have schemes like this traditionally been seen as a “bad thing” by conservation groups? An incomplete appreciation of the gearing of impact must be one reason. Another may be an ideological aversion to the active management of a natural system. But all aquifers in south east England are managed to a degree: better by far to manage them intelligently to suit all desired outcomes. A cynicism about schemes which are usually proposed by water companies might be another reason!

Let’s put all these aside. Surely we need to engage in serious discussion about this idea?

Chalk Streams First appears to have brought all parties together: Ofwat, the water companies, EA and the NGO’s. But in the current draft plans it’s pace of instigation is still too slow / and the full version is at best uncertain.

The GUC transfer is a must have – so please support that in your responses – but let’s ask for a serious investigation of the groundwater insurance scheme too.

Much credit is due to John Lawson for the many, many hours of investigative work he put into the ideas I have summarised above.

One of the dangers of best-kept secret rivers is that they are more easily trashed. I have long known this, and more than once before have had to open up on the name of a beautiful stream that I enjoy walking and fishing in order to shout loudly how important it is.

I’ve not done this in New Zealand before, however, have not ever felt it was my place to. And I know that Kiwis, fishing guides especially, don’t like the names of their secret spots broadcast far and wide. So, I’ll keep the name of this place quiet for now – if you know it, you’ll know it – at least until I can find out more about the reasons behind what I saw yesterday.

Because yesterday, I felt like giving up. I was totally in the dumps. The struggle to champion the cause of pastoral spring streams (chalk streams being in that group, and at the very apex of pressure caused by humans) feels too much like an uphill one at times.

I’m on a tour of New Zealand with Simon Cain – also a passionate river-restorationist who I have known since 1991 – showing him all the unspoilt spring-creeks I have been going on about for so long, the rivers I like to model river restoration ideas on. I told him the stream we were going to look at was one of my favourites: “It’s kind of like the upper Frome,” I said. “Only maybe a 13th century Frome.”

You could pick all sorts of holes in my comparison. There were no mills on this stream. There are no mountains to the side of the Frome. But it painted a picture. And indeed this stream has also worn the impact of farming quite heavily in places, over the years. It is abstracted by pumps. One farmer on it makes no effort whatsoever to fence out the livestock and the riparian edges in that reach are nibbled and puddled bare. The very headwaters, which were once a marsh supporting the base-flow, have been arterially straightened in the past.

But somehow the river was still just lovely. And I have often cited the lowermost farmer – when chatting to other farmers, many of whom are not that happy about the new NZ law compelling the fencing out of livestock (it is causing problems with overgrowth of rank marginal vegetation) – as having managed the riparian strip to perfection ever since I had known the place and long since before the new law: a fence twenty to fifty meters back and very occasional grazing on the stream side. He had presided over a true spring-creek paradise.

Which is why I suspect the farmer here is not to blame. Why, having been apparently perfectly happy for many years with the co-existence of his farming and his spring-fed stream, would he suddenly take a hatchet to the latter and hack it to bits?

We noticed the silt on the bed as soon as we arrived, noticed spoil on the bank by the first pool: rocks and stones and dusty, ex-riverbed the colour of light earthenware under an unnaturally vivid green flush of nettles and docks and thistles: all the stuff that loves the arrival of river-bed nutrients on top the of the floodplain where they don’t belong.

My thought was a resigned “that’s a shame”. We were near a bridge and I know farmers do get a bit heavy handed with the digger around bridges, in a (usually misguided) effort to create greater conveyance of flow.

But then around the next bend we saw more of the same, only the digger had really gone to town here, pulling out the bed and inside point-bar, dumping it all up in the side. The work had been done only a few months ago and already the stream was notching its way back upriver. Already the stream – in other words – was demonstrating the utter futility and pointlessness of the works, because it was now eroding really badly, with the banks slumping in and drastically undercut because of the excessively steepened gradient.

This continued for bend after bend. Apparently as far as we could go and further.

I felt too miserable after a mile or so and we turned back.

Then I remembered the photos I had taken here in 2020, expressly to capture the morphological features of the stream: the meander shapes, the relationship between the water surface and the flood-plain, the gently undercut banks and point-bars. All of which were now screwed. I hunted back on my phone to February 2020 and tried to line up a few before-and-after images. But I struggled to find the correct alignment between the stream and the hills: at least until I realised that not only had they dragged out the bed of the river, they’d tried to cut the meanders out too.

I was still just about thinking it was the farmer’s work and I was trying to fathom the “why?”. I was thinking: “They’ve had massive floods and done all this in an understandable, but misguided effort to drop the river back inside the banks.”

We slumped back to the car and in an effort to cheer both of us up I said to Simon that we’d drive up the valley to another bit I know. Only when we got there Simon looked out the window and said: “They’ve fucked this too. Look at all the gravel!”

And indeed, “they” had. Whoever “they” are.

By now I was thinking: this is the work of a flood defence department. Our own versions did all of this and more in the UK and Ireland. Only flood defence departments are this dim, careless and – I hate to say this but – entitled. I’ve thought about that last word, whether it is justified here, as the first two surely are. And I think it is, because when you go in and radically alter an ecosystem like a spring creek, it is surely beholden on you to understand what you are doing and carry out the works so that they achieve the desired outcome and not simply wanton destruction?

NZ’s spring creeks are globally very special. There just aren’t many rivers like these and most have been messed around with. NZ’s spring creeks have (thus far!) been modified less than most and some not at all. These streams should be seen as a national treasure, not drainage channels.

Later, asking around in town, we discovered that there had indeed been floods. The golf-course had been underwater and so had stream-side houses … miles downriver of the spring-creek vandalism, mind. Riparian property where a river belongs. It all made sense.

Only a flood defence department would steepen the gradient upriver in an attempt to alleviate flooding downriver. Only a flood defence department would make far worse the very problem they were trying to fix.

The river will now try to tear itself apart in order to win back the material it needs to put itself back together. As it does so, the water will travel more quickly, and downstream floods will be more aggressive: they will rise faster and bring with them way more mud, silt and stones.

Rivers flood. The only way to control flooding is to control where it happens. You can’t stop it. Allow it to happen in certain places in an effort to ensure it doesn’t in others. This stream has a two-stage form anyway, with secondary terraces way back from the main channel: you have to let it flood out to these or you will send all the water in even more of a hurry to the very property you are trying to protect.

One optimistic note: this stream will self-heal. Unlike chalk streams, it has the energy and the material to do so. Provided it is left alone. Which is now a very questionable proviso, because the notching and erosion will unleash a process which will appear in the minds of the men who did the work, to justify it in the first place.

And so we struggle on “boats against the current, born back ceaselessly into the past”.

More pictures of the destruction: