If you’ve seen the latest James Bond instalment you’ll be aware the scriptwriters had the task of tying together every storyline and character from the last 20 years into one resolution; As such that’s why we’ve been quiet at Tophill Low of late – irrespective of the tunneling works which are due to conclude for the new year, we have been doing the same; Just on the slightly less glamorous theme of Algae.
In short;
We’re building a new facility in the Water Works between
2022 and 2024 to improve drinking water quality.
We’re working in partnership with this scheme to minimise
disruption to local communities which will see replacement O res and D res East
hides in conjunction with long anticipated habitat improvement works, which
will concentrate any disruption into a single intensive block.
Please expect periods of partial or site closures in the
first half of 2022 whilst this work is undertaken subsequent to which we can
enjoy enhanced facilities and habitats.
Detailed;
So where do we start? – you’d better grab a cuppa this will
take some time;
The whole issue has its roots in nitrates. This graph illustrates nitrate levels at the spring line on the Yorkshire Wolds above us and the head waters of the river Hull.
There are various causes mooted but most would agree that
this is the output of modern farming practices, be it from the second world war
ploughing out of sheep pasture on the Wolds, to the continued application of artifical fertiliser
to land. The problem is in some cases,
water (and dissolved nitrates) is reckoned to take 60 years to pass through the
aquifer and emerge at the spring line.
The worry is that what we’re seeing now will not abate for half a
century even if every farmer on the Wolds stopped applying fertiliser tomorrow. In the impermeable valleys of the Yorkshire
Dales, Yorkshire Water frequently owns the catchment, and we can stipulate what is
applied and when to tenant farmers to secure water quality. Unfortunately, on the Wolds it is diffuse
from potentially thousands of private farms and all we can do is educate around
the most environmentally (and cost) efficient ways of maintaining crop
yields. There are some success stories;
YW have a great partnership with Birdseye that has seen cover crops used to
bind and secure soils from pea fields susceptible to run off, and there’s
possibly some connection with this abundant annual seed resource in the last
couple of winters, and the vastly increased numbers of wild geese lingering in
the Wolds and Humber?
Nitrates causes a range of issues not just for us. On some of the SSSI designated chalk springs
species are being lost as what should be clean nutrient and competition free waters are instead
growing prolific rank vegetation because they effectively have fertiliser in
the water. Down stream the river is
often choked with blanket weed causing the fly-fishing community issues as
trout runs need to be cut to allow the water to be seen, the boating community
at Bethell’s bridge have a specialist weed cutting boat to keep the river navigable
in summer, and at Hempholme Weir the Environment Agency has a weed boom and
dredger installed every summer to keep the tilting weir mechanism clear of weed
and functioning.
For us at Yorkshire Water we have strict limits on nitrates
imposed by the Drinking Water Inspectorate – the government regulator. The purpose of the two raw water reservoirs ‘D’
and ‘O’ built in 1959 is to dampen out peaks of poor-quality river water,
allowing us to abstract only water within tolerance and run off the 320 million
gallon reserves if not of treatable quality.
Unfortunately, now it is rare any water can be abstracted
within tolerance. As such to ensure
water quality for consumers is maintained Yorkshire Water installed a £14
million nitrate extraction plant in 2015 within Tophill Low WTW which ensures
we can maintain supplies within DWI limits.
Whilst this ensures there is no risk to consumers, the problem still remains of accumulated nitrates within the reservoirs themselves, which being shallow and of crystal clear chalk water combine with summer sun and heat to perfect conditions for algae.
Whilst not harmful itself there is a possibility this is
having an affect on the SSSI wildfowl numbers.
Compare the numbers below – those in orange are counts from
2006-2010. Those in blue from 2013 –
2018.
It’s perhaps telling the disparity in numbers is all around
the summer and autumn months when algal blooms are at their peak. All observations suggest that invertebrate
and fish populations are stable; One only has to watch the swifts last summer feeding
on emergent insects from the water in these videos;
Or the great crested grebes in autumn gorging themselves on jack pike after jack pike to see there’s no ‘biodiversity collapse’ – if anything its supercharged with biomass. Darren Smith;
Perhaps the issue is maybe water clarity as the reservoir can resemble a ‘pea soup’ in late summer – this clip of D res demonstrates the strange alien world of algal ‘forest’ beneath the surface:
We’re hoping to get some more images from beneath the waves as its likely the biggest habitat at the reserve no one sees.
Some have attempted to manage algae with ‘shade balls’
to prevent sunlight hitting the water;
However – thankfully it’s not very compatible with the SSSI
designation or our biodiversity / plastic waste aspirations!
Currently there is a lot of academic work and research being
channelled towards this conundrum looking at a whole array of factors and
solutions to reducing the algae in the reservoirs.
In the interim the problem is that the algae would create
taste and odour issues unless we take measures to treat that. Essentially we have a scaled-up version of the domestic water filter on
your kitchen worktop which features a carbon/charcoal element to
remove taste and odour. One point of note is that when first installed we reckoned it'd make a cracking vantage point for raptor watching...
For us on the nature reserve the only issue is at
the Lagoon process water outfall near the boardwalks. Many pass comment on ‘what the black mud is?’
– it’s the carbon filtration material; It’s inert and harmless as evidenced by both lagoons being one
of the best places for kingfishers in Yorkshire (the sticklebacks probably
taste really nice filtered!). The was the original purpose of the lagoons - they are sediment traps so accumulated mud from the water treatment process is the expected output.
Unfortunately, both lagoons were never built with de-silting
in mind in the 1950’s so have never been dredged, and the carbon dosing is
compounding the issues. As such to
pre-empt a failure we now have to undertake this. North Lagoon as a sediment lagoon is
currently full. The
water has to settle somewhere so currently it all goes through south lagoon
which has some capacity, but until north lagoon is rectified there is no plan b
or option to desilt south.
North Lagoon dredging
This job is scheduled to take place in Autumn 2022. Preparatory works are to be undertaken this
winter as the bund at the northern end has slumped not allowing the lagoon to
be raised for settlement capacity and needs rebuilding. As such in coming weeks contractors will be
removing willows and failing alders from the bund, and installing a pipe bridge
to allow access into the lagoon for plant after it has been dried this season;
As such expect some limited closures for preparatory works
this winter and in the coming autumn for the work itself.
Subsequent to this South Lagoon is the next to be tackled
based on the outcome of this job – and will likely utilise infrastructure being
installed off the back of the current tunneling program.
That said all this is a remedy not a cure. Ensuring the lagoons can function merely buys
us time.
The Quality Scheme
This is a multi million pound upgrade and what we may term
‘Tophill Low III’ (following from Tophill Low II in 1999 and the original in
1959 – it’s the installation of new more efficient filter beds to deal with the
algae issues at source in the Water Treatment works.
This is forecast to run into 2024 and will not impact the
Nature Reserve significantly barring year one – largely at our own request.
The reason for this is that there is no spare land for the
new infrastructure. The only location is
an area of ground we commonly to refer to as ‘Mt. Tophill’. It’ll be unknown to most regulars and
features on no maps but it’s a heap of inert material left from decades of WTW construction
works. As the pictures below show it is
probably the highest landform for 4 miles in any direction and as we have
remarked ‘if it was in the right place it’d be a cracking vantage point for
birding’ but unfortunately it currently only views the roofs of the surrounding
private residences so isn’t an asset we can utilise;
As it’d become overgrown it had become home to many
protected great crested newts – extensive surveys were carried out last spring
to gauge the population size;
To manage that we brought in Nibbles and co goats last spring
to browse and keep all the vegetation down and deter any birds from starting
nesting within the habitat ensuring no nests would be damaged when the newt
fences were installed in July;
Allowing safe rehoming of 22 great crested newts and 25
palmate newts from the mound - part of over 80 from the wider collection areas.
This clears the way for much of that material to be removed
from the build area. Now with the volume
of wagon movements that would come at huge customer expense, in carbon emissions and
in disruption to local communities – but we have a need for it within the
Nature Reserve which will benefit the habitats and visitor facilities and save
all the above impacts.
Much of this material will remain as it will be a visual and
noise barrier for adjacent residences.
The intention is that this will be landscaped and seeded with hay
collected from the O reservoir hay meadows to deliver wildflower and insect rich hay meadow to compliment the reserve and may well
see the goats back at appropriate times to graze the escarpment which it is
hoped will become a pleasant outlook for residential properties on site.
Hide Replacements
Over the last few years we have had a program of replacement for the 1980’s and 90’s stilt hides. These were class leading and well-engineered in their day often by regulars whom still visit to this day:
Unfortunately,
the materials have unavoidably deteriorated as they were built to the budget of
the original 1993 Tophill Low NR launch.
Some hides like the South Marsh and back to back hides are
built on stable concrete slabs and have survived well and should continue to do
so with regular maintenance;
The two lagoon hides and Watton NR we were able to build
new sub-structures beneath them and give a new lease of life despite their old
telegraph and larch log legs failing.
However, where we have had elevated hides requiring major refurbishment,
we’ve had to make tough decisions on their future. Such as the old south lagoon inlet hide –
their time had been and passed and no longer looked over good vistas due to
habitat change and were but a liability to pull down:
The former D res north hide was occasionally useful in the
right light – but the majority of the time it faced due south into the
sun. To get the height to see over the
walls it needed to be on stilts all of which were rotting and which would need
rebuilt at a cost of many thousands with a fairly precipitous set of steps
which won’t satisfy the equality act, or our own aspirations for an accessible
site – all to support a hide which would have had a minority of occasional users;
As such we elected to do something totally different and
construct the Izzard hide instead;
And its fair to say that has yielded much more interest and
visits to site than a refurbished D would have.
That’s not to say we have written off the idea of a D res north
hide. We still have ideas for the future
that would deliver the originals intended function much more effectively…
The original North Marsh hide was something of a horror show
by 2008;
And was successfully replaced in 2009 with the current well-loved
structure – and was our first use of earth to create a permanent, low
maintenance accessibly entrance to an elevated hide;
In doing so we also created habitat in the form of the D
woods pond:
We scaled this up for the former D res car park hide in
2017;
Creating both the reception hide;
And the associated pond from the disability access ramp
creation;
Whilst we have tried to limp on some of the others we have reached the end of the road with them – and modern regulations such as CDM and safety controls such as working at heights mean we can’t undertake some of the jobs we’d have previously jumped in with volunteers and done;
Much loved by gull enthusiasts – we recognise East Hide is a
viewing location which needs to stay and cater for serious birders giving a
commanding vista of the D reservoir. Alas
its rotting supports, asbestos roof and non-compliant access mean we have to
look at replacement rather than refurbishment.
We’ll also be moving the path back away from the SSSI
reservoir to reduce disturbance.
This is going to mean some limited felling of pine and larch
trees, and therefore initial closures for this around new year. Subsequently there will be a prolonged
closure whilst earthworks are undertaken from February which may restrict
access to the whole northern site, and subsequently through D woods until we
have new paths in place in spring.
The finished product should be a stable hide that is
accessible for all, much reduced in maintenance and SSSI disturbance and gives
a lot more interesting walk and more diverse habitat than previously.
The other hide due for replacement is ‘L’ hide on O reservoir and is the more ambitious project of the two;
This hide when built was started on the right concept – it’s on a mound – but unfortunately it wasn’t quite high enough and set too far back from the reservoir so never really worked; The near side of O res is always hidden so you can only observe wildfowl and gulls on the far side of the res.
Likewise if it was a little higher then you could get a view of the river towards Hempholme and Leven Carrs and the new habitats there along with their burgeoning crane and raptor communities – but it’s not quite there. It also is still built on legs and has no disability access and is all on failing supports again so it’s one we need to start over with.
So, the idea is to go higher and add to this mound and
incorporate disability access.
We’re still developing the precise details on the hide or viewing area specification itself but the intention is it will deliver commanding views of O reservoir and the surrounding scrub and wetlands.
We want an open aspect that will make this a brilliant vantage point for surveying raptors and wetland birds through the river Hull corridor such has been had in the past here.
This elevated position will also be host to a MOTUS
array. Read here for full details.
Essentially recent advances to telemetry and miniaturisation
have allowed the development of transmitters which don’t have the prohibitive
bandwidth hosting costs of satellite tracking systems. Currently blackcap is the only species
sanctioned for trial in the UK as the BTO is correctly taking a cautious
approach to rolling out the technology – but in the states they have successfully
been attached to all manner of birdlife, and even dragonflies, monarch
butterflies and bats. Due to the low
energy transmission the system relies on a transmitting animal passing within a
few km of a receiver station. So, the
more stations there are, the more likely it is to be picked up. The networks are extensive in the Americas
but embryonic in the UK. Yorkshire
Water’s Biodiversity team have funded the installation of three MOTUS arrays in
East Yorks at the Deep in Hull, RSPB Bempton Cliffs and Tophill Low, which will
be in addition to established arrays at Spurn bird obs and the LDV NNR.
Going forwards this scientific emphasis will be linked to
the bird ringing station at Tophill Low which will be re-housed in a relocated
shed with more interpretation on returns and their work.
Data needs to be transmitted and the receiver powered so
this is to be incorporated within an overhaul of the reserve’s failing 30-year-old
camera coaxial and power cable which will allow reliable powering of the
predator fence around SME, the moth traps and nocmig audio recordings. Essentially this new hillock will be
something of a Tophill ‘Menwith Hill’ with an array of wildlife monitoring and
tracking technologies all focused upon it.
The intention is to get a reliable and high quality picture signal back
to the reception hide so we can scan the wetlands remotely. Likewise we’re hoping high speed internet
will finally make it to Tophill which will finally allow us to get that footage
out. When lockdown started in 2020 we
attempted to stream footage but the internet was so slow we could only get a
few fragments out of the barn owls before we had to give up on our near dial up speeds:
The hide mound will entail a larger footprint and we’ll be extending back into the woodland behind. As we’re felling elements of it, we have taken the opportunity to fell the lot and start again with similar dormouse / scrub woodland habitat. Currently its scots pine which is none native to the area and ash which is suffering badly from die back. None of the weedy trees here are growing strongly in the wet heavy clay soils when you consider they are the same age as those in D woods, and nor do we want them to.
In D woods we’re embracing canopy trees with the heronry, sparrowhawk
nests etc and all they bring – but at the southern end of the site we want low
dense nesting habitat and scrub for warblers, bullfinches and wintering
thrushes which complements our wetlands, and eliminates predator perches to
benefit nesting wetland birds.
If we’re on with tree works, we want to do the rest whilst
mobilised. So that means also the ash
avenue which is at the very south of the site around and beyond Watton NR hide;
This avenue is a self-generated row of ash which is now suffering from die back and in time would become a hazard to pedestrians on the public bridleway. It is too small to be a viable woodland and simply acts as a vantage point for carrion crows (complete with their nest /dining table set within it) fragmenting valuable reedbed and grassland on South Scrub and Watton NR. We are intending to take this down to pollard height – trees which survive the current ash die back can regrow as dense warbler habitat we will maintain with volunteers.
To reach and extract timber without negatively impacting on stewardship
meadows we’ll be cutting new rides through the rank hawthorn scrub similar to
that which we did in 2009 to further diversify and create valuable edge habitat
– continuing our Higher Level Stewardship work to take S Scrub from bad on the
right below – to good on the left;
JJ Hopkins, 1996
On exactly the same concept is the pollarding of the copse adjacent to South Marsh East.
We’ve already been undertaking much with volunteers this winter on SMW and need to bring these trees into a size maintainable with hand tools.
Some of you may remember the
lockdown scenes where the local common buzzards undisturbed by visitors were
using these tall trees to launch attacks which effectively wiped out much of
the breeding birds on the marsh in 2020.
The more open the vista – the earlier warning nesting birds get of
attack and can collectively mob and deter predators.
The intention is to get it away from 40 foot predator perches;
And instead managed as dense pollard woodland as we've already done a lot previously with volunteers - home to blackcaps, garden warblers, bullfinch - rather than carrion crow and buzzard;
The same applies to the same predator perch / un-biodiverse
/ stunted pine plantation next to east pond.
This is to go leaving the hawthorn scrub for warblers augmented by more native
species.
We’ll finally get round to extracting the timber from O reservoir wood felled for tree safety works last winter which will be planted up with species more faithful to the river Hull than Balsam poplar. So that means alder / downy birch / alder buckthorn / sessile oak wet woodland species as future willow tit habitat. The felling of the poplars at O res was due to them collapsing across the road to O res two years ago;
And unfortunately, this is a forewarning of the rest of
those at Tophill Low. They were planted
as a cash crop in the 1960’s with the promise of ready money from match
wood. Unfortunately, there’s not much
market in matches now – and we are left with a legacy of trees which are poor
for biodiversity, short-lived and worst prone to either root lifting or the
crowns shearing and collapsing unpredictably as above.
We had already started this program back in 2011 when we felled over
600 of them at what is now Hempholme Meadow:
In the recent storms Arwen and Barra we conducted office
work from home not due to Covid, but because of the risk posed by these trees
above the warden offices. We’ve
tolerated them as long as we can – but again if we are mobilised for serious
forestry, now is the time to make that hard decision to remove them where they
are close to paths and roads. They are
big and impressive trees, and it will be a loss from the Tophill Low’s
landscape, but it is the right time to make that call. It’s unfortunate they weren’t planted as oaks
etc back in 1966, but forestry at that time meant cash return – not
biodiversity, landscape value or carbon capture.
So, the car park will look different. We’d have liked to have done something like
carvings etc – but unfortunately the wood is light and porous (and hence good
for absorbing paraffin in matches) and any work would rot within a few
seasons. So, the best we can do is
replant with more sympathetic, stable and biodiverse trees – likely oak as its
deep tap root penetrates the 1950’s landscaping well as evidenced by some great
specimens in D woods which dwarf the supposed quick growing pines around
them.
And to complete the picture we will be felling remaining poplars around McBean hide and re-pollarding willows which we last did in 2011 and have become too large for our volunteers to tackle and again are all shearing unpredictably.
All material harvested will be utilised as biofuels for
renewable energy and any income used to offset the much higher costs of this
work (as the felling and extraction is complex and costly, so we’d like to
reassure that all work is being undertaken for habitats and safety and is not
for any financial gain).
One additional benefit of the poplars being removed is that
it removes the risk from the area around the butterfly border to make space for
an exciting new development. For the
last few years we have had a small polytunnel setup for propagating woodland
plants.
And subsequently we have been using it to propagate the rare greater water parsnip for a Yorkshire Water commitment to re-establishing colonies along the river Hull corridor:
Amy and the team have been busy with in recent months on Skerne Wetlands and Leven Carrs;
Unfortunately this old facility has been lost to the footprint of the quality scheme but in recompense we will receive a new polytunnel inspired by the excellent facilities at Nosterfield Nature Reserve we visited this summer;
Our intention is to develop a purpose made facility for
collecting and propagating wetland plants to re-establish around Tophill Low,
river Hull and Yorkshire Water sites in coming years. Once up and running this will be an exciting
new volunteer opportunity amongst several others we’ll be promoting in coming
months…
And to support this we're in the process of upgrading the volunteer welfare facilities post covid. Previously up to 15 volunteers were crammed within a 10x10' office - so we're installing new temporary facilities pending the 2025 quality scheme completion, whom are borrowing and refurbishing or replacing the former wildlife centre / social club as their contractor welfare facilities, which we will receive back as a swish and permanent home for Tophill Low's volunteer operations.
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All this work may all seem dramatic – but Tophill Low is a
working and dynamic site which it always needs to be remembered is primarily a
drinking water production site for Hull.
It’s easy to walk it and romanticise it is ‘wilderness’ or ‘untouched’
whereas in reality it is another step in its evolution. To keep this within perspective here is
Tophill Low within many of our lifetimes in 1946 as a pastoral farm (complete
with the former Lowe – which gives us our name - the small hillock / island in
the Hull Valley bulldozed in 1959 to create reservoir embankments);
The whole site almost without exception was levelled in
1959;
This is now the car park!;
By 1979 the site was still barely vegetated – many of the
trees we’re managing now did not exist; South Scrub is pure grassland, the
south marshes were yet to be excavated and we even had a cricket pitch still!;
What has always been consistent as now is that there are
areas of the site which are not worked or disturbed; allowing wildlife to
colonise and fully exploit all the new habitat opportunities the dynamic
environment Tophill Low offers. So,
expect some disruption over coming months.
Undoubtedly it would have been great to undertake this during the
lockdowns etc to minimise impacts – but as you’d imagine contractors and plans
have equally been delayed during this time.
We’re still yet to attain our pre-flooding / pandemic visitor and
volunteer numbers so we’d rather condense all this and complete it so we can
get back to a permanent normality.
As such there will be closures to parts of and potentially
the whole site depending upon contractor activities. We will try and advertise work schedules on
the blog so visitors know what to expect when planning their visits. When we know more on the impact and scale of
this we will be determining the effects on the costs and schedule for current
March 31st membership renewal date.
In the first instance we will be closing South Scrub and
Watton NR hide with effect from approximately Tuesday the 4th January until
further notice due to initial forestry and access work.
The tunneling program is winding down with one crane now being dismantled;
but we see restrictions on the O reservoir access continuing into Jan.
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As you'd imagine planning that lots takes some of our time - but what do we do with our spare? Well we also have another project besides Tophill - our Water Work for Wildlife project:
