River Teme fish rescue

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The River Teme is one of England’s finest lowland rivers. It rises near Newtown in Wales, meanders through Shropshire and Worcestershire before joining the mighty River Severn just below Worcester. It is a Site of Special Scientific Interest for its entire length.

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Despite its size, however, sections of its upper reaches are prone to drying out during periods of dry weather. This is a fairly frequent occurrence, happening, on average, around once every three years. The stretch most at risk is from Knighton to the confluence with the River Clun at Leintwardine.

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Drying out happens very quickly with low flows changing to a completely dry river bed within a day or two.

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Because the upper parts of the Teme rely on catchment runoff (rather than groundwater) for its flow, an extended period of dry weather quickly translates into low flows and then drying out. That is what has happened this year. The record-wet year of 2012 topped up our reservoirs and groundwater reserves very nicely but the lack of rainfall runoff for the last month (combined with high temperatures and evaporation) has resulted in the upper Teme (and other similar rivers) starting to dry out.

Fishy haven

The Teme is an excellent fishery and is home to a wide range of game and coarse fish. It is very popular with anglers who travel great distances to sample its challenges. The upper Teme is an especially valuable spawning ground for salmon and trout.

You may have thought that a drying river wouldn’t cause too many issues as the fish (being sensible creatures) would just move downstream as things dried out. The problem is that as the flows reduce , large, deep pools of water get cut off as the main river bed becomes dry. The fish tend to seek these pools out as they are deeper and cooler and tend to contain cover (weeds and fallen trees).

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The sun then gets to work on these pools, warming them quickly and oxygen levels in the water fall quickly. Obviously, in time, the pools themselves will dry out.

Launch the rescue team

We monitor high risk river areas like the upper Teme on a regular basis during dry weather. Our fishery officers have years of experience of where and when to look.

Once we know fish are becoming stranded and rescue is possible we scramble our rescue teams from Shrewsbury, Kidderminster and Tewkesbury (depending who’s closest).

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We use electrofishing to catch the fish in the pools. A small electric current is passed through the water which is sufficient to momentarily stun fish. There is quite an art in knowing where to look for the fish and how to efficiently get the optimum charge to the right spot!

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Members of the rescue team scoop them up in nets as they come to the surface and put them into buckets of water.

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The fish are then transferred to a large aerated tank of water towed by a landrover. This keeps them safe and happy until the rescue is complete. They are then taken downstream to a location where flows will be maintained and released.

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Teme haul

During the morning of 18th July we rescued around a hundred large fish from a dozen or so pools. Sadly the small fish and fry cannot be rescued. Some beautiful brown trout were saved as well as salmon parr, stone loach and bullheads.

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In addition we scooped up lots of brook lamprey and returned them to a safer place.

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Work like this is made possible by the money we receive from rod licence sales. We hope that anglers agree that it is important work in safeguarding the natural fish stocks in our rivers.

If you see and dead fish or fish in distress please call our incident hotline 0800 80 70 60

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Nothing bore-ing about the Severn Estuary

Big tides go in cycles depending on the alignment of the moon and earth, and, to a lesser extent, all the other planets in the solar system. If you want the detail have a look here https://metofficenews.wordpress.com/2015/02/20/super-tides-the-weather-and-coastal-flood-risk/

The cycle is about 18 years and February 2015 saw some of the biggest tides in that cycle. This is big news on the Severn Estuary where the tidal range (the difference in water levels between high and low tide) is huge – up to 15 metres at Avonmouth.

The Severn Estuary is like a huge funnel. Tidal sea water pushes up the Bristol Channel and gets increasingly contrained by the narrowing channel, raising levels dramatically. The bigger the tide, the greater the rise.

The most spectacular result of high tides on the estuary is the world famous Severn Bore.  Large tidal bores (which is what the Severn bore is) are actually very unusual and only happen at a handful of locations across the world where there is a large tidal range. The Severn Estuary has the third largest tidal range in the world (behind the Bay of Fundy in North America and Ungava Bay in Canada).

Bores happen when the front edge of the advancing tide becomes contrained by the sides of the estuary, forcing the water up into a wave. It is pushed along by the millions of tonnes of water in the advancing tide behind.

The Severn Bore can usually be seen between Sharpness and Maisemore Weir in Gloucester, a distance of around 20 miles. It travels at a speed of 8-13 miles an hour.

The height of the wave can be anything from a few inches to over six feet. This is largely dependent on the size of the tide but is also influenced by wind, weather systems over the Atlantic and the amount of fresh water coming down the river. Bore forecasts are available well in advance and give them a star rating, the the best (biggest) being five star bores. You can find the forecasts here: http://www.thesevernbore.co.uk/timetable/4586702434

Watching the bore is a great experience. It makes an amazing rumbling sound which you can hear well before you see the wave. The wave itself and the boiling, tumultuous water pushing it seem completely alien on an estuary that is usually fairly calm and placid.

Not surprisingly the spectacle attracts thousands of sightseers and also large numbers of surfers who travel great distances to ride the wave (with varying degrees of success!). Keen surfers try to catch the wave three times during a single pass (usually at Newnham, then Minsterworth and finally Gloucester).

At the Environment Agency we’re more interested in the hour after the bore has passed. This is the time when water levels rise dramatically and very quickly. The rise can be 15 metres at Avonmouth, 10 metres at Sharpness and 6 metres at Minsterworth. This rise is just as spectacular as the bore itself, although the majority of bore watchers do not stay to see it.The impact of the tide is felt much higher up the river than Gloucester. Amazingly, during the February high tides the river at Upton in Worcestershire (about 60 miles from the estuary) was pushed into reverse twice a day. The graph below shows how normal flows of about 100 tonnes of water per second travelling downstream changed to an upstream flow of up to 40 tonnes per second in a matter of minutes. There was also an accompanying rapid rise in water levels of over half a metre. Incredible!

We have miles of flood defences along the length of the Severn Estuary which protect over a thousand homes and businesses. Few people notice most of them as they look like natural grass banks. However, if they weren’t there high tides would routinely cause extensive flooding across the estuary. When high tides are imminent we check all our defences to ensure they are in good working order. This is no small task given the extent of the defences and the remote nature of parts of the estuary.

After the high tides and storms of 2014 some of our defences were damaged. We spent the autumn and early winter carrying out Over £3 million of repairs so they would be ready for the huge tides of 2015. In February they received a good test (like Minsterworth here) and performed perfectly.

There are more very big tides in 2015 (especially in March and September). We’re ready for them.

Why not get out yourself and experience a truly world class natural phenomenon.

Video courtesy @theocair 

Arc Boat 50 arrives in Shropshire!

ARC-Boat number 50 will be the newest recruit to the Environment Agency Shropshire team, helping us issue quicker and more accurate flood warning information to local communities.

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During times of high river levels, the boat may be seen at sites along the river Severn including Montford, Shrewsbury, Ironbridge and Bridgnorth. The boat will be used to survey the river bed of the Severn, Teme and Tern, sending important information to our teams.

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By measuring river flows at a full range of levels our flood models are massively improved. The flow data allows calibration of the flood models that in the past could never be gained across the full range.

Without actual flow data our flood models are theoretical which is OK, but rivers are dynamic systems that change massively over time and this new flow data allows our people to calibrate the models much more accurately. Better calibrated flood models mean much better flood predictions and therefore more timely and correctly issued flood alerts / warnings.

The boats are manufactured by HR Wallingford in Oxfordshire and have been sold to customers around the world including in Canada, New Zealand, France, Azerbaijan. The Environment Agency already has around 30 of these boats in operation across England, but this one is special as it is the 50th to be produced.

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The boats are remote controlled using electric motors and measure the speed and depth of the water to enable it to calculate river flow. They allow us to easily and safely reach places where humans can’t, such as under bridges or during high-flows/floods. Ultra-sound pulses, similar to that used to scan pregnant women, are used to collect important data from the river.

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The boats can operate in river speeds of up to 3 metres a second, meaning they’re capable of dealing with most flows the River Severn has to offer.
As well as collecting flow data, the new boats also scan the river beds. This gives staff information about any debris build up which could cause flooding. It also allows staff to get a much better understanding as to what exactly is happening beneath the river surface.

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Little boats with a serious job to do

Among our many roles, we are responsible for the collection of information about the water cycle. We gather a variety of river level/flow data, weather and climate information and groundwater data.

Across Midlands region we have almost 500 measurement sites along our rivers. These range from our primary sites where a telemetry system automatically takes 96 readings each day, to logger sites where data may be manually downloaded once a month.

Much of this river level information is available online via the environment agency website here:

http://www.environment-agency.gov.uk/homeandleisure/floods/riverlevels/default.aspx

As well as measuring levels of water in rivers, we also need to measure flow. We can do this by using either a structure such as a weir or flume, or by putting equipment in the river. The results we get always have to be calibrated (checked) and this is where our lovely mobile boats and acoustic measurements are used.

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The level and flow data we get is of vital importance as it is used to make key decisions in areas such as flood warning and forecasting, water resource management & abstraction and discharge management.

Our telemetry data also provides the triggers for flood warnings to be issued as well as the building blocks for our flood models which trigger flood defence deployment and the advice we give to our partners during times of flooding and drought.

We measure flow using sounds waves and the Doppler effect. This is the change in frequency of a sound wave for an observer moving relative to its source (so I’m told!).

Sensitive sensors are mounted on the underside of small boats and manoeuvred across the river. This is done either with ropes, cableways (bit boring) or more recently using our remote controlled boat (great fun).

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As the sensor moves across the water surface, it fires high frequency sound waves to the bed of the river. These waves are then bounced back from the bed of the river and the return waves are altered by the Doppler effect of the flowing water. We measure this shift to give an accurate measurement of water speed or velocity.

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The sound beam also measures the river depth and a GPS and built-in compass measures the width.

We then use basic maths to calculate flow – Q (flow) = V (water speed) x A (Area) (Width x depth)

As well as telling us the flow of the river, our boats also give a screenshot of the river channel shape. This is useful to establish if there are any underwater blockages within the channel that need removing or whether future erosion is going to affect the site.

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Our little Q boats have been doing brisk business over the last few weeks’ flooding, helping to ensure our flood information and advice is as accurate as it can be.

An underground river

Parts of the River Frome in Gloucestershire have dried out completely in the last couple of weeks. We’ve had a few reports from people concerned about what’s caused it and whether it will return to its former glory. Here are some answers.

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Not all of the river is affected, but a fair stretch to the east of Stroud, in the Frampton Mansell area is now completely dry.

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The drying out is a completely natural phenomenon. It happens most years, and is the result of the local geology.

The River Frome flows over highly permeable (porous) rock formations such as limestone and sandstones which also make up the principal aquifers in the Stroud area. Aquifers are underground water reserves, bound up within rock formations. Also, in its upper reaches, the River is mainly groundwater fed. As the groundwater table declines in dry periods below the bed of the river it experiences the drying out episodes which we are seeing now. Any flowing water is now beneath the surface! Extensive faulting (cracks and gaps in the rocks) in the area also locally contributes to losses of river water into the underlying bedrock via these features.

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When we get some rain the groundwater level will rise back to the surface and the River will reappear.

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Because the process happens quite slowly fish and insects tend to naturally move away from the drying area and then return once flows return.