Cefni Resevoir & Cors Bodeilio

As part of the MSc we are learning about the benefits of constructed/treatment wetlands. Natural wetlands provide many ecosystem services with a major one being natural biofilters removing excess nutrients from water ways. A treatment wetland can be developed with aims of removing pollutants from waste waters via sedimentation and uptake through the wetland plants.

This field trip started at the Cefni Reservoir, which is a small reservoir in the centre of Anglesey managed by welsh water. The small rivers and streams entering the Cefni have been identified as potential areas to create mini-constructed wetlands. These wetlands could help improve water quality entering the reservoir and also improve areas for biodiversity.

To determine where the constructed wetlands would be best placed water samples were taken from each of the inflows, where they would be taken back to the lab to be tested for pollutant levels. (This was done prior to our field field trip by experts, we also took samples to get a feel for the process).

Different constructed wetland systems would be more efficient at removing certain pollutants/excess nutrients than others...

Free water surface system (FWS)

Sandec/Eawag depiction of a FWS

A FWS constructed wetland allows water to flow above ground, exposing the water to the atmosphere and direct sunlight. Meaning there are aerobic and anaerobic zones for the complete removal of Nitrogen from the system (one of the main pollutants entering the Cefni reservoir). 

Moving to the other side of the reservoir we estimated the flow rate of one of the streams into the reservoir using a very high tech method, which involved a spade, pipe, bucket, jug and stop watch. A small dam was created with the pipe through the middle (as seen in the picture on the left), a small amount of water (around 1L) was collected from the outflow using the jug at timed intervals - which could then be used to calculate the flow rate.

Cors Bodeilio
After discussing potential treatment wetland ideas to help purify the water entering the Cefni Reservoir we travelled to Cors Bodeilio which we had previously visited during the LIFE Conference - a blog post on that can be found here. The LIFE project aimed to restore the delicate fen habitat at Cors Bodeilio with aims to restore the peatlands not only for carbon storage but also to store and purify water, before releasing it at a manageable rate to provide drinking water to Cefni reservoir.

There are a number of constructed wetlands at Cors Bodeilio that remove the nutrients from the surrounding farmlands to prevent eutrophication of the natural fen habitat. These wetlands have however been subject to subsidence and more funding is required to restore the wetlands to full working order - which is key for maintaining the delicate fen.

Day out with CEH

As part of my MSc I have to undertake a research project with a company partner. My partner is the Center of Ecology and Hydrology (CEH). My project will focus on green house gas emissions from peatlands. Britain’s peatlands hold most of our terrestrial carbon stock, and play an active role in climate regulation through uptake of carbon and emission of methane. Much of this resource has been impacted by land-management activities, such as drainage, burning and intensive agriculture, and the protection and restoration of UK peat lands is crucial. To measure gas emissions from different areas at Cors Erddreiniog (blog post here) columns were inserted into ground - which a gas measurement machine (Los Gatos) can be placed on to measure the gas flux. I went out with a few of the CEH crew to set up some of these columns - placing them in areas of the site with different management techniques and then trying to stick them in the ground with minimal disturbance, for which the GHG flux could be measured over the summer when I start my project!

Wetlands... sent from above?

It's no secret that our weather is getting worse, this time last year we were blanketed by a thick layer of snow, and now we are facing the third brutal storm in less than a month. Both events are abnormal for the UK, could climate change be to blame? Chief MET scientist Dame Julia Slingo that "all the evidence" is pointing toward climate change as an explanation for the extreme weather.
With rain continuing to batter the UK causing chaos pretty much everywhere, is there anything that could be done to reduce the catastrophic effects of the worst floods we've had in decades?
Well thankfully, David Cameron has come to the rescue with the gallant statement "Money is no object in this relief effort. Whatever money is needed we will spend it." So worry not, everything that has been damaged in the record-breaking deluge will be fixed or replaced... until next time.
The main methods currently in place to reduce flooding include;

Dredging - A process where silt is removed from a river bed to increase it's water capacity. The method is costly and potentially harmful to the environment.

Flood Barriers - Temporary demount-able lightweight metal structures that are used to keep rising water levels at bay.

Look pretty don't they? Sure they work, but they are a temporary solution to a more permanent problem which needs to be addressed. Funny how the leaders of this country only begin listening to people when disaster strikes. Speaking on a visit to Purley (a severely flooded town on the River Thames) Labour leader Ed Miliband said: "It's clear that flood defence needs to be more of a priority for government. If there's one thing we know about the effects of extreme weather, it is that the costs, financial, human and other costs, of not acting are much greater than the costs of acting, and it is a totally false economy to say, 'Don't act'."


The government needs to start acting now listening to scientists who suggest natural flood management systems, as prevention is always better than a cure.

The welsh government is planning to invest £20m into flood control, but how exactly would this help? The Minister for Natural Resources, Alun Davies, has broken it down like this...

• £7 million for flood defense improvements to protect 627 homes and 72 businesses in Crindau, Newport 
• £6 million for river management works and improvements to tidal defenses to reduce flood risk for 387 homes, 52 businesses and the fire station in Roath, Cardiff 
• £1 million to fund the replacement of flood defense walls that will help protect 127 homes, 15 businesses and the main road through Penclawdd, Swansea
• £1 million for improvements to tidal embankments along the Severn Estuary to reduce the flood risk to part of the M4 motorway, 833 houses and 197 businesses in Portland Ground and Tabbs Gouth, Newport 
• £5 million to improve existing flood defense walls that will help protect 166 homes, 102 businesses, the fire station and ambulance station in Dolgellau, Gwynedd

Replacement, improvement and management of man made defence systems seem to be the key words in this list but could this investment be put to better use elsewhere, for example in conserving and improving wetland systems?

Could wetland systems be a natural way to prevent flooding?

A joint statement prepared by English Nature, the Environment Agency the Department for Environment, Food and Rural Affairs (Defra) and the Forestry Commission state that

Drainage of floodplains is a relatively recent historic phenomenon. For example, the Somerset Moors were largely untouched before 1200, and systematic drainage of large areas did not get underway until about 1770. By the 1930’s only a quarter of historic floodplain wetlands remained in England, mainly in the form of periodically flooded grassland and grazing marsh. The vast majority of natural floodplain woodland has also been lost.

Somerset has been severely affected by the recent floods, would there have been a different outcome if the Somerset moors weren't drained all those years ago? Probably.

Wetland systems are often undervalued in the UK, peat-lands alongside rivers can act as natural sponges trapping water during periods of heavy rainfall. Wetland vegetation slow the speed of flood waters distributing them slowly, reducing erosion and flash flooding. In areas where peat-land has been drained in favour of agriculture (Somerset Moors) the risk of flash flooding, much like we've seen in the past month, is increased.

Preserving and restoring wetlands, together with other natural practices such as the re-introduction of the Beaver into the UK (BBC article here) can provide a valuable level of flood control which should be taken into serious consideration if the government want to prevent flooding in the future.