Show the Love for Halvergate Marshes
Mark Smart - Senior Site Manager of Berney Marshes and Breydon Water
The impact of climate change
Whether you’re a climate change sceptic or completely accept it, we must all appreciate that our weather systems are changing and becoming increasingly unpredictable.
Gone are the balmy summer days I remember as a child and teenager in the 80s, and gone are the predictable, traditional English seasons and their associated rain fall patterns that controlled my working life on farms throughout the early 90s and in more recent times for the RSPB as Site Manager of Berney Marshes.
If we want to maintain our reserves to provide high quality habitats for our existing wetland species, and create new habitat for the species that we are expecting to gain in the future, then we have to make changes. We also have to change our approach to water management.
Drone image of Halvergate Marshes works - Jeff Kew (RSPB)
At RSPB reserve Berney Marshes, in the heart of the Norfolk Broads, we have been trying to think outside the box, developing water management systems that will not only protect the reserve from times of drought, but also ensure the provision of water to one of the UK’s largest areas of wet grassland, Halvergate Marshes.
Berney marshes is a 700ha grassland site that sits within the 3500ha of Halvergate marshes. The ability to hold and manage water is one of the biggest challenges we face in the management of this amazing landscape.
Water is the life blood, the very elixir that draws in wildlife through the spring and winter months, but it is becoming difficult to achieve the levels that are needed in terms of quality, quantity and at the right time of year.
Without water, the area would not be able to support approximately 300 pairs of breeding waders or the 100,000 wintering waterfowl, or provide local farmers with safe grazing for their cattle and enable them to deliver their High Level Stewardship commitments.
Over the past 2 years, we have been working closely with the Water Management Alliance (on behalf of the Broads Internal Drainage Board) and the Environment Agency to design and build a water storage system that will overcome some of these problems as well as create new habitat for our expected new colonists.
Drone image of Halvergate Marshes - Jeff Kew (RSPB)
The current situation
Two sides of the area are surrounded by tidal rivers. More and more salt water is being pushed up these river systems from Great Yarmouth, meaning it is increasingly difficult to find points in the tide when fresh water can be drawn in through the main sluice onto the marshes.
When the sluice was first located on the River Bure in pre-Victorian times, it was never anticipated that salt water would start being pushed further and further up the system, reducing the time that fresh water was available.
But this is what we are seeing today. The time window available to let water onto the site has dramatically reduced, particularly in the summer when river flows are at their lowest, allowing the salt water to be pushed up the river systems.
Map showing the new fleet scheme. The blue line and red route (which depicts the new fleet route) show the existing main water supply. The green line shows the lower level drain. Blue hatch demonstrates new semi-natural washland, and the buff areas are existing RSPB managed land.
Cue the innovative new design
Thanks to the construction of our innovative new design, more water can be stored in a purpose-built washland right in the heart of Halvergate Marshes, all on RSPB land. This area, approximately 80ha, (equivalent to 80 football pitches) will be filled up when water quality is suitable through the winter and spring months, then gradually fed across Halvergate Marshes when required. With time, this semi natural washland will develop to support a rich habitat of wetland species which might include include long-legged colonists such as crakes, herons, spoonbills, black-winged stilts and ibises.
New channel being excavated
The beauty of this design is that we are using the natural contours of the ground to create a network of ‘islands’ surrounded by shallow water. The water will come and go as water is let on and off the washland into the surrounding grassland. This will ensure that ditch communities full of important aquatic plant, invertebrates and mammals are supported on the reserve and across the rest of the marshes and ensure local farmers can continue to safely graze the marshes with livestock as they have done for centuries, without the risk of the animals becoming poisoned by salt water.
When fresh water is available at the sluice it will be let in to refill the area, thus creating an ever-changing dynamic system. The partnership of the WMA engineering expertise coupled with the RSPB wetland management and creation expertise has ensured a design that will work for everyone. It won’t be the standard reservoir type design with high bank holding back large volumes of water back. It will take us back to what the area might have looked like pre-1400 before the Dutch drained the marshes to convert them to grazing marshes.
One of 6 aqueducts that have been installed
12,000 cubic meters of clay have been excavated to enable the construction of 6 aqueducts, creating 8km of new bank, and 4km of new channel ranging from 7-15m wide, allowing us to hold an additional 60,000 cubic meters of water! By the time the work is completed 6 new scrapes will have been dug to provide material for the new banks and 12 new water control structures will have been installed.
All of this will have been carried out with little to no impact on the native wildlife, as demonstrated by the breeding waders who had their best year in 2017, but to reduce the impact on some of the specialist ditch species such as water voles, large scale mitigation works were and continue to be carried out before the main engineering works begun.
Water vole mitigation prior to the main work starting
All in all this has been a huge project, but one that I am proud to say will ensure a good water supply for years to come.
Sorry for the confusion. The blue line shows the current route in place before the new scheme begun - it is still there. The red line shows the new fleet scheme, which is nearly finished - and together these make up the existing water supply. Hope this helps.
Great stuff. Many thanks for the detailed account of what's happening. All very exciting.
Sounds great. A real gain for the wildlife. Nice to have a map and some numbers too, to give it perspective, with the pictures. Don't think I understand the description of the map though. Does it contradict itself about whether the red and blue lines are the old or new supplies?
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