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You are here : At Home > Corporate > Environment > River restoration > River Ivel
The River Ivel is a chalk stream which flows north through Bedfordshire to join the River Ouse at Tempsford. Chalk streams are globally rare habitats. Of the 260 chalk streams in the world, 224 of them are in England and 10% of those are located within our supply area.
Chalk streams are rivers that receive most of their water from underneath, from the underground chalk aquifer (water bearing rock). As the water bubbling up through the riverbed has been naturally filtered by the chalk, it is often described as being ‘gin clear’ and is full of dissolved minerals that support many species of plants and animals.
Over the centuries, chalk streams have been altered for many reasons including: moving them from the lowest point on the landscape to higher up to work with field boundaries or create a bigger area for agriculture, being straightened to act as mill races for industry, or relocated for housing development. These changes mean that the rivers are less resilient to extreme climatic conditions such as flood and drought, as they no longer operate in a natural way.
The course of the River Ivel has been heavily modified along its length, and the wetland area around the springs and the headwaters of the river are no exception. For around 100 years, up until the 1940s, a large part of the site was used as commercial watercress beds, extending across much of the area adjacent to the river channel. Much of this area was subsequently used as the Baldock tip where they used dredged material from nearby rivers to partly cap the tip.
Seasonal Wetland Enhancement Area River Ivel through Ivel Springs Nature Reserve
As the name Ivel Springs Nature Reserve suggests, springs found on site are the source of the River Ivel. Springs occur where the groundwater moves through cracks and tunnels in the chalk and flows out at the surface. The location of a spring depends on the features in the geology, the groundwater level, and the existing surface level. Springs often move up and down the landscape, depending on the level of the groundwater which naturally changes seasonally.
The flow from a spring at one location may increase following rainfall as more groundwater bursts out at the surface. It can also stop flowing completely during a lack of rain as the groundwater no longer meets the surface at this location.
You might not know but groundwater reaches its highest level in Spring following rainfall over the Autumn and Winter period and reaches its lowest level in Autumn following the lack of rainfall (and any rainfall being used by plants) over Summer.
Groundwater abstraction for public water supply or irrigation can also impact on a spring’s flow due to the localised dip in groundwater levels.
Since 2015, we have been monitoring the River Ivel’s headwaters to understand any impact of local groundwater abstraction. The data collected informed our investigation and options appraisal process which was taken forward with the Environment Agency.
Key Investigation findings:
Taking the above findings into account, we considered numerous different options that could help improve the resilience of the River Ivel at Ivel Springs Nature Reserve.
The options appraisal identified that the most environmentally effective option would be a combination of river support from a groundwater borehole and river restoration. This proposal is endorsed by the Environment Agency and Affinity Water are working to:
Below outlines the sequence of events.
We are still working to develop the outline design for the river support (augmentation) borehole and infrastructure, to date we have:
We have recently finished an outline design for the seasonal wetland during which we:
The design shown below was the most popular option and we will now begin developing this into a more detailed design, which we will present again to stakeholders for their opinions.
The existing surface water outfall and the pond it flows into will stay in place. This pond will feed into a sedimentation pool. The purpose of this pool is to hold surface water for long enough for any particles to drop to the bottom. Around the edges of the pool there will be a ledge with marginal plants (plants that grow around pond edges) for extra habitat variation. This pool will flow into a wet woodland and series of two cells. The cells will either contain marginal plants or reeds, which filter the water. Cell 2 will then flow into the River Ivel.
Registered office: Tamblin Way, Hatfield, Hertfordshire, AL10 9EZ.
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