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You are here : At Home > Corporate > Environment > River restoration > River Ivel

Revitalising the River Ivel

We are working to revitalise the River Ivel by supporting the river with groundwater and improving chalk stream characteristics through a river restoration scheme.

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.

Images of the river Ivel before the augmentation works begin

Seasonal Wetland Enhancement Area                            River Ivel through Ivel Springs Nature Reserve 

  • Why are we doing this?
    We are working with the support of the Environment Agency and others to Revitalise Chalk Rivers. The aim is to make chalk rivers in our supply area more natural again so that they are less likely to suffer prolonged damage from low flows during drought conditions, a loss of habitat from high flows during flood conditions and have a good variety of chalk stream characteristics which support different wildlife.
  • What happens at 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.

  • How has data informed our decisions?

    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:

    • The local groundwater abstractions have the potential to influence groundwater levels in the Ivel Spring area.
    • Groundwater quality is suitable for direct input into the River Ivel, to provide river support (this is also known as an augmentation scheme). An augmentation scheme is where groundwater is pumped into the river to benefit the local environment.
    • The morphology (shape and structure) and the ecology of the River Ivel has been impacted by historic alterations of the channel. The presence of structures like weirs act as blockers both for free water movement and the free movement of wildlife up and downstream. Structures that cause flow to slow down or stop completely also leads to a silty river bed, as fine material drops out of slow moving water, covering the gravels which means less habitat for species that rely on clean gravels and a variety of flows.
    • A former sewage treatment works close to the springs, used to discharge treated effluent into the wetland and springs area, adding to the flow in the River Ivel. The site now pumps sewage to Letchworth for treatment, reducing the input of water in to the Ivel at Ivel Springs Nature Reserve.
    • The channel in this area has been heavily modified in the past and is largely straight and wide which is not the natural characteristics of a chalk stream headwater which should be narrow and meandering.

    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.

  • What are we proposing?

    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:

    • Implement a river support (augmentation) scheme where groundwater is pumped into the River Ivel.
    • Enhance a seasonal wetland, fed by surface water runoff, to reduce the risk of poor water quality and improve the habitat.
    • Carry out river restoration work which could include re-meandering the river channel and the modification of structures to create a more characteristic chalk stream.
    • Change our local groundwater abstraction license to reduce the amount by approximately 228 million litres per year from 2025.

    Below outlines the sequence of events.Image showing circled numbers 1 2 3 4 5 6 7

    1. Construct the River Support Borehole
    2. Test the Borehole
    3. Enhance the Seasonal Wetland
    4. River Restoration (including modifying riverbed levels)
    5. Test River Support (using overland pipes to determine best location for the river support)
    6. Final Pipeline Installation to Enable the River Support
    7. Additional River Restoration (subject to agreement from landowners)
  • What will the river support borehole look like?

    We are still working to develop the outline design for the river support (augmentation) borehole and infrastructure, to date we have:

    • Carried out walkovers and field surveys with our consultants to assess site conditions e.g. understand the lay of the land
    • Reviewed all existing information including where local utilities are located.
    • We are working to investigate power supply options for the river support (augmentation) borehole.
    • We are planning to carry out ground investigation works intermittently between December 2021 and January 2022 to inform the outline design development.
  • What will the seasonal wetland look like?

    We have recently finished an outline design for the seasonal wetland during which we:

    • Carried out walkovers and field surveys with our consultants to assess site conditions e.g. to inform models of water flows, and understand the lay of the land
    • Collected soil samples to make sure soils are suitable for reuse around the site
    • Calculated how much time the seasonal wetland could be wet and dry (known as water balance calculations)
    • Met with stakeholders on site to discuss possible opportunities, constraints and gather local knowledge
    • Developed two outline design options to present to stakeholders at a drop-in event in Baldock
    • Took feedback from the walkovers and drop-in events to finalise the outline design.

    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.

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