At the inception of the HWMP, one of the options suggested for enhancing water availability and natural river flow was aquifer recharging. This was not taken forward immediately due to lack of resource, but is now being considered.
Managed Aquifer Recharge (MAR) is the intentional recharge of water to suitable aquifers for subsequent recovery or to achieve environmental benefits. The concept is to flood an area to allow water to infiltrate naturally or take excess water and deliberately introduce water into the aquifer via a well/borehole. Managed aquifer recharge (MAR) is not a new concept and is used throughout the world – for example 8% of Thames Water’s public supply comes from MAR and subsequent recovery. It offers an alternative to using reservoirs to store excess water. This is predicated on the assumptions that there is available space within the aquifer to store the water and that it can be re-extracted when needed. A vital element is to ensure there is no deterioration in water quality as a result and that river/stream flows are maintained or enhanced. The diagram below illustrates the concept.
Natural aquifer recharge can be enhanced by re-connecting the river with its flood plain, deliberately flooding or winter irrigation of land or using rural Sustainable Drainage Systems (soakaways, swales, etc) to introduce water into the aquifer. This type of project, one form of river enhancement has been completed at Easton and it has been suggested that recharge downstream of Wickham Market might deliver significant benefit to water supplies further down the catchment. These projects will be pursued as part of the wider work on natural flood management and enhancement of the river environment, with the added benefit of aquifer recharging.
MAR by introducing water through an injection well/borehole requires high quality water and has a number of technical difficulties – and as such is likely to be more suitable for water companies and larger projects.
The key to the value of MAR is to understand the effectiveness of infiltration measures and water quality implications and a trial is being set up, in conjunction with the East Suffolk Catchment Partnership’s/ERDF Project Topsoil, to undertake this monitoring. A sub-group has been convened to take this idea forward, which if successful could be rolled out more widely as, for example, an extension of the Felixstowe Peninsula concept of utilising drainage water, in place of building a holding reservoir.
As this concept is being seen as an alternative to using reservoirs for storage it will also be necessary to quantify any costs, including carbon balance, for comparison with a reservoir, before utilising it more widely.
Notes from the MAR sub group meetings are available on the left of the page.