Heikal Saleh

Aquifer storage of stormwater as a drought mitigation strategy

Urban areas have a high degree of impervious surfaces which lead to the generation of a substantial amount of urban runoff which, unfortunately, isn’t utilised and ends up being conveyed to receiving water bodies. With the increasing stress on water resources due to climate change and rapid urbanisation, opportunities for reusing water must become a priority. Therefore, there is a clear need for developing sustainable urban water resources that will provide a security of supply to mitigate future threats such as droughts while providing additional benefits to the environment and society. Traditional engineering solutions have opted for the construction of large expensive infrastructure to provide this security.

Managed aquifer recharge (MAR), a technique involving artificially recharging water into aquifers and recovering it at a later period when required, is a novel technology that has proven to be successful in other parts of the world such as Australia and the USA. Unfortunately, there is a dearth of information on the practice in the UK. This study, therefore, assesses the opportunity and feasibility of using this technology in an urban setting with urban runoff as the recharge water. The urban runoff will need storage and pre-treatment prior to injection into the ground and therefore a sustainable drainage system (SuDS) will be included in a SuDS-MAR scheme integrated into an urban setting.

A case study in London was taken to assess the feasibility and identify the challenges that would impede the success of the scheme. GIS and analytical computations were used to aid in this assessment. Results indicate that several challenges exist in implementing the scheme in an urban area. These include the size of land required for retention and treatment, optimally locating the ASR well to reduce costs while considering other constraints, accurately assessing the suitability of an aquifer, and high water quality requirement dictated by the groundwater SPZs. A better location for the case study may address some of these challenges. The travel time was also assessed which revealed the potential of a river augmentation application using the Harwich Formation aquifer. Further work on groundwater modelling using FEFLOW will be able to give a clearer understanding of the subsurface movement of the water. The cost assessment revealed that operational cost amounted to more than the capital costs due to the pumping energy required. The study thus revealed challenges and findings that could be used as a stepping stone towards furthering research on MAR in the UK.