Developing Managed Aquifer Recharge (MAR) to Augment Irrigation Water Resources in the Crag Aquifer of Coastal Suffolk, Eastern England

Fresh groundwater resources in coastal areas in eastern England are under pressure from increased demand for domestic and irrigation water supplies and face an uncertain future due to the additional pressures of climate change. Faced with the need to find innovative solutions, managed aquifer recharge (MAR) offers the possibility of storing excess winter high flows underground for later abstraction during periods of peak demand. Given its favourable hydrogeological properties, the Pliocene Crag aquifer in Suffolk was selected for a demonstration MAR scheme with the purpose of supplying additional irrigation water during periods of high summer demand. The source water for recharge is a drainage channel that would otherwise discharge to the River Deben estuary. This water is of good quality in having a low nitrate concentration, although monitoring is required to ensure that chloride does not exceed a regulatory threshold of 165 mg L-1. In a trial of the scheme in June 2022, 12,262 m3 of source water were recharged to the aquifer raising groundwater levels by 0.3 m at the centre of the recharge mound with no detrimental impact on local water features. During this period, the source water quality remained stable with a chloride value of ~120 mg L-1. The recharged water was successfully abstracted from the Crag aquifer during the following July-September for use in supplementing surface irrigation reservoirs during an exceptionally dry period. The main limitation of the MAR scheme was the Crag aquifer hydraulic conductivity. Although it is relatively easy to recharge the aquifer through an array of buried slotted pipes, the rate of abstraction from the two site boreholes restricted the yield from the scheme. However, installing additional boreholes to increase abstraction has the disadvantage of making the MAR scheme economically less viable, albeit adding to the wider sustainable use of water resources