The Benefits of Spatially Targeted Water Level Management for Salinity Reduction in a Coastal Aquifer

This paper describes the results of a modelling investigation into reducing salinity impacts within a drained lowland coastal aquifer through management of drain water levels, and specifically assesses whether targeted water level management changes deliver similar levels of salinity benefit to subcatchment-scale changes. Water level increases across an entire pumped drainage system result in the largest simulated reductions in intrusion of saline groundwater, but they are also associated with greater adverse hydrological impacts. Similar reductions in saline inflows can be achieved by targeting the same increases in drain water levels to those areas in which an understanding of soils and drains indicates good drain-aquifer connectivity. Changing policy priorities will require land drainage operation and management to evolve. This study has shown that revised water level management regimes should not be based on optimisation against a single target, such as salinity reduction, but that acceptable solutions must be sought with local communities that balance the apportionment of costs and benefits at the appropriate scale, taking into account impacts outside of the immediately drained area.