Impacts of groundwater abstraction and tree encroachment on groundwater-dependent wetlands

Project summary (maximum 4000 characters): Wetland ecosystems make a vital contribution to human health and well-being, yet the world is rapidly losing this important habitat (Ramsar Convention on Wetlands 2018). Alkaline fens in agricultural lowlands in particular have suffered. A common pressure on this type of wetland is abstraction for water supply that changes the water flow and level regime, which in turn allows invasive species to encroach. Here, we examine the impact of tree encroachment and groundwater abstraction on Greywell Fen. This is a nationally important alkaline fen that is thought to be in unfavourable due to the hydrological impacts of a nearby groundwater abstraction and increased evapotranspiration from tree encroachment. As part of the water company commitment to sustainability, abstraction will cease in the near future to restore groundwater inflows to the fen. However, the long term implications of this intervention are unclear because the relative contribution of different pressures against a backdrop of changing climate and wider catchment management needs to be considered. The main aims of this project are to: (1) assess the respective importance of groundwater abstraction and tree encroachment on fine-scale hydrological patterns at Greywell Fen using historical and current field observations and appropriate hydrological modelling, (2) assess the hydrological effects of a range of abstraction mitigation and vegetation management scenarios; and (3) investigate the value of using non-standard datasets such as seepage, sub-daily groundwater levels and soil temperature to calibrate hydrological models in groundwater-dependent wetlands.