The effects of the Eurasian beaver (Castor fiber) on hydrology in UK headwater streams

The Eurasian beaver (Castor fiber) is the first mammal to be reintroduced to the UK, gaining native status in Scotland in 2016. Beavers are habitat engineers known to substantially alter river hydrology. Beaver dams slow water and route it through a variety of flow pathways causing increased surface water storage and, in some cases, the potential to change surface-groundwater exchanges with implications for local water table elevations on adjacent floodplains. Other effects may include reduced downstream peak discharge, and increased base flows. The importance of these processes at larger spatial scales (e.g. catchment scale) is largely not understood. Moreover, the growing number of beavers in the UK means that river managers will need to develop evidence-based management strategies for the hydrological changes caused by beaver dams. The principal aim of this thesis is to advance the understanding of how beaver dams affect stream flow and the hydrology of the adjacent floodplain at scales that range from an individual beaver dam to a small catchment (2.2 km2). The following research questions will be addressed: Research Question 1: What effect do beaver dams have on water level and stream discharge from the scale of an individual beaver dam to a small catchment? Research Question 2: What effect do beaver dams have on the hydrology of the adjacent floodplain from the scale of an individual beaver dam to catchment scale? Research Question 3: Can a pond leveller be an effective tool to reach a compromise in water level that is sufficient for beavers and also reduces the impact of beaver ponds on agricultural use of the adjacent floodplain?