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

欧亚海狸是第一种重新引入英国的哺乳动物，于2016年在苏格兰获得原生地位。海狸是已知的栖息地工程师，可以极大地改变河流水文。河狸水坝减缓水流，并使其通过各种流动路径，导致地表水存储增加，在某些情况下，还可能改变地表水-地下水交换，从而影响邻近泛滥平原的当地地下水位高程。其他影响可能包括减少下游峰值流量和增加基流量。这些过程在更大的空间尺度(例如集水区尺度)的重要性在很大程度上还没有被理解。此外，英国越来越多的海狸意味着河流管理者将需要为海狸大坝造成的水文变化制定基于证据的管理策略。本文的主要目的是在从单个河狸坝到一个小流域(2.2平方公里)的范围内，促进对河狸坝如何影响河流水流和邻近滩地的水文的理解。将讨论以下研究问题：研究问题1：从单个海狸水坝的规模到一个小流域，海狸水坝对水位和河流流量有什么影响？研究问题2：从单个河狸大坝的规模到集水区的规模，河狸大坝对邻近滩地的水文有什么影响？研究问题3：池塘平整器能否成为一种有效的工具，以使水位达到足以满足海狸的要求，并减少海狸池塘对邻近滩地农业利用的影响？

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?