The effects of forest management on water quality

Water quality is generally high in watercourses draining forested areas. However, forest management can lead to detrimental effects on water quality and the aquatic environment. Key concerns include diffuse pollution, carbon transport and harmful effects on freshwater ecology.Here, we undertake a review of the effects of a range of forestry activities including cultivation and site preparation, fertilisation and harvesting on water quality. We attempt to summarise the literature across a wide geographical area focusing on empirical studies.Studies report a wide range of water quality impacts after forest operations including sediment delivery, nutrient losses, carbon transport, metal and base cation releases, and changes to acidity and temperature.Spatial and temporal resolution is an important consideration. Changes in water quality at the local scale are often not seen at the catchment level and the effects of operations may be manifest many years after the work was carried out, highlighting the importance of monitoring at an appropriate spatial and temporal scale.The development of best management practices (BMPs) such as the use of buffers, low impact techniques and phased felling have led to significant changes in operational activity, reducing and, in some cases, preventing impacts on water quality. We highlight some of the most effective techniques that can protect water quality from cultivation, drainage, fertiliser and harvesting operations.We also take a forward look to technological, methodological and climatic developments that may alter forest management effects on water quality.