Potential impact of groundwater augmentation of river flows on fisheries: a case study from the River Ouse, Yorkshire, UK

Many lowland rivers in the UK are under increasing pressure from abstractio n of water for potable supply or irrigation. Many schemes, both existing an d proposed, attempt to mitigate the loss of flow by augmentation from upstr eam reservoirs or pumping of groundwater into adjacent rivers. The impact o f flow regulation by reservoirs is well documented, but little attention ha s focused on the effect of groundwater augmentation on the biota, particula rly fisheries, in the receiving river. The present paper examines the poten tial effects of pumping groundwater into minor tributaries of the Yorkshire Ouse in England on the cyprinid fisheries downstream of the discharge poin ts and in the main river channel. Concerns were raised with respect to poor water quality and reduced water temperature. In particular, it was predict ed that small reductions in river water temperature brought about by discha rge of cold (less than or equal to 10 degrees C) groundwater could have ser ious detrimental effects on cyprinid fish recruitment and juvenile growth i n the receiving river, leading to a decline in stocks.