Evaluating alternative river management options in the tidal Ouse using the QUESTS1D model.

The tidal Ouse forms a significant part of the Humber river system in Eastern England, which provides the largest UK fresh water source to the North Sea and a valuable habitat for fish. However it suffers from dissolved oxygen (DO) sag in summer, exacerbated by the industrial effluent discharged at Selby. A one-dimensional water quality model, QUESTS1D, as utilized by the Environment Agency (EA) has been used to evaluate the effectiveness of management options based on exploiting spatial distribution of the assimilative capacity of the river as an alternative to implementing more stringent effluent consents. Significant improvements in water quality of the tidal Ouse are predicted compared to the effects of tightening effluent consents. A system of water quality functions is derived in this paper for quicker and more direct predictions of water quality, which will be useful in future research when combined with other analyses. Taking account the assimilative capacity in policy making, this paper suggests that a combined water management framework should be applied to ensure the required water quality.