Author(s): Fei Wang; Binliang Lin; William B. Rauen; Yuheng Ren
Linked Author(s): Fei Wang, Binliang Lin
Keywords: River-lake system; Water diversion; Water Quality; Tracer experiments; Numerical modelling
Abstract: Long residence times and low mixing of water in lakes has been known to cause severe water quality problems, particularly where the water body is subjected to effluent discharges, hydro-climatic extremes and/or significant water extractions. In this study an idealised river-lake system was assessed by hydraulics laboratory experimentation and 2D numerical modelling. A water diversion scheme was implemented to simulate lake recharge by river water in dry periods and under augmented flows. Fluorescent tracer experiments and related computer simulations were conducted to assess the performance of different parts of the system before and after implementing the diversion scheme. The analysis was based on residence time distribution curves, mean detention times and overall solute distribution patterns obtained for the simulated lake. The results showed that such measures improved flushing, as seen from the perspective of reducing the mean detention time. However, recharge alone had little impact on the overall mixing level in the lake waters due to poor cross-sectional flow distribution. This could lead to localised water quality problems in stagnant and circulating flow regions, despite the interventions, and could impact, for instance, water supply and fisheries productivity. The effect of inserting a flow deflector near the lake inlet combined with flow augmentation was then assessed and was found to positively affect the distribution of solutes, by mitigating the occurrence of dead zones. It is concluded that additional measures to water diversion may need to be considered to achieve the goal of enhancing water quality in a recharged lake.
Year: 2013