Abstract: The method of treating water pollution by reestablishing hydraulic connection between lakes and diverting water from a nearby river to the lake group which is seriously polluted is getting wider attention in shallow lake areas. To investigate the variation of hydrodynamics and water quality after lake connection and diversion, we built a 2-D model coupling hydrodynamics and water quality. The Project of East Lake Network in Wuhan was taken as research background. In this model, unstructured grid was adopted to fit the complex boundary, and lake topography and climate conditions were adequately reflected. In addition, the input, transport and transformation of nutrients and pollutants as well as the growing conditions of some algae such as cyanobacteria were taken into account. Moreover, field measurement data in June 2006 and June 2007 were used for the calibration and validation of the model parameters. Then the variation of indexes including BOD₅, TP, TN and Chl-a in three diversion conditions and three connection conditions after 30 days of stable operation were simulated based on the measured data in June 2012.Results suggest that wind force is still the major factor which induces the change of lake flow field for larger lakes in a water diversion project; in the presence of the same diversion flow, different diversion conditions has different effects on the water quality improvement. Dividing dikes in shallow lake group bring difficulties to the control of lake pollution, whereas setting up artificial island at suitable position of the shallow lake has no great impact on the water quality variation.

Key words: shallow lake group, hydrodynamic-water quality coupling model, scheme of water diversion, wind-driven current, Scenario Planning Method