Modelling habitat suitability for fish in the fluvial and lacustrine regions of a new Eco-City

An eco-hydraulic model was used to determine the levels of fish habitat suitability in the fluvial and lacustrine regions of a new Eco-City. This model has been developed by combining a depth integrated hydrodynamic and water quality model with a habitat suitability index model. Carps were selected as the target species because they represent the major fish population in the study area. Water depth, flow velocity and dissolved oxygen (DO) were used as the suitability indicators. Hydrologic data recorded during 2001–2010 were analysed to determine the base flow, average flow and high flow rates, which were used to represent the discharges in the river for the three stages of the carp life cycle: overwintering, spawning and growth, respectively. Numerical model simulations were undertaken to determine the levels of habitat suitability for carps to live at these three life stages. The model results indicate that under the current flow regime the habitat suitability level in the lacustrine region is too low for carps at the growth and overwintering stages. DO depletion, overriding the role of velocity and depth, is attributed to the poorly suited habitat conditions in the lacustrine region. To improve the suitability conditions in the lacustrine region, a DO enhancement scheme was used. Model results show that the scheme has significantly enhanced the water quality, with the ideally suited area increased from 24.4% to 67.9% for the overwintering stage and from 44.5% to 77.5% for the growth stage. Due to the high flow requirement for carps to spawn in the fluvial region, further numerical model simulations were undertaken to investigate the effect of flow augmentation on the carp spawning habitat suitability. Non-traditional water obtained from recycled domestic and industrial wastewater in the Eco-City was used as an additional water resource. The analysis indicates that the Eco-City has sufficient non-traditional water to meet the high flow requirement for carps to spawn in the fluvial region.