Development and application of a hybrid model to analyze spatial distribution of macroinvertebrates under flow regulation in the Lijiang River

Alteration of natural flow regime due to reservoir operation imposes serious impacts on the aquatic ecosystem. To investigate the effects on the spatial distribution of macroinvertebrates, this study developed a hybrid ecohydraulics model which integrated a two-dimensional water quality module with an artificial neural network (ANN) based macroinvertebrate habitat module. The developed model was applied to a compound channel in the middle of the Lijiang River, where the flow in dry season has been largely modified by the Qingshitan Reservoir in the upstream. Semisulcospira amurensis (S. amurensis) which is the dominant macroinvertebrate species in the whole river basin was studied. The simulation and comparison results indicate that in general the flow regulation in dry season has negative impacts on the distribution of S. amurensis. The distribution area decreases, and in particular it becomes seriously fragmented. The model can be used through scenario analyses to adjust reservoir operation, so as to improve river management for ecological interest. In addition, the hybrid approach proposed in the paper has great potentials in studying this type of problems. (C) 2011 Elsevier B.V. All rights reserved.