The Impact of River Sand Mining on Aquatic Ecological Environment: A Case Study of the Lishui River

River sand mining can meet construction needs and economic development, but it has an impact on the aquatic ecological environment, and there is still a lack of quantitative research in this area. Therefore, this study used a one-dimensional river water quality model and a one-dimensional stable sediment transport model to establish the heavy metal diffusion water quality model and the suspended solids disturbance model, and applied them to a case study of Li County Liujiahe-Ershengtan sand mining in the Lishui River. The results show that the concentration of heavy metals decays slowly, which has a certain impact on the water quality of downstream rivers; while the suspended solids concentrations can be reduced to normal levels not far downstream. The research methods and conclusions provide reference for river water quality planning, river sand mining planning, and siting of water intake and sewage outlets.