Physical limnology of a typical subtropical reservoir in south China

Abstract

Liuxihe Reservoir (23°45′50″N; 113°46′52″E) is a valley-type subtropical reservoir in south China. The reservoir behaves as a warm monomictic water body that is stratified throughout the year except for a short mixing period in winter. During stratification, vertical circulation was very weak and the hypolimnion was anoxic. The metalimnion range and thermocline location were affected significantly by the outlet height. Spatial and temporal variations in turbidity indicate that suspended matter was predominantly clay minerals with low organic contents. The behavior of turbid currents entering the reservoir was determined by density differences between inflow and impounded water. Because of particle size, shape of suspended matter, and weak vertical circulation, the suspended matter persisted in the water column for months. The water clarity of the lacustrine zone was affected significantly by water level variation, which is considered a comprehensive effect of stratification, resuspension, landforms, and hydrologic condition of the reservoir. Management recommendations on withdrawal selection and water level regulation are proposed to improve water quality.