Uncertainty and Sensitivity Analysis of Phosphorus Model Parameters in Large Shallow Lakes

Abstract

Lake Taihu was chosen as a typical large shallow lake, and a diagenesis model of phosphorus was established based on environmental fluid dynamic code (EFDC). The uncertainty of the simulation results and the sensitivity of 16 parameters related to phosphorus migration and transformation in the diagenesis model were analyzed using Latin hypercube sampling (LHS), generalized likelihood uncertainty estimation (GLUE), and regionalized sensitivity analysis (RSA). The results showed that the temporal and spatial distribution of phosphate and total phosphorus in Lake Taihu was extremely uneven. Furthermore, the uncertainty of the diagenesis model had a strong influence on the simulation of phosphate and total phosphorus. For phosphate in the overlying, wind and wave disturbance at the 'sediment-water' interface was stronger in shallower water regions. The circulation of water in the bay area, where the dissolved oxygen content was low, was poor, which was conducive to the release of dissolved phosphorus in the sediment. For total phosphorus in the overlying water, the granular phosphorus and dissolved organic phosphorus contents in the central lake area were greatly affected by parameter uncertainties in the diagenesis model. The sensitive parameters mainly consisted of two kinds related to oxygen and dynamic characteristics, respectively. For large shallow lakes, the importance of parameter sensitivity in diagenesis models is no less than for hydrodynamic and water quality models. For large shallow lakes, the calibration of sensitive parameters should, therefore, be given attention when simulating the phosphorus content of areas with complicated water quality and sediment distributions.