Environmental Sciences Research Institute

Lake water quality models

Brian Rippey and Louise Grieve

Models for nutrients and phytoplankton biomass in lakes, especially for phosphorus and chlorophyll a, are the most important scientific and practical achievement in Freshwater Sciences, yet their accuracy in lakes with high nutrient concentrations is known to be poor. As it is these lakes that need to be managed, they are the focus of this research project, the aim of which is to develop and validate models to predict annual total phosphorus and chlorophyll a concentrations in lake water. Better formulated models are also needed, as the overall behaviour of lakes is changing as a result of changes in climate; we can no longer assume that the seasonal patterns in air temperature, sunshine and precipitation will remain constant and so the models need to be able to accommodate these changes.

The physicochemical properties from over 500 lakes, world-wide, have been collated in order to create and independently assess the accuracy of new lake models; the main properties are mean and maximum water depth), area, volume, chlorophyll a, lake total phosphorus, inflow total phosphorus, lake total nitrogen, lake water colour, hydraulic load, hydraulic residence time and whether the lake thermally stratified or not. Our model building methodology is now Structural Equation Modelling.