Keywords

WQSAM; remote sensing; water quality; South Africa; algal growth

Location

Session D4: Water Resource Management and Planning - Modelling and Software for Improving Decisions and Engaging Stakeholders

Start Date

12-7-2016 3:10 PM

End Date

12-7-2016 3:30 PM

Abstract

The Water Quality Systems Assessment Model (WQSAM) uses the concept of requisite simplicity within the context of modelling water quality of data scarce South African surface waters. Although WQSAM has successfully simulated the frequency distribution of observed historical nutrient data for various catchments in South Africa, the validation of algal and macrophyte growth processes in the model is a challenge because of a lack of observed data. Remote sensing data can provide an estimate of algal growth within reservoirs. Therefore, this study aimed to validate the WQSAM simulations of algal growth using remote sensing estimations of primary production in reservoirs. Algal growth was simulated for the Loskop and Kwena dams in South Africa. For the same dams, chlorophyll a (chl a) was evaluated using MEdium Resolution Imaging Spectrometer (MERIS) data. For the validation, modelled algal biomass was converted to a maximum/minimum band of chl a using observed relationships from the literature. The WQSAM simulations showed a stronger seasonal trend within algal growth than the MERIS data, with summer peaks and winter lows. However, the MERIS chl a data in all cases fell within the band of chl a produced by WQSAM. This study broadly verified the simulations of algal growth by WQSAM using remote sensing data. Although a rigorous validation between model simulations and remote sensing data was not possible, this was expected due to the approach of requisite simplicity adopted by WQSAM as well as the uncertainties associated within the relationship between algal biomass and chl a and within remote sensing data.

 
Jul 12th, 3:10 PM Jul 12th, 3:30 PM

The validation of algal growth processes in a water quality model using remote sensing data

Session D4: Water Resource Management and Planning - Modelling and Software for Improving Decisions and Engaging Stakeholders

The Water Quality Systems Assessment Model (WQSAM) uses the concept of requisite simplicity within the context of modelling water quality of data scarce South African surface waters. Although WQSAM has successfully simulated the frequency distribution of observed historical nutrient data for various catchments in South Africa, the validation of algal and macrophyte growth processes in the model is a challenge because of a lack of observed data. Remote sensing data can provide an estimate of algal growth within reservoirs. Therefore, this study aimed to validate the WQSAM simulations of algal growth using remote sensing estimations of primary production in reservoirs. Algal growth was simulated for the Loskop and Kwena dams in South Africa. For the same dams, chlorophyll a (chl a) was evaluated using MEdium Resolution Imaging Spectrometer (MERIS) data. For the validation, modelled algal biomass was converted to a maximum/minimum band of chl a using observed relationships from the literature. The WQSAM simulations showed a stronger seasonal trend within algal growth than the MERIS data, with summer peaks and winter lows. However, the MERIS chl a data in all cases fell within the band of chl a produced by WQSAM. This study broadly verified the simulations of algal growth by WQSAM using remote sensing data. Although a rigorous validation between model simulations and remote sensing data was not possible, this was expected due to the approach of requisite simplicity adopted by WQSAM as well as the uncertainties associated within the relationship between algal biomass and chl a and within remote sensing data.