A modelling approach to simulate Chlorophyta and Cyanobacteria biomasses based on historical data of a Brazilian urban reservoir

Carolina Cerqueira Barbosa,Ricardo Tezini Minoti,Lenora Nunes Ludolf Gomes

doi:10.4136/ambi-agua.2713

Carolina Cerqueira Barbosa, Ricardo Tezini Minoti + Show 1 more

Open Access

https://doi.org/10.4136/ambi-agua.2713

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Abstract

A process-based model was used to simulate a hindcast based on the worst historical water quality condition of a tropical urban reservoir. Paranoá Lake is located in Brasília-DF, Brazil, and went through intense eutrophication in the 70s and 90s, with an important cyanobacterial bloom event in 1978. The parameters of phytoplankton were calibrated, focusing on the group of Chlorophyta (green algae) and Cyanobacteria (blue-green algae) at four depths (1, 10, 15 and 20m). The results indicated that the model was able to reproduce the Cyanobacteria biomass in comparison with the observations (RMSE=22-29.10-3 mgC L-1). On the other hand, the simulated Chlorophyta biomass showed good agreement with the observed data only in the bottom layer (RMSE=29. 10-3 mgC L-1 at 20m). In the hindcast simulation, the model was able to predict a significant increase in cyanobacterial biomass facing a water quality deterioration. In the meantime, the simulated Chlorophyta biomass decreased, which may indicate the phytoplankton group succession in response to the environmental conditions.

Highlights

Water bodies in urban areas play an important role in providing water for multiple uses, especially drinking water supply and recreational activities
The model was able to represent some of the seasonal variations of the Chlorophyta biomass in Paranoá Lake, especially in the wet season
The sensitivity analysis and calibration of phytoplankton identified the parameters related to growth, light, and respiration as being the most important for the simulation of Chlorophyta and Cyanobacteria in Paranoá Lake

Summary

Introduction

Water bodies in urban areas play an important role in providing water for multiple uses, especially drinking water supply and recreational activities. The deterioration of water quality in these environments is the result of several factors, mainly the increase in nutrient loadings due to anthropogenic activities and higher sewage release in those watersheds. Ecological modeling is the result of the demand to comprehend biotic responses to environmental impacts, as abiotic criteria are not sufficient to represent the full complexity of aquatic systems. The ecological models have been applied, mainly, coupled with hydrological models on a basin scale (Munar et al, 2018; Tambara et al, 2017; Silva et al, 2016), for the understanding of the spatial-temporal distribution of cyanobacteria and climate change (Fadel et al, 2019; Rigosi et al, 2014), as well as to understand the succession of toxic cyanobacteria (Chia et al, 2018; Fadel et al, 2017; Vinçon-Leite et al, 2017; Burford et al, 2016)

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