Preprint has been published in a journal as an article
DOI of the published article https://doi.org/10.1590/2236-8906-72/2019
Preprint / Version 1

Garças Reservoir trophic state dynamics: a 20-year synthesis

##article.authors##

  • Denise de Campos Bicudo Instituto de Botânica, Núcleo de Pesquisa em Ecologia, Avenida Miguel Estéfano 3687, 04301-012 São Paulo, SP, Brasil
  • Jacques Everton Zanon Instituto de Botânica, Núcleo de Pesquisa em Ecologia, Avenida Miguel Estéfano 3687, 04301-012 São Paulo, SP, Brasil https://orcid.org/0000-0002-9619-4393
  • Carla Ferragut Instituto de Botânica, Núcleo de Pesquisa em Ecologia, Avenida Miguel Estéfano 3687, 04301-012 São Paulo, SP, Brasil https://orcid.org/0000-0002-4313-1436
  • Samantha Borges Faustino Instituto de Botânica, Núcleo de Pesquisa em Ecologia, Avenida Miguel Estéfano 3687, 04301-012 São Paulo, SP, Brasil https://orcid.org/0000-0003-3531-2082
  • Carlos Eduardo de Mattos Bicudo Instituto de Botânica, Núcleo de Pesquisa em Ecologia, Avenida Miguel Estéfano 3687, 04301-012 São Paulo, SP, Brasil
  • Luciane O. Crossetti Universidade Federal do Rio Grande do Sul, Instituto de Biociências, Departamento de Ecologia, Avenida Bento Gonçalves 9.500, 91549-000 Porto Alegre, RS, Brasil

DOI:

https://doi.org/10.1590/2236-8906-72/2019

Keywords:

eutrophication, management, phosphorous, shallow reservoir, water quality

Abstract

The Garças Reservoir history reveals a remarkable case of human impacts resulting from the urbanization pressure over the 20th century. It is a shallow tropical system located in the Parque Estadual das Fontes do Ipiranga, a protected area within the city of São Paulo, São Paulo State, Brazil. Based on a comprehensive dataset (1997-2017), we evaluated the water quality temporal change using a trophic state index (TSI); in addition, we also verified whether the management procedures improved the water quality. Mechanical removal of macrophytes (1999) triggered an abrupt change from eutrophic-supereutrophic to the hypereutrophic state with feedback mechanisms. After five years (2005), a slowdown in the internal P loading process occurred, followed by the installation of the secondary wastewater treatment in the city zoo two years later (2007). Both processes promoted the beginning of water quality improvement. In 2011, TSI first dropped to supereutrophic state with the temporary diversion of the sewage effluent from the São Paulo State Department of Agriculture. This effluent was finally inactivated (2014) and the system sustained the supereutrophic state. TSI responded well to the historical key events related to the control of sewage effluents. After 11 years from the permanent impact of macrophytes removal, current results have demonstrated improved health of the system. It is absolutely necessary to improve the sewage treatment from the city zoo to continue the reservoir recovery considering that since 2014 it has been the only external phosphorous loading to Garças Reservoir. The history of Garças Reservoir can offer a better understanding of wrong management strategies and the vulnerability of tropical shallow systems to eutrophication.

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Posted

2020-05-12

Section

Biological Sciences