Correlations chart: Tool to analyse the dynamics of water quality parameters

Abstract

The search for statistical techniques and forms of graphical representation that can explain the most relevant correlations among limnological variables can help interpret phenomena in a body of water. The objective of the article was to propose a graphical representation of the correlations among limnological variables applied in the contributing basin of the Dr. João Penido reservoir, in Juiz de Fora, Minas Gerais state, Brazil. Six sections were monitored monthly from May 2012 to April 2014, analysing 15 water quality parameters and their statistical correlations. The correlations were represented graphically with the program Gephi 0.8.2-beta. The influence of organic matter (of natural and anthropogenic origin resulting from pasture runoff and sewage) on water quality was verified, with an observed increase in water quality parameters especially nitrogen and phosphorous, oxygen consumed, chemical oxygen demand, turbidity and total suspended solids. It is concluded that the correlation chart assists in the understanding of the dynamics of the water quality parameters at the different sites analysed.Gráfico de correlações: Ferramenta para análise da dinâmica de parâmetros de qualidade da água RESUMO: A busca de técnicas estatísticas e/ou formas de representação gráfica que consigam explicar as correlações mais relevantes entre as variáveis limnológicas podem auxiliar na interpretação dos fenômenos atuantes naquele corpo d´água. O objetivo do artigo é propor uma representação gráfica das correlações entre variáveis limnológicas aplicada na bacia de contribuição da represa Dr. João Penido, em Juiz de Fora, Minas Gerais, Brasil. Foram monitoradas seis seções mensalmente de maio de 2012 a abril de 2014, sendo analisados quinze parâmetros de qualidade da água e estes correlacionados estatisticamente. As correlações foram então representadas graficamente através do Programa Gephi 0.8.2-beta. Verificou-se a influência da matéria orgânica na qualidade da água, de origem natural e antrópica, oriundos de escoamento superficial das pastagens e do esgoto doméstico, observando uma piora nos parâmetros de qualidade da água com destaque para o nitrogênio e fósforo, oxigênio consumido, demanda química de oxigênio, turbidez e sólidos suspensos totais. Conclui-se que o gráfico de correlação auxilia no entendimento da dinâmica entre os parâmetros de qualidade da água do local analisado. Palavras-chave: recursos hídricos, variáveis limnológicas, bacia hidrográfica

Impact of Changes in Land Use and Land Cover in the Contribution Basin of Doutor João Penido Water Supply Reservoir of Juiz de Fora, MG, Brazil

“…Regarding the results, they demonstrated that the class Forest brought a significant increase in DO and a significant decrease in TN, TP and TS. The pasture caused a significant increase in coliforms, TS and TP, being possible to notice, on the other hand, a decrease in DO, corroborating the results found by Rocha et al (2019a) in work carried out in that same area. The class Urbanization caused a significant increase in DO, coliforms, turbidity, conductivity and a significant decrease in TN.…”

“…Vanzela et al (2010) also found a positive correlation between DO and pasture. The positive correlation with the nutrients TN (tau = 0.32) and TP (tau = 0.23) can also point to the effect of the transport of nutrients from these activities to bodies of water (Rocha et al, 2019a). Similar results with the nutrients TN and TP were observed by Buck et al (2004).…”

“…The classes were defined from an observation of the landscape through images of the region studied, using the Google Earth Pro, other related works (Ribeiro, 2012;Casquin, 2016;Oliveira, 2018;Rocha et al, 2019a;Rocha et al, 2020) and the study of the land use and land cover manual published by the IBGE (2013). Several studies use the identification of the different uses of land located around the area of a reservoir to assess the impact on water quality (Clément et al, 2017;Mehdi et al, 2015;Nguyen et al, 2017).…”

“…An adequate supply of DO is essential for the maintenance of self-depuration processes in natural aquatic systems (CETESB, 2016). According to Rocha et al (2019a), DO is a fundamental parameter for aquatic life, and an environment with low dissolved oxygen can be considered polluted. In the case of the CBJPR, the factors that can reduce the concentration of DO are the presence of organic matter and nutrients.…”

Groundwater quality assessment using geospatial and statistical approaches over Faridabad and Gurgaon districts of National Capital Region, India

“…This ultimately helps in decision-making to monitor the water quality. Although a highly positive or negative (i.e., close to + 1 or − 1) value of r typically indicates a strong correlation, it is essential to assess the statistical significance or confidence of the correlation (Helena et al 2000;Rocha et al 2019). This can be achieved by the p value test.…”