Correlation of turbidity and suspended sediment concentration in natural water flow using alternative data of water treatment plant, case of study in the upper Jundiaí river, Brazil

ABSTRACT

Measurements of suspended sediment discharge are greatly significant and represent a basic need for the initial assessment of the effects caused by this process and for the subsequent formulation of management actions. Also, considering that obtaining direct hydrosedimentological data is not a trivial and low-cost task due mainly to the special and temporal variability of the phenomenon, substitute technologies are well employed for monitoring watersheds. Among these are turbidity measurements, described in many papers. An adaptation of this technique was designed and performed in this study for the verification and secondary use of turbidimetric data carried out by a drinking water treatment company at the closing point of the upper part of the Jundiaí river watershed, in the city of Campo Limpo Paulista, São Paulo state. Direct measurements with traditional samplers and valuations of particle size distribution throughout the hydrological year were used to establish empirical correlations between the suspended sediments concentration and turbidity. The definition of the most appropriate adjustment was carried out based on the statistical analysis of the linear regression parameters (R², Value-p, MSPE, and PRESS) and residue statistics, thus adopting the model with piecewise regression by turbidimetric ranges (250 NTU), which in turn, presented low overestimation of the SSC for high values of turbidity. The definition of the historical series of suspended sediment discharge with hourly temporal resolution for the study site validated the main objective of reusing secondary data with hydrosedimentological purposes, highlighting the plausible applications for different places where there are insufficient resources for the installation and use of in situ turbidity equipment.

KEYWORDS:

• Turbidity
• surrogate monitoring of suspended sediment transport
• hydrosedimentology in watershed

Acknowedgements

We would like to thank for the support from São Paulo Research Foundation (FAPESP) for financial support and Fund for Support to Teaching, Research and Outreach Activities for the master's scholarship for the first author. The authors thank the Basic Sanitation Company of the State of São Paulo and Department of Water and Electric Energy, for making data available. The authors thank Espaço Escrita of Universidade Estadual de Campinas for the grammar and spelling revision of the final text.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was support by grant number 2017/0991-2 from the São Paulo Research Foundation (FAPESP). We also thank the Fund for Support to Teaching, Research and Outreach Activities (FAEPEX) by grant number 2300/19 and finally, Brazilian Water Research Center (BWRC) by case number 2019/11353-8 (FAPESP).