Water quality of São Paulo reservoirs: the weight of evidence

Abstract

Eutrophication is a historical and recurring process and cannot be neglected in Brazil. Based on Atlas Sewers, from 2018, there are about 95 million people in equivalent sewage released in nature, untreated in the country. This scenario allows us to conclude that it is essential to maintain active water and sediment quality monitoring programs, with the information available in open public reports, with studies at each monitoring point, but other approaches are also interesting, complementary to face-to-face studies. Thus, the main objective of this work is to study in a comparative way different and different reservoirs of São Paulo, incorporating different looks, lines of chemical, biological and toxicological evidences, such as water quality analyzes (metals, phytoplankton, zooplankton, thematic maps of chlorophyll a and DS, the latter estimated by algorithms in satellite images), sediment and toxicity tests. It is hoped that the weight of the evidence will allow better qualification of the quality of the studied reservoirs. In order to do so, estimation equations will be used, and thematic maps generated with Sentinel 2 satellite images (A and B). However, due to the scope of this proposal, only the reservoirs that make up the T23KLP, Guarapiranga, Billings, Rio Grande, Rio das Pedras, Taiaçupeba, Jundiai, Biritiba Mirim, Ponte Nova and Paraitinga reservoirs will be used. public supply and generation of hydroelectricity. The choice of these reservoirs is also due to the proximity to the headquarters of this work. In order to generate the equations, the field data provided in the Inland Water Quality Report in the State of São Paulo, produced annually by Cetesb (Environmental Company of the State of São Paulo), from 2015 to 2019, will be used. the location of monitoring stations and Chla and SD concentrations for each station. Just for Billings, there are four monitoring points run monthly each year. The images will be downloaded with dates of a maximum of three days before or after the date of collection and tested algorithms for Chla and SD, in linear, logarithmic, exponential and polynomial adjustments, to obtain the best correlation, aiming to relate their respective indexes with data of field. The TSI calculation followed the classical equations of Carlson and Lamparelli (Cetesb). In 2019 and 2020 samples will be taken in these reservoirs, in at least three collection stations per reservoir, to validate the algorithms. The concentrations of the nitrogen and phosphorus series, Chla and metals, as well as phytoplankton and zooplankton (qualitative and quantitative aspects) will be studied in the profile of the water mass (temperature, dissolved oxygen, pH and electrical conductivity - multiparameter probe) and sediment (metals and toxicity tests). It is also expected to observe if there is any pattern, with the dam area in many reservoirs more lentic and less eutrophic when compared to the upper part, besides obtaining a diagnosis on the ecological quality of the reservoirs studied, based on many lines of evidence (AU)