**1. Introduction**

The Rodrigo de Freitas Lagoon (LRF) is a permanent area of leisure for the inhabitants of Rio de Janeiro and the site of important rowing and canoeing competitions such as those of the 2016 Olympic Games—it is one of the picture postcard panoramic scenes of the "Wonderful City." As well as its topographical features, this region includes parks, areas for sport, a skating rink, a heliport, a path for walking, and a cycle track; in effect, it is one of the main tourist centers in the city and famous for its landscapes.

The LRF has been suffering from the environmental effects of anthropic activities which have been practiced for decades, including the inputs of organic matter responsible for phenomena such as the constant eutrophication of the water bodies [1]. Rosso [2] suggests that the main culprits of the problems that have been detected are the intense urban occupation of the hydrographic basin, together with the growth of anthropic activities and a lack of compliance with elementary standards of urbanism or the basic regulations for environmental sanitary conditions such as sewage systems and urban drainage.

In view of its importance, the LRF has become a frequent target of controversy with regard to the quality of its water. More recently, the Lagoon has given way to speculation about whether it could be safely used for the rowing and canoeing events in the Olympic Games, in a way that would not put the competitors at risk. However, after a period of delay and heated debate with specialists being consulted and other interventionary measures, the events went ahead as planned without causing any subsequent problems.

The LRF has attracted a good deal of concern because of its valuable socioeconomic and environmental attributes and its great exposure in the national and international media with regard to the quality of its waters. The Lagoon is widely used by the public, and this includes recreational activities of a secondary kind or, in other words, activities in which contact with the water is sporadic or accidental and there is little likelihood of ingesting it. It is also used by traditional fishermen whose subsistence has depended on it for many generations.

As in the case of Fonseca and Santoro [3], as well as other lagoons along the coast of the State of Rio de Janeiro, the LRF has aroused interest among academics owing to the extent to which it has undergone adverse natural phenomena such as stagnation and the deterioration of the quality of its water, the release of gases, silting, and the huge fish mortality rate.

The poor circulation and renewal of the waters of the Lagoon mean that the seawater which enters in small quantities and at a slow speed in its depths—where it is more dense—becomes anaerobic in a short time and full of gases, and this is further aggravated by the oxidation of the already present organic matter [4, 5]. The existence of natural barriers like Piraque Island, on the east shore, and Caicaras Island, on the south shore, underlines the difficulty faced by the Lagoon in being regularly replenished by the affluent rivers and the entry of water from the sea.

Several interventions have been made, in particular over the past few years, with a view to improving the environmental conditions of the Lagoon. These include the following: (a) a greater degree of surveillance with regard to the construction and irregular waste disposal in the sewers and drainage system, (b) the improvement of the alteration and renewal of the waters by adhering to stricter standards, and (c) forging a better link with the sea through the Jardim de Alah (Garden of Allah) Canal and its respective floodgate. A comprehensive environmental monitoring system was also installed which was based on frequent analyses of various physicochemical and bacteriological parameters at strategic points placed along the Lagoon; this formed a solid database for the support of decision-making, as well as the management and planning of preventive and control measures.

The objective of this research study is to analyze the data from the environmental monitoring which was carried out in the LRF. The purpose of this is to determine the conditions of the quality of the water that is not in compliance with the regulatory standards, as well as the failure to adhere to these parameters, especially with regard to the limits of CONAMA 357/05. On the basis of this analysis, the aim is to relate these failures to the occurrence of environmental degradation and anthropic activities, as well as the

**25**

*Environmental Monitoring of Water Quality as a Planning and Management Tool: A Case…*

managerial and operational shortcomings with regard to the Lagoon. Some measures are recommended to mitigate these adverse effects and improve the environmental conditions of this vital and emblematic hydric body in the city of Rio de Janeiro. The chapter is divided in a way that can make it easier to discuss and reach a conclusion about the results obtained from monitoring the quality of the water in the LRF. It sets out by characterizing the features in the area under study and reflecting on the environmental monitoring that is carried out. Following this, there is a methodological description and examination of the implications of the analyses conducted of the water in the Lagoon through physicochemical and biological data.

The Rodrigo de Freitas Lagoon is situated in the southern zone of the city of Rio de Janeiro, between two mountains (Sumare and Corcovado) and the seafront of Ipanema, and is also bordered by the districts of Humaita and Gavea. With an area

, its drainage basin covers a large part of the districts of Gavea, Jardim

, a perimeter of 7.8 km, and an average

[6]. It was noted that after the sand removal works that were

Botânico (the Botanical Gardens), Ipanema, and Leblon, including the Lagoon, which necessarily serves as a storage basin in the periods of heaviest rainfall. The

depth of the order of 2.80 m, with a maximum of 4.0 m and a volume of approxi-

The LRF is replenished by the rivers that flow down from the surrounding slopes and currently this water is salubrious. The main rivers concerned are the Rios dos Macacos e Cabeca (Rivers of the Monkeys and Head) which flow into the Lagoon through the Rua (Street) General Garzon Canal and River Rainha (Queen), which is currently being diverted by the Avenida Visconde de Albuquerque Canal (**Table 1**) [7]. The interconnection of the Lagoon with the sea is being effected by the Jardim de Alah, a man-made canal which is 800 m long and has a width which ranges between 10 and 18 m, although one section of its depth is 0.70 m (**Figure 1**). The RIOAGUAS Foundation is responsible for controlling the level of the water feature of the Lagoon by operating the sluices in the canals of the Jardim de Alah, from Visconde de Albuquerque and General Garzon, with a view to improving the environmental conditions of the LRF and the bathing in the Ipanema and

TECMA (Environmental Technology) [8] states that it is essential to take note of the rivers and canals linked to the Rodrigo de Freitas Lagoon to obtain a full understanding of its complexity, insofar as any alteration in the quality or volume of the

Serious flooding has been recorded in the region, especially in the less steep areas of the basin that are closest to the water feature of the Lagoon—such as in J. Botanico. This occurs during periods of heavy rainfall, together with a rise in the water level of the LRF. At these times, the floodgates of the Jardim de Alah Canal are opened, to allow the outflow of water to the sea, as well as the floodgates of the General Garzon Canal, with the aim of preventing the overflow of the water of this canal and hence extensive flooding in the surrounding area. However, this management of the sluices of CGG is only undertaken as a secondary strategy when the outflow of the water to the sea through the floodgates of the Visconde de

carried out on the bed of the Lagoon during the period preceding the Olympic

Games in 2016, some parts showed a greater depth than 4.0 m.

inflow system can affect the dynamics of these waters.

Albuquerque Canal is not a sufficient response to the crisis [11].

*DOI: http://dx.doi.org/10.5772/intechopen.88687*

**2. General characterization of the scope of the study**

**2.1 Relief, hydrography, and vegetable coverage**

LRF has a water feature of about 2.2 km<sup>2</sup>

of 32 km2

mately 6,200,000 m3

Leblon beaches.

*Environmental Monitoring of Water Quality as a Planning and Management Tool: A Case… DOI: http://dx.doi.org/10.5772/intechopen.88687*

managerial and operational shortcomings with regard to the Lagoon. Some measures are recommended to mitigate these adverse effects and improve the environmental conditions of this vital and emblematic hydric body in the city of Rio de Janeiro.

The chapter is divided in a way that can make it easier to discuss and reach a conclusion about the results obtained from monitoring the quality of the water in the LRF. It sets out by characterizing the features in the area under study and reflecting on the environmental monitoring that is carried out. Following this, there is a methodological description and examination of the implications of the analyses conducted of the water in the Lagoon through physicochemical and biological data.
