Waters that spring from the serene fountain...
So begins the song by the poet Guilherme Arantes, who set the water cycle to music in Planeta água. We learn about the cycle of this precious liquid from an early age - observing the processes of precipitation, infiltration, water percolation, and transpiration into vapor. These interconnected mechanisms allow water to circulate between the air and the earth. The final spillway of water is the ocean, the destination of everything that has come from the continent. On its way, rainwater can seep into the ground, carrying the water table. Part of it evaporates. A third part runs off in small torrents that flow down tree trunks, form rivers, and bathe lakes, and bays. The water flowed like this, in serene springs - down the slopes of the Tijuca National Park, in the countless rivers that later bathed Guanabara Bay, in the lands of the Tamoios Indians and many other peoples.
In the formation of a city named after a river - which turned out to be a large bay - the Rio de Janeiro of empire times was bathed by rivers that still exist, but today are all canalized. Within the Tijuca National Park, the Jacó River, with its tributary the Perdido River, joins the Andaraí River to form the Joana River, which crosses the great Tijuca until it joins the Maracanã River, which in turn receives the waters of the Trapicheiros River and the Comprido River until it flows into the Mangue Canal. Diverted from their original routes by irrational urbanization, many rivers flow into the Mangue Canal. On the southern slope of Tijuca Park, the Paineiras River flows into the Carioca River, which has also been canalized and flows into Flamengo Park (Fig. 1 - map).
The forest has always been an ally of the river. Planted on its banks, it helped prevent silting, keeping the rivers and streams filled with water in quantity and quality. The abundance of water sustained life in the city. There were aqueducts in the squares where people went to find water for their homes since there was no plumbing.
An old aqueduct - from Arcos Velhos da Carioca - brought water to Campo de Santo Antônio. Thus, the fountain in Largo da Carioca was the first in the city, next to the staircase leading to the Convent of Santo Antônio.
Many fountains were built between the 18th and 19th centuries, one of them being the Pyramid Fountain, which although it no longer holds water, is a reference point in the architecture of Praça XV de Novembro (Fig. 2 - Pyramid Fountain).
But despite the many rivers, the risk of water shortages was always a threat. Many of the supply problems stemmed from the deforestation of the hillsides where the springs were located. At the time of the Empire, the frequent lack of water in the city was attributed to the deforestation of the springs in the Tijuca forest, which at the time was occupied by coffee plantations.
In 1861, the Emperor ordered the reforestation of the Tijuca Forest. This pioneering reforestation project in the urban area was carried out by six enslaved people - Constantino, Eleutério, Leopoldo, Manoel, Matheus, and Maria - who, together with Manuel Archer, restored the forest by planting over a hundred thousand saplings of various trees. Seedlings of cedar, cinnamon, peroba, jacarandá, pau-ferro, jequitibá, jaca, aroeira, and many others had already been acclimatized and produced in the Botanical Garden. Others came from Pedra Branca, in Rio's West Zone. The reforestation took approximately thirteen years of planting. It was then maintained and continued by the region's residents, who sought to beautify the places in the middle of the forest, opening up the current internal paths. As a result of the recovery of the forest and its rivers, the Tijuca Forest National Park was created, as a natural, cultural, and historical heritage site, making it the most visited protected area in the country (figure 3).
The balance in the relationship between man and nature involves the use and occupation of the land and the use of its water systems. This balance is noticeable in certain social groups, such as indigenous peoples, who occupy approximately 5% of the planet's surface and are responsible for preserving 85% of the territory they occupy. But this is not always the case. Often, land use has been carried out without proper, integrated management to minimize environmental impacts and guarantee the conservation of natural resources. In the countryside, unsustainable agricultural practices have transformed the landscapes near rivers, due to the suppression of riparian forests. In the city, rivers and streams are buried by the urban fabric.
The importance of riparian forest
Accelerated deforestation of riparian forests contributes to increased erosion processes in the soil and, especially on hillsides, has transformed rivers, causing silting and, in many cases, the drying up of springs and small streams. Not to mention sewage and waste. It is these impacts that contribute to altering the dynamics of rivers, favoring soil infertility due to the erosion process and the use of chemical products, compromising the natural environment. But the good news is that it is possible to reverse the process.
The effect of riparian forest
In their natural state, rivers and streams are protected on their banks by vegetation called riparian forests, made up of plants that can tolerate being soaked for a certain period (Figure 4 ). The name "ciliary" refers to the eyelashes in our eyes. Just as eyelashes protect us from dust or particles entering our eyes, the riparian forest is by analogy the eyelashes of streams.
Another important role of the riparian forest is to hold back sediment. The river flows and its current carries sand, gravel, earth, and sediment. During heavy rains, the riparian forest acts as a sieve, preventing sediment from the land from falling excessively into the water, causing what is known as siltation, i.e. the deposit of soil in the riverbed. Without riparian vegetation, the amount of soil in the river becomes shallower and shallower. What's more, the river without vegetation gradually loses its bank, and the soil becomes detached due to landslides (Fig. 4 )
When we plant the riverbank, it gradually returns to its natural condition. Water loss decreases as the vegetation takes hold. The springs start gushing again. It's impressive.
Rethinking the green structure of cities is indeed possible. Recover the riparian forest too. Many springs flow freely through the land and can be revitalized. Linear parks - green areas around the riverbank in the urban space - are already a reality in several metropolises. We'll follow some of the actions underway in the next few posts.
Suggested reading:
CORREIA, A. M. Terra Carioca - Fontes e Chafarizes, in: Revista do Instituto Histórico e Geográfico, Rio de Janeiro, RJ, volume 170, 1935.
MATTOS, R.A.A. A gestão sustentável de recursos hídricos. Regional experience and challenges: the case of flood control in the Joana river basin - Rio de Janeiro - 2004. Master's Degree, Graduate Program in Environmental Engineering, UERJ, 109 p.
SARMENTO-SOARES, L.M. The river of my childhood. Chronicle. Available at: http://nossacasa.net/nossosriachos/tiririca/category/cronicas/
Tijuca National Park - available at https://parquenacionaldatijuca.rio/historia-do-parque-nacional-da-tijuca/
Monuments of Rio - available at http://www.monumentosdorio.com.br/antigo/br/esculturas/monumentos.htm
Luisa Maria Sarmento-Soares
SDG 3, SDG 11, SDG 14, SDG 15
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