Brazil has an area of 8,516,000 km² with approximately 214.3 million inhabitants [1]. Of this area, 10.9 thousand kilometers are coastal [2]. The country has the largest hydrographic network on the planet, with multiple rivers and relatively few lakes.  The Trata Brasil Institute points out that 84.2% of the population has access to water, configuring approximately 35 million Brazilians without access to this resource.  The southeast region has the best and largest coverage of access, presenting 91.5% of the population with access to treated water. There is still a layer to be considered in access to water in Brazil –  due to the often old water distribution networks, the country presents loss rates of 40.3% in the distribution systems, approximating a loss of almost 7.5 thousand Olympic swimming pools per day. The sewage treatment situation is different. Trata Brasil in its most recent data shows that 51.2% of the country’s sewage is treated, and that there are almost 100 million Brazilians who still lack access to this service.  The central-west region shows better numbers with 60.5% of the sewage being treated. [3]

Water, as a fundamental element for the existence of life, necessary in most socioeconomic activities, is a natural resource that is in constant transformation, not only by unbridled development[4], but also, through all the changes that the hydrological cycle has undergone as a consequence of climate change [5].

In Brazil, water directed to the population, among the Brazilian constitutional tools can be grouped into water for consumption and basic sanitation, urban development and health. Together, the Union, states and municipalities must improve sanitation conditions. The states are responsible for those responsibilities referred to metropolitan regions. In the case of the municipalities, as they are the holders of the sanitation service, the activities associated with the supply of water for consumption may fall into the category of local interest. [6]

In 2020 the new Sanitation Legal Framework was instituted in Brazil, establishing in force of law that by 2033 sanitation services need to be universalized in the country. The goal established by the framework instituted in law 14.026 of July 15, 2020 presents a specificity of reaching the population with rates of 99% water and 90% with sewage [7]. Already characterizing an exception for 2040 in places where it is identified as unfeasible to meet the general deadline.

For this, investment in the sector needs to happen in a significant and constant way, enabling access to services while reducing carbon emissions. The sanitation sector is responsible for a portion of GHG emissions in Brazil. The Waste sector (where sanitation is included), was responsible for 4.4% of GHG emissions in Brazil, this sector includes emissions from domestic and industrial wastewater treatment, as pointed out by the Greenhouse Gas Emissions Estimates System [8].

Water and climate are interconnected factors, in the Brazilian system, water for human consumption is seen as a constitutional provision on sanitation and potability, so it is up to the Unified Health System (SUS) to participate in the formation of policy and implementation of actions for basic sanitation, control and inspect food, as well as beverages and water for human consumption [6]. This integrated way of looking at water and climate is a strategic direction that can direct good practices for the use and protection of water resources.

Recife

When we think about urban development, the use of water is linked to the configurations of land use and occupation, particularly urban land, and it is the municipalities’ responsibility to “manage” the land in order to promote, when appropriate, a territorial planning by means of control and use of land, parceling and occupation. Cities like Recife, with a vast metropolitan region and area of influence deal with these dynamics. It is also necessary to develop social functions that guarantee the well-being of the inhabitants through a well-structured and up-to-date Master Plan, since to guarantee habitability, urban dwellings depend on the supply of drinking water. Urban planning, of municipal competence, has a direct impact on the demand for drinking water and, consequently, sanitary sewage [9]. These relations over the years and the development of cities have increased water insecurity, not only because of the way cities have developed, but above all, with the increase in extreme weather events that Brazilian cities, such as Recife and its Metropolitan Region (RMR) have faced.

Recife is a city in the state of Pernambuco with an area of 218,843 km², where approximately 1,661,017 people live. [10] Government data shows that 142.99km² of the territory is urbanized, which represents 65.5% of the territory [11] and that the city has 69% adequate sanitary sewerage [12]. Data from 2010 also points out that 206,761 people of the population live exposed to the risk of floods, mudslides and mudslides, which corresponds to 12.5% of the population – The last census that translates this risk was conducted in 2010, it is possible that this number has increased. Recife is also a coastal city where 7.43% of the territory is made up of hills, presents the Atlantic Forest biome as predominant and has a humid tropical climate.

The city is home to the largest Metropolitan Region in the North-Northeast of Brazil, The Metropolitan Region of Recife (RMR) or Greater Recife, concentrates 65% of the GDP of the state of Pernambuco and comprises 14 municipalities.

Places like the RMR effectively suffer the consequences of disordered urban growth that reflects on the entire environmental system. Factors such as lack of basic sanitation, presence of dumps, inadequate waste collection, poor distribution in land use and occupation contribute directly to the pollution load that affects rivers and estuaries [4].

The city is surrounded by water, where the Capibaribe River stands out as one of the main water bodies in the municipality, responsible for influencing the city’s historical urbanization process. The Capibaribe river basin is one of the best known in the state of Pernambuco, covering a drainage area of 5,557.41 km², bordering 42 municipalities. The main river of the basin, the Capibaribe River, plays a very important social and economic role in water supply and industrial development in the state. The estuarine area of the Capibaribe River is approximately 19 km² complete

Recife and its waters are directly influenced by tides, presenting mangroves in urbanized areas, which makes the Capibaribe River a nursery for species. Throughout its urbanization process, the city disregarded this characteristic, occupying expressively bank areas. In an urbanistic movement that impacts the relationship of the population with the waters, it is estimated that from the twentieth century onwards the city’s rivers became invisible. [14]

Studies prove that the Capibaribe river basin represents one of the largest exporters of nutrients and organic matter to the coastal zone in Pernambuco [15]. Estuaries are complex environments, which have a significant amount of nutrients available and participate in the regulation of the natural hydrological system. The environmental impacts associated with urban growth have contributed to the elevation of the organic load in these environments by increasing oxygen demand. The researcher Eliete Zanardi-Lamardo shows that there is a high degree of degradation of the Capibaribe River estuary, pointing out eutrophic to hypereutrophic areas due to the several galleries that discharge domestic and industrial effluents in the area of influence of the study [16].

This relation of socio-economic and environmental importance of Recife with its waters has a long history. For example the formation of Recife’s harbor, which originated through improvisation and adaptation of fishermen, its official foundation dates back to 1918, and is responsible for giving the city the title of Capital while modifying all its urban and infrastructure structure. Most of its constructions near the sea date from the 20th century. The  journalist João Vitor Pascoal ably tells this story in the Diário de Pernambuco [17].

Currently, the Metropolitan Region of Recife has the Suape Industrial Port Complex. Connected to more than 250 ports around the world, it is considered the strategic public port in the Northeast region of Brazil, moving more than 23 million tons of cargo annually, and being within 800km of seven out of nine capital cities in the Northeast region [18]. The port complex started construction in 1983 and since then it is a recurring issue for the population in the Metropolitan Region of Recife, especially for the environmental controversies arising from its construction.  For example, many studies relate the increase in the number of shark attacks on urban beaches in the region to the expansion works [19], [20]. One of the biggest challenges in many ports is the biggest concern of specialists when it comes to Suape: the constant dredging to ensure the depth and operability of the port. Researcher Múcio Banja Fernandes, in an interview to Marco Zero content says that “The spigot of the outer harbor, perpendicular to the coast, created an obstacle for the littoral drift that carried to the north the sediments brought by the Tatuoca River. Without this force, the sediments brought by the river end up silting up the outer harbor” [21].

One of the biggest challenges of the Metropolitan Region of Recife is the increasingly recurrent landslides. When they occur, especially during rainy periods, these episodes cause physical and environmental damage, and in extreme cases, death.. Researcher John Kennedy Ribeiro de Santana in his article “Análise evolutiva da ocupação dos morros da cidade do Recife” points out that one third of the city is located in areas of high topographic elevation, generally occupied by low-income people. The 2010 Census places the city of Recife as the fifth ranked city in Brazil for the highest number of inhabitants in hilly areas prone to landslides and natural disasters [12].

In RMR, most of these landslides occur in thin layers and in recent years have intensified especially during atypical rainfall events [22]. The researcher Cristiane Ribeiro de Melo in her thesis, discusses slope movements, addressing that these are commonly generated by an excessive amount of water in heavy precipitation, pointing out that rainfall is a triggering agent of landslides in a scenario of unstable slopes [23].

Recife has a Local Plan of Climate Action, which brings together a projection of joint actions in the areas of Mobility, Sanitation, Energy and Resilience with short, medium and long term goals aimed at climate mitigation and adaptation, besides presenting a commitment of carbon neutrality by 2050 [24]. The scientific community of the region studies and follows the dynamics of water, sanitation and climate in a comprehensive and multidisciplinary way, the main universities have laboratories that produce quality and renowned science, such as the Oceanography Department of UFPE that has a scientific journal and the LSA, Environmental Sanitation Laboratory, also of UFPE [25] and [26].