Integrated measures for preservation, restoration and improvement of the environmental conditions of the Lagoon Olho d'Água basin
Introduction
The Olho d'Água is the main natural lagoon in the coast of Pernambuco and one of the biggest inside an urban area in Northeast Brazil (Fig. 1). It is situated near the delta of the Jaboatão and Pirapama rivers, with a water link through a rectified channel (Olho d'Água Canal) at the mouth of the Atlantic Ocean, in Jaboatão dos Guararapes County, Recife Metropolitan Region (RMR). Population in the basin, municipality and RMR are 200,000, 700,000 and 3,000,000 inhabitants, respectively. The Lagoon Olho D'Água has the following characteristics: length, 3 km; maximum width, 1.9 km; maximum depth, 1.5 m; average depth, 0.5 m; surface area, 3.75 km2; average salinity, 15‰ (dry season, 5‰; rainy season, 29‰); and catchment area of 33.5 km2. In the basin area, average climatic conditions are: air temperature, 27±5°C; humidity, 80%; average annual rain precipitation, 1800 mm.
The water uptake is mostly due to the water precipitation over the surface. During the summer (October–February), evaporation and infiltration are higher compared to precipitation, resulting in several isolated ponds. During the rainy season (March–September), the water level increases, since precipitation is higher and evaporation and infiltration are lower. As a consequence, flooding occurs, resulting in temporary wetland zones. Small drainage channels are responsible for the water flow. The main contributing channel is the Setúbal Channel with northward flow from the basin to the lagoon.
Since the infrastructure and economical development have not increased in the same pace as population growth, significant increase of low-income settlements occurred. Industrial activities near the lagoon include chemical and metallurgical manufacturers. There are also clothes, shoes and tissue industries.
Even though the lagoon basin is of protection interest, there has been a strong social and economical pressure for housing and construction near the lagoon, due to its available land, excellent location and, recently, tourism activities. As a consequence, many natural resources have been destroyed and problems concerning health, sanitary, environmental, social and economical conditions have arisen. The lagoon is polluted by industrial and domestic wastewaters without proper collection and treatment. Discharge of municipal solid wastes in the lagoon basin is also a common practice. Moreover, the banks of the lagoon are also affected by the illegal construction.
Integrated measures involving several institutions are necessary for preservation, restoration and improvement of the environmental conditions of the Lagoon Olho d'Água basin. The municipality (PMJG, 1991) has established general guidelines for urban development and land use. Among these, the main sanitation action is the construction of low-cost sewage system with smaller and decentralised treatment plants. A survey on the sanitary and environmental conditions for this purpose has been done (Kato et al., 1996).
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Sanitary infrastructure
The sanitary infrastructure is a responsibility of the state and municipal government. COMPESA, the Pernambuco State Water and Sanitation, is responsible for the water supply and the sewage system, whereas the municipality is responsible for the solid wastes management and operation systems, and for the urban drainage system. The water supply in the catchment area is regularly distributed by COMPESA. However, some areas near the lagoon are not supplied by the public water distribution system.
Environmental problems
Between the lagoon and the sea, there is an important environmental zone called Candeias Marsh (27 km2). It is a natural obstacle between the beaches and the lagoon. Despite the urbanisation, especially near the beaches, there are still some remaining areas of original sandbanks. The occupation in these areas has doubled in the last 10 years, representing a threatening to the ecological equilibrium (Leal, 1995).
Sedimentation and water pollution by domestic sewage are other environmental
Integrated measures
Surveys and specific studies on the environmental situation in the Lagoon Olho d'Água catchment and neighbouring area allowed the identification of the main problems and addressed the needs to meet the social and environmental requirements Silva, 1989, Cirilo and Asfora, 1996, Kato et al., 1996, Lins and Assis, 1997. Based on these studies, guidelines were established for preservation, restoration and improvement of the Lagoon Olho d'Água environment. Improved conditions for fishery,
Option for wastewater collection and treatment
In terms of sewage collection in the catchment area, three main neighbourhoods, Piedade, Candeias and Barra de Jangada, forming a narrow belt of 7 km×800 m, are in general considered in the sanitary projects due to the social and economical characteristics. The population density of this area is as high as 400 inhabitants/ha. This beach zone is typically residential but besides the skyscraper type flats, many hotels, restaurants and several other commercial buildings have been built in the last
Conclusions
A sewage system plays an important role in the environmental protection. Since there is an environmental program for protection, restoration and development of Lagoon Olho d'Água under consideration by the municipality of Jaboatão dos Guararapes, it would be advisable and profitable that a new sewage project could be adapted based on its guideline actions.
The choice for wastewater treatment should consider the local economical situation, the local technological development and environmental
Acknowledgements
The authors wish to acknowledge the support of staff members of the municipality of Jaboatão dos Guararapes and the collaboration of many people of some communities in the lagoon catchment during the fieldwork. The help of A.S. Santos, S.T. Magalhães, C.L. Schuler, D.A. Dias, J.C. Morais, A.L. Silva and R. Fonseca is acknowledged as well.
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