Relevant Information and Detailed Analysis of the Problems

Sources of Degradation in the San Juan River Basin
and its Coastal Zone

The SJRB comprises four subsystems: Lake Nicaragua, the San Juan River, the Indio-Maíz River Biological Reserve, and the Tortuguero Plains Conservation Area. These last two subsystems comprise four small but very important basins integrated naturally in the San Juan River hydrological system. These are the basins of the Indio and Maíz rivers in Nicaragua and Colorado and Tortuguero rivers in Costa Rica.

The Lake Nicaragua subsystem--with a surface area of 23,848 km² from its headwaters to its outlet in the vicinity of San Carlos, source of the San Juan River--has three sectors with very different features:

• The sub-basins of the rivers on the eastern side, where the rivers go progressively from an intermittent flow to a permanent one as they approach the southern side, owing to increased rainfall.

• The sub-basins of the rivers on the western side, which are characterized by short distance courses and gradual slopes.

• The sub-basins of the rivers on the southern side, which originate in Costa Rican territory and only a part of their courses crosses Nicaraguan territory. This sector also includes several wetlands, habitat of migratory and local species of great ecological value. Caño Negro wetlands, a RAMSAR site, is among them.

In addition, although not included in the project area, Lake Managua, located on the northwest, has been connected at times with Lake Nicaragua.

The San Juan River subsystem is the only surface outlet from Lake Nicaragua. With a surface area of approximately 10,937 km², the San Juan River Basin has a climate characteristic of the area that drains in the Caribbean Sea, with annual average rainfall gradually increasing from 2,000 mm close to San Carlos to some 6,000 mm in North San Juan. This subsystem is divided into two sectors:

North Sector, with an approximate surface area of 2,347 km², whose tributaries flow down from elevations of some 400 to 600 masl. All the rivers that flow into the San Juan River from this sector cross Nicaraguan territory only.

South Sector, with a surface area of approximately 8,590 km², is the source of the main tributaries of the San Juan River. Some of these originate in the Costa Rican territory at elevations of some 3,000 masl, in the Central Volcanic Cordillera, and have more extensive drainage areas than the North Sector tributaries. This subsystem is characterized by steep slopes and high rainfall, which give the rivers a heavy flow.

The Indio-Maíz River Biological Reserve subsystem has a surface area of approximately 2,463 km² and is one of the areas in Nicaragua with the most biodiversity. However, is also one of the most fragile areas in the basin due to its ecological characteristics, which include very high rainfall, soils with limited capacity, and deficient drainage; an abundance of wetlands and water bodies; a predominance of extraordinarily diverse forests for which the conditions of exploitation are fragile, posing regeneration problems because of the close interconnectedness of its ecological systems through hydrological flows and environmental humidity; and its extraordinary biological diversity. Seven hundred forty-five plant species, 110 species of birds, 32 species of mammals, and over 32 species of crustaceans and fish have been identified within this subsystem. It is one of the national areas where virgin forest is preserved.

The Tortuguero Plains Conservation Area subsystem has a surface area of approximately 1,321 km². Like the Indio-Maíz River Biological Reserve, this area that falls within Costa Rican territory is one of the zones marked by the greatest biodiversity and ecological fragility in the South Sector of the Basin, owing to its ecological features. These features include: very high rainfall, soils with limited capacity, and deficient drainage; an abundance of wetlands and water bodies; a predominance of extraordinarily diverse forests for which the conditions of exploitation are fragile, posing regeneration problems because of the close interconnectedness of its ecological systems through hydrological flows and environmental humidity; and its extraordinary biological diversity.

This section of the TDA explains in detail the current and emerging environmental problems of the basin, as well as their causes. It should be noted, however, that the order in which these are presented in each case does not indicate either priority or the importance of the problems.

During the process of identification of the main current and emerging environmental problems, which limit, reduce, and/or pose a threat to the possibility of integrated management of water resources and the sustainable development of the SJRB, a number of issues were identified. As previously noted, these were grouped into eight categories. The first five represent the perceived major environmental problems, as shown in Table 1.1. The last three categories further explain the interactions (causes and effects) of institutional, social and economic aspects with the five major perceived problems. The problems grouped in these categories relate to:

• Soil degradation and sedimentation

• Ecosystem degradation

• Water quality

• Water resources use

• Overexploitation of natural resources

• Political, legal, and institutional framework for the integrated management of the SJRB

• Economic development

• Social areas

• Over-Exploitation of Natural Resources

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