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CHAPTER 7. MANAGEMENT

7.4. Management of Reservoirs in Latin America

7.4.3. Ecotechnologies for Watershed/Reservoir Management

Basic principles

Three unifying principles to reservoir management are fundamental:

1. Reservoirs have a filling phase that sets up the whole spectrum of functioning of the system.
2. Reservoirs have a dam with a structure, which sets up the boundary of the upstream/downstream system.
3. Reservoirs have an operational system that controls the ecological conditions upstream/downstream.

The dynamics of reservoir construction and functioning take into account the watershed as a unit. Thus the management of the watershed/reservoir complex is the main objective. Ecotechnology is here defined as the use of technological means for ecosystem management based on a profound knowledge of principles of ecosystem functioning. This knowledge is then transferred to management in such a way that costs of recovery and the whole process of recovery and multiple uses are minimized. Thus, the use of theory for sound environmental management directed towards long-term sustainability is emphasized.

The principles to be taken into account to manage watershed/reservoirs are as follows:

Ecosystem principles to be considered in watershed/reservoir management:

• Ecosystems conserve energy and matter
• Ecosystems store information
• Ecosystems are dissipative
• Ecosystems are open systems
• Ecosystems are contrained
• Ecosystems are differentiated
• Ecosystems are multiple feedback systems
• Ecosystems are capable of homeostasis
• Ecosystems have capacity to adapt and self-organize

The management procedures that effectively regulate the reservoir functioning are based on the following measures:

• Control of pulses
• Control of succession
• Maintaining/restoring biodiversity
• Control of excess nutrients
• Control of eutrophication
• Taking into account the interaction upstream/downstream

Several methods were applied to reservoirs in Latin America, in an effort to implement adequate technologies for management. These methods were:

• Reforestation of the watershed with native species, as a means to retain biodiversity
• River restoration - restoration of the tributaries with several low cost techniques
• Wetland recovery and conservation in order to provide buffer systems to the reservoirs
• Preinpoundment of tributaries in order to prevent loads of nutrients and suspended material to the reservoirs
• Reintroduction of native species of fishes
• Maintenance of preserved areas as buffer systems in the watershed (forest fragments)
• Lake shore management
• Control of retention time
• Removal and chemical isolation of sediment
• Reservoir mixing
• Biomanipulation
• Reduction of light penetration
• Regulation of algal blooms (by several techniques)

Example: São Paulo State Reservoir

São Paulo State has a hydropower-installed capacity of 10x10⁵ MW. Several large dams were built up in the last 60 years to develop this energy source. The remaining hydropower is 2,800 MW allowing for the implementation of small hydroelectric plants.

Constructed originally for hydropower, these reservoirs are now an important basis for regional development since their multiple uses are increasing: for example the six reservoirs in Tiete River now encompass a 820 km of waterways. Multiple use of these reservoirs include, therefore, hydropower, navigation, tourism, recreation, and biomass production (fisheries and aquaculture).

These activities are all potential sources of eutrophication. A total approximately 25 million people are living in the lower and upper Tietê River. Untreated sewage, non-point sources of nitrogen and phosphorus, are the main causes of rapid eutrophication. Toxicity from agriculture is another source of contamination. The intensive land use activities has originated a high level of deforestation and sediment transport into the reservoirs accelerating aging, reducing primary production of phytoplankton, and interfering with navigation and recreation. The large-scale growth of water hyacinths, such as Eichhornia crassipes, is one of the most important consequences of this rapid eutrophication and general deterioration of water quality. The institutional developments to implement a recovery of these systems are:

• Organizing a consortium of river basin committees of 40 towns and villages along the Tietê River. This consortium will promote surveillance actions, independent environmental audits, and the management of selected sub-basins that are at a critical level of eutrophication and contamination.
• Enforcing environmental laws and turning compulsory the wastewater treatment.
• Initiating campaigns for environmental conservation and education in order to include community participation in the process.
• Implement strict evaluation (qualitative and quantitative) mechanisms for new developments such as large recreational aquatic parks, hotels, docks, and channels.
• Stimulating the privatization of wastewater of treatment and the water distribution in the municipalities.

A large source of contamination and eutrophication in São Paulo State, and especially in the Tietê River, is the discharge of untreated sewage in the São Paulo Capital. This is a very important (e.g., more than 60%) source of nitrogen and phosphorus downstream resulting in a large-scale eutrophication process now spreading to 300 km from São Paulo in the western direction.

Integration of management, operation, monitoring, and modeling at the level of São Paulo town is one of the initiatives that have been taken in order to develop new procedures for control of eutrophication and recovery, and optimization of management.

As for the six reservoirs downstream of the middle Tietê River basin (Figure 7.15), the waterway authority now controls the whole system and is the major leading organization for the water quality. All the integration of institutional initiatives and the optimization of management will depend on the articulation power and catalyzing capacity of the waterway authority.

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