Outorga dos direitos de uso dos recursos hídricos na piscicultura: o caso do reservatório Acauã-PB.

Abstract

Water rights, which is one of the managing instruments present in the Law nº. 9.433/97 represents a legal component of great importance for the development of any enterprise in water resources management environment, amongst them the intensive pisciculture in special fish farms denominated tank-nets. This system of culture presents high productivity and inferior initial investments than the required for conventional systems of production. In Brazil, especially in the Northeast region, its accelerated growth is characterized by the culture of a fish called tilápia of Nilo, and it has been pulling the attention of the managing authorities, due to its potential polluting effect, that can provoke the acceleration of the eutrophication of water bodies designated for multiple uses. The necessity of promoting a sustainable management of the water resources management, where the development of income generating activities does not modify the quality of the water, hindering other uses to which sources had been destined, motivated this research, that has as its main goal proposing a methodology to water rights of use of the water resources management for the tank-net pisciculture in reservoirs used for human supplying. For this, scenario planning simulations and analysis of the support capacity calculation models used by the Executive Agency of Management of Waters of Paraíba (AESA) and by the National Agency of Waters (ANA) for water rights designated to the tilápia do Nilo tank-net culture in a eutrophic reservoir in the State of Paraíba have been made. Both models evaluate the limit of the total amount of phosphorus that will be released into the source by the intensive pisciculture activity and it will be expressed as the maximum number of tank-net that can be installed in a specific aquatic body. The models consider as a calculation variable the volume, the average depth of the water body, the number of fish for tank-net, the amount of fish food used during the culture, to the total amount of phosphorus attributed to the fish food and excrements, among others parameters. The study case was Acauã Reservoir, located at half course of the Paraíba River region, in the State of Paraíba. The evaluation of the capacity of support for both the models, indicate little influence of the pisciculture as a degradation activity, due to the total amount of phosphorus generated for the source. However, it is observed that the current qualitative conditions of the studied reservoir do not allow proceeding with for the pisciculture water rights. The modification of this situation will be possible throughout the implantation of management measures in the hydrographic bay, where the reservoir is located. This way, planning scenes have been simulated which allow the gradual reduction of the total amounts of DBO5, DQO, nitrogen and phosphorus that arrive in Acauã. Therefore, it is possible to conclude that only after the implementation of these measures it will be possible to water rights the pisciculture in Acauã. As for the models used, it is necessary the understanding of considerations and simplifications inherent to those models by the authorities responsible for the water rights emission.