Análise do impacto das captações superficiais consideradas insignificantes em uma sub-bacia hidrográfica: estudo de caso da bacia do Rio Utinga/Ba.

Abstract

The CNRH has established several criteria to define insignificant off stream water use flows in order to allow the issuance of the correspondent water rights. However, the state owned rivers have their flow level of insignificance defined by their respective state government, without necessarily considering the cumulative effect of the whole set of uses. The general objective of this text, that is predominantly quantitative, is to evaluate the impact of the insignificant superficial water uses within a watershed. State and National water users data registers have been accessed as well as digital model images of Utinga River watershed and fluviometric data from the number 511700000 station. These data were treated and analyzed in Qgis 3.16, Hidro 1.4 and Excel® softwares for delimitation of the basin area and selection of abstraction points, the obtaining of the respective reference flow and the determination of the total volume abstracted. Aiming to access the impact on the water flow subject to issuance of water rights, it was applied the indicator proposed by ANA (2013) after some adaptation. The Q90 flow found was 0.964 m3/s, and the grantable flow was 0.77 m3/s, in addition, 575 insignificant uses and 45 granted uses were found, corresponding to a capture of 12.19% and 68.74% of the grantable flow, respectively. These percentages, together with the total already claimed, but not yet granted, draw attention to a problem of demand exceeding availability, demonstrating the impact of such uses on water availability, especially insignificant uses on the remaining flow.