Identification of the degree of impact of dams on the hydrologic regime of semi-arid rivers: an evaluation of the DHRAM method

Naiah Caroline Rodrigues De Souza,Andrea Sousa Fontes,Sandra Maria Conceição Pinheiro,Lafayette Dantas Da Luz

doi:10.1590/2318-0331.011716093

Naiah Caroline Rodrigues De Souza, Andrea Sousa Fontes + Show 2 more

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https://doi.org/10.1590/2318-0331.011716093

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Abstract

ABSTRACT The flow regulation that results from the implantation of dams causes consequences to the river ecosystems due to the modification on the characteristics of the hydrologic regime. The investigation of these changes become relevant, mainly in semi-arid regions where there is a great amount of these hydraulic structures and lack of such analyzes. Considering the above, this paper aims to evaluate the Dundee Hydrological Regime Alteration Method (DHRAM) through the classification of the degree of impact of dams located on rivers Itapicuru, Paraguaçu and their tributaries, verifying the adequacy of its use to represent the semi-arid hydrologic regime. Thereby, the DHRAM was applied in three versions: considering the thresholds that define the scores to classify the degree of impact in its original set (accordingly to Black et al. (2005)); with the adjustment of those thresholds to local conditions; and, with the regrouping of variables and adjustment of thresholds. The results showed that the method in its original set is applicable to semi-arid rivers, however it tends to be very restrictive against the high natural hydrologic variability characteristic of these rivers, and it ends up pointing to a high degree of alteration for dams that are known for not causing a very siginifcant flow regulation. The DHRAM with the regrouping of variables and the adjustment of thresholds presented the classification that approached the most to the known characteristics of the studied dams, being useful for the evaluation of the impact of dams still in project, and also to guide the adoption of operating rules that minimize the most significant hydrologic alterations that are identified.

Highlights

Ecosystems evolve naturally from variations of conditioning factors, whether biotic or not, in time and space
Such results allowed to achieve the aim of this work of evaluating the application of the Dundee Hydrological Regime Alteration Method (DHRAM) in the Itapicuru and Paraguaçu rivers as well as their tributaries verifying the adequacy of its use for representing the characteristics of semi-arid rivers
The results referring to the original version of DHRAM showed that its application should be developed with caution, as it tends to increase the degree of impact of dams in relation to the adjusted version considering the regrouping of variables

Summary

Introduction

Ecosystems evolve naturally from variations of conditioning factors, whether biotic or not, in time and space. As the flow regime is the driving force in river ecosystems (JUNK et al, 1989; STANFORD et al, 1996; POFF et al, 1997; BUNN; ARTHINGTON, 2002; BATALLA et al, 2004), the alterations of parameters that characterize hydrologic variability can cause dramatic effects on aquatic organisms, riverside species, flow of energy within the system, sediment movement and interactions in the floodplain (POFF et al, 1997). Those dependent on this one, the implementation of reservoirs in the country has provoked several interferences, among those there are alterations on the connectivity of the river with the riparian zone and the disturbance of the hydrological regime as Stevaux et al (2012) identified in the Paraná River, in Brazil. The implantation of reservoirs causes alteration in the water quality as well (FANTIN-CRUZ et al, 2015), besides geomorphological alteration and on sediment transport

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