Abstract
Abstract. Frequently, to assess the life expectancy of Brazilian reservoirs, bedload flux has been estimated by using formulas (e.g. the Einstein equations) or by assuming that bedload represents a fixed percentage of the suspended load. This study was carried out to characterize the bedload flux on the basalt scarps of southern Brazil. The bedload was measured over the course of 12 stormflows. The results demonstrated that the bedload flux–streamflow relationship was adequately described by a potential mathematical function. Bedload flux selectively transported particles smaller than D50 surface and subsurface bedstream sediments. When considering the bedload flux–streamflow relationship, the flux ranged from a minimum of 0.24 g m−1 s−1 for a streamflow of 0.53 m3 s−1 to a maximum of 44 g m−1 s−1 for a streamflow of 1.3 m3 s−1. The percentage of bedload/suspended load varied between <1% up to 60%, and this variation was strongly associated with peak flow.
Highlights
In Brazil, 85% of electricity is generated by hydroelectric dams installed primarily in the southcentral region of the country, several new dams are currently under construction in the Northern region as well (ANEEL, 2014)
For each bed load transport rate, the particle size of the sediment was characterized according to the where: qsml refers to the bedload transport rate (g s-1 m-1), m is the dry mass of the sediments collected over 40 measurements (g), w is the width at the mouth of the equipment (m) and t is the total sampling time for the 40 samples (s)
The beginning of the bedload transport was identified at >0.40 m3 s-1 which corresponds to a flow velocity of about 0.8 m s-1
Summary
In Brazil, 85% of electricity is generated by hydroelectric dams installed primarily in the southcentral region of the country, several new dams are currently under construction in the Northern region as well (ANEEL, 2014). This article seeks to characterize the bedload flux and the ratio of bedload to suspended load in a step-pool stream representative of the conditions on the basalt scarps of southern Brazil.
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