Potential impact of small hydroelectric power plants on river biota: a case study on macroinvertebrates associated to basaltic knickzones

Abstract

Small hydroelectric power plants (SHP) have been considered as an alternative for the generation of electricity with reduced environmental impacts. Nevertheless, no studies have addressed changes in a particular kind of river macrohabitat commonly affected by SHPs, the knickzones. This study aimed to assess the impact of a SHP construction on the aquatic macroinvertebrate fauna associated with two basaltic knickzones located in Sapucaí-Mirim River, Southeast Brazil. The first, considered as a functional knickzone, follows the natural dynamics of the river flow and preserves the original rock substrate. The second, considered as non-functional knickzone, was permanently flooded after the SHP construction and the consolidated rock substrate was changed by fine sediment. Sampling was carried out in two seasonal periods and the data were analysed through multivariate analysis. It was observed differences in composition and structure of the macroinvertebrates community between the knickzones and periods. The functional knickzone exhibited a much higher richness, 72 taxa compared to 44 in the non-functional, as well as a large number of exclusive taxa (38, being only nine exclusive to the non-functional). Diversity, equitability and density mean values were also higher in the functional knickzone. The limnological parameters varied significantly between dry and rainy seasons but not between the distinct knickzones. This kind of macrohabitats and its potential role for the rivers biodiversity is practically unknown. In the scenery of fast SHP expansion, further studies and protection measures are necessary.

Hydropower dams and reservoirs and their impacts on Brazil’s biodiversity and natural habitats: A Review

“…Consequently, environmental impacts of SHPs include those associated with the dam's construction and land flooding by the reservoir, with loss of biodiversity, and potential habitat fragmentation, as well as post-construction alteration to flow regime and water quality [15,1,13,12]. A set of SHPs in the same hydrographic basin can cause social and environmental damage comparable to that of large hydroelectric plants [16].…”

Forest loss is significantly higher near clustered small dams than single large dams per megawatt of hydroelectricity installed in the Brazilian Amazon

“…Since multiple SHPs are often developed along the same portion of a river, an assessment and management at the watershed scale is needed to successfully mitigate the cumulative impacts of multiple small dams (Couto and Olden 2018). In Brazil, there is a growing concern about small and large dams within other biomes as well, and a number of studies have recently evaluated their impacts on aquatic and terrestrial fauna (Arantes et al 2019, Ruocco et al 2019, Alho 2020, Campos et al 2020, on bird communities (Abreu et al 2020, Alho 2020, and on human populations (Sgarbi et al 2019, Moran 2020, Santos et al 2020.…”

An Environmental Flow Framework for Riverine Macroinvertebrates During Dry and Wet Seasons Through Non-linear Ecological Modeling

“…For example, the construction of hydropower plants has destroyed the natural conditions of streams. In addition, the original ecological balance and seasonality of streams have been disrupted by the decrease in flow, cutoff of water flow, and dry up of rivers (Wellnitz, 2014;Ali et al, 2019;Branco et al, 2019;Ruocco et al, 2019). The construction of small hydropower plants has a small impact on the chemical factors, but it has a large impact on physical factors such as the flow velocity and water depth of the stream (Wang et al, 2013).…”