Run‐of‐river dams as a barrier to the movement of a stream‐dwelling amphibian

Small run-of-river hydropower dams and associated water regulation filter benthic diatom traits and affect functional diversity

Knowledge of benthic diatom traits can help understand ecosystem function and guide biodiversity conservation. This is particularly important in rivers on which there are small run-of-river dams, which currently receive less attention. These dams generate power by drawing water from upstream and discharging it downstream after a large drop in penstock. We examine 15 functional diatom traits in habitats upstream, surrounding, and downstream of 23 small run-of-river dams in Xiangxi River, China. We compare the effects of these small dams on benthic diatom species traits, and taxonomic and functional diversity, from 90 sites. Dams change local environmental (e.g., channel width, flow velocity, depth) and physicochemical (e.g., dissolved oxygen, water temperature) variables, and a shift in diatom life forms and guilds is apparent, from taxa with strong attachment and low profile in high velocity waters (i.e., H1, H2 and H4) to those with weak attachment or that are planktonic below dams and outlets (i.e., H3 and H5), and towards high profile taxa below dams. Significant differences in biodiversity, particularly in functional richness, redundancy, and evenness, are apparent. Species and functional diversity indices are influenced by physical and chemical environmental factors (especially flow velocity and water depth). We found that diatom functional traits reflect longitudinal changes in flow and ecological condition, and suggest that monitoring such traits could be useful in adjusting flows to minimize ecosystem impacts. To maintain ecological flow and reasonable water depth within rivers we advocate for improved connectivity, carrying capacity and resilience of water ecosystems via a long-term, trait-based understanding of the impacts of small run-of-river dams.

Small Hydropower Plants' Proliferation Would Negatively Affect Local Herpetofauna

Hydropower plants (HPPs) have a strong environmental impact on freshwater wetlands. Small diversion HPPs (SDHPPs) with 0.1–10 MW of installed power, redirect water from small mountainous rivers into several-kilometer-long tubes, disrupting complex dynamics of local aquatic food webs and their interactions with neighbor terrestrial food webs. It certainly affects local aquatic communities, but it is often neglected that two highly threatened vertebrate groups—amphibians and reptiles—which live in and around these wetlands, could be affected as well. In the Balkan peninsula, a part of Southeastern Europe, SDHPPs recently became very attractive and profitable for potential investors after they were proclaimed as eligible for subsidies from the national budget. As a result, in year 2020, the maximal projected number of SHPPs in the Balkans increased to 4,556. According to the literature data, ~28% of amphibian species in the Balkan Peninsula use small rivers and streams in the upper parts of watersheds as feeding, breeding and/or nursery habitats. Additionally, 38% of the total number of reptile species in Europe are registered in the hilly/mountainous areas of the peninsula, and 33% of these species strictly need humid habitats. The attempt of this mini-review is to present the facts which show that SHPPs and DSHPPs, in the way they are currently being installed, present harmful energy solution for the biodiversity of the mountain parts of Balkan peninsula, particularly for local amphibian and reptile populations which rely on lotic aquatic ecosystems and/or humid terrestrial habitats.