Effects of hydropeaking on benthic invertebrate community composition in two central Norwegian rivers

Abstract

Hydropower regulations can have dramatic impacts on river ecological communities. The operation of hydropower stations is related to power demands, but their releases in the receiving water body causes sudden changes in flow, which in turn affect the biota. The effects of such flow variations on benthic invertebrates is not fully understood. Here, we studied the effects of duration and intensity of hydropeaking on benthic invertebrates in two rivers over a 3.5‐year period. We used both quantitative (Surber) and semiquantitative (kick samples) sampling methods to compare the ramping zone with the permanently water covered zone downstream of the hydropower plant, and with corresponding unaffected upstream areas. The ramping zone had a different invertebrate community composition and lower benthic density than other areas, especially after hydropeaking. Mayflies and chironomids were most negatively affected by hydropeaking and oligochaetes largely unaffected. Chironomids and the mayfly Baetis rhodani were able to recolonize the ramping zone and almost reach densities similar to deeper areas within 48 days following hydropeaking. The relative abundance of filter feeders tended to increase and gatherers/collectors tended to decrease from the ramping zone towards the deep, permanently water covered areas. In corresponding areas upstream of the power plant, the relative abundance of different functional feeding groups was the same in the mid‐channel and shore sites. Our study shows that hydropeaking has clear impacts on the functional structure of benthic invertebrates below the power plants. The ecological impact of hydropeaking on invertebrate communities should thus be taken into account, for example, by reducing the amplitude and duration of flow fluctuations.

Seasonal effects of a hydropeaking dam on a downstream benthic macroinvertebrate community

“…Many species would not have been collected with our methods, and the use of other techniques and instruments would be required to sample them (e.g., Peterson grab sampler and Hess sampler). Taxa that are sensitive to regular wetting and drying are more likely to be found in deeper areas of the channel below hydropeaking facilities, whereas tolerant species tend to inhabit the edge habitat (Jones, ; Kjaerstad, Arnekleiv, Speed, & Herland, ). This speaks to key questions regarding sampling design to understand impact.…”

Levantamento De Macrofungos No Parque Nacional Dos Campos Gerais, Paraná, Brasil

“…A hidroeletricidade é uma alternativa frente aos combustíveis fósseis, contudo, os impactos ambientais decorrentes da instalação e operação de usinas hidrelétricas sobre invertebrados, e mais especificamente sobre a entomofauna ainda são incipientes (KJAERSTAD et al, 2018). Os impactos estão relacionados à supressão da vegetação, remoção de terra, compactação do terreno e alagamento que podem destruir remanescentes de vegetação, alterar a dinâmica do ecossistema afetado e impossibilitar a permanência de espécies de animais (MORAN et al, 2018).…”

The Impact of Hydropeaking on Juvenile Brown Trout (Salmo trutta) in a Norwegian Regulated River

“…Benthic macroinvertebrates are potentially vulnerable in shallow riffle habitats [18,19]. Invertebrate abundance in rivers affected by hydropeaking demonstrates a lateral gradient from the most exposed areas having a low overall abundance through to the permanently wetted zone, which has invertebrate abundance and diversity similar to natural systems or unaffected reaches [20,21]. The prevailing opinion is that repeated drift or involuntarily downstream migration induced by hydropeaking depletes the benthic macroinvertebrate community [22].…”