Hydropeaking intensity and dam proximity limit aquatic invertebrate diversity in the Colorado River Basin

Ecosystem-size relationships of river populations and communities

Knowledge of ecosystem-size influences on river populations and communities is integral to the balancing of human and environmental needs for water. The multiple dimensions of dendritic river networks complicate understanding of ecosystem-size influences, but could be resolved by the development of scaling relationships. We highlight the importance of physical constraints limiting predator body sizes, movements, and population sizes in small rivers, and where river contraction limits space or creates stressful conditions affecting community stability and food webs. Investigations of the scaling and contingency of these processes will be insightful because of the underlying generality and scale independence of such relationships. Doing so will also pinpoint damaging water-management practices and identify which aspects of river size can be most usefully manipulated in river restoration.

Impacts of hydropeaking: A systematic review

Hydropower is commonly considered a renewable energy source. Nevertheless, this does not imply an absence of impacts on the riverine ecosystem, the extent of which is expected to increase in the coming years due to the energy transition from fossil fuels to renewable sources and for the climate change. A common consequence of hydroelectric power generation is hydropeaking, which causes rapid and frequent fluctuations in the water flow downstream of hydropower plants. The review incorporates 155 relevant studies published up until November 2023 and follows a systematic review method, Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), which is a multi-stage systematic procedure for the identification and selection of research documents. The selected studies highlighted several prominent impacts of hydropeaking on aquatic environments. The primary effects include alterations in flow patterns, modification of water temperature, changes in sediment dynamics and fluctuations in dissolved gas levels. These alterations have been found to affect various aspects of aquatic ecosystems, including fish growth, behavior, reproductive success, habitat, and migration patterns, and benthic macroinvertebrate communities. Furthermore, hydropeaking can also lead to habitat fragmentation, erosion, and loss of riparian vegetation, thereby impacting terrestrial ecosystems that depend on the aquatic environment. Despite the body of literature reviewed, several knowledge gaps were identified, underscoring the need for further research. There is limited understanding of the long-term ecological consequences of hydropeaking and its cumulative effects on aquatic ecosystems. Additionally, there is lack of consensus regarding the quantification of ecosystem services, economic impact, soil moisture content, and weighted usable area due to flow fluctuation and global evolution of energy production from renewable energy sources. Addressing the identified research gaps is crucial for achieving a balance between energy production and the conservation of freshwater ecosystems in the context of a rapidly changing global climate.

Linking Macroinvertebrates and Physicochemical Parameters for Water Quality Assessment in the Lower Basin of the Volta River in Ghana

The health of the lower basin of the Volta River in Ghana was evaluated in January-February and May-June 2016 using physicochemical parameters and benthic macroinvertebrates sampled at 10 locations. Selected environmental variables were compared to accepted environmental water quality standard values where applicable. Principal component analysis (PCA) and redundancy analysis (RDA) were used to analyse the association between the benthic macroinvertebrates distribution and physicochemical variables. Pesticide concentrations were generally below the limit of detection 0.01 and 0.005 µg/L for organophosphate/synthetic pyrethroid and organochlorines respectively. Nutrient levels were also generally low; however, significant differences existed between the values of physicochemical parameters at the different sampling sites and seasons (Monte Carlo permutation test; p = 0.002), as well as between the abundance of macroinvertebrates at the different sites and seasons (p = 0.002). The environmental variables dissolved oxygen (DO), phosphate, pH, substratum (p < 0.05), turbidity, conductivity, total dissolved solids, total solids and nitrate (0.05 < p < 0.10) significantly explained the variation in macroinvertebrate composition between sampling stations in the Volta River. Polypedilum fuscipenne, was positively correlated with turbidity and DO concentrations; Physa sp., Centroptilum sp., Centroptiloides sp., Phaon iridipennis and juvenile fish were positively correlated with nitrate concentration and pH and negatively correlated with turbidity and DO. Polluted sites were dominated by the snail Lymnaea glabra. This demonstrates that physicochemical parameters and macroinvertebrates could be applied to describe the water quality and improve the biomonitoring for water resources management and the environmental protection in the Lower Volta River.