Suchergebnisse

AbstractThe concept of environmental flows has been developed to manage human alteration of river flow regimes, as effective management requires an understanding of the ecological consequences of flow alteration. This study explores the concept of macroinvertebrate sensitivity to river flow alteration to establish robust quantitative relationships between biological indicators and hydrological pressures. Existing environmental flow classifications used by the environmental regulator for English rivers were tested using multilevel regression modelling. Results showed a weak relationship between the current abstraction sensitivity classification and macroinvertebrate response to flow pressure. An alternative approach, based on physically derived river types, was a better predictor of macroinvertebrate response. Intermediate sized lowland streams displayed the best model fit, while upland rivers exhibited poor model performance. A better understanding of the ecological response to flow variation in different river types could help water resource managers develop improved ecologically appropriate flow regimes, which support the integrity of river ecosystems.

AbstractThis paper presents a study of 10 English chalk streams in the River Thames Basin historically affected by abstraction of groundwater. Using macroinvertebrates, macrophytes and river discharge records from across 76 monitoring sites, and spanning the period 1992–2009 we assess how the communities change over time. River discharge is seen to be the most influential variable in biological community composition, and is used to calculate the annual average river discharge (in m3/s) needed to sustain different biological assemblages at each study site, from the lowest to the highest expression of fluvial aquatic community development. This represents a bottom‐up or site‐specific approach to the determination of ecological flow thresholds, from which more empirical trends may be inferred at regional level. The approach also provides a useful understanding of the timescales involved in the recovery of communities from drought.