1. River–floodplain interactions (i.e. lateral connectivity) are a major driver of the structure and function of the biota in floodplain waterbodies. Therefore, the enhancement of lateral connectivity is a key focus of large river restoration. The Rhône River restoration project in France includes an array of floodplain habitats and restoration measures, offering opportunities to test the predictability of changes in taxon abundance after connectivity restoration. 2. Quantitative samples of benthic macroinvertebrates taken before restoration were used to derive generalised additive models (GAMs) relating the density of taxa to an index of lateral connectivity. The index combined the diversity of sediment grain size, its organic content, vegetation cover and the water’s electrical conductivity. GAMs were used to predict changes in taxon density and between-site (i.e. beta) diversity 2 and 4 years after restoration at 34 sites (14 unrestored, eight reconnected to the river, six dredged, six restored by increasing river flow). 3. Observed post-restoration changes included an increase in the density of rheophilous taxa and an increase of beta-diversity among restored sites. Fifty-four GAMs (27% of the taxa) were selected for post-restoration predictions. Predictions from these models matched observations for a set of Trichoptera and other taxa with large density changes after restoration. The quality of predictions of density changes was poor on average among sites, but higher for sites where large changes in lateral connectivity occurred. Taxon-level predictions partly explained increased beta-diversity in restored sites, suggesting that predictions based on a subset of individual taxa can be used to predict community-level changes. 4. Our models can guide restoration measures in the Rhône and other rivers. Our results also show the benefit of diversifying restoration actions at the scale of entire floodplains. Post-restoration trajectories should be monitored over long periods to improve the identification of the key environmental predictors of biotic changes, especially at the less connected floodplain sites

In floodplain ecosystems, the lateral hydrological connectivity between the main river channel and the secondary channels plays a major role in shaping both the habitat conditions and the macroinvertebrate diversity. Among other threats, human activities tend to reduce the lateral connectivity, which increases floodplain terrestrialization and induces a loss of aquatic biodiversity. Consequently, the restoration of lateral connectivity is of growing concern. We studied four secondary channels of the Rhône floodplain that were subjected either to no restoration or to three different restoration measures (river flow increase only, flow increase plus dredging and flow increase plus reconnection to the river). Macroinvertebrate and environmental data were analysed one year before and during a period of five years after restoration. We expected a progressive increase of lateral connectivity according to the type of restoration. Changes in macroinvertebrate assemblages were predicted to be towards more rheophilic communities and proportionally related to the changes in lateral connectivity.In the reconnected channel, lateral connectivity increased and remained high five years after restoration. In the dredged channel, the immediate increase of the lateral connectivity metric induced by sediment removal was followed by a rapid decrease. In the unrestored channel and the channel only influenced by flow increase, the metric remained constant in time. The macroinvertebrate composition and the rarefied EPT richness changes were proportionally related to the changes in lateral connectivity. Alien species richness and densities increased progressively in all channels after restoration. Our results showed that modifications of the lateral connectivity lead to predictable changes in macroinvertebrate diversity. Synergistic interactions between restoration and longer‐term changes (e.g. climatic change, invasion of alien species) encourage long‐term monitoring to assess the durability and trends of restoration measures. Copyright © 2012 John Wiley & Sons, Ltd.

Floodplains are simultaneously among the most species-rich and the most threatened ecosystems. Alien aquatic macroinvertebrates contribute to this threat but remain scarcely studied in the lateral dimension of floodplains. We modelled the realized ecological niches of the alien species occurring in 24 floodplain channels of the Rhône River. Environmental variables depicting the ecological niches were associated to the lateral hydrological connectivity and light availability, both being modified during floodplain restoration works. Eight alien species were observed and they demonstrated either ubiquity or a restricted niche, with no link to the date of introduction. For most of them, the main river channel appeared as an important dispersal route in the lateral dimension of the floodplain. An increase of both lateral connectivity and light availability favoured most of the modelled species. Consequently, we recommend that sector-scale restoration programmes preserve varying levels of lateral connectivity for floodplain channels to prevent the expansion of alien aquatic macroinvertebrates.

There is a growing need to improve our understanding of catchment flow generation processes, especially in alpine watersheds, where the aquatic biodiversity is dependent upon the types of water sources and their seasonal dynamics. In order to identify and quantify the potential sources that contribute to stream runoff, Water samples were collected and discharge was measured. Other physical variables like electric conductivity and water temperature were also collected twice a day, once in the morning and once in the evening. These measurements continued for two to four consecutive days. In situ measurements were done for temperature, electric conductivity and turbidity of water at different temporal scale. Mass spectrometry was done to analyze silica and sulfate along with chlorine. Three different water sources were identified based on their physiochemical characteristics: glacier melt water, quickly routed surface runoff, and slowly routed ground water. Principal component analysis was performed in order to reduce dimensionality of the chemistry data independently in two hydrological years. End member mixing analysis was carried out for morning and afternoon data to describe the daily variation of runoff components. Our study suggests that glacier melt component has a strong daily variation, which influences the magnitude and timing of peak flow. A sign of early melt and accumulation can be seen in this watershed based on the studied years