Freshwater ecosystems and aquatic biodiversity are threatened globally by five pervasive processes – water pollution, flow modification, destruction or degradation of habitat, overexploitation, and invasion by exotic species (Dudgeon et al., 2006). River impoundment (dams, weirs), water diversions and consequent modifications to flow regimes have some of the most destructive effects on aquatic species and ecosystems (Vörösmarty et al., 2010). Altered flow and sediment regimes affect channel and floodplain form, riparian systems, freshwater habitats and aquatic biodiversity (Bunn and Arthington, 2002; Poff and Zimmerman, 2010). As well as large dams, many human interventions at catchment scale intercept or exacerbate overland flows and influence the hydrology and biogeochemistry of rivers and their floodplains (Allan, 2004). Human activities on the land surface, in river channels and underground have disturbed natural resource regimes (water, sediments, nutrients, organic matter) to such an extent that many aquatic systems are degraded, freshwater biodiversity is declining rapidly and ecosystem services have been lost in many of the world's river basins (Strayer and Dudgeon, 2010; Vörösmarty et al., 2010).