Effects of human-driven water stress on river ecosystems: a meta-analysis

Abstract

Human appropriation of water resources may induce water stress in freshwater ecosystems when ecosystem needs are not met. Intensive abstraction and regulation cause river ecosystems to shift towards non-natural fow regimes, which might have implications for their water quality, biological structure and functioning. We performed a meta-analysis of published studies to assess the potential efects of water stress on nutrients, microcontaminants, biological communities (bacteria, algae, invertebrates and fsh), and ecosystem functions (organic matter breakdown, gross primary production and respiration). Despite the diferent nature of the fow regime changes, our meta-analysis showed signifcant efects of human-driven water stress, such as signifcant increases in algal biomass and metabolism and reduced invertebrate richness, abundance and density and organic matter decomposition. Water stress also signifcantly decreased phosphate concentration and increased the concentration of pharmaceutical compounds. The magnitude of signifcant efects was dependent on climate, rainfall regime, period of the year, river size and type of water stress. Among the diferent causes of water stress, fow regulation by dams produced the strongest efects, followed by water abstraction and channelization.