Flow regimes profoundly influence river organisms and ecosystem functions, but regulatory approaches often lack the scientific basis to support sustainable water allocation. In part, this reflects the challenge of understanding the ecological effects of flow variability over different temporal and spatial extents.

Here, we use a process-based hydrologic model to simulate 23 years of natural flow regime in 100 reference bioassessment sites across the Adige River network (NE Italy), also identifying typical nivo-glacial, nivo-pluvial, and pluvial reaches. We then applied stream-network models to investigate the relationships between hydrologic and macroinvertebrate metrics while accounting for network spatial autocorrelation and local habitat conditions.

Macroinvertebrate metrics correlated most strongly with maximum, minimum and temporal variation in streamflow, but apparent effects varied across flow regime types. For example: i) taxon richness declined with maximum streamflow in nivo-glacial streams, but increased in the pluvial ones; ii) invertebrate grazers increased proportionately with flow variation in nivo-glacial streams but declined in pluvial streams. Spatial Stream Network models revealed that most variation in macroinvertebrate metrics was associated with spatial patterns, although local land-use and water quality also affected benthic invertebrate communities, particularly at lower elevations,

These findings highlight the importance of developing ecological flows in ways that reflect specific hydro-ecological and land use contexts. Our data also illustrate the importance of spatially explicit approaches that account for auto-correlation when quantifying flow-ecology relationships.