Table 3. Some possible links between flow categories and ecosystem functioning in Western Cape rivers, South Africa.

Flow category
Ecosystem link
Dry-season low flows
Maintain perenniality and thus wet habitat for survival of aquatic species, trigger emergence of some insect species
Wet-season low flows
Maintain wetbank vegetation and fast-flow habitat
Intra-annual flood 1
Trigger fish spawning in mid-dry season, flush out poor-quality water
Intra-annual flood 2
Trigger fish spawning in early dry season, flush out poor-quality water
Intra-annual flood 3
Sort sediments by size, maintain physical heterogeneity, flush riffles, scour cobbles
Intra-annual flood 4
Sort sediments by size, maintain physical heterogeneity, flush tree seedlings from edge of active channel
1:2 yr flood
Maintain tree line on banks, scour out sedimented areas in active channel
1:5 yr flood
Maintain lower part of tree/shrub vegetation zone on banks, deposit sediments in riparian zone
1:10 yr flood
Maintain channel, reset physical habitat, maintain middle part of tree/shrub zone
≥1:20 yr flood
Maintain channel, reset physical habitat, maintain top part of tree/shrub zone