Environmental flow components (EFC) are the flow and its processes required to maintain the ecological environment of rivers, including low-flow, extreme low-flow, high-flow pulses, small floods, and large floods, a total of 34 ecologically significant indicators in five groups (Table 3). The inter-annual fluctuation of river flow patterns can be described in detail by EFC, and the threshold division of flow events related to EFC can be found in Richter & Thomas (2007).
Indicators used in EFC and ecological function
| Groups . | Indicators . | Ecological function . |
|---|---|---|
| Low-flow (1–12) | Monthly low-flow | Maintain groundwater levels in floodplains, provide drinking water for terrestrial animals, etc. |
| Extreme low-flow (13–16) | Peak, duration, timing, frequency | Expand the species of floodplain plants and prevent the invasion of alien species, etc. |
| High-flow pulse (17–22) | Peak, duration, timing, frequency, rise rate, fall rate | Shape physical characteristics of river course and maintain normal water quality conditions, etc. |
| Small flood (23–28) | Peak, duration, timing, frequency, rise rate, fall rate | Provide clues to fish migration and spawning, recharge water levels in flooding areas, control the population structure and distribution of floodplain plants, etc. |
| Large flood (29–34) | Peak, duration, timing, frequency, rise rate, fall rate | Maintain the balance of species in aquatic and riparian communities, and promote material exchange in channels and floodplains, etc. |
| Groups . | Indicators . | Ecological function . |
|---|---|---|
| Low-flow (1–12) | Monthly low-flow | Maintain groundwater levels in floodplains, provide drinking water for terrestrial animals, etc. |
| Extreme low-flow (13–16) | Peak, duration, timing, frequency | Expand the species of floodplain plants and prevent the invasion of alien species, etc. |
| High-flow pulse (17–22) | Peak, duration, timing, frequency, rise rate, fall rate | Shape physical characteristics of river course and maintain normal water quality conditions, etc. |
| Small flood (23–28) | Peak, duration, timing, frequency, rise rate, fall rate | Provide clues to fish migration and spawning, recharge water levels in flooding areas, control the population structure and distribution of floodplain plants, etc. |
| Large flood (29–34) | Peak, duration, timing, frequency, rise rate, fall rate | Maintain the balance of species in aquatic and riparian communities, and promote material exchange in channels and floodplains, etc. |
Note: Numbers 1–34 represent various indicators.