9. Environmental flows

Question 1

Environmental flow (ecological flow)

Answer 1

the flow of water in a natural river or lake that sustains healthy ecosystems and the goods and services that humans derive from them
→ water for people and nature

Question 2

Threats to rivers (5)

Answer 2

• habitat alteration (altered hydrology, channelization)
• pollution
• invasive and nuisance species
• exploitation
• climate change

Question 3

What does estimating environmental flows involve?

Answer 3

Establishing the quality, quantity, and temporal distribution of water required to maintain key components, functions, and processes of aquatic ecosystems, as well as ecosystem services on which people depend
→ often means establishing the minimum quality, quantity and temporal distribution of water required

Question 4

What are the flow components needed to be considered when establishing environmental flow requirements? (5)

Answer 4

• extreme low flows
• baseflows (or low flows)
• high pulses (higher than norm but below flood level)
• overbank flow (small floods)
• floodplain maintenance flows

Question 5

What should be considered for each of the flow component? (5)

Answer 5

• magnitude
• frequency
• duration
• timing
• rate of change

Question 6

How are hydrologic metrics chosen?

Answer 6

They are chosen such that they are
- strongly linked to ecological condition
- usable as water management targets

Question 7

examples of hydrologic metrics (3)

Answer 7

• timing of flood peaks
• duration of zero-flow periods
• percent of summer flow diverted

Question 8

Environmental flows should consider:

Answer 8

• minimum amount of flow
• variation in flow regimes
  1. low flows
  2. seasonal highs
  3. flood peaks
  4. extraordinary events

Question 9

Environmental flows should be

Answer 9

• legally defensible
• scientifically defensible
• administratively defensible