Ecosystem management of regulated rivers Flashcards
(31 cards)
List three major ecological effects of hydropower on rivers.
- Loss of natural flow patterns
- Habitat fragmentation
- Reduction in riparian and fast-flowing habitats
Why is flow important in river ecosystems?
It supports biodiversity by linking habitats longitudinally, laterally, and vertically, maintaining gradients in soil moisture and nutrients. Creates dynamic systems.
What are the five components of a natural flow regime?
- Magnitude
- Frequency
- Duration
- Timing
- Rate of change
What happens when the magnitude of the flow regime is changed with regulation?
Increased variation –> flushing of organisms
Stabilised flow –> dominance of competitive species, reduced productivity and litter break down rates, riparian species can not establish
What happens when the frequency of flow regime is changed with regulation?
Increased variation –> increased erosion, decreased habitat availability
OR
Decreased variation –> reducing flushing of sediments, dominance of competitive species
What happens when the timing of flow regime is changed with regulation?
Loss/change of seasonal variability –> Decreased habitat availability, interupted life cycles, invasion of alien species
What happens if duration of flow regime is changed with regulation?
Prolonged low flows –> changed abundance and diversity, physical stress for aquatic organisms
Prolonged flooding –> changed riparian communities
Shorter low flows –> increased availability of aquatic habitat
Shorter floodings –> upland vegetation establish
What happens when the rate of change of the flow regime is changed with regulation?
Fast changes in water level –> Flushing/stranding of aquatic organisms, undermined banks, failed reqruitment and establishment of riparian organisms
What is hydropeaking?
Hydropeaking refers to the practice of releasing water from reservoirs in hydropower plants to meet fluctuating energy demand, resulting in rapid and frequent changes in river flow.
What are some biological consequences of hydropeaking?
Standing water:
- no food for filtering insects
- behavioral changes in fish
- no redistribution of organic material
- loss of oxygenation of channel substrates
- higher water temperatures
Start/stop water level fluctuation:
- stranding of fish
- erosion of riparian areas
- increased drift of benthic fauna when starts occur
- freezing of organisms (?)
What are common invasive species due to altered flow regimes?
Salt Ceder (Tamarix spp.) and water hyacinth (Eichhornia spp.)
In what conditions does the invasive Salt ceder (Tamarix) have a competitive advantage over Populus and Salix?
In dryer conditions because it has deeper roots, these conditions are caused by a changed flow regime
What is the definition of Environmental Flows?
“Environmental flows describes the quantity, quality and timing of water flows required to sustain freshwater and estuarine (brackish water) ecosystems and the human livelihoods and well-being that depend on these ecosystems”
How does mimicking natural water levels help riparian vegetation?
It increases the area suitable for vegetation, supports seed germination, and reduces erosion from flooding and hydropeaking.
What types of restoration help riparian areas in hydropeaking reservoirs?
Use of natural erosion protection like boulders, restoring seasonal variability, and limiting zero-flow periods.
What are common ecological benefits of dam removal?
Restores fish migration routes, improves water quality, reconnects habitats, and increases biodiversity.
What are typical short-term ecological impacts after dam removal?
Increased sediment load causing suffocation and abrasion to aquatic life; however, these effects are usually short-lived.
How does dam removal affect sediment transport?
It restores natural sediment flow, rebuilding downstream habitats and estuaries.
What challenges are associated with dam removal?
Potentially high costs, potential release of contaminants, community opposition, and uncertainty in ecological responses.
How does dam removal impact local communities?
It can improve public safety, restore cultural sites, and enhance recreational opportunities, but may also face resistance due to economic concerns.
What are some effects of hydropower on rivers and streams? (6 listed effects)
- Loss of reaches with higher flow velocity and lake like reservoirs throughout the river
- Diversion hydropower causes depleted reaches with no or only a fraction of the original flow
- Few are modified for passage, most are total barriers causing fragmented ecosystems, sediments + nutrients build up in reservoirs
- Natural flow and water level patterns are altered
- Many riverine species have become threatened
- Many riverine ecosystems have shrunk in extent
The flow regime preforms different services for the riverine ecosystems. Bunn & Arthington (2002) grouped those services according to four different principles. What are those 4 principles?
- Biotic diversity, caused by channel form, habitat complexity and patch disturbance.
- Life history patterns (Flowers and seeds, growth strategy)
- Lateral and longitudinal connectivity
- Natural regime discourages invasions
Show in the hydrograph what aspects of the flow regime is important for the different principles.
- Regular flow and drought (disturbances)
- Reproductive triggers from increased flow in the beginning of the season, variability of peak flow, seasonal predictability, stable base flows at end of season
- Dispersal triggers from increased flow at beginning of season, high peak flow creating access to floodplains
- A natural and variable regime
What are two common organisms in stabilised water levels, that causes problems?
Water hyacint and algal blooms, cause dense stands on the water surface
