Measuring impacts and a UK perspective- Environmental impacts of hydropower Flashcards
What is a method for collecting empirical data?
Tagging/ telemetry
What are Passive integrated tags (PIT)?
- over 12 million fish are tagged
- Tags are small (12mm X 2.1mm)
- Tag life longer than fish’s (only activated by PIT monitoring reciever at dam)
- As they pass the recievers, data about the fish is stored
- This allows the migration of smolts to be tracked through the river
PIT tag readers aid management and research e.g. based on the ID numbers, groups of fish can be directed to the river or to barges
What are the advantages and disadvantages of PIT tags?
Advantages:
- only cost ca. £1.50-£2.50 each
- No internel power so tag life= longer than fish life
- Tags are small so eay to implant and less likely to impact swimming performance
- Fixed readers can automatically record fish passage
Disadvantages
- Fish only detected if in close proximity to the readers
- Relatively ineffective in saline waters due to water conductivity (but not completely impossible to use them).
What are radio tags?
Wildlife radio tags typically use brief pulses of the carrier frequency
- Extends tag life
- Easier for humans to detect discrete pulsed signals against the continuous noise from FM broadcasts
- Often used to gain animal positions, monitor movements or recapture the animal
- Can store behavioural/ environmental information
What are advantages and disadvantages of radio telemetry?
Advantages:
- Mobile tracking by foot, car, boat, plane, etc fish can be detected without needing to be near fixed antennas
- Fixed antennas can have a large ranges (up to 1 mile)
- Finer resolution information compared to PIT tags
- Allows migratory routes to be calculated
Disadvantages
- More expensive than PIT tags, sample size reduced if working on a budget
- Battery supply means tags are larger and have limited life expectancy
- Surgery more invasive
- Fairly ineffective in saline conditions (radio waves travel poorly)
What are acoustic tags?
- Transmit an underwater sound pulse or ping that is detected by a hydrophone (up to 25/sec or 1 every 16 secs)
- Tags programmed allowing indentification of individual fish
- Tags can be small (
What are the advantages and disadvantages?
Advantages:
- Fixed array of hydrophones allows 3d positioning of fish
- fine- scale behaviour can be ascertained (
- Fish don’t need to be close to hydrophones (as with PIT readers)
Mobile hydrophones can be used to actively track fish in real time
Function well in saline water
Disadvantages
Trade off between ping rate (resolution) and tag life:
> Size of tag and tag life
- Mobile tracing harder as hydrophones need to be submerged
- Less effective in noisy
What did williams et al 2001 study find?
As more dams came online- survival decreased
- However since the 70’s survival improved significantly
- Improvements in downstream bypass facilities
- Changes in dam operations
- Smolt to adult returns (SARs) remained low- unlikely to be related to direct mortality of smolts within the HEP
What did muir et al 2001 study show on the impact of a dam on the downstream migrating smolt life stage?
- Estimated rates of survival through different routes on 2 snakes river Dams
Results:
- Spill bays without flow deflectors = 98.4 - 100%.
- Spill bays with flow deflectors = 92.7 – 100%.
- By-pass systems = 95.3 – 99.4%.
- Turbines = 86.5 – 93.4%.
Management Implications:
- How best to operate dams
- Efforts to improve bypass efficiency and survival should continue
How does the release of hatchery fish impact wild fish?
Release of hatchery Chinnok salmon into columbia basin since 1990:
- Massive > in hatchery releases over last 100 years
- Now over 130 m juvenile Chinook released per yr
- Approx. 75-80% of adult returns are from hatchery origin
Levin et al. 2001
Juvenile and adult passage counts recorded at Lower Granite Dam (700km from Pacific Ocean)
Data used to estimate survival from juvenile outmigration to adult spawning migration
SARs typically 0-5%
Fluctuations in ocean conditions impact food availability
High numbers of hatchery released fish increase > competition for food
Density dependent mortality of wild fish, a highly depleted stock
Hatcheries could hinder the recovery of wild stocks
When would a hydropower development in the UK require an EIA?
“Installations for hydroelectric energy production” are listed under Schedule 2.
Decisions on EIA requirements based partly on “thresholds”
For hydropower, the threshold is if “The installation is designed to produce more than 0.5 megawatts”
Developments over 5 MW = much more likely to require an EIA
Developments under 0.5 MW may still require an EIA
Developments are judged by virtue of their nature, size and/or location
What are the issues that are often identified during the screening process often relate to?
- type of turbine to be used
- impacts on ecology (e.g. fish migration and provision of fish passess/ screens)
- impacts on hydrology/ geomorphology (e.g. seasonal flow variation and sediment transport)
Research and development aim at reducing these issues
How would you mitigate injury/ mortality to downstream moving fish?
- Hydrostatic pressure converters
- Archimedes screw turbines
- Compressible bumper rather than a steel and hard rubber edge
How would you mitigation habitat fragmentation?
Fish passes:
> Pool and weir pass (5% efficiency)
> Denil pass (0% efficency)
Poor efficiency for certain species
Develop and use more effective solutions
plastic grate for vertical climb
