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Flashcards in Freshwater Ecosystem Recovery Deck (21)
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1
Q

Streams+ Rivers, Ponds+ Lakes and Wetlands

A

1) black water rivers high acidity so kills bacteria.
2) temperature fairly evenly distributed between the body of water. Water layers may occur varies in temperature in different levels.
3) vast areas which flood could have different purposes throughout the year, e.g. grassland. Got to have water at some point throughout the year. Over half the worlds wetlands have disappeared since 1900.

Changing anyone of these processes or factors may affect the overall balance of the water quality –> determining factors. Leads to a functional aquatic ecosystem.
Past the industrialisation and development stage will then mean that countries will focus and look at their ecosystem services.

2
Q

Benthic Assemblages

A

Algae, bacteria, fungi, invertebrates. Transforms matter and energy into life. Bottom of food chain.

Unique adaptations provide valuable services. Break down organic material.
Break down organic matter within the water in order to purify it and make it fresher.

3
Q

Colorado River

A

flowed to Mexico and to the Gulf of California. Rich wetlands, one of the most regulated rivers in the world, flow down that river is in now way natural. Lots of sediment within the rivers. Changing the seasonality, relatively warm in the river because it is protected from the frost. Due to over abstraction the water barely ever reaches the estuary in Baja California, only 10% may reach it. Sediment may be supplied by algae. Not a lot of water actually reaching Mexico. Took 1.5 million m3.
US and Mexico water agreement carried on after 2017, instead of pulses they had sustained flow.
Water shortage in the US is continuing therefore impacting upon Mexico.

4
Q

Habitat Alteration

A

Inappropriate land-use or poor management (afforestation, overgrazing, land drainage).
SFO built on an estuary, by 1961 –> 90% of wetlands have disappeared .
Urban industrial and agricultural development. London many rivers built over to be used as sewers e.g. River Westbourne or River Fleet. 14 or so restoration projects.

Inappropriate development of recreation and navigation.

5
Q

Over Abstraction of groundwater and surface water

A
-Donor Basin:
Serious environmental Impacts 
Reduced flows
Threats to endangered species
-Recipient Basin:
Strong dependence on IBT
No demand management
On-going water shortages
Needs supplementation
Groundwater
-Over-exploitation:
Desalination
recycling
Economic benefits in Recipient Basin at cost to Donor Basin
Catalyst for social conflict 
Mitigation costs high

Dams and reservoirs, in japan as of 2005, only 3 rivers were not dammed, stop fish migration.
Of 30,000 rivers in Japan, only 3 were not dammed or modified in 2005.
Since 1980s, many restoration programs
Fish migration/pathways constructed
Restoration of wet paddy fields
River restoration

6
Q

Fish Passes

A

Need to consider cumulative impact of dams
50% fish pass is considered good – but each additional dam would reduce migrant populations
Only 12.5% of stock would remain after 3rddam
Also need appropriate conditions above passage (access to spawning grounds and nursery areas)

7
Q

invasive plant and animal species

A

The rich endemic ichthyofauna of Lake Victoria in Africa have been reduced by
predatory Nile perch (to convert trash fish to consumable fish), massive fish which grows up to 2m too big for previous fishing methods
overfishing (30 mill inhabitants around Lake)
eutrophication (correlated with increase in population)

8
Q

Restoration and Rehabilitation

A

Restoration: a complete structural and functional return to the natural ‘pre-disturbance’ state.
Rehabilitation: a partial structural and functional return to the natural, ‘pre-disturbance’ state.

9
Q

3 main aspect of rivers which require restoration work

A

The channel
The channel margins
The floodplain

10
Q

Los Angeles River

A

turned into a concrete drain in 1940’s to prevent flooding.
Increase speed of flow/capacity of channel by:
widening, deepening the channel to increase cross sectional area
increasing the channel slope by removing meanders
Removal of in-channel obstructions to decrease hydraulic roughness and hence increase flow velocities
Disconnection of the river from it’s floodplain
(Flood barriers, levees, walls etc also do this)
Increases available energy
River out of equilibrium
Bed erosion; cutting new meanders
Increase in peak discharge
Ecological and environmental degradation

11
Q

IWRM: Flood risk

A

Hard Engineering approach can cause environmental problems. Integrated Hard/Soft Engineering methods, which takes account of ESS more favoured now
Reconnect river to floodplain
Restore to create additional targeted floodplain storage
Slow and lower flood wave (decrease flood peak, release water later)

12
Q

Natural Flood Risk Mitigation Methods + Restoration methods include

A
  • trees or channels or flows of trees.
  • Restoring meanders to straight rivers
  • Enhancing redundant river channels (backwaters)
  • Enhancing straight river channels
  • Reverting and supporting river banks
  • Modifying river bed levels, water levels and flows
13
Q

Urban Pressures on Rivers

A
  • Much larger population than rural areas
  • Many competing uses
  • However, more people also mean more money to restore or rehabilitate.
  • Restoration of the Pasig River.
14
Q

Invasive Species

A

Zebra mussels are paving the shallows of the Great Lakes, displacing native mussels and changing ecosystems.
Quagga mussels are outcompeting xebra mussels lower lakes. Introduced 2005 from Ukraine
Transported by hitch-hiking on boats (ballast water), barges, sea-planes, engines, hulls, anchors, bait buckets, SCUBA gear etc
Low in fat and shell has no nutritional value therefore fish use lots of energy to crush and digest it. Mussels displace other more energy-rich food sources. Leads to fish decline
Filter feeders accumulate pollutants and pass them up the food chain. They eat food that native fish need to survive and clog-up water intakes for urban water supplies and power plants.

15
Q

How do we restore?

A

Control and eradicate harmful non-native species
Electric fields for silver carp (stuns, they float), or trawler net
Mussels: chlorine, metal-based solutions, filtering systems, hot water , pesticide development (bacteria)
Pollution control
Greater regulation of point-source pollution
Clean up Persistent Pollutants
Re-introduce native fish species
Lake trout, wild lake sturgeon (most < 25 yrs old)
Fishing closures (sturgeon)
Fish barrier removal
Work to identify, restore, protect habitat
Spawning reefs
Foster CC resiliency
Education
Science-based adaptive management approach

16
Q

Dealing with Eutrophication

A

Map Ecosystem & how it functions
Interaction of soil, groundwater, surface water, key processes at interfaces => how nutrients move from site to sea
Clarify cost-effective & sustainable measures
Ensure nutrients optimally used for crop cultivation
Capture and reuse of nutrient run-offs
Countermeasures in stagnant surface waters

17
Q

Lakes and Ponds Restoration

A

Artificial circulation (destratification)
Phosphorous removal (dredging / scraping)
Phosphorous inactivation using
Aluminium salts / iron / calcium (precipitation and settlement)
Riplox process (oxidation of top 10-20 cm of sediment)
Biomanipulation – food web management
Periphyton management – algae harvested to remove nutrients from system
Pre-treatment – wetlands/detention basins/ upstream reservoirs to remove inflow of nutrients

Hypolimnetic aeration
Liming for Acid Lakes
Dilution/flushing
Sediment removal
Nutrient diversion
18
Q

Wet Lands

A

distinction limited by lack of standardization of terms, est. 1.3 billion hectares if global wetland.
½ of world’s wetlands have disappeared since 1990 (WWF)
USA 50% degraded or destroyed
Risks:
Land conversion, Drainage schemes, Infrastructure development
Construction of dykes and dams
Extraction of water/minerals/peat
Overharvesting/overexploitation
Introduction of invasive species
Eutrophication, pollution, siltation
Tourism

19
Q

Great Plains Wetlands Restoration

A

The number of prairie ponds in North America has rebounded from less than 2 million in 1989 to about 4 million in 1996.
The duck population rose from less than 8 million to nearly 12 million, mostly due to the North American Waterfowl Management Plan (and water availability)

20
Q

Wetland Restoration Projects

A

Engineering solutions
Backfilling canals
Removal of contaminated groundwater
Biological interventions
Re-establishing wetland lands
Hydrological management
Eg increase effective inundation across floodplains
Reintroduction of drying cycles
Ramsar Convention (1971) provides framework for preservation and rational use of wetlands and resources
BUT wetland restoration is controversial because of the uncertainty about what is necessary to create and restore wetland structure and function (eg germination requirement, seed viability, seedling growth)

21
Q

Dam impacts on fish resources – mitigation and avoidance measures

A
  1. Dam location
    Should consider species migration
  2. Integrated hydropower schemes
    E.g. Lyon = electricity, industrial development, navigation, tourism
    3.Management of spillway design
    Multiple offtake levels to help reduce thermal gradient across reservoir, help turbidity, control quality of discharges
  3. Spillway /outlet design and downstream aeration
    Shape of spillway influences downstream water quality and can increase downstream turbulence and aeration
  4. Vegetation clearing
    Removal before reservoir filling (soft vegetation (leaves) decay can affect water quality, hard vegetation (roots, trunks) can be beneficial)
  5. Filling schedule
    Some reservoirs can take years to fill
    Filling should take place in rainy season
    Downstream flow releases during impoundment should mimic seasonal flow patterns
  6. Reservoir aeration
    Increased aeration leads to growth of food sources and precipitation of contaminants
  7. Fish Passes