Transcript Effects of Human Involvement in the River Ecosystem

Effects of Human Involvement
in the River Ecosystem
Jonathan Sexton
Australia
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Water can be a
scarce resource
Dam rivers to
create reservoirs
50% of water
stored in ten large
reservoirs
Store largest
amount of water in
reservoirs in the
world
Water used for
recreation, cities,
animals and plants
Tallowa Dam
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Shoalhaven
River
 43m high,
520m long,
50m wide
 Creates a
physical
barrier
Tallowa Dam Con’t
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Upstream of dam 10 fish species extinct
 Fish not able to utilize spillways
 Competition between species decreased
 Short term answer = restock fish
Problems of Dams
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Fish confined to smaller and different
habitats
 Breeding and water condition change
 Food sources and availability change
 Upstream and downstream fish look and
behave differently
Change in Population
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Fish accumulate downstream of dam
 More susceptible to predators
 Disease spreads rapidly
 Not able to reproduce at high rates
Non-Native Species
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Able to gain a foothold
 Can be a new species or old
species that was present in
small numbers
 Once a foothold is gained
they are able to move into
neighboring river systems
Water Flow
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Water flow is
lessened
 Less erosion
power
 Allows nonnative plants to
gain foothold
 Willows in
Snowy River
floodplain
Policies
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Water Conservation and Irrigation Commission
– Created in 1971
– Maximize water usage
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Nation Strategy for Ecologically Sustainable
Development
– Created in 1991
– Gave environment an aliquot of total water
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Aliquot- least amount of water that the environment can
survive with without damage
Snowy River
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Hydroelectric dam built in 1974
 Less diversity physically and biologically
 River channels narrow
– Only gets 1% of daily flow
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Restoration plan
– Give the river 27% of yearly flow
 More water in the rainy season
Murray-Darling Basin
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14% of total landmass
– Rivers, floodplains and red gum forests
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20 different species of water birds
 Seasonal flooding has not occurred in many
areas for years
Changing the Water Flow
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2000 entire forest flooded
 Bird populations increased
 Egret species breed for first
time since 1975
 Water cap put in place
 Basin needs 40% more water to
stabilize
Indicators
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Amount of water and its condition
 Aquatic plants
 Microscopic organisms
 Fish and Birds
Water
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Surface area
 Salinity
 Depth of water
– Influences temperature, water chemistry and
light attenuation
Aquatic Plants
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Provide shelter and food
for mammals, birds, fish
and bacteria
 Convert CO2 into O2
 Not best indicator
– Cattle grazing nearby can
trample and eat
vegetation
Microscopic Organisms
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Include free floating bacteria, biofilms,
zooplankton and fungi
 Bottom of the food chain
 Hydrological factors affect them
Fish and Birds
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Reproducing
 Abundance
 Birds not best indicator
– Able to fly to new nesting sites
– Able to fly far distances in search of food
Conclusion
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Humans change the environment drastically
 We are seeing the errors in our ways and
now trying to fix them
 More expensive to fix