Effects of Human Involvement Effects of Human Involvement in the River Ecosystemin the River Ecosystem
Jonathan Sexton
AustraliaAustralia 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 DamTallowa DamShoalhaven
River43m high,
520m long, 50m wide
Creates a physical barrier
Tallowa Dam Con’tTallowa Dam Con’tUpstream of dam 10 fish species extinctFish not able to utilize spillwaysCompetition between species decreasedShort term answer = restock fish
Problems of DamsProblems of Dams
Fish confined to smaller and different habitats
Breeding and water condition changeFood sources and availability changeUpstream and downstream fish look and
behave differently
Change in PopulationChange in Population Fish accumulate downstream of dam More susceptible to predators Disease spreads rapidly Not able to reproduce at high rates
Non-Native SpeciesNon-Native Species
Able to gain a footholdCan 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 FlowWater Flow Water flow is
lessened Less erosion
power Allows non-native
plants to gain foothold
Willows in Snowy River floodplain
PoliciesPolicies
Water Conservation and Irrigation Commission– Created in 1971– Maximize water usage
Nation Strategy for Ecologically Sustainable Development– Created in 1991– Gave environment an aliquot of total water
Aliquot- least amount of water that the environment can survive with without damage
Snowy RiverSnowy River
Hydroelectric dam built in 1974Less diversity physically and biologicallyRiver channels narrow
– Only gets 1% of daily flowRestoration plan
– Give the river 27% of yearly flow More water in the rainy season
Murray-Darling BasinMurray-Darling Basin
14% of total landmass– Rivers, floodplains and red gum forests
20 different species of water birdsSeasonal flooding has not occurred in many
areas for years
Changing the Water FlowChanging the Water Flow
2000 entire forest floodedBird populations increasedEgret species breed for first
time since 1975Water cap put in placeBasin needs 40% more water to
stabilize
IndicatorsIndicatorsAmount of water and its conditionAquatic plantsMicroscopic organismsFish and Birds
WaterWater
Surface areaSalinityDepth of water
– Influences temperature, water chemistry and light attenuation
Aquatic PlantsAquatic Plants
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 OrganismsMicroscopic Organisms
Include free floating bacteria, biofilms, zooplankton and fungi
Bottom of the food chainHydrological factors affect them
Fish and BirdsFish and BirdsReproducingAbundanceBirds not best indicator
– Able to fly to new nesting sites– Able to fly far distances in search of food
ConclusionConclusion
Humans change the environment drasticallyWe are seeing the errors in our ways and
now trying to fix themMore expensive to fix
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