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 Dam

Shoalhaven River

43m 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 flow

Restoration 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