Effects of Human Involvement in the River Ecosystem Jonathan Sexton

Australia 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 Shoalhaven River 43m high, 520m long, 50m wide Creates a physical barrier

Tallowa Dam Con’t 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 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 Fish accumulate downstream of dam More susceptible to predators Disease spreads rapidly Not able to reproduce at high rates

Non-Native Species 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 Water flow is lessened Less erosion power Allows non- native plants to gain foothold Willows in Snowy River floodplain

Policies 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 River Hydroelectric dam built in 1974 Less diversity physically and biologically River 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 Basin 14% of total landmass – Rivers, floodplains and red gum forests 20 different species of water birds Seasonal flooding has not occurred in many areas for years

Changing the Water Flow 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 Amount of water and its condition Aquatic plants Microscopic organisms Fish and Birds

Water Surface area Salinity Depth of water – Influences temperature, water chemistry and light attenuation

Aquatic 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 Organisms Include free floating bacteria, biofilms, zooplankton and fungi Bottom of the food chain Hydrological factors affect them

Fish and Birds Reproducing Abundance Birds not best indicator – Able to fly to new nesting sites – Able to fly far distances in search of food

Conclusion Humans change the environment drastically We are seeing the errors in our ways and now trying to fix them More expensive to fix