Effects of Human Involvement in the River Ecosystem

1. Effects of Human Involvement in the River Ecosystem Jonathan Sexton

2. 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

3. Tallowa Dam • Shoalhaven River • 43m high, 520m long, 50m wide • Creates a physical barrier

4. 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

5. 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

6. Change in Population • Fish accumulate downstream of dam • More susceptible to predators • Disease spreads rapidly • Not able to reproduce at high rates

7. 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

8. Water Flow • Water flow is lessened • Less erosion power • Allows non-native plants to gain foothold • Willows in Snowy River floodplain

9. 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

10. 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

11. 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

12. 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

13. Indicators • Amount of water and its condition • Aquatic plants • Microscopic organisms • Fish and Birds

14. Water • Surface area • Salinity • Depth of water • Influences temperature, water chemistry and light attenuation

15. 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

16. Microscopic Organisms • Include free floating bacteria, biofilms, zooplankton and fungi • Bottom of the food chain • Hydrological factors affect them

17. 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

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