1. Effects of vegetation on hydrology in Australia

3. Characteristics of Oz veg n Sclerophyllous (Eucalypts, acacia) –“hard leaves" - small, tough evergreen leaves. The hard cells within the leaves maintain a rigid structure at low water potentials, instead of collapsing. –Fire ‘loving’ n Widespread …

9. Effects of vegetation on hydrology/hydraulics

10. Issues associated with vegetation and hydrology/hydraulics n Input to water tables = Salinity n Proportion of water to Runoff –Salinity revegetation –Fire and water supply n Water quality = Temperature

11. Dryland salinity

12. Note: break-of-slope salinity + regional water tables (low slope) Infiltration: 0.5 – 5mm/a15 – 150 mm/a

13. State/Territory2050 New South Wales1 300 000 Victoria3 110 000 Queensland3 100 000 South Australia600 000 Western Australia8 800 000 Tasmania90 000 Total17 000 000 $A250m/a $R1.2 Bn/a

14. Prognosis? n “Parachute” n Response time? n 50 – 1500 years

15. Effects of vegetation on runoff

17. Variability of annual peak discharge vrs. Catchment Area

19. n More variable precipitation? n El Nino? n Evergreen vegetation? (Evapotranspiration ???) n (ET) = 100 to 200 mm > per year than deciduous Why is Australian RO more variable?

20. Deciduous Rain Runoff

21. Evergreen Runoff Rain

22. Surface-cover

23. Effects of landuse (vegetation) on stream flows?

24. Eucalypt Woodland 0 200 400 600 800 1000 4006008001000120014001600 Pasture Mean annual rainfall (mm) Mean annual yield (mm) Eucalypt Forest Pine Forest from Vertessy and Bessard (1999) The impact of afforestation on mean annual yield (the MAYA model)

25. The impact of afforestation on daily flows (Tumut, NSW) 0.01 0.001 0.1 1 10 0 20406080 100 Pasture Percent of time that daily flow is exceeded Daily flow (mm) Pines (5-10 years) from Tumut experiment, NSWSF

26. Reduction in annual yield (mm) 0 50 100 150 250 450 0 100 200 300 400 020406080100 reduction (mm) % planted area Estimated annual yield reduction

27. Evapotranspiration will increase Groundwater recharge will reduce Water yields will reduce Low flows will reduce Peak flows will reduce *** We can predict these changes reasonably well *** In summary, after afforestation:

28. The dilution effect: a plausible afforestation scenario upland afforestation commences lowland groundwater relaxation may start flow salt concentration years 0100540 80

29. Runoff and water supply + fires

30. Limits to effects of cover on hydrology? n Urban extremes? n Above 20 year floods, landuse is irrelevant n Catchment is saturated and all catchments behave like concrete!

31. Study Site: Echidna Creek, SEQ Riparian Rehabilitation project: Commenced March 2001 Whole sub-catchment ~4km stream frontage Stock exclusion Off-stream solar powered stock watering Concrete crossings Revegetated with native riparian species (rainforest) 2m plant spacing Funded by: South East Qld Water Quality Monitoring Strategy Managed by: Maroochy River Catchment Coordinating Committee

32. Before After

33. Echidna Creek - Maximum temperature summer 2001/2002 Forested stream Cleared streams

34. Water temperature in small streams PREDICTED WATER TEMPERATURE INCREASES IN A NZ PASTURE STREAM (Rutherford et al. 1997) Mayflies About 3km length of riparian vegetation is required to restore a Natural’ water temp. 50% of Mayflies die after 96 hrs at 23oC. 50% shade from riparian vegetation will ensure survival

35. Summary n Sclerophyllous vegetation affects all aspects of hydrograph n Clearing, fire = rising water table and salinity n Reforestation = decreasing runoff n Shade = decreased water temperatures

36. Next lecture n Other controls on the hydrograph n Regionalisation n Begin on geomorphology!