What is hydrology?

1. What is hydrology? The term comes from the Greek: ὕδωρ“hydōr” = water + λόγος “logos” = study or knowledge of. Sub-disciplines: Hydrometeorology, climatology, oceanography, limnology, potamology, hydrography, hydrogeology, geomorphology, hydrogeochemistry, hydropedology, ecohydrology, hydroecology, hydraulic engineering, etc. Is an important part of most disciplines: Agriculture, biology, engineering (civil, geotechnical, mechanical and mining), geology (exploration, petroleum, environmental, mine), natural resource management (catchment, environment), urban planning, economics, politics, history, etc.

3. Global water budget (Gleick, 1996)

4. Of the remaining 4 stubbies, 2 represent the frozen water (you can’t drink them either) Of the remaining 2 stubbies, 1¾ represent the groundwater (you can’t see the beer) The rough guide to the global water budget... Let’s say that the global water budget was represented by 100 stubbies of ginger beer (8 dozen and four stubbies) The eight dozen represent the salt water in the ocean (you can’t drink them) Of the remaining ¼ stubby, some of it is salty or contaminated That leaves less than half a glass of amber fluid immediately available to quench your thirst.

7. Catchment scale An open system

8. About water management... Because the hydrologic cycle circulates water within human time-frames, groundwater is generally regarded as a sustainable resource. Hydrologic Equation: Input – Output = Change in Storage I – O = DS Hydrology is classic Systems Science.

9. Groundwater – dependent rivers Most rivers south west Victoria depend on groundwater for environmental flows Gaining stream receives groundwater baseflow into the stream Barwon River Naringhil Creek Losing stream leaks surface water into the groundwater storage

10. Data source: Bureau of Meteorology West Moorabool River catchment Scotsburn rainfall record

11. Climate change? • Among geologists it’s a contentious debate • Question is: • Our climate may be warming, but is it because of our activities, or is it natural? • “Not being sure” is not an excuse to do nothing The Earth’s geological record shows huge variation in magnitude, frequency and amplitude of climatic change. Some of this may be related to the effects of other species

12. Water Consumption in Victoria Irrigation 76.2% Farm & stock 4.4% Melbourne urban 11.0% LaTrobe Valley industry 3.0% Regional urban 5.4% We use more than 80% of our water to grow plants

13. World Water Council “There is a water crisis today. But the crisis is not about having too little water to satisfy our needs. It is a crisis of managing water so badly that billions of people – and the environment – suffer badly” (2000)

14. Drinking water – most beneficial use Ranges from $2/1l bottle to $1/Kl or $0.001/l Urban supply $0.001/l Irrigation/industrial/dairy $3/Ml – or $0.000003/l Plus pumping costs Domestic/stock Desalinisation - $1500/ML Aesthetic - tourism Environmental flows Water value

15. H2O facts • 50% of the world’s wetlands have disappeared in the last century • 3,900 children die each day from water borne diseases • 1.1 billion live without clean drinking water • Daily per capita use of water in residential areas: • 200 litres in Europe • 350 litres in North America and Japan • 10-20 litres in sub-Saharan Africa

16. What controls where rain falls? • Highly variable distribution • At all scales – country to backyard variation • Altitude, aspect, slope, ocean temperature Cooler air Weather direction Measurement, angle of rain

17. About Units... Some hydrologic processes are measured by depth and others by volume. Rainfall and evaporation are measured by depth (usually millimetres) One cubic metre (m3) = 1000 litres One millimetre depth over one hectare = 10m3 10cm depth over one hectare = 1000m3 = 1Megalitre (ML) Rainfall and evaporation are also by rate (mm/hour, mm/day, mm/year)

18. Measuring precipitation

19. Measuring precipitation World Meteorological Organisation (WMO) Standard rain gauge Pluviometer

20. Automated recording of several measurements Phone or telemetry reading

21. Evaporation Pan

22. Pan Evaporation conversion to Evapotranspiration Pan reading over 24 hours (minus rainfall input) ET = Pan reading x Pan factor Pan factor ~ 0.5 to 0.8 usually ~ 0.75

24. Direct measurements Weight changes Deep drainage

25. ET = Si + PR + IR –Sf - DE ET = Evapotranspiration in a given time period Si = Initial soil water volume Sf = Final soil water volume PR = Precipitation into lysimeter IR = Irrigation water into lysimeter DE = Drainage of water from lysimeter Hydrologic equation I – O = ΔS

26. Runoff • Volume of runoff depends on: • Rainfall intensity and duration • Type of surface (pervious or impervious) • Area of catchment Nolans Road, Napoleons, Vic. February 2005

27. Low intensity rainfall = infiltration

28. High intensity rainfall = infiltration + runoff

29. Runoff a surface Thick vegetation = low volume, slow runoff Paved area = high volume, fast runoff

30. Rational EquationThe rational method is used around the world for peak flow estimation of small rural drainage basins and is the most widely used method for urban drainage design.  The rational method equation is given below:Q = kCiAwhere:Q - peak flow (m3/s).k - conversion factor equal to .00278 (metric).C - dimensionless runoff coefficient.i - rainfall intensity (mm/hr).A - catchment area (ha). http://www.lmnoeng.com/Hydrology/rational.htm

31. Measuring Runoff Q = vA Q = Discharge (m3/s) V = velocity (m/s) A = Cross sectional area (m2)

32. weirs price current meters dilution gauging moving boat method ultrasonic velocity probe electromagnetic volumetric rising air float width contractions culverts equations Measurement techniques

33. Measuring streamflow velocity • Float & stopwatch • Current meter • Ultrasonic flow gauge

35. factors affecting flow in stream channels • cross-sectional dimensions • cross-sectional shape • slope • boundary friction

36. Measuring flow • Q = vdA = vidAi =  vi bi hi (where dAi = bi hi) bi Stream bed profile hi Plan view across measuring line vi

39. Gauging Stations Curdies River gauge, Heytesbury region, Vic

40. Stream gauges - components

41. V-notch weirs Cheap, reliable, easy to install, accurate 90o V-notch weir Q = 1.379 H5/2 Q = discharge (m3/s) H = height of water (m)

43. Flow calculations (hydraulics) Manning equations http://www.lmnoeng.com/manning.htm

44. http://www.lmnoeng.com/manning.htm

45. Manning’s Coefficient • Gravel 0.025 • with boulders 0.04 • earth 0.05 • concrete • smooth 0.012 • rough 0.015

46. Example - Wide River B A S=.0002, H=2m B=20m, n=0.03 • P=B+2H=24m • A=BH=20(2)=40m • R=A/P=40/24=1.67m • v=(1/n)R2/3S1/2=(1/.03)(1.67)2/3(.0002)1/2 =.67 m/s = 67 cm/s H

48. 100 Lag time Discharge m3/hr Storm flow 50 8 6 Rainfall (mm) 4 Groundwater baseflow 2 time Peak discharge Falling limb Rising limb

50. Varying flow conditions A stream may switch from a gaining stream during low flow conditions to a losing stream during flood conditions