Hydraulic Engineering and Water Management

Transcription

1 Hydraulic Engineering and Water Management for Umwelt und Bioressourcenmanagement 3 rd Lecture LVA Cedomil Josip JUGOVIC H81 Department of Water, Atmosphere and Environment H816 Institute of Water Management, Hydrology and Hydraulic Engineering

2 Quick Review Water Management Modern concept Water resources sustainability Hydraulic Engineering Fundamentals Mass, density, pressure, viscosity, flow velocity Pipe flow / channel flow

3 Discharge determination Uniform and nonuniform flow

4 Discharge determination Velocity distribution depends: on river bank roughness, river bed and channel shape

5 Discharge determination Laminar and turbulent flow When fluid particles move in smooth paths without lateral mixing: laminar Viscous forces dominate Identified by the Reynolds number

6 Discharge determination

7 Discharge determination Steady flow Velocity at any point does not change with time Engineers usually confronted with unsteady flow Unsteady flow

8 Measuring Flow Hydrometry the science of measuring the various parameters characterizing flow in natural or artificial waterways and pipelines. Main variables: The level of the surface of gravitational water H [m] The flow rate in the river or discharge Q [m 3 /s] or [l/s]

9 Measuring Flow Producing a hydrogram from a limnigram via a rating curve.

10 River Gauging Meathods Pitot tube

11 Measuring Flow Stage Gauge Float gauge Inclined and vertical staff gauge. Principle of float gauge.

12 Discharge Measurements

13 Gauging with Current Meters Current meters adapted to different operating methods.

14 River Gauging Methods The aim of the gauging methods is to determine flowing water quantity Q in a river through the selected cross section (measuring cross section), in time interval of one second. Waterbody Width of water level B Measuring vertical Measuring points Fig. Water quantity passing through the measuring crosssection in periode of 1 sec.

15 River Gauging Methods The volume of the water body is calculated from measurements. The measuring cross section is surveyed and the flow crosssection surface F (m2) was calculated.. Crosssection area Width of water level B F Fig. flow crosssection surface F (m 2 )

16 River Gauging Methods v j WSP Flow velocities between bottom and water surface are recorded h i v 2 Measured velocities define a velocitypolygon v 1 Sohle Fig. Velocitypoligon in vertical i

17 River Gauging Methods By integrating over the depth h i, the discharge q i (specific discharge) which belongs to this measuring vertical, will be calculated q i h i v j dh (m 2 /s) By integrating the specific discharge q over the water surface width B, the water discharge through the measured crosssection is calculated Q 0 B 0 qdb (m 3 /s)

18 River Gauging Methods Width of water level B Discharge Q q 2 Area of observed cross section F q 1 Measuring point Measuring vertical Bed Fig.: Graphical representation of the measured crossection and the amount of water discharge Q

19 River Gauging Methods Average flow velocity v m Q F (m/s)

20 h (m) v (m/s) q (m 2 s) River Gauging Methods Analysis of a current meter measurement : Brandgrabenbach measurement 2 Q = 9,07 m 3/ s L.U. h 1 =1,8 6 q 1 =0,6 q 2 =0,72 q 3 =0,9 q 4 =0,6 q 5 =0,2 5 v 1 =0,25 v 2 =0,31 WSP 3 v 3 =0,42 9 v 4 =0,32 5 v 5 =0,23 0,25 0,29 0,27 0,20 1,41 1,10 0,78 0,31 h 2 =2,3 0 0,40 0,39 0,30 0,21 1,88 1,41 0,78 0,31 h 3 =2,1 9 0,49 0,50 0,43 0,38 1,88 1,41 0,78 0,31 h 4 =2,19 0,41 0,42 0,31 0,21 1,88 1,41 0,78 0,39 h 5 =1,1 0 0,27 0,30 0,28 0,21 0,85 0,62 0,46 0,231 v (m/s) l (m) B=14,51m Scales: Geometrye: l,h : 1cm :: 1m Velocity: v,v : 1cm :: 0,5m/s Spec. discharge: q : 1cm :: 0,2m 2 /s

21 Water level h (m) River Gauging Methods From a practical consideration often at different water levels (stages), measured discharge Q and put in relation to corresponding observed water level. This is a relationship is called a rating curve. Relationship between discharge and water level (rating curve) Fitted ratin curve Q=f(h) Results of discharge measurements Discharge Q (m 3 /s 1 )

22 "Chemical" Gauging or Gauging by Dilution Used in mountain or steeply inclined rivers Involves injecting the river with a concentrated solution of a tracer and determining what portion of this solution is diluted by the river

23 Gauging by Dilution

24 Constant Flow Gauging Assumed that: Q in river is constant q of tracer is equal to that of injection and insignificant to Q homogeneous

25 River Gauging Methods Tracer dilution methods Differ in: The nature of the markers The nature of the addition of the marker in flowing water Requirements: No health risk High water solubility Chemical and physical stability Efficient measuring technique

26 River Gauging Methods Tracer injection Continuous addition Sudden addition

27 River Gauging Methods Continuous addition Q q C C 1 2

28 River Gauging Methods Sudden addition Q t 0 ( C t m C 0 ) dt

29 Concentration (mg/l) River Gauging Methods 40 Calibration curve E tg mg * cm l * S Conductivity ( S/cm)

30 Conductivity (us/cm) River Gauging Methods 210 Conductivity change I 130 L t 0 Time (s) t

31 River Gauging Methods t Conductivity L ( S/cm) L t L 0 ( S/cm) t (s) I ( S/cm*s) 09:27: :27: :27: :28: :28: :28: :28: :28: :33: :33: :33: :33:

32 River Gauging Methods Q t t 0 ( C C ) 0 dt t m Q E t t 0 ( L L ) 0 dt t m Q m( kg) *10 mg * cm E( ) * I( l S 6 S * cm s ) ( mg * l * S ( mg * cm * * cm) S * s) ( l ) s

33 Watershed Geographic unit Topographic watershed Drainage divides correspond with crests of watershed Effective watershed Includes the underground borders of the system

34 Watershed

35 Watershed

36 Watershed Hydrological Response Hyetograph and hydrograph

37 Orders of a River Strahler Stream Order Classification

38 Orders of a River Characteristic Lengths and Dimensions Length of watershed LcA Length of main river L Characteristic lengths of a watershed