Lake and Stream Hydrology 2009 UJ UH

Lake and Stream Hydrology 2009 UJ, UH & TPU Timo Huttula JY/BYTL& SYKE/VTO www. environment. fi

Contents v v v Hydrometeorological measurements Hydrological measurements in lakes Hydrological measurements in streams 19. 3. 2018 Lake and stream hydrology T. Huttula 2

Precipitation measurements 19. 3. 2018 Lake and stream hydrology T. Huttula 3

Evaporation pans, CLASS-A and GGI-3000 19. 3. 2018 Lake and stream hydrology T. Huttula E 0=P- W 4

Lake station on lake Råksjö, Sweden Evaporation is measured by using flux measurements at several hights 19. 3. 2018 Råksjö Lake and stream hydrology T. Huttula 5

Ground water level v v 19. 3. 2018 Water level is measured in pipes, which are placed so that they are deep enough to reach the ground water level Here we see an on line system The water level variation is measured with pressure sensor Data logger collects the data and they are sent with GPS data transfer Lake and stream hydrology T. Huttula 6

Meteorological measurements related to lake water currents v v v Winds are most important driving force for water movements in ice free lakes Short wave radiation from sun is the major heat source for the lake, esp. in summer Long wave radiation from clouds and atmosphere is important over the whole year 19. 3. 2018 Lake and stream hydrology T. Huttula 7

Regional and local effects in wind field v v Seasonal weather pattern Diurnal variation Topographic effects Constructions or other effects made by man v buildings, bridges, clear cutting 19. 3. 2018 Lake and stream hydrology T. Huttula 8

Station ? ? v v Airport: synoptic data, winds (8/day), air temperature (4/day), solar radiation (sometimes) At the lake: when airport data is not available or is not representative On the lake: best method, expensive and laborious to install Atmospheric models can provide sufficient data for lake studies 19. 3. 2018 Lake and stream hydrology T. Huttula 9

Wind station recording wind speed and direction in Kigoma at Lake Tanganyika 19. 3. 2018 Lake and stream hydrology T. Huttula 10

Meteo station on a moving platform: R/V TANGANYIKA EXPLORER Two masts of the weather station on the roof; the wind sensors attached to main mast and other sensors mounted on the starboard side of the roof 19. 3. 2018. Lake and stream hydrology T. Huttula 11

Lake hydrlogogical measurements v v v CTD- probe Droques Moored current meters ADCP Optical instruments 19. 3. 2018 Lake and stream hydrology T. Huttula 12

Conductivity. Temperature. Depth-probe 19. 3. 2018 Lake and stream hydrology T. Huttula 13

Drogues; history v v v Ancient: Anything floating with current has been used Operational network along Finnish coast from 1910 to 2 nd World War on light house ships After the war around the world (wood pieces, apples, post cards, flow crosses and cylinders) Positioning from shore by eye, triangle measurement, radars Satellite buoys 15 years in seas Since 10 years GPS provided new possibilities 19. 3. 2018 Lake and stream hydrology T. Huttula 14

A droque at the depth of 5 m in Lake Issyk-Kul v A drogue consists of: v v Cylinder : diameter of 60 cm, height 100 cm Cross: A 4 size (21*29 cm) Rope: 2 -3 mm Buoy: Diameter about 10 -15 cm, shape: ball or double cone . IAA. pdf 19. 3. 2018 Lake and stream hydrology T. Huttula p-. 109 15

Drogue measurement v In simplest way: v v v v You need droques, a boat and manual GPS in one vertical you can follow a large group of drogues in horizontal direction 300 -500 m spacing is practical waves and darkness are problem lights and radar reflectors Accuracy: GPS with 12 channels gives about 6 m drifting distance of 60 m gives 10 % accuracy for droque measurement How long time for a measurement? v v v Let’s expect a water velocity of 5 cm/s time=distance/velocity For 60 m travel you need time=(60 m)/(0. 05 m/s)=1200 s = 10 min 19. 3. 2018 Lake and stream hydrology T. Huttula 16

Drogue measurement, 2 v In simplest form: boat and manual GPS v v in one vertical you can follow a large group of drogues in horizontal direction 300 -500 m spacing is practical waves and darkness are problem lights and radar reflectors 19. 3. 2018 Lake and stream hydrology T. Huttula 17

Datasheet for drogue measurement 19. 3. 2018 Lake and stream hydrology T. Huttula 18

A drogue with GPS buoy A result from lake Jyväsjärvi at 14. 9. 2002. Wind was blowing weakly from north. Two drogues were placed at the depth of 0, 72, 7 m. They were connected to the automatic GPS buoy. 19. 3. 2018 Lake and stream hydrology T. Huttula 19

+/- of drogues v v +++ very inexpensive, major cost is the cost of GPS (about 300 USD) +++ practical and easy to use ++ good learning and teaching tool -- laborious for long term measurements 19. 3. 2018 Lake and stream hydrology T. Huttula 20

Moored current meters v v v v v For collecting time series of currents Velocity measured on basis of propeller or impeller revolutions Available for more than 30 years Recording capacity 2… 12 months Moderate cost Buoy – rope- meter (1)-…meter (n)- anchor Deployment with surface buoy or subsurface buoy Representative sites: bathymetric survey, tentative model application, current mapping with ADCP Not on navigational routes Risk of loss 19. 3. 2018 Lake and stream hydrology T. Huttula 21

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Statistical analysis of currents v v v Cartesian components direction information included Filtering important time scales Auto correlation and spectral analysis principal periods of oscillation Cross correlation is there any correlation between currents at different sites? ? Regression analysis factors causing currents 19. 3. 2018 Lake and stream hydrology T. Huttula 23

Lake Karhijärvi 7. 7. - 16. 8. 1993 19. 3. 2018 Lake and stream hydrology T. Huttula 24

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+/- of Aanderaa RCM v v v + inexpensive ++ durable and rugged +++ widely used -- not possible to measure near boundaries -need several instruments to cover the vertical and horizontal variation of currents 19. 3. 2018 Lake and stream hydrology T. Huttula 26

Acoustic Doppler Current Profilers; History v v v v 1982, First model by RD Instruments, Self contained 1983, Vessel mounted version 1986, five 75 -1200 k. Hz, SC, VM and direct reading In Finland since 1987 R/V Aranda (VM) and 1989 R/V Muikku 1991, RDI BB-generation 1995, RDI, Workhorse 1997, Sonn. Tek 1998, Norrtek 19. 3. 2018 Lake and stream hydrology T. Huttula 27

ADCP is a radar, 1 v v v Four beams. Angle 200 Measures the floating velocity of particles Reflectors are mostly zooplankton 19. 3. 2018 Lake and stream hydrology T. Huttula 28

ADCP is a radar, 2 v v Sends pulses (= pings) about 10 -20 times in second Integrates over certain volume (eq. 1 m thickness), width of the samples is O(1 m) Movement of instrument platform has to extracted (bottom tracking or GPS can be used) Accuracy depends on integration time 19. 3. 2018 Lake and stream hydrology T. Huttula 29

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Sound velocity v v Absorption of energy is dependent on density Long waves decay less than short waves Water density is mainly dependent on temperature and salinity Reflections from density boundaries 19. 3. 2018 Lake and stream hydrology T. Huttula 31

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Acoustic Doppler current profiler, RDI Workhorse IAA. pdf 19. 3. 2018 p. 18, p. 69 Lake and stream hydrology T. Huttula 33

Contaminated layer near boundaries in ADCP measurements Also near transducer surface an off-set is left. It’s thickness is about one layer thickness 19. 3. 2018 Lake and stream hydrology T. Huttula 34

+/- of ADCP v v v v +++ Collects lot of data + Fairly good software + Quite easy to use, --Tuning and data interpretation is demanding - Older ADCP’s: for seas ++New products ++Costs are coming down 19. 3. 2018 Lake and stream hydrology T. Huttula 35

Stream hydrology, measurements v Geometry v v Water level measurements v v v Leveling meters, distance meters Staff gauges Automatic water level recorders River discharge v v v Floating objects Propellers and integration ADCP Volumetric measurement Constructed systems v Weirs 19. 3. 2018 Lake and stream hydrology T. Huttula 36

Pressure sensor 19. 3. 2018 Lake and stream hydrology T. Huttula 37

River discharge measurments site v v Water current direction should be the same in whole cross section Cross section morphology should not change in time Super critical flow site downstream Typical sites are v v v 19. 3. 2018 Lake and stream hydrology T. Huttula Lake outlet In let channel of a hydropower station Bridge 38

Spatial measurements 19. 3. 2018 Lake and stream hydrology T. Huttula 39

Q-measurement with a propeller 19. 3. 2018 Lake and stream hydrology T. Huttula 40

Q-data processing by using grapahical integration 19. 3. 2018 Lake and stream hydrology T. Huttula 41

Measuring Q in a creek 19. 3. 2018 Lake and stream hydrology T. Huttula 42

Qmeasurement s with a propeller and ADCP 19. 3. 2018 Lake and stream hydrology T. Huttula 43

In direct Q-measurement: state discharge curve v v v v 19. 3. 2018 Lake and stream hydrology T. Huttula In channel Q=f(W) This applies, if we have a supercritical flow region downstream near the measurement site It implies that the disturbances downstream are not effecting to our measurement site We fir an empirical curve to the data After that we need to measure only water level variations and we use the curve to calculate the Q Easy and economic way to obtain Q data! A reduction correction may be needed during ice cover time 44

Using constructed systems for Q- measurement v v Q from energy production data of hydropower station Using small dams or weirs v v v In figure and equation on the left v v 19. 3. 2018 Super critial flow We have different wier equations for different opening. In those Q is expressed as a function of weir width and water depth and angle of the opening. C=empirical weir constant a=height of the opening in weir b=breadth of the opening h 1= free water level height above the weir Lake and stream hydrology T. Huttula 45

Weirs 19. 3. 2018 Lake and stream hydrology T. Huttula 46

Turbidity meters l l Transmissometer model BTG Scattering meter model D&A OBS 3+ 19. 3. 2018 Lake and stream hydrology T. Huttula 47

Integrating suspended sediment sampler 1=inflow pipe 2=air outlet pipe 3=bottle for the sample 4=rope 5=vane 6=lead cover 19. 3. 2018 Lake and stream hydrology T. Huttula 48

Bottom load samplers 19. 3. 2018 Lake and stream hydrology T. Huttula 49