lake and stream hydrology 2009 uj, uh & tpu timo huttula uj/bytl& syke/vto

Lake and Stream Hydrology 2009 UJ, UH & TPU

Timo Huttula

UJ/BYTL& SYKE/VTO

www.environment.fi

18.04.23 Lake and stream hydrology T.Huttula

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Contents

At UJ&UH Lectures 1-6

Video Field period in Konnevesi

Examination To be discussed

Lecture notes and copies from books Material distributed during field period Web pages:

http://users.jyu.fi/~thuttula/Lake&Stream_Hydrology/

At TPU Lectures 1-3

Video Field period in Konnevesi

Examination To be discussed

Lecture notes Material distributed during field period Webpages:

http://users.jyu.fi/~thuttula/Lake&Stream_Hydrology/


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Lectures

1. Lakes and rivers 4.9.

2. Basics of hydrological measurements 4.9.

3. Three practical examples of lake and stream hydrology = ”Problem of the day” (Huttula& Krogerus)

15.9. and 16.9.

4. Steady and unsteady river flow 9.9.

5. Material transport in rivers 9.9.

6. River ice 25.9.

7. Reports on field measurement results (students give short presentations) 30.9


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1. Lakes as a part of the hydrological cycle

Hydrological cycle and hydrological processes The importance ot the lakes What is a lake? Lake morphology What is the role of lakes in hydrological cycle? Lakes in Finland Basic hydrological statistical parameters Human impacts on lakes


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Hydrological cycle


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Watershed, catchment, river basin…


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Units in hydrology

Fluxes are expressed in mm/time or m3/s Flux= mass or volume /(time*surface area) One liter of water weights about 1 kg If we put one liter of water on a surface area of A=1 m* 1m, the

water height (h) will be 1 mm


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Hydrological variables and their units

Variable Notation Unit

Precipitation P mm/day, mm/h

Evaporation E mm/day, mm/h

Infiltration I mm/day, mm/h

Runoff R mm/day, mm/h

Discharge Q m3/s, l/s

Water level W m


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Why lake hydrology is important in Finland?

In Finland we have 187 888 lakes ( min. size 50 m*10 m)

Sensitive for pollution More 50 % of Finnish population still drink

treated lake water Important recreational value Legislative reasons


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In global scale

Lakes contain important amount of fresh water

Water storages Vulnerable in many ways Important sources of protein Recreational value Preserving of their ecosystem


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What is a lake?

A mass of still water situated in a depression of the ground without direct communication with sea (Encyclopedia of Britannica, 1962)

Baltic Sea is not a a lake, Aral and Caspian Sea are


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Morphological characteristics of lakes

Area, A (km2) Volume, V (km3) Mean depth z mean ,(m) Maximum depth zmax ,(m) Length of main axis, l long ,(m)

Shore line length l sh ,(m)

Inflow I or outflow O, (m3/s) Retention time tr=V/O , (years)


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Lake Pääjärvi

Area 13.5 km2


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Morphology…

Shore line length l sh ,(m)

Inflow I or outflow O, (m3/s) Retention time tr=V/O , (years) Hypsographic curves

A=f(W) V=f(W)


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Morphology:Fetch The wind effect length on

the lake: Lf = the mean length of

the lines from the observation site, when lines are taken in 90 0

angle towards wind direction (=direction from where wind is coming from)

Important for wave and erosion calculations


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Lakes in Finland


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Typical for Finnish lakes

Shallow: 95*total volume of Finnish lakes = volume of Lake Baikal Short retention or renewal time Cover 32700 km2 (10 %) of Finnish territory Fragmented and form a river like water course system Loaded presently by agriculture Eutrophication is the number one problem Water budget:

Direct precipitation on lake surface is 14 % of annual water budget Evaporation from lake surface is 12 % of annual water budget No ground water flow to lake Mean annual water level variation is 103 cm (in period of 1961-80)


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Lakes in FinlandLake Location of the

outletArea

km2

Saimaa Imatra 1147

Inari Inari 1102

Päijänne Asikkala 1054

Oulunjärvi Vaala 893

Pielinen Eno 868

Kallavesi Leppävirta 513

Keitele Äänekoski 500

Iso-Längelmävesi Kangasala 410

Puulavesi Hirvensalmi 325

Lokka Sodankylä 317

Mean depth =7.2 m

Deepest sites:

1: Lake Päijänne 95.3 m

2: Inari 91.8 m

3: Suvasvesi 89.6 m


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Lakes in hydrological cycle Water storages Smooth out the water level fluctuation in

water course In upper lakes: Rapid water level change

and short duration Downstream lakes: Lagged response and

moderate response Deep lakes act like sedimentation tanks The rate of change in water quality is

related to retention time

t

Q

Downstream lake

An upper lake


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Mean and extreme values in time series

MQ = mean annual discharge MHQ=mean high (flood) discharge during the observation period

like 30 years MNQ =mean low (dry) discharge during the observation period like

30 years MW = mean annual water level MHW and MLW like for the discharge


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Annual

Month MQ HQ NQ

Year 1 2 3 4 5 6 7 8 9 10 11 12

1990 11 10 9 10 33 25 16 17 18 19 21 16 17 33 9

1991 13 12 11 13 25 29 30 31 22 25 26 27 22 31 11

1992 8 10 9 11 23 27 28 29 20 23 24 25 20 29 8

1993 7 13 12 13 36 28 19 20 21 22 24 19 20 36 7

1994 6 4 4 4 8 10 10 10 7 8 9 9 7 10 4

1995 3 8 7 6 7 23 18 11 12 13 13 15 11 23 3

1996 13 12 13 43 33 21 22 23 25 27 21 17 22 43 12

1997 7 6 6 17 16 13 13 14 13 14 12 11 12 17 6

1998 4 4 4 8 10 10 10 10 8 9 9 9 8 10 4

1999 3 4 4 5 10 9 7 7 7 7 8 7 6 10 3

2000 2 2 2 3 5 5 4 4 4 4 4 4 4 5 2

For period MQ HQ NQ MHQ MNQ

1990-2000 14 43 2 23 6


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Human impacts on lakes

Regulation Drainage Sewage input Construction like embankments, bridges, piers, … Dredging Thermal pollution


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Example

Lake area is A=100 km2. A very heavy rain fall occurs and 100 mm precipitation will fall on the lake in six hours. How much that is in m3/s ? We do not consider in and outflows.

Area A=100 km2=100*1000*1000 m2=1*108 m2

Precipitation P=100 mm=0,1 m . So we put h=0,1 m Time t=6 h=6*3600s=21600 s Q=Ah/t=1*108m2*0.1 m/(21600s) = 463 m3/s

lake and stream hydrology 2009 uj, uh & tpu timo huttula uj/bytl& syke/vto

Documents

lake hydrology

hydrology slide

stream hydrology t

hydrology http

hydrology fluxes

lake morphology

hydrological cycle slide

practical examples of