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

2. 9.6.2015Lake and stream hydrology T.Huttula 2 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&S tream_Hydrology/ http://users.jyu.fi/~thuttula/Lake&S tream_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&Str eam_Hydrology/ http://users.jyu.fi/~thuttula/Lake&Str eam_Hydrology/

3. 9.6.2015Lake and stream hydrology T.Huttula 3 Lectures 1. Lakes and rivers4.9. 2. Basics of hydrological measurements4.9. 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 flow9.9. 5. Material transport in rivers9.9. 6. River ice25.9. 7. Reports on field measurement results (students give short presentations)30.9

4. 9.6.2015Lake and stream hydrology T.Huttula 4 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

5. 9.6.2015Lake and stream hydrology T.Huttula 5 Hydrological cycle

6. 9.6.2015Lake and stream hydrology T.Huttula 6

7. 9.6.2015Lake and stream hydrology T.Huttula 7 Watershed, catchment, river basin…

8. 9.6.2015Lake and stream hydrology T.Huttula 8

9. 9.6.2015Lake and stream hydrology T.Huttula 9 Units in hydrology  Fluxes are expressed in mm/time or m 3 /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

10. 9.6.2015Lake and stream hydrology T.Huttula 10 Hydrological variables and their units VariableNotationUnit PrecipitationPmm/day, mm/h EvaporationEmm/day, mm/h InfiltrationImm/day, mm/h RunoffRmm/day, mm/h DischargeQm 3 /s, l/s Water levelWm

11. 9.6.2015Lake and stream hydrology T.Huttula 11 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

12. 9.6.2015Lake and stream hydrology T.Huttula 12 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

13. 9.6.2015Lake and stream hydrology T.Huttula 13 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

14. 9.6.2015Lake and stream hydrology T.Huttula 14 Morphological characteristics of lakes  Area, A (km 2 )  Volume, V (km 3 )  Mean depth z mean,(m)  Maximum depth z max,(m)  Length of main axis, l long,(m)  Shore line length l sh,(m)  Inflow I or outflow O, (m 3 /s)  Retention time t r =V/O, (years)

15. 9.6.2015Lake and stream hydrology T.Huttula 15 Lake Pääjärvi Area 13.5 km 2

16. 9.6.2015Lake and stream hydrology T.Huttula 16 Morphology…  Shore line length l sh,(m)  Inflow I or outflow O, (m 3 /s)  Retention time t r =V/O, (years)  Hypsographic curves  A=f(W)  V=f(W)

17. 9.6.2015Lake and stream hydrology T.Huttula 17 Morphology:Fetch  The wind effect length on the lake:  L f = 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

18. 9.6.2015Lake and stream hydrology T.Huttula 18 Lakes in Finland

19. 9.6.2015Lake and stream hydrology T.Huttula 19 Typical for Finnish lakes  Shallow: 95*total volume of Finnish lakes = volume of Lake Baikal  Short retention or renewal time  Cover 32700 km 2 (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)

20. 9.6.2015Lake and stream hydrology T.Huttula 20 Lakes in Finland LakeLocation of the outlet Area km 2 SaimaaImatra1147 Inari 1102 PäijänneAsikkala1054 OulunjärviVaala893 PielinenEno868 KallavesiLeppävirta513 KeiteleÄänekoski500 Iso-LängelmävesiKangasala410 PuulavesiHirvensalmi325 LokkaSodankylä317 Mean depth =7.2 m Deepest sites: 1: Lake Päijänne 95.3 m 2: Inari 91.8 m 3: Suvasvesi 89.6 m

21. 9.6.2015Lake and stream hydrology T.Huttula 21 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

22. 9.6.2015Lake and stream hydrology T.Huttula 22 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

23. 9.6.2015Lake and stream hydrology T.Huttula 23 Annua l MonthMQHQNQ Year123456789101112 199011109 332516171819211617339 1991131211132529303122252627223111 1992810911232728292023242520298 19937131213362819202122241920367 19946444810 78997 4 1995387672318111213 1511233 1996131213433321222325272117224312 1997766171613 141314121112176 1998444810 89998 4 199934451097777876 3 2000222355444444452 For periodMQHQNQMHQMNQ 1990- 200014432236

24. 9.6.2015Lake and stream hydrology T.Huttula 24 Human impacts on lakes  Regulation  Drainage  Sewage input  Construction like embankments, bridges, piers, …  Dredging  Thermal pollution

25. 9.6.2015Lake and stream hydrology T.Huttula 25 Example  Lake area is A=100 km 2. A very heavy rain fall occurs and 100 mm precipitation will fall on the lake in six hours. How much that is in m 3 /s ? We do not consider in and outflows.  Area A=100 km 2 =100*1000*1000 m 2 =1*10 8 m 2  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*10 8 m 2 *0.1 m/(21600s) = 463 m 3 /s