Lake and Stream Hydrology 2009 UJ, UH & TPU Timo Huttula UJ/BYTL& SYKE/VTO

Lake 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: tream_Hydrology/ tream_Hydrology/  At TPU Lectures 1-3 Video Field period in Konnevesi Examination To be discussed Lecture notes Material distributed during field period Webpages: eam_Hydrology/ eam_Hydrology/

Lake and stream hydrology T.Huttula 3 Lectures 1. Lakes and rivers Basics of hydrological measurements Three practical examples of lake and stream hydrology = ”Problem of the day” (Huttula& Krogerus) and Steady and unsteady river flow Material transport in rivers River ice Reports on field measurement results (students give short presentations)30.9

Lake 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

Lake and stream hydrology T.Huttula 5 Hydrological cycle

Lake and stream hydrology T.Huttula 6

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

Lake and stream hydrology T.Huttula 8

Lake 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

Lake 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

Lake and stream hydrology T.Huttula 11 Why lake hydrology is important in Finland?  In Finland we have 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

Lake 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

Lake 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

Lake 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)

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

Lake 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)

Lake 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

Lake and stream hydrology T.Huttula 18 Lakes in Finland

Lake 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 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 )

Lake 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

Lake 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

Lake 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

Lake and stream hydrology T.Huttula 23 Annua l MonthMQHQNQ Year For periodMQHQNQMHQMNQ

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

Lake 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