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

Lake and stream hydrology T.Huttula 2 Contents  River characteristics  River hydraulics  Example from wet temperate region

Lake and stream hydrology T.Huttula 3 River characteristics  Water movement is determined by a slope along the longitudinal axis of the channel  In general we limit ourselves to one dimensional spatial analysis  Variables: Length, (m), water level W (m), cross sectional area A (m 2 )  Cross sectional area can vary significantly  Most important variable is the discharge Q (or flow rate). It’ s unit is m 3 s -1. For small rivers or creeks it can be expressed as ls -1  Water body is expected fully mixed, incompressible and acting as an ideal fluid  Short retention time as compared to lakes Lake Päijänne surface level is about 76 m above sea. Distance from Kalkkinen is about 100 km from sea. What is the mean slope of a hypothetical river from lake to sea? Slope= 76 m/(100*1000 m)=0,00076

Lake and stream hydrology T.Huttula 4 Time and space scales of hydrological phenomena  Note that the storage units are expressed hear as mm over the surface!

Lake and stream hydrology T.Huttula 5 Duration curves

Lake and stream hydrology T.Huttula 6 What determines the discharge duration? Example from Japan

Lake and stream hydrology T.Huttula 7 Examples from humid temperate region  Temperate: no extremes  Humid: abundant water storages, still large varions. Mean annual evaporation 500 E 0  Well known ecohydological region, rich in research  Long cultural history  diverse land use  Anthropogenic effects to H-processes are significant locally and also regionally

Lake and stream hydrology T.Huttula 8 Formation of runoff and discharge in this region  Stream discharge is here a sum of groundwater flow, surface runoff and overland flow  Their share varies in space and time  ”Quick flow”, in UK 40 % from precipitation of a certain precipitation event. It can vary from 1% (chalky soil)…77% (clay)

Lake and stream hydrology T.Huttula 9 Annual water balance  In this region run off is R=f( annual precipitation, water vapor deficit in air, soil properties)  Figure: Beult  good correlation, Pang  bad correlation, because soil is very porous (chalk)

Lake and stream hydrology T.Huttula 10 Monthly Q-duration curves 1(2)  Expresses the duration as % of the time in each month.  The duration curves or surface are expressed as 100, 90, 75, 50,25,10, 5 ja 0%:n

Lake and stream hydrology T.Huttula 11 Monthly Q-duration curves for seasonal studies 2(2)  Comparing the curves we can see the effects of watershed factors on river Q- regime  The two rivers here are only 100 km apart  Danube obtains waters from Alps. Watershed is mainly in regions of permanent snow. This means that rain (P) and melting are important factors forming Q  steady duration curves in II…VIII. Dry winter months  Tisza: waters come from North. No permanent snow on watershed => peak and valley in duration curves happens in the same time for each curve  tells about the similar repeated behavior of the Q in the years cycle.

Lake and stream hydrology T.Huttula 12 River discharge  Several classifications for rivers.  Comparisons can be made most effectively if the homogenous and representative catchments  Left we see the share of monthly discharge about the annual total ( catchments)   most have max during winter  In West Europe P max is in winter and evaporation max in summer  large variations in winter and summerQ  In continental regions P max is in summer as evaporation max  steady Q over the year  In regions with snow we have spring melting and then also spring flood

Lake and stream hydrology T.Huttula 13 River discharge 2(2)  Geological effects can be seen in figures on left  Pang: Catchment soil is chalky  slow changes in hydrographs  Kym, clay soil  drastic changes  Q-Pang (SE UK ) ja Q-Wurm(N Germany) are comparable  different inputs summed up produce similar Q time series

Lake and stream hydrology T.Huttula 14 Substances transported in a river: Sediments transport  Total substance transport=sediment transport + soluble substance transport  Sediment transport or suspended solids transport happens in suspension and as a bottom transport  Bottom transport in the ecohydrolgical region is small: 1….11 % of the sediment total transport  Suspended solids yield is inversely related to watershed area. Load decreases as A increases.  In Germany: yield is mostly 50 t/km 2 /y, range 6…300 t/km 2 /y  UK: also 50 t/km 2, on wet upper lands even 500 t/km 2 /y and less than 1 t/km 2 great flat watersheds or watersheds with impervious soil  Largest yields: Waipoa/NZ 7000 t/km 2 /y

Lake and stream hydrology T.Huttula 15 Suspended solids distribution in a river u=velocity C=suspended solids concentration

Lake and stream hydrology T.Huttula 16 Transport of soluble substances, natural streams  The variation is normally less that the suspended solids transport  It is a function of atmospheric load, soil chemistry and precipitation  In UK the soluble substances yield is : 10…400 t/km 2 /y  In wet regions soluble substance transport has larger values as the suspended solids transport  In SW UK the solutes consists 55…77 % of the total river substance transport  In France 68% of the total river substance transport  In Poland 93-95% of the total river substance transport

Lake and stream hydrology T.Huttula 17 Suspended solids transport in River Tornionjoki