Transcript WET_Lake_Stream_2

Lake and Stream Hydrology 2009
UJ,UH, &TPU
Timo Huttula
JY/BYTL& SYKE/VTO
www.environment.fi
Contents
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River characteristics
River hydraulics
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Example from wet temperate region
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River characteristics
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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 Lake Päijänne surface
sectional area A (m2)
level is about 76 m
Cross sectional area can vary significantly
above sea. Distance
Most important variable is the discharge Q (or
from Kalkkinen is about
flow rate). It’ s unit is m3s-1. For small rivers or
100 km from sea. What
creeks it can be expressed as ls-1
is the mean slope of a
Water body is expected fully mixed,
hypothetical river from
incompressible and acting as an ideal fluid
lake to sea?
Short retention time as compared to lakes
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Slope= 76 m/(100*1000
3
m)=0,00076
Time and space scales of hydrological phenomena
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Note that the storage
units are expressed
hear as mm over the
surface!
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Duration curves
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What determines the discharge duration?
Example from Japan
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Examples from
humid temperate
region
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Temperate: no extremes
Humid: abundant water storages, still large varions. Mean annual evaporation
500<E0<1000 mm and precipitation P>E0
Well known ecohydological region, rich in research
Long cultural history  diverse land use
Anthropogenic effects to H-processes are significant locally and also
regionally
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Formation of runoff and discharge in this region
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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)
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Annual water balance
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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)
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Monthly Q-duration curves 1(2)
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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
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Monthly Q-duration curves for seasonal studies
2(2)
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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.
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River discharge
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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
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River discharge 2(2)
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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
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Substances transported in a river: Sediments transport
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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/km2 /y, range 6…300
t/km2 /y
UK: also 50 t/km2, on wet upper lands even 500 t/km2 /y
and less than 1 t/km2 great flat watersheds or
watersheds with impervious soil
Largest yields: Waipoa/NZ 7000 t/km2 /y
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Suspended solids
distribution in a river
u=velocity
C=suspended
solids
concentration
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Transport of soluble substances, natural streams
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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/km2 /y
In wet regions soluble substance transport has larger values as the
suspended solids transport
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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
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Suspended solids transport in River Tornionjoki
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