14 Assessment of Some Diurnal Streamwater Profiles in Western …
485
The air temperature recorded inside S , ug˘ au Gorge has a special shape because of
the canyon-type morphology of the river valley in the studied area. The air temperature minimum occurs at 7:00, while the maximum is at 12:00 (Fig. 14.16c). S , ug˘ au
River is fed by karst groundwaters which impose a weak mean diurnal variation
of water temperature (diurnal minimum occurs at 8:00; diurnal maximum occurs at
15:30).
Water time series that span over winter often has days with a very flat diurnal peak
of temperature or an irregular diurnal increase in temperature because of the reduced
flow during winter, correlated with ice formation. Such days are usually those when
water temperature falls below 1 °C. In opposition, a very preeminent diurnal peak
is often present during summer. Similar behavior applies to the evolution of other
water parameters. Diurnal peaks of any parameter are disturbed/erased during and
immediately after rainfalls.
14.6 Conclusions
The water monitoring sites have revealed similar diurnal shapes of the temperature,
level and electrical conductivity in areas with the natural flow: afternoon maximum
water level and temperature and minimum electrical conductivity; the opposite events
occur early in the morning. For both water and air parameters, the moments when
minima occur are less temporally variable than those of maxima, at all sites. The
water parameter which is common to all sites in this study is the temperature. The
water temperature recorded diurnal cycles with amplitudes, when using the detrended
time series, ranging from 0.095 °C (site 21, S , ug˘ au River) to 2.978 °C (site 5, Bobîlna
River).
The natural particularities of the monitoring sites can greatly impact the results of
measurements. The evolution of air parameters can explain the evolution of the water
parameters in natural areas, but it is only partly useful in areas with intense human
activity, such as the areas where dams and hydroelectric plants exist. Smoothing
techniques may be applied to all mean profiles in order to obtain more abstract
representations of diurnal evolution in every site.
14.7 Recommendations
The analysis of a physical, chemical or biological parameter of a river should take
into account the diurnal cycle. The cycle may be useful for estimating a representative
average of a day, for including a daily variation into analysis or for removing the
diurnal oscillation/noise from the long term evolution of a time series. The figures in
this study can be used for estimating absolute or percentage changes of a parameter
relative to its average value, during a day, for rivers in the study area or nearby.
485
The air temperature recorded inside S , ug˘ au Gorge has a special shape because of
the canyon-type morphology of the river valley in the studied area. The air temperature minimum occurs at 7:00, while the maximum is at 12:00 (Fig. 14.16c). S , ug˘ au
River is fed by karst groundwaters which impose a weak mean diurnal variation
of water temperature (diurnal minimum occurs at 8:00; diurnal maximum occurs at
15:30).
Water time series that span over winter often has days with a very flat diurnal peak
of temperature or an irregular diurnal increase in temperature because of the reduced
flow during winter, correlated with ice formation. Such days are usually those when
water temperature falls below 1 °C. In opposition, a very preeminent diurnal peak
is often present during summer. Similar behavior applies to the evolution of other
water parameters. Diurnal peaks of any parameter are disturbed/erased during and
immediately after rainfalls.
14.6 Conclusions
The water monitoring sites have revealed similar diurnal shapes of the temperature,
level and electrical conductivity in areas with the natural flow: afternoon maximum
water level and temperature and minimum electrical conductivity; the opposite events
occur early in the morning. For both water and air parameters, the moments when
minima occur are less temporally variable than those of maxima, at all sites. The
water parameter which is common to all sites in this study is the temperature. The
water temperature recorded diurnal cycles with amplitudes, when using the detrended
time series, ranging from 0.095 °C (site 21, S , ug˘ au River) to 2.978 °C (site 5, Bobîlna
River).
The natural particularities of the monitoring sites can greatly impact the results of
measurements. The evolution of air parameters can explain the evolution of the water
parameters in natural areas, but it is only partly useful in areas with intense human
activity, such as the areas where dams and hydroelectric plants exist. Smoothing
techniques may be applied to all mean profiles in order to obtain more abstract
representations of diurnal evolution in every site.
14.7 Recommendations
The analysis of a physical, chemical or biological parameter of a river should take
into account the diurnal cycle. The cycle may be useful for estimating a representative
average of a day, for including a daily variation into analysis or for removing the
diurnal oscillation/noise from the long term evolution of a time series. The figures in
this study can be used for estimating absolute or percentage changes of a parameter
relative to its average value, during a day, for rivers in the study area or nearby.