14 Assessment of Some Diurnal Streamwater Profiles in Western …
467
14.2 Review of the Literature Describing Diurnal
Streamwater Profiles
There are multiple diurnal cycles in stream water, corresponding to the multiple
parameters that may be taken into account, and all cycles are interdependent [21].
For example, the streamwater temperature, which has higher amplitudes during the
summer, baseflow and in shallow streams [22, 30], is higher during the daytime
and decreases the water viscosity. The decreased viscosity generates improved water
infiltration into the ground, leading to decreased streamflow during this time of the
day [14]. This effect is similar to that generated by the increased evapotranspiration
during the daytime [2].
The most numerous studies about diel cycles in rivers are about river level and/or
discharge. This is due, from a historical point of view, to the earlier availability of
the instruments needed for measuring these parameters and to the strict necessity to
measure them firstly. Secondly, studies about diel thermal cycles follow, mainly due
to the ease of technical access to the required instruments (specific thermometers
and loggers). Other physical, chemical and even biological properties of river waters
were also measured to observe if diurnal periodicities exist (e.g. turbidity, electrical
conductivity, pH, oxidation-reduction potential, dissolved oxygen, chlorophyll).
The diurnal cycle of a streamwater parameter is similar to a sinusoid [9] or a
smoothed saw-teeth evolution of data values (this is due to the asymmetric behavior
in the increase and decrease processes). Troxell [27], Wicht [31], Burger [11], Rycroft
[25] and Tschinkel [28] observed the diel variations in river level and linked them
to the similar evolution in the groundwater nearby. Callède [13] observed that, in
the absence of atmospheric precipitation, the diurnal evolution of river discharges is
modelled by the diurnal cycle of the air temperature and sunshine, mainly through
evapotranspiration. High waters do often miss diurnal oscillations, which are almost
always detectable during base flow (between rain events).
The diurnal evolution of a river parameter can also exhibit natural periodicities
due to direct water evaporation, atmospheric precipitation, thawing, freezing, tides
[13, 15, 18] and even due to occult precipitation [13]. Oceanic tides are causing
oscillations in tidal rivers. Earth and atmospheric tides cause semidiurnal oscillations
in rivers by using the groundwater tides as a proxy [3, 5, 8, 16].
Not only the natural factors but also the anthropogenic ones are the cause of diurnal and subdiurnal oscillations in the evolution of a streamwater parameter. Water
abstraction from groundwater is one of the most widespread human indirect intervention on river flow characteristics [20, 29], in our case because of the daily cycle
of human activities. Dams have the most evident impact on rivers, especially due
to regular flow change and hypolimnetic water releases, which affects temperature
[24]. Regulated rivers do often have human-induced periodic oscillations that override entirely the natural oscillations. Wastewaters from urban areas influence water
flow, temperature and chemistry on a daily cycle [4, 17].
To explain the evolution of a streamwater parameter, meteorological measurements are involved. Benyahya et al. [1] observed that microclimate data collected
467
14.2 Review of the Literature Describing Diurnal
Streamwater Profiles
There are multiple diurnal cycles in stream water, corresponding to the multiple
parameters that may be taken into account, and all cycles are interdependent [21].
For example, the streamwater temperature, which has higher amplitudes during the
summer, baseflow and in shallow streams [22, 30], is higher during the daytime
and decreases the water viscosity. The decreased viscosity generates improved water
infiltration into the ground, leading to decreased streamflow during this time of the
day [14]. This effect is similar to that generated by the increased evapotranspiration
during the daytime [2].
The most numerous studies about diel cycles in rivers are about river level and/or
discharge. This is due, from a historical point of view, to the earlier availability of
the instruments needed for measuring these parameters and to the strict necessity to
measure them firstly. Secondly, studies about diel thermal cycles follow, mainly due
to the ease of technical access to the required instruments (specific thermometers
and loggers). Other physical, chemical and even biological properties of river waters
were also measured to observe if diurnal periodicities exist (e.g. turbidity, electrical
conductivity, pH, oxidation-reduction potential, dissolved oxygen, chlorophyll).
The diurnal cycle of a streamwater parameter is similar to a sinusoid [9] or a
smoothed saw-teeth evolution of data values (this is due to the asymmetric behavior
in the increase and decrease processes). Troxell [27], Wicht [31], Burger [11], Rycroft
[25] and Tschinkel [28] observed the diel variations in river level and linked them
to the similar evolution in the groundwater nearby. Callède [13] observed that, in
the absence of atmospheric precipitation, the diurnal evolution of river discharges is
modelled by the diurnal cycle of the air temperature and sunshine, mainly through
evapotranspiration. High waters do often miss diurnal oscillations, which are almost
always detectable during base flow (between rain events).
The diurnal evolution of a river parameter can also exhibit natural periodicities
due to direct water evaporation, atmospheric precipitation, thawing, freezing, tides
[13, 15, 18] and even due to occult precipitation [13]. Oceanic tides are causing
oscillations in tidal rivers. Earth and atmospheric tides cause semidiurnal oscillations
in rivers by using the groundwater tides as a proxy [3, 5, 8, 16].
Not only the natural factors but also the anthropogenic ones are the cause of diurnal and subdiurnal oscillations in the evolution of a streamwater parameter. Water
abstraction from groundwater is one of the most widespread human indirect intervention on river flow characteristics [20, 29], in our case because of the daily cycle
of human activities. Dams have the most evident impact on rivers, especially due
to regular flow change and hypolimnetic water releases, which affects temperature
[24]. Regulated rivers do often have human-induced periodic oscillations that override entirely the natural oscillations. Wastewaters from urban areas influence water
flow, temperature and chemistry on a daily cycle [4, 17].
To explain the evolution of a streamwater parameter, meteorological measurements are involved. Benyahya et al. [1] observed that microclimate data collected