MEASUREMENT OF TIME OF TRAVEL
IN THE VOLYNKA EXPERIMENTAL BASIN
Jiri HOLECEK
Institute of Hydrodynamics of the Czechoslovak
Jan VOCEL
Academy of Sciences, Czechoslovak Socialist Republic
ABSTRACT
Measurements of the time of travel in the Volynka stream as well as in its tributaries
were provided for the purpose of hydrograph analysis and for further designated
problems. The technique of measurement and the evaluation of results with regard
to the controlling morphologic and hydraulic factors are described in the first part of
this paper. The second part contains a description of new chemical indicators utilized
for the measurements with particular reference to their excellent chemical properties,
measurability at low concentration, non-toxicity and moderate price. The method
described can be used for different types of basins.
RÉSUMÉ
Les mesures de temps du cours au bassin expérimental de la rivière Volynka.
On a fait les mesures du temps de propagation sur la rivière Volynka ainsi que sur
ses affluents, pour être capable de faire l'analyse de l'hydrogramme et pour résoudre
des problèmes liés aux projets hydrologiques. Le système des mesures et l'évaluation
des résultats influencée par les facteurs morphologiques et hydrauliques forment le
contenu d e la première partie de cet article. La seconde partie, est la description de
nouveaux indicateurs chimiques employés dans les mesures grâce à leurs parfaites
qualités chimiques en ce qui concerne leur concentration insignifiante, leur manque de
nocivité e t leur coût de revient peu élevé. L'emploi de cette méthode convient pour
des types différents de bassins.
TRAVEL TIMES, METHODS OF MEASUREMENT AND APPRAISAL (Hydrological part)
To solve the broader tasks of analysis of the general hydrograph it was necessary
as one subsidiary task to determine travel times. A knowledge of these times is essential
for the determination of the composition and rise of flood waves. The shape of the
hydrograph is, apart from size, intensity and rain distribution in the catchment area,
primarily dependent on the travel times and the characteristics expressing the state of
water storages in the basin.
This paper presents a summary of the findings gained in the solution of this subsidiary task at the experimental basin of the Institute of Hydrodynamics of the Czechoslovak Academy of Sciences o n the Volynka river (Balek-Holecek 1964).
By travel time between two sections on a stream we understand the time interval
that passes between the occurrence of the peak of the flood wave in a certain section
and the corresponding occurrence of the peak of the flood wave in the section downstream. Somestimes the travel time is related not to the peak of the flood wave but to
the centre of gravity of the hydrograph in the sections under observation; both travel
times are approximately equal since the position of the centre of gravity with regard
to the peak has a time relation (Linsley, Kohler, Paulhus 1949). An essential and
important limitation of this definition is that between the observed sections there
should b e no important tributary; also the flow from the intermediary basin should
be negligible. If this limitation is not fulfilled, the ascertained time interval is not
the true travel time but merely the travel time of a flood wave between the con299
sidered sections, which may differ very much with regard to the various sizes of the
different components through whose superposition the resultant wave occurred.
Whereas comparatively much work has been done on travel time of flood waves,
on the basis of which, for instance, water-stage relations between two or more stations
are derived, we rarely meet papers on travel times; when we do, they tend to be in
subjects related to hydrology (sanitary engineering). We do not come across papers
dealing with travel times for the purposes of the hydrologie genesis of flood waves or
hydrograph analysis. It is practically impossible to obtain sufficient quantities of suitable
data on travel times for our purpose (i.e. hydrologie genesis of flood waves) from
water-stage recorders at the experimental basin on the Volynka river. This is because
the Volynka is a small mountain rivulet, where nearly every tributary in the comparatively dense river net (fig. 1) plays a considerable part in the formation of flood waves
and runoff in general, and the ascertaining of travel times by the described technique
of analysing the hydrographs is practically impossible.
It is, however, possible to relate travel time not only to floodwaves (CollinsWright 1964, Manczak 1964), but in some cases, as for instance in the solution of our
subsidiary task, it is necessary to ascertain it also for low and medium discharges during
periods without precipitation. For this reason, and for the reasons mentioned in the
preceding paragraph, it has been necessary to develop a new technique for the measurement of travel times and the method of their appraisal for the task under consideration.
TECHNIQUE OF MEASUREMENT OF TRAVEL TIMES AND THE METHOD OF THEIR APPRAISAL
The technique of measurement and choice of chemical tracers will be described in
a later part of this paper in which details of the chemistry will be found.
The method of appraisal of the measured values of travel times is as follows.
The basic hydrologie characteristic for the appraisal of measured values of travel
times was the long-term mean discharge for the given section, obtained from basic
data collected by the Hydrometeorological Institute for the period 1931-1960. At the
time of the initial dosage of the tracer or of the passage of the tracer through a certain
section, the ascertained discharge was expressed by a relative number K. (K = QilQ,
where Qi is the instantaneous discharge dor the given section and Q is the long-term
mean discharge in the same section). The measured values of travel times were added
in the form of dimensionless values a to these values of K, averaged for the given reach
of the river. Through points determined by the corresponding values a, K, curves were
plotted as on graph 2. The curves on this graph are marked by the same numbers as
the various reaches of the river course on figure 1.
The values a. are the ratios of the travel time and the length of the particular reach,
expressed in absolute numbers, arising from the use of scales for length and time.
From these curves it is easily possible to read the mean velocity at the particular reach
for the respective mean discharge K. The reciprocal value of a read from the curves
(reciprocal because it is included in the calculation as the ratio of time to route) must
be reduced (multiplied) by a coefficient fir, expressing the difference of the time and
length scales used (in our case fir = 1/7, 2m]s;firhas the dimension of velocity, because
a is introduced into the calculation as a dimensionless number—the ratio of two lengths).
From the curves on graph 2 the nomogram of travel times within limits of relative
discharge 0,35 £j K g 25 previously chosen were derived for the entire route of the
main flow of the Volynka (fig. 3). In the same way the nomograms for the main t ributaries of the Volynka—the Sputka and Peklovka rivers—were deduced. During the
analysis of the curves relating x and K and of the derived nomograms of travel times it
was found, for example, that two similar curves for the a, K relationship correspond to
two reaches, approximately equally long, of various streams of the same character
of river channel as far as shape and roughness are concerned, and differing only in
300
slope. This similarity is entirely logical if we consider that these curves implicitly include
factors of roughness, channel shape and discharge; their deviation in the direction of
the a. axis is then caused by the difference in slope. On the other hand, in a reach of
a stream with a better developed channel (smaller roughness, less meandering) higher
velocities occur even for lower slopes. And it has further been ascertained that travel
times are equal for equal relative discharge ^(considerably different in absolute terms)
for two different stream shaving the same characteristics of slope, roughness and channel
shape. These facts lead to the assumption that it might be possible to derive a wider
validity of the above-mentioned relations. In the next stage of the research a series of
experiments will be carried out for this purpose.
Fig. 1 — System of Streams.
301
0,70'
0,50-
0,35-
0,05J
Fig. 2 — Relation between relative discharge K and values a, for particular reaches
on the Vollynka and Sputka rivers.
302
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303
It was necessary (with regard to the sensitivity of the physico-chemical method used
for the determination of tracers) to determine beforehand a suitable size of addition
for the intended experiment, taking into consideration instantaneous boundary
conditions, i.e. dilution, sorption and discharge. An empirical relation (naturally
specific for the particular flow) was first derived during several preliminary experiments
for the approximate determination of the quantity of tracers necessary for the reach
under consideration. On the x axis in figure 4 the travel time is plotted in seconds,
which implicitly includes factors of velocity and discharge, and on the y axis the relative
concentration cr. (cr= c0/cmax; where c0 is the instantaneous concentration at the
beginning of the experiment using the gulp method for addition and c m a x is the previously chosen value of the necessary maximum concentration in the last cross section
under consideration; cr is thus a dimensionless value). An approximate knowledge of
cmax in the last cross section is necessary with regard to the detection capacity of the
method used, since the situation might arise when—because of considerable dilution—
it is not possible to register the indicator at all, or at best only its peak without any
possibility of reliable extrapolation to the zero value.
30n 17 0 2 / I
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Fig. 4 — Dependence of travel time of tracers on their relative concentration.
Two lines are plotted in figure 4; the upper for high content of organic matter, the
lower line for a lower content of organic matter. These lines approach each other for
large values of t, i.e. over a longer period of time the influence of sludge in the lower
304
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Fig. 5 — Quantitative appraisal of travel times of tracers through the particular reaches
during one experiment.
reaches is noticeable. For illustration, figure 5 shows the quantitative evaluation of the
time history of the tracers in various reaches during one experiment. The concentration
of the tracers in mg/litre are plotted on the y axis and time on the x axis. In the lower
part of the graph the discharge in the given cross section at the time of passage of the
tracers is plotted. For every concentration curve, information is added on the quantity of
tracers found, as well as the percentage of the quantity originally added, as well as an
identification of the section. Changes in concentration depend on the extent of dilution
and adsorption; inter alia, the latter is mainly a function of the quantity of organic
matter contained in the water.
Figure 6 clearly shows the difference between travel times of the tracer and travel
times of flood waves. The travel times actually measured are plotted as crosses in the
305
o
o,
s
a
o
hour
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Fig. 6 —• Mass curve of travel time of the tracer and travel time of flood waves for one experiment.
306
respective verticals; the travel times read from the derived nomograms are shown as
strongly marked lines in the verticals of the corresponding sections. In the lower part
of the graph the summation curves of travel times of the tracer and the travel times of
flood waves are drawn. The error between the value of the travel measured and read
from the derived nomograms does not exceed 5 p.c. of the measured value. The travel
time of flood waves is related to the peak of the stages in the respective section. The
tracing material (9 kg KI) was added into the peak of the floodwave in section 34 at
a distance of 31,55 km from the terminal section.
CONCLUSION
Generally the travel time of the tracer must not be confused with the travel time of
the flood wave. With the use of factors characterising the state of the water stored in
the basin, such as antecedent precipitation indices, antecedent discharge indices, and
further climatic indices, such as precipitation, temperatures, complement for saturation
of moisture and sunlight the nomograms derived make possible, both in method and
qualitatively, an entirely different approach to the solution of the complicated problem
of determining the composition of flood waves and the analysis of a general hydrograph
in comparison with methods generally used so far. The method described above for
measurement and appraisal may also be used in the measurement of discharges or
studies of related fields, where the need for a knowledge of travel times especially for
mean-low and low discharges has recently become a very important problem, as may
be seen from the increasing number of studies on this subject.
APPLICATION OF POTASSIUM IODIDE TO HYDROLOGICAL STUDIES (Chemical part)
A knowledge of the travel time is not only a basic hydrologie characteristic necessary
for more extensive hydrologie studies, but also helps in ascertaining the self-purification
capacity of rivers and the determination of biological processes taking place in natural
waters.
It was our task to ascertain suitable tracers which would meet the following conditions : sufficient sensitivity, non-toxicity, absence from surface water and minimum
adsorption. It was further necessary, with regard to the fact that the experimental basin
of the Volynka river at some points is densely populated, to use colourless material.
For these reasons radio-isotopes and fluorescent dyes could not be used. Potassium
iodide (or sodium iodide) was found to be the most suitable substance fulfilling all
conditions. It was tested both in the laboratory and in the field. The laboratory tests
carried out with this material were fully confirmed by numerous practical tests in the
Volynka basin. At the same time experimental flow measurements were carried out
by means of potassium iodide.
The practical use of tracers is limited by the presence of colloids and fine dispersions
present in natural waters near the river banks and bottom. All substances are adsorbed
by these materials, but in varying quantities. That is why sorption is the main criterion
of usability of the various tracers. To test the suitability of potassium iodide as a tracer,
a preliminary study was carried out based on the method of static saturation to find
the retention of this substance in samples of soil through which potassium iodide is
presumed to pass.
For comparison static saturation was at the same time also carried out with fluorescein. Even though static saturation experiments offered only an approximate picture
of the behaviour of potassium iodide andfluoresceinunder natural conditions, nevertheless they clearly showed substantially better results for potassium iodide than for
fluorescein.
307
DETERMINATION OF IODIDE
The overwhelming majority of natural waters does not contain any iodides at all;
only in some underground and mineral waters are certain quantities of iodides present.
This is why the ascertaining and verification of a suitable method for the determination
of iodides and further modification of the method for use with natural waters was the
most important criterion in the proposed use of potassium iodide in the tracing
technique. Many analytical methods for the determination of iodides (volumetric,
colorimetric, potentiometric, polarographic and possibly also chromatographic) are
marked by insufficient sensitivity or require too long a period of time. In many other
methods substances present in natural waters (for instance chlorides) interfere; a further
interference may be seen in the fact that only I~ or h may be determined, and not the
summation of/ - and h- As the most suitable, very sensitive and simple method for the
determination of iodides, the catalytic ultramicrodetermination of iodine in drinking
water was chosen. (Feigl F., Jungreis E. — 1958). The method was modified for the
determination of iodides in natural waters with a content of 5-20 mg/1 of organic
matters. The method is based on the catalytic acceleration of redox reaction between
chloramine-r(sodium-p-toluenesulfonchloramide) and tetra base-acetate (N, N'-tetramethyldiaminodiphenylmethane acetate) catalysed by the presence of iodide-iodine
according to the reaction :
CIO~+2I-+2H+ = Ci~+H 2 0 + I2
(CH3)2N-<f
VCH2-<
VN(CHs)2+l2 =
H
(CH 3 ) 2 N^f
V
C H
=^
>=N(CH 3 )2+2H++2I-
Their summation gives the reaction
>~CH2-Kf
>-N(CH )2+C10"
y~VcH^^v>
H
(CH3)2N-<f
3
= (CH3)2 ti-^~\-Cn=/
=
\ = N (CH 3 ) 2 +C1-+H 2 0
in which the catalytically effective iodide-iodine does not appear any more. The blue
colour of the quinoidal compound, suitable for colometric determination, changes
from green to yellow, which may also be used for colorimetric determination. The
maximum of the absorption spectrum of blue colouring is at a wavelenght of
A = 600 m/j., yellowish-green at a wavelenght of À = 460 m/t. To obtain a wider
concentration range both absorption spectra were therfore used. The reaction is strongly
influenced by the pH value, so that the solution must be buffered; the influence of
some substances present in surface water may partially inhibit the reaction and shift
the maximum colouring (this leads to the necessity of plotting a chronometric curve).
The determination of the optimal quantity of chloramine-T is governed by the content
of organic matters present in the natural waters. The presence of phenols and their
derivatives up to a concentration of 1 mg/1 does not interfere with the determination.
From the substances commonly present in surface waters only a large quantity of Fe
interferes. The reaction is very selective and when the correct conditions are observed
is entirely suitable for the determination of iodide as a tracer.
308
INJECTION OF TRACER AND SAMPLING
The tracer was added abruptly by the so-called gulp method. Sufficient quantities
of the tracer (depending on the discharge, velocity, length of reach, percentage of
adsorption, sensitivity of the analytical method in the determination of the substance,
etc.) were added in a solution into the line of current of the river at a certain,previously
marked point. Samples from a certain section were collected during a period determined
by the distance from the point of injection. The samples of water were immediately
analysed in a mobile field laboratory.
COMPARISON OF POTASSIUM IODIDE AND FLUORESCEIN (URANINE) IN THE MEASUREMENT
OF TRAVEL TIMES
Comparison was carried out to verify the results of the static saturation experiments
with both compounds. First potassium iodide was injected in quantities of 2 kg and
after three hours 1 kg of fluorescein was injected at the same point. The two compounds
were injected abruptly in section 43 in a dissolved state (see fig. 1). Section 41 (2,17 km
distant from the point of addition) and section 39 (4,98 km distant from the point of
addition) were chosen for sampling. After evaluating the samples, concentrations against
time were plotted, and the quantities found by planimetering the areas obtained. The
différence between the initial concentration c0 and the concentration found c indicates
the percentage of adsorption of the material. In the case of fluorescein, adsorption was
higher in all sections under observation. The peaks and bases of the separate graphs
were in full agreement for the travel times calculated from the beginning of the tracer
addition. The time bases of the waves in both cases, with regard to the coinciding
flow conditions, were identical. The experiment confirmed the conclusions made on
the basis of laboratory tests and showed the suitability of potassium iodide for use as
a tracer. In one short reach of the river the flow velocity was also measured using
potassium iodide. The accuracy of this method was excellent and due to the short
distance (in comparison with travel time) not influenced by adsorption.
CONCLUSION
After evaluating the literature referring to the use of various tracers in hydrology,
and having regard to the entirely specific conditions in the Volyftka river basin, potassium iodide was used for the first time as a tracer, after laboratory (non-radioactive)
and field tests. By the use of a suitable analytic ultramicromethod it was found possible
to determine this compound in concentrations of only 1 ppb by a very simple manner
under field conditions and without time- consuming preparation of the samples.
Tracer experiments of this type are relatively inexpensive and can be performed with
few personnel.
O n the basis of numerous experimental results obtained in the laboratory and referring
in particular to the sorption property1 of this substance, verification and modification
of the above-mentioned analytical method and comparison of the results obtained with
fluorescein, practical tests were made of measuring travel time in the above mentioned
basin. Practical measurements fully confirmed laboratory results both under unfavourable conditions and on very long reaches of the river. (The tracer was observed on a
45 k m long reach, i.e. far beyond the borders of the basin, with a discharge of up to
11 m 3 /s., using an initial dosage of 9 kg of potassium iodide).
T h e use of potassium iodide is limited not only to the measurement of travel times,
but may also be used in the measurement of rate of flow, diffusion and dispersion
characteristics of the river. For a series of experiments to be carried out in the near
309
future, the use of another two compounds that do not react with each other is being
considered, with similar properties as potassium iodide, by the aid of which it would
be possible to ascertain the hydrodynamic components of flood wave celerity. The first
substance would be added to the ascending branch, the other into the descending
branch, and the third possibly into the peak of the wave.
REFERENCES
x
( ) BALEK-HOLECEK, The Volynka Experimental and Representative Basin, Institute
of Hydrodynamics, Czechoslovak Academy of Sciences, Basic data.
(2) COLLINS M., WRIGHT, K., Journal American Water Works Association, June 1964.
3
( ) Dub OTO, Hydrolôlia, hydrografia, hydrometria, Bratislava 1957.
(4) LINSLEY, KOHLER, PAULHUS, Applied Hydrology, New York 1949.
(5) MANCZAK, H., Prace histitutu Gospodarki Wodnej, No. 3, vol. II, 1964.
( 6 ) SONS, E., Die Wasserwirtschaft, No. 10, Juli 1952.
(7) FEIGL F., JUNGREIS E., Zeiischr. f. Anal. Chem., 161, 87, (1958).
310