© Acta hydrotechnica 18/28 (2000), Ljubljana
ISSN 1581-0267
75
UDK: 556.08 UDC: 556.08
Strokovni prispevek Professional paper
HIDRA VLIČ NA USTREZNOST MERILNIH MEST
ZA MERJENJE PRETOKOV
HYDRAULIC VERIFICATION OF FLOW MEASURING SITES
Uroš CERAR
Primož BANOVEC
Franci STEINMAN
V č lanku je predstavljen pomen meritev pretokov in opis metodologije za presojo ustreznosti
merilnih mest za merjenje pretokov. Izvajanje meritev pretokov lahko zahteva sam tehnološki
proces, kjer je pretok, izmerjen z določ eno natanč nostjo, pogoj za uspešno izvajanje nadzorovanega
procesa, lahko pa ga zahteva tudi upravni akt, kot na primer sklop predpisov, ki obravnavajo
meritve emisijskega monitoringa. Usposobljenost za meritve pretokov zahteva specifič na znanja,
orodja in izkušnje, posebnosti pa so tudi v samih postopkih. Razvit je bil postopek za preverjanje
merilnih mest za meritve pretokov, s katerim lahko z uporabo različ nih orodij verificiramo
primernost in ustreznost merilnega objekta. Ta postopek je v osnovi mogoč e razč leniti na naslednje
tri elemente: meritve hitrostnega polja in izrač un pretokov, verifikacija po mednarodnih standardih
in preverjanje ustreznosti hidravlič nih robnih pogojev z matematič nim modeliranjem. Predstavljena
je uporaba metodologije na dveh primerih.
Ključ ne besede: kanalizacija, odpadne vode, modeliranje, meritve, pretok, hidrologija
This paper presents the significance of flow measuring and a description of the methodology for the
hydraulic verification of flow measuring sites. Flow measurements may be necessary within the
technological process where the flow data, measured with defined accuracy, are vital for  the
control of the process l. It can be also requested by an administrative act, for example, emission
monitoring regulation. Specific knowledge, devices, experience and, at times, special procedures,
are needed for the measurements. With years of experience, a procedure for hydraulic verification
of flow measuring sites has been developed. Basically, it consists of three elements: velocity field
measurements with flow calculation, verification of the measurement device regarding the
international standards applied and verification of hydraulic boundary conditions with
mathematical modeling. The application of this methodology on two case studies is presented.
Keywords: sewer, wastewater, modelling,  measurements, discharge, hydrology
1. UVOD
Ena od temeljnih fizikalnih velič in v
hidrotehniki je vsekakor pretok. Podatke o
pretokih potrebujemo pri nač rtovanju novih in
sanaciji starih objektov, pri spremljanju in
modeliranju pojavov v naravi in laboratorijih,
pri nadzorovanju procesov v industrijski
proizvodnji, pri spremljanju emisij iz virov
onesnaževanja in še v mnogih drugih primerih.
Meritve se lahko izvajajo občasno ali
kontinuirano, odvisno od cilja in potreb
meritev. Izvajanje meritev pretokov lahko
zahteva sam tehnološki proces, kadar je
1. INTRODUCTION
One of the fundamental physical quantities
in hydraulics is a flow. Accurate flow data are
necessary in many fields of engineering. For
example, the construction of new and the
reconstruction of old hydraulic structures,  the
observation and modelling of processes in
nature and laboratories, industry process
control, for the monitoring of emissions
pollution sources and in many other cases.
Measurements can be made periodically or
continuously, depending on goals and needs.
Flow measurements can be required by the

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
76
pretok, izmerjen z določ eno natanč nostjo,
pogoj za uspešno izvajanje nadzorovanega
procesa, lahko pa ga zahteva tudi upravni akt,
kot na primer sklop predpisov, ki obravnavajo
meritve emisijskega monitoringa.
Usposobljenost za meritve pretokov zahteva
specifična znanja, orodja in izkušnje,
posebnosti pa so tudi v samih postopkih.
Merilne metode za merjenje pretokov lahko
delimo na :
− neposredne in
− posredne.
Neposredno merjenje izvajamo z volumsko
metodo, kjer neposredno merimo pretok s
pomočjo umerjene merilne posode in z
merjenjem časa polnitve in z metodami
mešanja substanc v vodno maso. Pri posrednih
metodah pretok običajno izrač unamo
na podlagi meritev velič in, ki so funkcija
pretoka.
Posredne metode lahko v osnovi delimo na:
− metode površina-hitrost
− metoda naklon - površina
− metode z  uporabo merilnih korit in jezov.
2. VRSTE MERILNIH OBJEKTOV
Merilne objekte lahko razdelimo v tri
glavne skupine, ki imajo tudi vsaka svoje
posebnosti pri umerjanju in verifikaciji:
a) Merilni objekti za merjenje pretoka, opisani
v standardih (SIST, CEN, ISO, DIN
standardi): Glavna skupna lastnost merilnih
naprav za meritve pretokov, ki so
zabeleženi v skladu z določ ili standardov je,
da se izvaja pretvorba iz ene merilne
velič ine (npr. globine) preko fizikalno –
analitičnih transformacij neposredno v
merjeno velič ino (pretok). Ta preprost nač in
pretvorbe merjene enote v velič ino moč no
olajša kalibracijo in verifikacijo tovrstnih
merilnih objektov. Primeri tovrstnih naprav
so Venturijevo korito, Khafagi Venturijevo
korito, ostrorobi prelivi in zareze, jezovi s
široko krono, ipd.
b) Merilni objekti, opisani v strokovni
literaturi: Ti objekti spadajo nekako vmes,
med objekte, opisane v standardih in tiste,
technological process where the flow data are
measured with the defined accuracy necessary
for successfully controlling the process; but,
on the other hand, flow measurements can also
be required by regulation, for example, a
regulation regarding emissions monitoring.
Qualification for performing flow
measurements requires specific knowledge,
experience, instruments and the use of certain
procedures. We can divide flow measurements
methods into two groups:
− direct methods
− indirect methods
A direct measurement is possible with the
volumetric method, where we measure
discharge with a calibrated measuring tank and
the time of filling the tank, and with dilution
methods, where we mix conservative
substances with the body of water. By indirect
methods we usually calculate the discharge
from the measurements of values that are
related to the discharge.
Indirect methods are:
− Velocity - area methods;
− Slope - area method;
− Critical depth methods.
2. TYPES OF MEASUREMENT
STRUCTURES
We can divide measurement structures into
three main groups, each having their own
specifics for calibration and verification:
a) Flow measurement structures defined with
standards (SIST, CEN, ISO, DIN
standards): The basic common
characteristic of this type of measurement
structures, described in the standards, is that
we execute the transformation from one
measuring value (for example, depth)
through the physical and analytical
relations, directly into the measured value
(discharge). This simple way of
transformation enables easier calibration
and the verification of these measuring
structures. Venturi flumes, Khafagi Venturi
flumes, sharp and broad crested weirs, etc.
are typical representatives.
b) Flow measurement structures described in
technical literature: These structures are
somehow between the structures defined in

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
77
ki so specifič ni za vsakega proizvajalca.
Nekateri, bolj specifič ni merilni objekti za
meritve pretokov, so namreč zabeleženi in
relativno dobro opisani v strokovni
literaturi, vendar (še) niso bili uvršč eni med
standardne. Še vedno spadajo v skupino
objektov, ki jih je mogoč e verificirati preko
preprostih pretvorb. Ta skupina merilnih
objektov je več ja od skupine, opisane pod
toč ko a), primeri pa so Terzaghijev jez,
Cipolletijev jez, H-korito ipd.
c) Merilni objekti zunaj standardov
(verifikacija po navodilih proizvajalca): Ta
skupina merilnih objektov zajema objekte
za merjenje pretokov, ki so specifič ni
izdelek določ enega proizvajalca. V mnogih
primerih neposredni odnos med merjeno
velič ino (ali več merjenimi velič inami) in
pretokom ne obstaja, temveč je nač in
izvrednotenja določen s proizvajalč evo
specifikacijo. Zato je kalibracija in
verifikacija tovrstnih merilnih mest
nač eloma bolj zahtevna v primerjavi z
objekti pod toč ko a) in b).
3. STANDARDIZACIJA MERITEV
PRETOKOV
Standarde lahko definiramo kot
dokumentirane dogovore, ki vsebujejo
tehnič ne specifikacije in kriterije v obliki
pravil, navodil ali definicij karakteristik. Z
njimi naj se zagotovi kakovost pri uporabi
materialov in izdelkov in izvajanju procesov
ter delovanju služb. Uporaba standardov je
namenjena poenotenju izrazov in  postopkov
pri delu, v našem primeru meritev pretokov,
hkrati pa omogoča tudi lažjo strokovno
komunikacijo.
V našem prostoru uporabljamo na področ ju
meritev pretokov v glavnem poleg slovenskih
SIST standardov še mednarodne ISO in
nemške DIN standarde. Uporaba standardov je
sicer neobvezna, vendar pomeni
standardiziranje postopkov in obdelav meritev
obič ajno predpogoj za kakovostno izvedbo
postopkov. Potreba po standardizaciji pa se
pojavi vsekakor, č e želimo uspešno nastopati
na mednarodnem tržišč u.
Na področ ju meritev pretokov je največ je
the standards and the structures specific for
any certain manufacturer. Some of them,
more specific structures, are described
relatively well in the literature, but they
have still not been included in the
standards. They are also in the group of
structures that can be verified through
simple transformations. This group of
structures is larger than group a); for
example, the Terzaghi weir, the Cipolleti
weir, the H-flume, etc.
c) Flow measurement structures not defined in
the standards or in technical literature
(verification by manufacturer instructions):
This group of measuring structures includes
structures and devices that are not
standardised in any manner, and which are
usually produced by a certain manufacturer.
In many cases, the relationship between the
measuring value (or more measuring
values) and the discharge does not exist, but
it is defined by manufacturers’
specifications. Calibration and verification
are, in general, more difficult than for the
structures of type a) and b).
3. STANDARDISATION OF
DISCHARGE MEASUREMENTS
Standards are documented agreements
containing technical specifications or other
criteria as rules, guidelines, or definitions of
characteristics. With standardisation, we
ensure the quality use of material and
products, the execution of processes and the
operation of services. Standardisation creates
uniform terminology and makes technical
communication easier.
In Slovenia, the Slovenian SIST standards,
as well as international ISO and German DIN
standards, are generally applied in the field of
liquid flow measurements. The use of
standards is not obligatory, but standardisation
of the procedures and the processing of
measurement data is usually the first step in
obtaining reliable measurement results. The
need for standardisation appears, in any case,
if we would like to compare any results
obtained.
In the field of the measurement of fluid
flow, the largest set of standards was adopted

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
78
število standardov sprejela mednarodna
organizacija za standardizacijo (ISO).
Področje meritev pretokov je zajeto v
standardni klasifikaciji pod šifro 17.120. Do
konca leta 1999 je bilo sprejetih skupno 33
standardov s področ ja meritev v zaprtih vodih
(1 7.1 20.1 0) in 61 standardov s področ ja
meritev v odprtih vodih (17.120.20) ter 1
standard skupen za obe področ ji(1 7.1 20.01 ).
DIN norme obsegajo na področ ju meritev
pretokov (17.120) 29 standardov za meritve
pretokov v zaprtih vodih, 1 standard za
meritve v odprtih vodih (DIN 19559) in 1
standard za obe področ ji.
V Sloveniji deluje na področ ju
standardizacije Urad za standardizacijo in
meroslovje  (USM). Sprejemanje standardov
poteka preko tehnič nih komisij, ki so po
področjih podobno organizirane kot pri
mednarodni ISO organizaciji. Skupno je bilo
do leta 1999 sprejetih 17 SIST standardov s
področ ja pretokov v zaprtih vodih, medtem ko
področ je pretokov v odprtih vodih SIST
standardi še ne pokrivajo.
Opis metod merjenja pretokov v odprtih
kanalih najdemo v standardih ISO 8363 in ISO
9824 in DIN 19559. Standard DIN 19559 je
kot metoda dela predpisan za izvajanje
monitoringa odpadnih vod po Pravilniku o
prvih meritvah in obratovalnem monitoringu
odpadnih vod (UL RS 35/96).
4. VERIFIKACIJA MERILNIH
MEST
V Sloveniji so bili s sprejetjem Pravilnika o
prvih meritvah in obratovalnem monitoringu
odpadnih vod (UL RS 35/96) določ eni
zavezanci za monitoring. Z uvedbo takse na
količ ine in vrste polutantov, ki obremenjujejo
okolje, stalno narašč a potreba po kakovostnih
meritvah pretokov odpadnih vod in
koncentracij snovi v njej.
Določ itev masnega pretoka (pa tudi celotne
mase, npr. v 1 letu) nekega polutanta
predstavlja t.i. sestavljeno meritev in je
odvisna od časovnega spreminjanja
koncentracije in pretoka odpadne vode, zato je
treba oba parametra izmeriti enako kakovostno
oz. z enako natanč nostjo.
by the ISO organisation. The measurement of
fluid flow has the standard classification
number 17.120. By the end of 1999, 33
standards regarding flow in closed conduits
(17.120.10), 61 standards regarding flow in
open channels (17.120.20) and one general
standard for the measurement of fluid flow
had been adopted by the ISO.
The DIN standards have 29 standards
regarding flow in closed conduits, one
standard regarding flow in open channels (DIN
19559) and one general standard.
In Slovenia, the state institution responsible
for the field of standardisation is the Office for
Standardisation and Metrics (USM). Standards
are adopted by technical committees inside the
USM, which is organised similarly to an ISO
organisation. By 1999, 17 Slovenian (SIST)
standards addressing the flow in closed
conduits had been adopted, but the SIST
standards still don't cover flow in open
channels.
Standards ISO 8363, ISO 9824 and DIN
19559 describe methods of measurement flow
in open channels. Standard DIN 19559 was
adopted as a working method for the
monitoring of wastewater discharges
according to the Regulation of first
measurements and the operational emission
monitoring of wastewater (Official Gazette of
Republic Slovenia No. 35/96).
4. VERIFICATION OF
MEASUREMENT SITES
The regulation of first measurements and
the operational emission monitoring of
wastewater (Official Gazette of the Republic
of Slovenia No. 35/96) determines who must
carry out the monitoring of wastewater
discharges. With the taxation of the large
polluters according to their pollution
discharges, the need for the quality
measurement of discharges and concentrations
is growing.
With the need to determine the mass flow
of the pollutant (or mass within, for example,
one year), the combined measurement of
discharge and concentrations is performed. It
is, of course, necessary to measure both
parameters with a similar accuracy in order to
obtain useful results.

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
79
Pri samem nač rtovanju meritev pretokov je
predvsem pomembno, da imamo jasno
definiran cilj (namen) meritve in določ ilo,
kakšna je zahtevana natanč nost meritev. Pri
izbiri merilnega mesta moramo pogosto
upoštevati omejitve glede razpoložljive
energije, saj so merilna mesta pogosto
določ ena na izbranih strateških lokacijah na
obstoječ ih kanalizacijskih sistemih, t.j. npr. na
iztokih iz č istilnih naprav, na priključ kih
več jih onesnaževalcev na javno kanalizacijo
ipd, kjer ni na voljo energije za meritev
pretokov. Nač rtovanje merilnega mesta je zato
kompleksen proces, pri katerem je treba
upoštevati veliko dejavnikov. Največ jo vlogo
pri tem igrajo hidravlič ne razmere na širšem
odseku merilnega mesta in robni pogoji, npr.
vpliv visokih vod odvodnika na delovanje
merilnega objekta.
V praksi se lahko pojavljajo številne napake
na merilnih objektih :
− napaka pri projektiranju geometrije in
umestitve merilnega objekta,
− napaka zaradi neustrezne nastavitve merilne
opreme,
− napaka neustrezne izvedbe merilnega
mesta,
− vpliv dolvodne zajezitve na merilno mesto,
− vpliv neustreznih dotoč nih razmer (deroč i
tok, neenakomeren tok v profilu, povratni
tokovi),
− prevelika nihanja pretokov za vzpostavljeno
merilno mesto (zunaj merilnega območ ja),
− motnje zaradi spreminjajoč e se vsebine
odpadnih snovi v vodi (umazanija,
odlaganje, zamašitve),
− agresivnost okolja (temperatura, kemizem),
− motnje v merilnem profilu (vzorč evalniki,
odvzemi itd.).
Pogoj za normalno obratovanje merilnega
objekta je tudi, da nimamo prisotnosti plavja in
sedimentov. Obseg velikosti pretokov, v
katerem objekt omogoč a zadovoljivo merjenje
oz. merilni obseg naprave je definiran z
najmanjšim in največ jim pretokom in je
pogojen z vrsto in velikostjo merilnega
objekta.
Sanacija neustreznih merilnih objektov v
mnogih primerih zahteva velika finanč na
vlaganja, ali pa sploh ni mogoč a, zato je
najbolje že v fazi nač rtovanja merilnega mesta
izvesti celovito presojo ustreznosti oz.
verifikacijo merilnega mesta.
The first important step in planning the
discharge measurements is a clearly defined
purpose and the accuracy of measurements.
When we choose the location of the
measurement site, the available energy on the
section is many times limited, because we
have measuring sites on the strategic points in
the system, for example WWTP outlets,
connections of large pollutants, etc.
Designing the discharge measurement site
is a very complex process, within which many
factors have to be considered, with hydraulic
boundary conditions in the section upstream
and downstream playing a very important role.
The most frequent irregularities on
measuring sites in praxis are:
− unsuitable geometry and location of the
measuring structure,
− mistake in the calibration of the measuring
instruments,
− construction faults of the measuring
structure,
− downstream backwater influencing the
measuring site,
− irregular upstream boundary conditions
(supercritical flow, irregular flow in profile,
backflows, etc.),
− excessive oscillations of discharge (outside
of the measurement range),
− quality changes in wastewater composition
(dirt, deposition, obturations, temperature,
foam),
− aggressive environment (temperature,
chemical mechanisms),
− irregularities and disturbances in the flow
structure (samplers, etc.),
It is very important to avoid the
sedimentation and stagnation of floating
objects during the operation of the site. The
full scale measurement range of the discharge
measurement site is defined by the minimum
and maximum discharge, and is dependent on
the type and size of the measurement structure.
We have to stress that the reconstruction of
irregular measurement sites sometimes
requires an excessive investment of effort,
making it, in many cases, impossible.
Therefore, it is important to perform the
necessary tasks at the design stage.

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
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Na Inštitutu za hidravlič ne raziskave in
Fakulteti za gradbeništvo in geodezijo –
Katedra za mehaniko tekoč in z laboratorijem
smo skupaj razvili postopek za presojo
merilnih mest za meritve pretokov, s katerim
lahko z uporabo različ nih orodij verificiramo,
v kakšnem stanju je merilni objekt ali
verificiramo ustreznost izbrane lokacije za
merilno mesto. Postopek je mogoč e razč leniti
na naslednje tri elemente:
a) Verifikacija skladnosti z obstoječ imi
standardi, strokovno literaturo ali navodili
proizvajalca. Cilj je preverjanje skladnosti
ureditve merilnega mesta s SIST, ISO, CEN
in DIN standardi. Č e merilno mesto ni
standardizirano, upoštevamo podatke iz
strokovne literature ali navodila
proizvajalca. Rezultat analize je določ itev
geometrijskih podatkov za nov merilni
objekt ali preverjanje odstopanj
geometrijskih podatkov za obstoječ e
merilno mesto in izrač un pretoka po
veljavnih enač bah.
b) Terenske meritve dejanskih hidravlič nih
razmer. Namen meritev je analiza dejanskih
razmer na merilnem objektu in/ali
predvideni lokaciji. Meritve obsegajo
izmero dvo ali trodimenzionalnega polja
hitrosti v merilnem prerezu (ISO 748 :
metode hitrost-površina)  in integracijo
hitrosti po prerezu za določ itev pretoka
(ISO 8363). Kadar je s pregledom
ugotovljeno, da je merilno mesto urejeno v
skladu z določ ili ustreznih standardov in so
zagotovljeni ustrezni robni pogoji na
dotoku in iztoku, izvajanje meritev ni nujno
potrebno, vendar pa z  meritvami
hitrostnega polja ugotavljamo tudi
neregularnosti na dotoku v merilni objekt.
c) Matematično modeliranje hidravlič nih
razmer. Cilj je preverjanje ustreznosti
hidravlič nih robnih pogojev za merilno
mesto. Pri merilnih objektih, v katerih se
pojavi kritič ni tok, je npr. pomembno, da ne
prihaja do zajezitev z dolvodne strani. Z
matematičnim modelom lahko tudi
analiziramo vplive morebitnih korekcij
geometrije merilnega objekta na natanč nost
meritev. Analize izvajamo z uporabo
enodimenzionalnih matematič nih modelov.
Z medsebojno primerjavo analiz po vseh
navedenih nač inih lahko, glede na deklarirano
natanč nost vsake od njih, presodimo ustreznost
novega ali obstoječ ega merilnega mesta in
predlagamo morebitne korekcije.
The Institute for Hydraulic Research and
The Faculty for Geodetic and Civil
Engineering - Chair of Fluid Mechanics, with
their laboratory, have developed a procedure
for discharge measuring site verification. The
methodology is useful for analysing existing or
planned locations of measuring sites. The
procedure can be divided into three main
elements:
a) Verification of accordance with existing
standards, technical literature or
manufacturer declarations. The goal is to
verify accordance of the discharge
measurement site with the requirements of
the SIST, ISO, CEN and DIN standards. If
the discharge measurement site is not
standardised, we use data from literature or
from manufacturers’ declarations. The
result of the analyses is to define the
tolerances for the existing measuring site,
the theoretical discharge calculation and the
geometry of the new measuring site.
b) Field measurements. The purpose of field
measurements is to analyse actual hydraulic
conditions at the measuring site or planned
location. Measurements consist of
determining a two or three-dimensional
velocity field in the measuring profile (ISO
748: method area-velocity) and the
integration of the velocity through the
profile to determine the discharge (ISO
8363). Field measurement of the discharge
is not obligatory if the measurement site is
standardised. In such cases, the verification
of the geometry and other requirements
stated in the standards is verified.
c) Mathematical modelling of hydraulic
conditions. The goal is to verify the
hydraulic boundary conditions of the
measurement site. At the measurement sites
at which critical flow is requested, an
influence of the backwater at the
downstream boundary condition is of
importance. It is also possible to analyse the
influence of geometric corrections to
measurement accuracy. We use one-
dimensional mathematical models.
Performing the analyses through each of the
three steps described above, it is possible, to
verify the location of the new or existing
measuring site or to propose eventual
correction measures.

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
81
Postopek je posebej primeren za merilne
naprave, ki jih zahteva zakonodaja, veljavna v
RS in zakonodaja EU. Č eprav Pravilnik o
prvih meritvah in obratovalnem monitoringu
odpadnih vod ter o pogojih za njegovo
izvajanje (Uradni list RS 35/96) predpisuje
uporabo standarda DIN 19559, se v praksi
izkazuje, da je v pravilniku (edini) predpisani
standard v svojih določilih presplošen.
Podrobneje obravnava le Venturijevo merilno
korito (DIN 19559-2), ostale merilne metode
pa so le na splošno obravnavane in niso
podrobneje opredeljene, kot npr. v ISO
standardih. Menimo, da je zato uporaba ISO
standardov v takih primerih primernejša, kot
dopolnitev predpisani metodi pa zelo smiselna.
Potreba po verifikaciji merilnih mest je
pomembna tudi z vidika izvajanja nadzornih
meritev s strani države ali njene pooblašč ene
ustanove. V času obratovanja merilnih
objektov za merjenje pretoka bo vsekakor
treba vzpostaviti tudi sistem nadzora  nad
izvajalci monitoringa. Postopek verifikacije
meritev, ki v primerih ugotavljanja
koncentracij različ nih snovi v odpadni vodi
poteka z medsebojno izmenjavo vzorcev, na
področ ju meritev pretokov ne pride v poštev.
Nadzornih meritev namreč ni mogoč e izvajati
na neustreznem merilnem objektu, ampak je
treba merilno mesto predhodno ustrezno
verificirati. Šele ko je doseženo, da se meritve
(ves č as) lahko ustrezno izvajajo, je mogoč obč asen , nadzorni pregled.
5. PRIMERI UPORABE
POSTOPKA VERIFIKACIJE
5.1 MERILNIK PRETOKA CČ N
DOMŽALE
Merjenje pretoka na iztoku CČ N Domžale
se izvaja s pomočjo Khafagi-Venturi
merilnika, širine korita 118 cm, s kratko
zožitvijo širine 52 cm. Merilnik je lociran pred
iztokom iz CČ N v Kamniško Bistrico. Cilj
naloge je bil, preveriti delovanje merilnega
mesta in določ iti krivuljo pretoka. Merilno
korito je prikazano na sliki 1.
The procedure is very suitable for
measuring sites requested by regulation
adopted in Slovenia and the European Union.
Experiences from the implementation of the
Regulation of the first measurements and
operational emission monitoring of wastewater
(Official Gazette of Republic Slovenia No.
35/96), which adopted DIN 19559, have
shown that this standard has guidelines which
are too general for the use of different
measuring methods, with exception of the
Venturi flume, which is described in part
19559-2. We consider the use of ISO standards
to be more reasonable than the  completion of
the adopted DIN method.
Verification of discharge measurement sites
is an important and necessary task with the
aim of supervising the discharge
measurements which are usually performed by
the polluters themselves, or by authorised
institutions. During the operation of discharge
measurement sites it is also necessary to
establish a supervising system.. Verification of
the pollution concentration measurements
through the exchange of wastewater samples is
applied for the verification of measurements in
the field of pollution monitoring. The same
mechanism is impossible to apply in the field
of discharge measurement. It is therefore
necessary to perform the verification of any
discharge measurement structure before it is
commissioned to its use. After the verification,
it is necessary to perform a periodical
verification of the measurement structure
within a regular time interval.
5. CASE STUDIES
5.1. FLOW MEASUREMENTS AT THE
WWTP, DOMŽALE
Discharge at the outlet of the WWTP,
Domžale was measured with a Khafagi
Venturi flume with  a width of 118 cm and a
short contraction of a width of 52 cm. The
device was located at the outlet from the
WWTP to the Kamniška Bistrica River. The
goal of the project was the calibration and
verification of the measuring site. The
measurement flume is showed in Figure 1.

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
82
Slika 1 . Khafagi Venturi korito na iztoku CČ N Domžale.
Figure 1 . Khafagi Venturi flume on the Domžale WWTP outflow.
V prvi fazi naloge so bili natanč no
izmerjeni in preverjeni geometrijski podatki
korita in ugotovljena odstopanja oz. tolerance.
Pri tem so bile smiselno uporabljene zahteve
standarda DIN 19559-2, ki takšnega primera
sicer ne obravnava, temveč le klasič no
Venturijevo korito z dolgo zožitvijo. Na
podlagi podatkov iz strokovne literature smo
določ ili teoretič no krivuljo pretoka.
Terenske meritve pretoka smo izvajali v
merilnem profilu pred zožitvijo. Uporabljali
smo nač in omerosojanja merilnega mesta, z
metodo merjenja hitrosti v posameznih toč kah
prereza in integracijo hitrosti po prerezu, za
izračun pretoka v skladu s smernicami
In the first phase of the project, the
geometrical data of the flume were inspected
and measured and deviations were recognised.
We used the requirements of the standard DIN
19559-2, which describes the classical Venturi
flume with a long contraction. We also defined
a theoretical discharge curve from the
literature.
Field measurements were carried out in the
measuring profile before the contraction. We
used a measuring site calibration with a
method of measuring velocities in profile, and
an integration of them in the profile, to
calculate the discharge according to the
guidelines of standards ISO 8363 and ISO 748.

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
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standardov ISO 8363 in ISO 748.
Meritve dvodimenzionalnega polja hitrosti
so bile izvedene v 21 toč kah prereza pri 7
različnih pretokih. Uporabljena je bila
brezkontaktna sonda za toč kovno meritev
dvodimenzionalnega vektorja hitrosti
ADVLab–2D,  z nazivno natanč nostjo
0,5 odstotka merilnega območ ja in resolucijo
0,1 mm/s, proizvajalca Nortek AS. Prednost
uporabe te sonde je poleg njene natanč nosti
tudi ta, da nima gibljevih delov, kot npr.
mersko krilo.
Za izrač un pretokov smo uporabili program
PRETOK7, ki izvaja integracijo merjenih
hitrosti po prerezu s funkcijo spline, ob
upoštevani polno razviti turbulenci v
merjenem profilu (slika 2).
Two-dimensional velocity fields were
measured at 21 points in the profile at seven
different discharges. A non-contact probe for
the point measurement of the two-dimensional
velocity vector ADVLab–2D, with an
accuracy 0,5 % of measuring range and a
resolution 0,1 mm/s from the manufacturer
Nortek AS, was used. Besides having good
accuracy, the probe has no moving parts,
which is an advantage if we compare it with
usual current meters.
We calculated the flow using the in-house
software PRETOK7. It executes the
integration of measured velocities through the
profile with the spline function at full
developed turbulence in the measuring profile
(Figure 2).
Slika 2. Izotahe merjenega profila pri pretoku 285 l/sek.
Figure 2. Velocity profile at discharge 285 l/sec.
Preverjanje hidravlič nih robnih pogojev
smo izvedli s pomoč jo programa HEC-RAS,
ustreznega za izrač un stalnega, zvezno se
spreminjajočega toka. Upoštevali smo
dejansko geometrijo korita, analizirali pa smo
tudi vpliv korekcij geometrije korita na izrač un
poteka gladin in pretokov (slika 3.)
Verification of hydraulic boundary
conditions were carried out by using the
program HEC-RAS 2.2, developed for the
calculation of steady and continuously
changing unsteady flow. We calculated the
flow with actual geometry, and analysed the
influence of geometric corrections on the
water levels and discharges (Figure 3).

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
84
Slika 3. Aksonometrič en prikaz izrač unanih gladin s programom HEC-RAS ver.2.2.
Figure 3. Acsonometric view of water levels computed with HEC-RAS ver.2.2.
Rezultati navedenih treh vrst analiz so
prikazani grafič no (slika 4).
Results of all different analyses are
presented graphically (Figure 4).
0
10
20
30
40
50
60
70
0.00 100.00 200.00 300.00 400.00 500.00 600.00
Pretok Q [l/s]
Višina H [cm]
Khafagi V. 
enač ba
meritev
HEC RAS
Khafagi +5%  
toleranč no
območ je
Khafagi -5%
Slika 4. Q-H diagram – primerjava rezultatov.
Figure 4. Q-H curves analysis.

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
85
Iz slike 4 je razvidno dobro ujemanje
rezultatov meritev pretokov z izrač unom po
teoretič ni enač bi, saj odstopanja niso znašala
nikjer več kot 3 odstotke. Izračun s
programom HEC RAS je bil namenjen
predvsem preverjanju robnih pogojev, zato
koeficient hrapavosti ni bil natanč neje
kalibriran. Rezultati so  zato le indikativni.
Kot konč ni rezultat naloge lahko strnemo,
da smo z meritvami in izrač uni dokazali, da je
merilni objekt ustrezno izveden, da so robni
pogoji ustrezni in je merilni objekt ustrezno
umešč en na iztoku iz č istilne naprave. Zato se
lahko kot kalibracijska krivulja v območ ju
meritev uporabi teoretič na krivulja pretoka
Khafagi-Venturi korita, kot ustrezno
nadomestilo določ bam Pravilnika o prvih
meritvah in obratovalnem monitoringu
odpadnih vod ter o pogojih za njegovo
izvajanje (Uradni list RS 35/96).
5.2. MERILNIK PRETOKA NA
KANALIZACIJSKEM SISTEMU
KAMNIK DOMŽALE
Merilnik pretoka je lociran na meji med
obč inama Kamnik in Domžale in je namenjen
ugotavljanju dotoka odpadne vode iz obč ine
Kamnik. Merilni objekt je klasič no
Venturijevo korito, širine korita 70 cm z dolgo
zožitvijo širine 47 cm.
Uporabljena je bila enaka metodologija
dela, konč ni rezultati analiz pa so prikazani na
sliki 5.
Odstopanja opravljenih meritev od
teoretič no izrač unanih pretokov so nekoliko
več ja, vendar še vedno v okviru dovoljene
toleranč ne meje po standardu DIN 1 9559-2.
Na podlagi te ugotovitve je bila v območ ju
meritev verificirana uporaba pretoč ne krivulje
po DIN standardu.
From Figure 4 we can identify a good
accordance of measured values with the
theoretical equation calculation, as difference
in the whole range of measurements is not
larger than 3%. Calculation with the program
HEC RAS served primarily for the controlling
of boundary conditions, so we didn't calibrate
the roughness coefficient, and the results are
only indicative.
In conclusion, we proved with
measurements and calculations that the
measuring site is properly constructed with
proper boundary conditions. The measuring
object is also suitably located on the outlet of
the WWTP. We can use, in the range of
measurements, a theoretical stage discharge
equation for the Khafagi Venturi flume, as an
adequate substitution of the guidelines of
Regulation of the first measurements and
operational emission monitoring of wastewater
(Official Gazette of Republic Slovenia No.
35/96).
5.2. MEASUREMENT SITE ON THE
SEWAGE SYSTEM OF KAMNIK AND
DOMŽALE
The flow measurement device is located on
the border between the communities of
Kamnik and Domžale, and serves to divide the
costs of the WWTP operation between the two
communities. The measuring structure is a
classical Venturi flume of 70 cm width, and a
length contraction of  47 cm width.
Equal methodology was used; the final
results of the analyses are presented in
Figure 5.
The deviations of measured values from
theoretical calculated values were slightly
larger, but still within the range of permitted
tolerance according to the guidelines of the
standard DIN 19559-2. According to this
statement, the usage of the DIN standard stage
discharge curve in the range of measurements
was verified.

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
86
0
5
10
15
20
25
30
35
0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00
Pretok Q [l/s]
Višina H [cm]
DIN 19559
Meritev
HEC RAS
DIN +5% 
toleranč no 
območ je
DIN -5%
Slika 5. Q-H diagram – primerjava rezultatov
Figure 4. Q-H curves analysis.
6. ZAKLJUČ EK
Ugotovitve lahko strnemo takole :
− meritve pretokov morajo biti kakovostno
izvajane in zahtevajo specifič na znanja,
− priporoč ljiva je uporaba standardov pri
načrtovanju merilnih objektov, oceni
izvedenega stanja in izvajanju meritev
pretokov,
− verifikacija merilnih mest je potrebna pred
zač etkom izvajanja monitoringa pretokov,
− elementi verifikacije obsegajo preverbo
skladnosti merilnega objekta s standardi,
meritve pretokov in matematič no
modeliranje hidravličnega delovanja
objekta,
− postopek verifikacije je v praksi pokazal
široko uporabnost, od verifikacije ureditev
do predlogov za premestitve oz. sanacije, pa
tudi vprašanj o razgradnji objektov, ki jih ni
mogoč e primerno usposobiti,
− Verifikacijo meritev (nadzorne meritve)
pretokov je mogoč e izvajati na verificiranih
merilnih mestih.
6. CONCLUSIONS
We can conclude with the following
remarks:
− To perform discharge measurements,
specific knowledge is needed.
− The usage of standards is necessary for the
planning of new discharge measurement
sites, the analyses of existing sites, and for
the discharge measurements for the
calibration procedure.
− Verification of the measurement site is
necessary before the structure begins
operation.
− Elements of measurement site verifications
must be in accordance with the standards,
field discharge measurements and the
mathematical modelling of the hydraulics.
− Procedure of verification is very useful in
praxis, from verification to the
reconstruction of the sites, but also opens
questions about the decomposition of the
measuring sites which don’t work properly,
− The verification of measurements
(supervising measurements) are only able to
be performed on verified measuring sites.

Cerar, U., Banovec, P., Steinman, F.: Hidravlič na ustreznost merilnih mest za merjenje pretokov -
Hydraulic Verification of Flow Measuring Sites
© Acta hydrotechnica 18/28 (2000), 75-87, Ljubljana
87
VIRI - REFERENCES
International Organisation for Standardisation (2000). ISO catalogue 2000, http://www.iso.ch/
Deutsches Institut für Normung (2000). DIN katalog 2000, http://www.din.de/ (in German).
MZT-Urad za standardizacijo in meroslovje (1999). SIST katalog 1999, Urad za standardizacijo in
meroslovje, Ljubljana. (in Slovenian).
Cerar, U. (2000). Standardi za meritve pretokov in natanč nost meritev (Standards for discharge
measurement and accuracy of measurements), Proceedings of the Proffesional seminar of
sanitary engineers 2000, Radenci, in press. (in Slovenian).
Banovec, P. (1996). Merilni sistemi (Measurement systems), Proceedings of Professional seminar
of discharge measurement, Portorož, 1 5-27. (in Slovenian).
Steinman, F., Banovec, P. (1996). Merski objekti (Measurement structures), Proceedings of
Professional seminar of discharge measurement, Portorož, 31 -50. (in Slovenian).
Cerar, U., Banovec, P. (1 999). Umerjanje merilnikov pretoka CČ N Domžale - iztok in Nožice
(Calibration of flow measurements at WWTP Domžale - Nožica outflow). Report, Hydraulic
Research Institute and Chair of Fluid Mechanics, 40p. (in Slovenian).
Naslovi avtorjev - Authors' Addresses
Uroš CERAR
Inštitut za hidravlič ne raziskave - Hydraulic Research Institute
Hajdrihova 28, SI – 1000 Ljubljana
izr.prof.dr.Franci STEINMAN, asist. Primož BANOVEC
Univerza v Ljubljani - University of Ljubljana
Fakulteta za gradbeništvo in geodezijo - Faculty of Civil and Geodetic Engineering
Katedra za mehaniko tekoč in z laboratorijem - Chair of Fluid Mechanics
Hajdrihova 28, SI – 1000 Ljubljana