© Acta hydrotechnica 18/29 (2000), Ljubljana
ISSN 1581-0267
83
UDK: 504.4:519.61/64:627.8(282.243.743) UDC: 504.4:519.61/64:627.8(282.243.743)
Strokovni prispevek Professional paper
TOPLOTNA OBREMENITEV SA VE DOLVODNO OD TRBOVELJ
THERMAL LOAD OF THE SA V A RIVER DOWNSTREAM FROM
TRBOVLJE
Andrej ŠIRCA
Prikazani so bili rezultati študije “Toplotna obremenitev Save v zvezi z izgradnjo TET3”, v kateri
smo obravnavali vplive sedanje in nač rtovane Termoelektrarne Trbovlje (TET), Nuklearne
elektrarne Krško (NEK) in bazenov spodnjesavske verige HE na temperaturno stanje Save. V
predavanju je bil na kratko podan uvodni del študije (analiza znanih podatkov), glavna pozornost
pa je veljala prikazu rezultatov uporabljenih 1D in 3D modelov. Iz teh je razviden velikostni red
vpliva posameznih bazenov spodnjesavske verige in toč kovnih onesnaževalcev (TET3, NEK) na
toplotno stanje reke. V vseh predstavljenih primerih je bil glavni poudarek študije na objektu v
Trbovljah, medtem ko sta bili NE Krško in veriga hidroelektrarn obravnavani poenostavljeno.
Ključ ne besede: toplotna obremenitev, akumulacije, pretoč ne hidroelektrarne, matematič no
modeliranje, termoelektrarna Trbovlje, nuklearna elektrarna Krško, reka Sava
Results of the study “Thermal load of the Sava River related to the construction of TET3”, are
presented, where influences of the existing and of the planned Trbovlje Thermal Power Plant
(TET), of the Krško Nuclear Power Plant (NEK) and of the reservoirs of the future chain of hydro
power plants on the Lower Sava River on the thermal state of the river were studied. A brief
presentation of the introductory part of the study (an analysis of the existing data) is given first
during the presentation, which is followed by a presentation of the results of the 1D and of the 3D
models. The aim of the latter was to illustrate the share of each future reservoir and of the point
pollution sources (TET, NEK) on the thermal state of the Sava River. A simplified description of
reservoirs and of the NEK cooling system were applied, while the TET was accounted for with all
available details.
Key words: thermal load, reservoirs, run-of-river hydro powerplants, mathematical modelling,
Trbovlje thermal powerplant, Krško nuclear powerplant, the Sava River
1. UVOD
Po izgradnji Termoelektrarne Trbovlje 3
(TET3) in zamenjavi uparjalnikov Nuklearne
elektrarne Krško (NEK) se prič akuje
poveč anje toplotne obremenitve reke Save.
Dodatne obremenitve bo prinesla tudi
zajezitev v bodočih akumulacijah
spodnjesavske verige hidroelektrarn. V
dosedanjih študijah (VGI-VGL, 1989; VGI,
1 991 ; IHR, 1 995; Č ehovin & Rodič , 1 996)
problematika ni bila obdelana v zadostnem
obsegu. Zato je bila pred izdelavo idejnega
projekta TET3 postavljena zahteva po jasno
definiranih ekoloških in iz teh izhajajoč ih
ekonomskih pogojih za obratovanje tega
objekta. V tehnološko-ekološkem delu študije
1. INTRODUCTION
An increase of thermal pollution in the Sava
River is expected after the construction of the
new Trbovlje Thermal Power Plant (TET3),
and after an increase of power at the Krško
Nuclear Power Plant (NEK). Additional loads
are expected, due to the retention of river
water along a future chain of HPPs along the
Lower Sava River. Since the problem was not
sufficiently elaborated in some recent studies
(VGI-VGL, 1989; VGI, 1991; IHR, 1995;
Č ehovin & Rodič , 1 996), a clear definition of
the environmental and economic conditions of
operation was required prior to the
construction of the TET3. Three combinations
of power plants were elaborated upon in the

Širca, A.: Toplotna obremenitev Save dolvodno od Trbovelj -
Thermal Load of the Sava River Downstream from Trbovlje
© Acta hydrotechnica 18/29 (2000), 83-95, Ljubljana
84
(Rajar et al, 1998) smo obravnavali tri
temeljne kombinacije objektov: obstoječ e
stanje (analiza), bodoče stanje brez
spodnjesavske verige in z novo TET3 ter
bodoč e stanje z verigo in TET3 (prognozi).
Ekonomski del študije bo predvidoma konč an
v letu 2000.
2. PODATKI
Velik del študije je predstavljalo zbiranje,
usklajevanje in dopolnjevanje podatkov,
potrebnih za modele. Potrebni so bili
hidrološki (pretok, rečna temperatura),
meteorološki (temperatura in vlažnost zraka,
insolacija, hitrost vetra) ter obratovalni
parametri za posamezne elektroenergetske
objekte (TET, NEK).
Sedanje stanje pretokov na obravnavanem
odseku smo ovrednotili s karakteristič nimi
količ inami: srednjimi, srednjimi nizkimi in
nizkimi nizkimi (najnižjimi zabeleženimi)
pretoki na posameznih vodomerskih postajah:
VP Litija, VP Radeče in VP Č atež
(preglednice 1 - 3). Zaradi medsebojne
primerljivosti prikazujemo v treh preglednicah
starejše rezultate (VGI, 1983), ki pa edini
kažejo razmerje med posameznimi postajami.
V konkretnih rač unih smo, kjer je bilo
mogoče, uporabljali najnovejše ali vsaj
novejše podatke. Okvirno velja, da so srednji
in srednji nizki pretoki v Radeč ah aritmetič na
sredina tistih v Litiji in Č atežu. Za nizke nizke
pretoke ni opaziti posebnih zakonitosti. Na VP
Č atež je zelo izrazito upadanje pretokov v
zadnjih desetletjih. To so potrdile kontrole na
profilu Krško, vendar bi bilo za popolnoma
zanesljivo trditev treba izdelati posebno
hidrološko študijo. Glede na splošno
neusklajenost podatkov iz različ nih obdobij bi
bila takšna študija potrebna pred zač etkom
ekstenzivnega izkoriščanja Save
(termoenergetika, hidroenergetika), seveda pa
bi morala temeljiti na najnovejših podatkih.
technological-environmental part of the study:
existing state (analysis), future state with the
TET3 and without the HPP chain and the
future state with both the TET3 and the chain
(both prognoses). The economic part of the
study is to be completed during the year 2000.
2. DATA
A great deal of study was dedicated to the
collection, harmonization and completion of
the input model data. Hydrological (discharge,
river temperature), meteorological (air
temperature and humidity, insulation, wind
speed) and operating parameters for the
particular power plants (TET, NEK) were
required.
Present discharges along the elaborated
stretch of the river were evaluated by
characteristic values: mean, mean low and
(absolute) minimum discharges at particular
gauging stations: GS Litija, GS Radeč e and
GS Č atež (Tables 1 – 3). In these tables, older
data (VGI, 1983) are given which are only
capable of displaying the mutual relations
between the stations. If it was possible, the
most recent, or at least the more recent data
were applied in the calculations. In general,
the mean and mean low discharges at Radeč e
can be obtained as the aritmetical means of the
corresponding values at Litija and Č atež.
There is no similar relation for the minimum
discharges. A trend of decrease in discharges
is evident at GS Č atež. Although it was
confirmed by some controls in the Krško
cross-section, a separate hydrological study
related to this topic would be neccessary. In
view of some further disagreements of data
from different time periods, such a study,
based on the most recent data, would also be
necessary prior to an extensive exploitation of
the Sava River (thermal power and
hydropower).

Širca, A.: Toplotna obremenitev Save dolvodno od Trbovelj -
Thermal Load of the Sava River Downstream from Trbovlje
© Acta hydrotechnica 18/29 (2000), 83-95, Ljubljana
85
Preglednica 1. Srednji pretoki Save za obdobje 1926-1975 (VGI, 1983).
Table 1.  Mean discharges of the Sava River for the period 1926-1975 (VGI, 1983).
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
leto
year
Q
sr-L
149 147 196 210 199 169 127 106 141 193 268 200 175
Q
sr-R
198 197 255 273 260 225 172 145 183 246 339 256 229
Q
sr-Č 265 267 350 356 332 286 217 177 226 321 440 336 298
L = Litija, R = Radeč e, Č = Č atež
Preglednica 2. Srednji nizki pretoki Save za obdobje 1926-1975 (VGI, 1983).
Table 2. Mean low discharges of the Sava River for the period 1926-1975 (VGI, 1983).
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
leto
year
sr
Q
n-L
75.9 73.5 91.8 114 107 87.4 71.4 56.8 55.0 75.8 103 96.7 45.8
sr
Q
n-R
106 104 129 155 145 120 99 81 76 101 140 129 64
sr
Q
n-Č 139 133 168 193 175 147 119 98 94 128 170 160 79
L = Litija, R = Radeč e, Č = Č atež
Preglednica 3. Nizki nizki pretoki Save za obdobje 1926-1975 (VGI, 1983).
Table 3. Minimum discharges of the Sava River for the period 1926-1975 (VGI, 1983).
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
leto
year
n
Q
n-L
34.4 34.8 41.4 38.5 55.9 41.9 34.1 29.4 27.7 24.4 33.0 46.6 24.4
n
Q
n-R
60.6 60.1 51.4 50.0 57.3 52.5 48.4 43.3 40.5 39.6 39.6 65.8 39.6
n
Q
n-Č 60.8 61.7 70.7 69.0 85.9 78.5 52.3 50.0 47.1 47.1 48.5 62.0 47.1
L = Litija, R = Radeč e, Č = Č atež
Za študijo ima poseben pomen spreminjanje
reč nih temperatur na obravnavanem odseku
med Litijo in državno mejo. V preglednici 4
podajamo srednje meseč ne temperature za
obdobje 1964 - 1975, kar pomeni, da je v njih
deloma že zajet vpliv TET2, ki je zač ela
obratovati v letu 1968. Poleg tega je zajet tudi
vpliv TET1. Ta je bila zgrajena kmalu po vojni
in je vzporedno s TET2 obratovala do leta
1 986. V Č atežu še ni upoštevan vpliv NE
Krško, ki je zač ela obratovati leta 1 983. Iz
navedenega je razvidno, da je pri oceni
sedanjega stanja nemogoče govoriti o
naravnem stanju, saj so vse analize temperatur
nastale že po izgradnji prvega objekta v
Changes of river temperatures along the
elaborated reach between Litija and the state
border are of special importance for the study.
The mean monthly river temperatures for the
period 1964 – 1975 are given in Table 4. In
these values, influences of the existing TET2
(in operation since 1968) and of  TET1 (in
operation since WW2 and until 1986, in
parallel with TET2) are included, while there
are not yet any intrinsic influences of the NEK
(in operation since 1 983) in Č atež. With all
this in view, the natural state of the river can
not be recovered, as all analyses were
performed long after the beginning of
electricity production in Trbovlje. Within the
framework of our recent study, only the

Širca, A.: Toplotna obremenitev Save dolvodno od Trbovelj -
Thermal Load of the Sava River Downstream from Trbovlje
© Acta hydrotechnica 18/29 (2000), 83-95, Ljubljana
86
Trbovljah. V okviru naše študije smo ocenili le
vpliv TET2, ki ob polnem obratovanju zvišuje
temperaturo Save za 0.16 (november) do 0.35
ºC (avgust), v letnem povpreč ju pa za 0.22 ºC.
Za izključ itev vpliva TET2 bi bilo treba te
vrednosti odšteti od podanih v preglednici 4,
vendar bi še vedno ostal vpliv TET1, ki ga
nismo ocenjevali. Porast srednjih temperatur je
v resnici manjši, ker TET2 ne obratuje ves č as
s polno moč jo, dejanski porasti v reki pa so
lahko tudi višji, ker je pretok spremenljiv in
pogosto nižji od srednjega.
Iz preglednice 4 je tudi razvidno, da se Sava
v hladnejših mesecih vzdolž toka ohlaja, v
toplejših pa v nekoliko več ji meri segreva.
Med Litijo in Radeč ami se ohlaja od decembra
do marca, med Radeč ami in Č atežem pa od
oktobra do marca. Na obeh odsekih, predvsem
pa na zgornjem, je zaradi nestalnega in
nedokumentiranega obratovanja TE objektov
nemogoče oceniti dejansko naravno
ohlajevalno zmogljivost reke. Zato smo
prisiljeni sedanje stanje z obratujoč imi TE
objekti upoštevati kot izhodiščno. Edina
izvedljiva alternativa za oceno naravnega
stanja bi bil zelo natanč en model, ki bi ga
morali kakovostno umeriti, za kar bi
potrebovali dobre in obsežne meritve.
Srednje vrednosti le malo povedo o
vsakoletnih kritič nih poletnih razmerah, ki
smo jih obravnavali v prognostič nih
simulacijah. Za primerjavo s temi rezultati so
ustreznejše srednje visoke temperature, ki so
za navedena tri vodomerne postaje prikazane v
preglednici 5, in visoke visoke temperature
(absolutni maksimumi obdobja), ki so
prikazane v preglednici 6. Pri razlagi zadnjih
dveh preglednic moramo upoštevati, da so
primerjave srednjih visokih temperatur v
različ nih profilih smiselne, primerjave visokih
visokih pa ne, ker ne gre za soč asne dogodke.
Ker gre torej pri  preglednici 6 za informativne
vrednosti, kako visoke temperature so bile tam
že dosežene, razlike med profili niso
prikazane. Poudarjene so le avgustovske
vrednosti, ker smo tudi v naših simulacijah
upoštevali avgustovske pretoke, hidrološke in
meteorološke razmere.
influence of TET2 was evaluated, which
increases the river temperature from 0.16 (in
November) to 0.35 ºC (in September) with an
annual average of 0.22 ºC. All these values
assume power production at nominal full rate.
We could thus eliminate the influence of the
TET2 from the values in Table 4, but
influences of the old TET1 would still remain
unclear. In reality, the increase of the average
river temperatures is smaller due to the usual
operation with lower power. But on the other
hand, it can be even greater, due to the
frequent occurence of natural discharges
which are lower than average.
From Table 4, a decrease of river
temperature along the river is evident during
the winter months,  while a somewhat stronger
increase is evident in the summer months.
Between Litija and Radeč e, cooling takes
place from December to March, while between
Radeč e and Č atež, it occurs from October to
March. Along both stretches, it is impossible
to determine the natural cooling capacity of
the river, due to the inconsistent and non-
documented operation of the thermal power
plants in Trbovlje. Therefore, the present state
of operation for the TET2 power plant is
assumed to be the initial state. The only
alternative for determining the present natural
state would be a precise and exactly verified
mathematical model, which is presently not
feasible due to extensive data requirements.
Average values give little information about
the critical summer conditions which were
elaborated in the prognostic simulations. More
suitable for comparison with these results are
the mean high temperatures shown for the
three relevant gauging stations in Table 5, and
the absolute maximum temperatures (of the
period), shown in Table 6. It must be taken
into account that comparisons of the mean
high temperatures in different cross sections
are acceptable, while those of the absolute
maximum values are not, since the latter are
not simultaneous events. As only informative
values are given in Table 6 to show the
possible extremes at different cross sections,
the differences between the cross-sections are
not calculated. August values are emphasised,
because the August values of temperature,
discharges and meteorological parameters
were used in the prognosticated simulations.

Širca, A.: Toplotna obremenitev Save dolvodno od Trbovelj -
Thermal Load of the Sava River Downstream from Trbovlje
© Acta hydrotechnica 18/29 (2000), 83-95, Ljubljana
87
Preglednica 4. Spreminjanje srednjih reč nih temperatur med Litijo in Č atežem pred izgradnjo NEK
za obdobje 1964-1975 (VGI, 1983) na podlagi meritev enkrat dnevno.
Table 4. Changes of mean water temperatures between Litija and Č atež before the construction of
the Krško NPP, period 1926-1975 (VGI, 1983) based on one measurement per day.
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
leto
year
T
LIT
4.4 5.1 6.3 8.6 11.1 13.1 14.7 15.0 13.1 10.2 7.7 5.3 9.6
T
RAD
3.5 4.4 6.2 8.8 11.7 14.2 16.3 16.7 14.3 10.9 7.8 4.7 10.0
! ! ! ! -0.9 -0.7 -0.1 0.2 0.6 1.1 1.6 1.7 1.2 0.7 0.1 -0.6 0.4
T
RAD
3.5 4.4 6.2 8.8 11.7 14.2 16.3 16.7 14.3 10.9 7.8 4.7 10.0
T
Č AT
3.0 4.2 6.1 9.1 12.7 15.3 17.3 17.3 14.3 10.6 7.2 4.2 10.1
! ! ! ! -0.5 -0.2 -0.1 0.3 1.0 1.1 1.0 0.6 0 -0.3 -0.6 -0.5 0.1
  T
LIT
 - Litija, T
RAD
 - Radeč e, T
Č AT
 - Č atež
Preglednica 5. Spreminjanje srednjih visokih reč nih temperatur med Litijo in Č atežem pred
izgradnjo NEK za obdobje 1964-1975 (VGI, 1983), na podlagi meritev enkrat dnevno.
Table 5. Changes of mean high water temperatures between Litija and Č atež before the
construction of the Krško NPP, period 1926-1975 (VGI, 1983) based on one measurement per day.
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
leto
year
sr
T
v-LIT
6.0 6.2 8.3 10.0 13.2 15.6 17.1 17.1 15.1 12.5 9.6 7.4 -
sr
T
v-RAD
5.7 6.3 8.7 11.0 14.2 17.3 18.8 19.3 16.8 13.5 9.7 7.1 -
! ! ! ! -0.3 0.1 0.4 1.0 1.0 1.7 1.9 2.1 1.7 1.0 0.1 -0.3 -
sr
T
v-RAD
5.7 6.3 8.7 11.0 14.2 17.3 18.8 19.3 16.8 13.5 9.7 7.1 -
sr
T
v-Č AT
4.8 6.4 8.9 11.6 15.5 17.8 19.6 20.1 16.9 13.9 10.1 6.4 -
! ! ! ! -0.9 0.1 0.2 0.6 1.3 0.5 0.8 0.8 0.1 0.4 0.4 -0.7 -
sr
T
v-LIT
 - Litija, 
sr
T
v-RAD
 - Radeč e, 
sr
T
v-Č AT
 - Č atežu
Preglednica 6. Spreminjanje visokih visokih reč nih temperatur med Litijo in Č atežem pred
izgradnjo NEK za obdobje 1964-1975 (VGI, 1983), na podlagi meritev enkrat dnevno.
Table 6. Changes of maximum water temperatures between Litija and Č atež before the construction
of the Krško NPP, period 1926-1975 (VGI, 1983) based on one measurement per day.
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
leto
year
v
T
v-LIT
7.4 8.4 11.3 12.4 15.8 18.0 21.0 20.5 17.0 15.1 11.7 9.0 -
v
T
v-RAD
8.0 8.4 10.4 13.0 17.2 19.0 21.2 22.1 18.5 16.6 12.4 8.7 -
v
T
v-Č AT
6.2 8.5 11.0 16.0 17.1 21.5 22.5 22.0 19.4 17.2 12.2 7.4 -
v
T
v-LIT
 - Litija, 
v
T
v-RAD
 - Radeč e, 
v
T
v-Č AT
 - Č atež

Širca, A.: Toplotna obremenitev Save dolvodno od Trbovelj -
Thermal Load of the Sava River Downstream from Trbovlje
© Acta hydrotechnica 18/29 (2000), 83-95, Ljubljana
88
3. MODELIRANJE
Glavni del šudije je predstavljalo
matematič no modeliranje toplotne dinamike
Save. Ustaljen pristop pri tovrstnih problemih
je, da se daljši reč ni odseki modelirajo
enodimenzionalno, posamezne lokalne težave
(bazeni, podrobnosti izpustov in zajetij) pa
več dimenzionalno - 2D ali 3D (Fischer et al.,
1979; Edinger & Geyer, 1965). Tako smo
ravnali tudi v našem primeru, v katerem smo
zaradi kratkega roka obdelali
enodimenzionalno tudi več ino bazenov. Ta
korak smo upravič ili s primerjavo s 3D
modelom (za bazena Vrhovo in Suhadol), ki je
kljub bistveno več ji kompleksnosti dal zelo
podobne rezultate kot 1 D model. Največ jo
pozornost smo posvetili dopolnitvi 3D modela
PCFLOW3D s toplotnimi č leni in razvoju
novega 1D termalnega modela za akumulacije,
HOTLAKES. V zač etni fazi smo razvijali tudi
poenostavljeni 1D nestacionarni model
THERMALS, ki pa ga zaradi pomanjkanja
meritev nismo mogli zadovoljivo umeriti in je
v študijo vključen zgolj informativno.
Predvsem zato, ker ga nameravamo v
morebitnih prihodnjih študijah dopolniti, saj je
tako rekoč edino orodje za vrednotenje
sedanjega, nezajezenega stanja. Vsi omenjeni
programi so podrobneje opisani drugje (Rajar
& Širca, 1998a; 1998b; Širca & Rajar, 1999).
Bazeni na Savi, zaradi več jih volumnov in
posebno zaradi poč asnejšega toka, drugač e
vplivajo na toplotne razmere kot sama reka
Sava. Na nezajezenem delu Save je zaradi
majhnih globin in več jih hitrosti prič akovati
skoraj popolno premešanje (in izenač enje)
toplote po globini, medtem ko v bazenih
meritve kažejo, da se zgornji sloji č ez dan
moč neje segrejejo kot spodnji. Razlika med
izmerjenima temperaturama površinskega in
spodnega sloja je poleti dosegla celo 3.6 ºC
(profil most Vrhovo, 1995-07-18-17:30).
Meritve, posebno pa še tridimenzionalni (3D)
matematič ni model, so pokazali zanimivo
toplotno dogajanje v bazenu. Po eni strani se
toplotno sevanje iz ozračja prenaša v
površinske sloje, ki se preko dneva grejejo, po
drugi strani pa se toplota delno meša po
3. MODELLING
Mathematical modelling of the Sava River
thermal dynamics was a main part of  the
study. The usual approach to such problems is
to model longer river reaches in one
dimension, while details of the local problems
(e.g. reservoirs, discharges and intakes) are
elaborated in more dimensions – 2D or even
3D (Fischer et al., 1979; Edinger & Geyer,
1965). This was also the case with our
simulations, where the majority of reservoirs
was modelled by an 1D model, due to short
time schedules. This simplification was
justified by comparisons of the 1D and 3D
models for the Suhadol and the Vrhovo
reservoirs, where a good agreement of results
was obtained in both cases, despite the much
higher complexity of the 3D model. Attention
was mainly paid to the inclusion of thermal
equations into the existing 3D model
PCFLOW3D and to the development of a new
thermal model for reservoirs, HOTLAKES. In
the initial phase, the simplified 1D unsteady
model THERMALS was also developed, but
was not verified to an acceptable extent due to
a lack of data. It is also presented
informatively. The reason for this is that our
intention for the further development of this
model in future studies as this is practically the
only tool for the evaluation of the present
unobstructed flow (without dams). Details of
all the programs are given elsewhere (Rajar &
Širca, 1998a; 1998b; Širca & Rajar, 1999).
Reservoirs on the Sava River represent a
different influence on the thermal state of the
river, due to greater retention volumes and due
to much lower velocities. Along unobstructed
reaches, a complete mixing (and vertical
temperature equalization) is expected, due to
high velocities and low flow depths, while
measurements in different existing reservoirs
show stronger or weaker daily thermal
stratification. In the Vrhovo Reservoir, the
difference between the surface and bottom
layers even reached 3.6 ºC (Vrhovo bridge,
1995-07-18-17:30). Both measurements and
the 3D mathematical model have shown an
interesting thermal dynamic in this reservoir.
On the one hand, radiation from the
atmosphere is transmitted into and stored in
the surface layers during the daytime hours,

Širca, A.: Toplotna obremenitev Save dolvodno od Trbovelj -
Thermal Load of the Sava River Downstream from Trbovlje
© Acta hydrotechnica 18/29 (2000), 83-95, Ljubljana
89
globini in prenaša v globlje sloje. Poleg tega se
voda giblje v smeri toka in z njo se prenaša
tudi toplota. Tipič ni č as, ki ga voda potrebuje
za prehod vzdolž celotnega bazena, je za nižje
pretoke v poletnem č asu 1 0 do 1 2 ur. Tako je
porazdelitev toplote v bazenu odvisna od
oddaljenosti obravnavane toč ke  od vtoka v
bazen, globine in od č asa. Kritič ne razmere
smo v vseh primerih (1D in 3D) prikazali z
dvema hidrometeorološkima scenarijema:
1. z vsakoletnimi kritičnimi (poletnimi)
razmerami, ki so bile ponazorjene z
dolgoletnim srednjim nizkim avgustovskim
pretokom in srednjo avgustovsko reč no
temperaturo. Klimatski vpliv smo
upoštevali z merjenimi podatki s postaje v
Krškem za povpreč no vroč poletni dan
1995-07-18
2. z ekstremnimi (poletnimi) razmerami z
majhno verjetnostjo nastopanja, ki so bile
ponazorjene z absolutno najnižjim
zabeleženim avgustovskim pretokom in
najvišjo, v letih 1 994 in 1 995, zabeleženo
reč no temperaturo. V tem primeru smo
vpliv meteoroloških parametrov upoštevali
v obliki teoretič nega vroč ega poletja, kot ga
po nemških avtorjih povzema VGI-VGL
(1989).
4. ZAKLJUČ KI
V sedanjih razmerah obratovanje TE
Trbovlje (TET2) z vidika toplotnega
onesnaženja Save ni problematično. To
potrjujejo tako izračuni, ki dokazujejo
usklajenost z veljavnimi vodnogospo-darskimi
pogoji (UL-RS, 1996a; 1996b; 1996c), kot
izkušnje upravljalcev, ki navajajo, da do
omejevanja proizvodnje do sedaj ni prihajalo
(sliki 1 in 2). Dolvodno od Trbovelj se Sava v
poletnem č asu segreva, v zimskem pa ohlaja.
Analiza vpliva bazena Vrhovo kaže, da se
vzdolž bazena voda v kritič nih razmerah
segreva za 0.4 - 0.5 ºC bolj, kot se je v
nezajezenem stanju. V izrednih razmerah se
vzdolž bazena segreje za približno 1 ºC,
primerjava z nezajezenim stanjem pa ni
mogoč a. V obeh primerih gre za poveč anje
povpreč ne temperature, ki mu moramo dodati
while on the other hand, the heat is also mixed
and transported into the lower layers. Due to
advection, a longitudinal transport of heat also
occurs. A typical time scale of the longitudinal
reservoir crossing (i.e. retention time) in the
summertime is from 10 to 12 hours. The
distribution of reservoir heat is thus dependent
on the distance from the beginning of the
reservoir, on depth and on time. Critical
conditions for the simulations with both the
1D and 3D models were described by two
hydrometeorological scenarios:
1. Typical critical (summer) conditions
which were described by the long-term
mean low August discharge and the mean
August river temperature. Climatic
conditions were assumed to equal
(measured) the dynamics from a typically
hot summer day, as recorded at the Krško
Meteorological Station on 1995-07-18
2. extreme (summer) conditions with a low
probability of occurence were approximated
by the absolute low August discharge and
the highest river temperature from the
period 1994 – 1995. Meteorological
parameters were taken from unknown
German authors (in VGI-VGL, 1989) in the
form of a » theoretically hot summer«.
4. CONCLUSIONS
Operation of the Trbovlje TPP (TET2) in
present conditions is not problematic from
the point of view of the thermal polution of the
Sava River. It is confirmed both by
calculations which show the implementation
of valid water management conditions (UL-
RS, 1996a; 1996b; 1996c) and by up-to date
experience without operative limitations of
production (Figures 1 and 2). Downstream
from Trbovlje, the Sava River is heated in
summer and colder in the winter months.
Analysis of the Vrhovo reservoir in critical
conditions shows an additional longitudinal
heating of 0.4 to 0.5 ºC, as compared to the
initial state without the reservoir. Under
extreme conditions, the longitudinal increase
equals 1 ºC, while such a comparison was not
possible for the unobstructed river. Both
increases are given for average temperatures,
but daily variations in the range ±1.5 ºC must

Širca, A.: Toplotna obremenitev Save dolvodno od Trbovelj -
Thermal Load of the Sava River Downstream from Trbovlje
© Acta hydrotechnica 18/29 (2000), 83-95, Ljubljana
90
še dnevna nihanja v razponu do ±1.5 ºC.
Zaradi dolgoletne prisotnosti TE objektov v
Trbovljah je njihov vpliv na toplotni režim
Save težko loč iti od naravnega. S tem mislimo
na prepletene vplive postopne izgradnje in
režima obratovanja TE objektov v Trbovljah,
dotoka Savinje, in morebitnih hidroloških in
klimatskih sprememb. Pogoste izjemne
hidrološke razmere v zadnjih 1 0 letih in oč itno
upadanje pretokov v zadnjih 20 letih kažejo
potrebo po popravkih hidrologije Save za
profil VP Č atež. Posredno kaže na spremembe
pretokov in temperatur tudi pogostejše
omejevanje proizvodnje NEK.
Bodoč e stanje s TET3 in brez verige HE:
Veljavne uredbe o emisijah toplote praktič no
ne omejujejo obratovanja bodoč ega objekta
TET3. Poveč anje toplotne moč i objekta s
sedanjih 1 57 MWt na 237 MWt bi povzroč ilo
dvig temperature v Savi, ki je linearno odvisen
od njenega pretoka. To pomeni ob obratovanju
objekta s polno moč jo ob vsakoletnih kritič nih
razmerah povišanje temperature v Savi za
največ 0.53 °C, v izrednih razmerah pa za
največ 1 .0 °C. Glede na rezultate rač unov z
verigo se opisana razlika med sedanjo in
bodoč o obremenitvijo med Trbovljami in
zajetjem NEK zmanjša v kritič nih razmerah za
12 odstotkov, v izrednih pa za 22 odstotkov.
Vsi rač uni in ocene v nezajezeni Savi so bili
narejeni ob predpostavki popolne
premešanosti. V sedanjih razmerah ni jasno,
ali je ta predpostavka izpolnjena, ker ustrezne
meritve na odseku Trbovlje-Savinja ne
obstajajo.
also be considered. Due to the long-term
existence of the Trbovlje TPP with a gradual
increase of power, changes in the operational
regime, the Savinja River tributary and
possible hydrological and meteorological
changes, it would be very difficult to divide
the influences of the TPP from the natural
ones. Frequent extreme hydrological events in
the last decade and the evident decrease of
discharges during the last 2 decades require an
update of the Sava hydrology for the Č atež
cross-section. An additional sign of river
temperature and discharge changes might also
be the repeated limitations of the Krško NPP
production in the summer months.
The future state with the TET3 and
without the HPP chain: Valid legislation
about heat emissions does not limit the
operation of the future TET3 plant. An
increase of thermal power from 157 MW
t
 to
237 MW
t
 would increase the Sava River
temperature proportionally and linearly to the
river discharge. Operation of the TET3 with
full power in critical conditions would increase
the river temperature by 0.53 ºC at the most,
and by 1.0 ºC at the most in extreme
conditions. According to the calculations with
the HPP chain, a decrease of difference
between the TET3 and TET2 influence is
expected downstream, with a reduction of 12%
in critical conditions and 22% in extreme
conditions, at the NEK cross-section. All
calculations for the unobstructed river assume
complete mixing. It is not certain, however,
whether this assumption is correct, as no
measurements are available for the Trbovlje-
Savinja tributary reach.

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91
0
2
4
6
8
10
12
14
16
18
20
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
temperatura (st. C) / temperature (deg. C)
naravno/natural
TET2
TET3
Slika 1. Temperatura Save pod Trbovljami ob srednjih nizkih pretokih.
Figure 1. Sava river temperature downstream from Trbovlje at mean low discharges.
0
2
4
6
8
10
12
14
16
18
20
22
24
26
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
temperatura (st. C) / temperature (deg. C)
naravno/natural
TET2
TET3
Slika 2. Temperatura Save pod Trbovljami ob nizkih nizkih pretokih.
Figure 2. Sava river temperature downstream from Trbovlje at minimum low discharges.

Širca, A.: Toplotna obremenitev Save dolvodno od Trbovelj -
Thermal Load of the Sava River Downstream from Trbovlje
© Acta hydrotechnica 18/29 (2000), 83-95, Ljubljana
92
17
18
19
20
21
22
23
24
TET SUH VRH BOS BLA KRS NEK BRE MOK
lokacija / location
temperatura (st. C) / temperature (deg. C)
naravno/natural
TET2
TET3
Slika 3. Narašč anje temperature Save vzdolž toka v kritič nih razmerah.
Figure 3. Increase of Sava river temperature along the stream in critical conditions.
20
21
22
23
24
25
26
27
28
29
30
31
TET SUH VRH BOS BLA KRS NEK BRE MOK
lokacija / location
temperatura (st. C) / temperature (deg. C)
naravno/natural
TET2
TET3
Slika 4. Narašč anje temperature Save vzdolž toka v ekstremnih razmerah.
Figure 4. Increase of Sava river temperature along the stream in extreme conditions.

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Thermal Load of the Sava River Downstream from Trbovlje
© Acta hydrotechnica 18/29 (2000), 83-95, Ljubljana
93
0.43
0.42
0.41
0.4
0.39
0.38 0.38
0.35
0.34
0.3
0.32
0.34
0.36
0.38
0.4
0.42
0.44
TET SUH VRH BOS BLA KRS NEK BRE MOK
lokacija / location
∆∆∆∆ T (st. C) / (deg. C)
Slika 5. Zmanjševanje razlike med obremenitvama Save s TET2 in TET3 v kritič nih razmerah.
Figure 5. Decrease of the difference between TET2 and TET3 influences in critical conditions.
0.83
0.8
0.76
0.73
0.68
0.65
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
TET SUH VRH BOS BLA KRS NEK BRE MOK
lokacija / location
∆∆∆∆ T (st. C) / (deg. C)
Slika 6. Zmanjševanje razlike med obremenitvama Save s TET2 in TET3 v ekstremnih razmerah.
Figure 6. Decrease of the difference between TET2 and TET3 influences in extreme conditions.

Širca, A.: Toplotna obremenitev Save dolvodno od Trbovelj -
Thermal Load of the Sava River Downstream from Trbovlje
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94
Bodoč e stanje z verigo HE, TET3 in brez
HE Suhadol. V študiji je bil prvikrat
ovrednoten vpliv izgradnje spodnjesavske
verige HE (IBE, 1963; 1995a; EIMV, 1996) na
temperaturno stanje Save. Rezultati kažejo, da
se vzdolž bazenov Vrhovo, Boštanj, Blanca,
Krško in Brežice temperature Save v kritič nih
poletnih razmerah zvišajo za 2.6 do 3.4 °C (v
stanju brez bazenov med VP Radeč e in VP
Č atež 0.8 °C), v izrednih razmerah pa za 5.3
do 6.6 °C (sliki 3 in 4). Pri tem gre le za
naravno ogrevanje zaradi pozitivne toplotne
bilance na vodni gladini. Največ ji delež dviga
ima zaradi velike površine bazen Brežice (0.9 -
1 .2 °C v kritič nih in 1 .6 - 1 .8 °C v izrednih
razmerah). Nižje ležeč i bazen Mokrice z dvigi
temperatur 0.4 - 0.5 °C v kritič nih in 0.6 - 1 .1 °C v izrednih razmerah dodatno zvišuje
temperaturo v mejnem profilu s Hrvaško.
Ocenjeno je bilo, da bo izgradnja verige
bazenov povzroč ila dvig temperature Save nad
zajetjem NE Krško za približno 1 .0 °C v
vsakoletnih kritič nih (primerjava s srednjo
visoko temperaturo) in do 5.3 °C v izrednih
razmerah (primerjava z najvišjo zabeleženo
temperaturo). V rač unih verige do državne
meje smo upoštevali bodoč o toplotno moč NEK 1379 MW
t
 (IBE, 1995b), vendar tako,
kot da bi hladilni sistem še vedno obratoval po
sedanjih pravilih vodnogospodarskega
dovoljenja (IJS-SEPO, 1989).
Glavni zaključ ek študije je, da poveč anje
moč i s TET2 na TET3 ne povzroč a bistvenih
težav termič ne polucije v Savi. Sama TET3 ne
bi imela omejitev glede na veljavne zakonske
predpise, razen v izrednih razmerah, ki pa bi
predvidoma nastopile le nekajkrat v življenjski
dobi objekta. Razlike med toplotnim
onesnaženjem TET2 in TET3 so majhne in se
vzdolž toka zmanjšujejo (sliki 5 in 6). Za zdaj
ni potrebe po omejevanju obratovanja verige
HE, razen v omejenem obsegu v bazenu
Suhadol, vendar le v izrednih razmerah.
The future state with the HPP chain, the
TET3 and without the Suhadol HPP. In this
study  the influence of the Sava River HPP
chain (IBE, 1963; 1995a; EIMV, 1996) on the
thermal state of the river was evaluated for the
first time. Under critical summer conditions,
an increase of temperature along the Vrhovo,
Boštanj, Blanca, Krško and Brežice reservoirs
is expected to equal 2.6 to 3.4 ºC (without the
reservoirs, an increase of 0.8 ºC occurs
between Radeč e GS and Č atež GS), while
under extreme conditions the increase would
reach 5.3 to 6.6 ºC (Figs 3 and 4). This
increase occurs due to the positive heat
balance at the surface of the reservoirs. The
greatest contribution to the increase is the one
from the Brežice Reservoir, with its large
surface area (0.9 - 1.2 °C in critical and 1.6 -
1.8 °C in extreme conditions). The
downstream Mokrice Reservoir, with increases
of 0.4 - 0.5 °C in critical and 0.6 - 1.1 °C in
extreme conditions, is an additional factor for
the increase of temperature at the SLO-CRO
state border. According to these estimations,
the Sava HPP chain might increase the intake
temperature at the Krško NPP by about 1.0 °C
in typical critical conditions, and up to 5.3 °C
in extreme conditions. In these calculations,
the future NEK thermal power of 1379 MW
t
(IBE, 1995b) was assumed, but only when
operating under presently valid water
management permit (IJS-SEPO, 1989).
The main conclusion of this study is that
an increase of power at Trbovlje would not
cause additional thermal problems
downstream. Except for some extreme events
occuring only a few times in a lifetime, there
would be no limitations in the operation of the
TET3, allowing for present environmental
legislation. The differences between the
influences of the TET2 and the TET3 would
be small, and would even decrease along the
stream (Figs 5 and 6). No need for limitation
of the HPP chain operation was detected,
except, again under extreme conditions, in the
Suhadol Reservoir.

Širca, A.: Toplotna obremenitev Save dolvodno od Trbovelj -
Thermal Load of the Sava River Downstream from Trbovlje
© Acta hydrotechnica 18/29 (2000), 83-95, Ljubljana
95
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Naslov avtorja - Author's Address
doc.dr. Andrej ŠIRCA,
IBE, Svetovanje, projektiranje in inženiring - IBE, Consulting Engineers
Hajdrihova 4, SI - 1001 Ljubljana