© Acta hydrotechnica 19/30 (2001), Ljubljana
ISSN 1581-0267
65
UDK / UDC: 504.4:510.5:556.53:582.26:627.81 Prejeto / Received : 24.8.2001
Izvirni znanstveni prispevek / Original scientific paper Sprejeto / Accepted : 21.12.2001
VLOGA PERIFITONSKIH ALG PRI DOLOČ ANJU EKOLOŠKO
SPREJEMLJIVEGA PRETOKA VODE V TEKOČ IH VODAH
THE ROLE OF PERIPHYTIC ALGAE IN THE DETERMINATION OF THE
ECOLOGICALLY ACCEPTABLE FLOW IN RUNNING WATERS
Nataša SMOLAR-ŽVANUT
Pri določ anju ekološko sprejemljivega pretoka (Qes) je treba poznati združbo perifitonskih alg, ker
predstavljajo zač etek prehranjevalne verige v tekoč ih vodah, se hitro odzivajo na spremembe v
okolju in ponujajo podlago in zatoč išč e številnim vodnim organizmom. Vrednost Qes mora
zagotavljati količ ino in kakovost vode, da ne pride do bistvenih sprememb v zgradbi in delovanju
združbe perifitonskih alg. V različ nih letnih obdobjih, v č asu nizkih pretokov vode v letih 1 998-
1 999, smo v reki Savi Dolinki na območ ju odvzema vode za HE Moste, in v reki Soč i, na območ ju
odvzema vode za HE Doblar in HE Ajba, ocenili vpliv odvzema vode na združbo perifitonskih alg in
na hidrološke znač ilnosti obeh rek ter opredelili vlogo perifitonskih alg pri Qes v tekoč ih vodah.
Rezultati so pokazali na kakovostne in koloč inske hidrološke, biološke, fizikalne in kemijske
spremembe pod pregradami. Rezultati hidroloških analiz so pokazali na bistveno spremenjen
hidrološki režim in prevladovanje prodnatih plavin s precejšnim deležem grobih zrn pod
pregradami. Posledica odvzema vode je, da fizikalno in kemijsko sestavo vode pod pregradami ne
uravnavajo več razmere v zgornjem delu poreč ja, temveč jo določ ajo dotoki pod mesti zajetja.
Stalen pretok in redko pojavljanje visokih voda pod pregradami sta vzrok za veliko raznolikost
perifitonskih alg in razlike v biomasi perifitonskih alg, v primerjavi s primerjalnimi mesti nad
pregradami.
Ključ ne besede: perifitonske alge, ekološko sprejemljiv pretok, odvzem vode
To determine ecologically acceptable flow (EAF), it is vital to have knowledge of the periphyton
community, since the algae represent the initial stage of the food chain in running waters, and
respond quickly to environmental changes and act as substrata and refuges for a number of water
organisms. The EAF value should assure such quantity and quality of water that substantial
changes in the composition and functioning of the periphyton community do not occur. In different
seasons of the years 1998-1999, during the period of low flows, the impact of abstractions on the
periphyton community and on hydrological characteristics was assessed in the Sava Dolinka River
in the abstraction section for the Moste power plant, and in the Soč a River, in the abstraction
sections for the Doblar and Ajba power plants. The role of periphytic algae in the determination of
EAF in flowing waters was defined. Results of the study show qualitative and quantitative
hydrological, biological, and physicochemical changes downstream of the dams. The results of the
hydrological analyses show substantial changes in the hydrological regime and a predominance of
gravel deposits with a considerable proportion of coarse grains downstream of the dams. Due to
abstractions, the physicochemical composition of water downstream of the dams is no longer
defined by conditions in the upper reaches of the river, but by tributaries downstream of the
catchment area. A constant flow, as well as a rare occurrence of high waters downstream of the
dams has given rise to a great diversity of periphyton and to differences in the periphyton biomass
here, compared with reference sites upstream of the dams.
Key words: periphytic algae, ecologically acceptable flow, water abstraction

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
66
1. UVOD
Za ohranjanje dinamike naravnih procesov
v vodotokih se je pojavila zahteva po
zagotavljanju ekološko sprejemljivega pretoka
vode (Qes). Definirali smo ga kot količ ino in
kakovost vode, ki zagotavlja ohranitev
naravnega ravnovesja v in ob vodotoku
(Vrhovšek et al.,1 994). Za določ itev ekološko
sprejemljivega pretoka vode (Qes) je, poleg
hidroloških, morfoloških in krajinskih
komponent vodnega ekosistema, potrebno med
ekološkimi parametri tudi poznavanje
perifitonskih alg. Perifitonske alge imajo velik
pomen pri ekološkem ravnovesju rek, saj
tvorijo organsko snov in imajo pomen pri
pretoku snovi in energije. Perifitonske alge so
najpomembnejši primarni producenti v
majhnih vodotokih in so hkrati uporabni
ekološki indikatorji stopnje onesnaženosti
(Wilhm et al., 1978).
Č eprav so v več ini raziskav določ evanja
Qes glavno vlogo namenjali ribam in
nevretenč arjem, so pri določ anju Qes na
potoku Radurlsbach v Avstriji leta 1 985 že
upoštevali perifitonske alge (Jäger et al.,
1 985). Pri določ itvi Qes za Alpbacher Ache v
Avstriji so opravili analizo hidroloških,
morfoloških in fizikalnih ter kemijskih
parametrov, analizo sedimentov, med
biološkimi parametri pa so vzorč evali
perifitonske alge in več je vodne nevretenč arje
(Pehofer et al., 1988). Rezultate analiz
perifitonskih alg so upoštevali pri določ anju
Qes na vodotokih Töss, Schächenbach in
Niemet v Švici (Bundi & Eichenberger, 1989).
Na Hrvaškem pa so pri določ anju Qes na reki
Cetini (Mišetić et al., 1 986) in na reki Žrnovici
(Bonacci et al., 1998) opravili tudi analize
perifitonskih alg. Pri določ anju Qes v Sloveniji
smo upoštevali rezultate perifitonskih alg, med
drugim tudi na reki Soč i (Vrhovšek et al.,
1 996a), Rižani (Smolar et al., 1 997), Selšč ici
(Smolar-Žvanut et al., 1 999a), Meži (Smolar-
Žvanut et al., 1 999b) in Savi Dolinki
(Vrhovšek et al., 1999).
1. INTRODUCTION
To maintain the dynamics of natural
processes in watercourses, it is vital to ensure
that the flow is ecologically acceptable.
Ecologically acceptable flow (EAF) may be
defined as such quantity and quality of water
which preserves the ecological balance in a
river and in the riparian zone (Vrhovšek et al.,
1994). To determine EAF, not only data on
hydrological, morphological, and landscape
components of an aquatic ecosystem are
needed, but also knowledge of periphyton. The
algae play a major role in the maintenance of
the ecological balance in rivers, since they
produce organic matter and are of importance
in the flow of matter and energy. They are the
most significant primary producers  in streams
and can also be used as ecological indicators
of pollution (Wilhm et al., 1978).
Most research on EAF determination deals
mainly with  fish and invertebrates. In 1985 a
study was carried out to determine the EAF for
the Radurlsbach Stream, in Austria, in which
periphyton was taken into account (Jäger et al.,
1985). The determination of the EAF for the
Alpbacher Ache Stream in Austria included an
analysis of hydrological, morphological, and
physicochemical parameters, a sediment
analysis and, among biological parameters, a
sampling of periphyton and of
macroinvertebrates (Pehofer et al., 1988). The
periphyton was analysed when the EAF was
determined for the Töss, Schächenbach, and
Niemet rivers in Switzerland (Bundi &
Eichenberger, 1989). In Croatia, periphyton
analyses were carried out for the Cetina
(Mišetić et al., 1 986) and Žrnovica (Bonacci et
al., 1998) rivers for the same purpose. In
Slovenia, periphyton analyses were taken into
account to determine the EAF for the Soč a
(Vrhovšek et al., 1 996a), Rižana (Smolar et al.,
1 997), Selšč ica (Smolar-Žvanut et al., 1 999a),
Meža (Smolar-Žvanut et al., 1 999b), and Sava
Dolinka (Vrhovšek et al., 1999) rivers.

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
67
2. MESTO RAZISKAV
Na reki Soč i smo izbrali območ ja odvzema
nad pregrado (SO1) in pod pregrado Podsela
(SO2, SO3), pod pregrado Ajba (SO4) ter na
pritoku Ušnica (USN) (slika 1),  na reki Savi
Dolinki pa nad (SA1, SA2) in pod pregrado
Moste (SA3, SA4, SA5) ter na pritokih
Završnica (ZAV) in Radovna (RAD) (slika 2).
Na vseh območ jih odvzema smo vzorč evali
perifitonske alge v različnih hidroloških
okoljih (glede na hitrost in globino vode) ter
merili hidrološke in fizikalno kemijske
parametre. Na območ ju odvzema smo število
odvzemnih mest izbrali glede na širino struge,
strukturo habitatov, globino vode in hitrost
vodnega toka. Območ je odvzema je obsegalo
preč ni prerez od levega do desnega brega
struge, v primeru zastajanja vode pa tudi
najbližji gorvodni in dolvodni tolmun.
2. STUDY SITE
In the Soč a River, sampling sites were
selected upstream (SO1) and downstream
(SO2, SO3) of the  Podsela Dam, downstream
of the Ajba  Dam (SO4), and in the Ušnica
Tributary (USN) (Figure 1). In the Sava
Dolinka River, they were selected upstream
(SA1, SA2) and downstream (SA3, SA4, SA5)
of the Moste Dam, and in the Završnica (ZAV)
and Radovna (RAD) (Figure 2) tributaries. At
all the sampling sites, the periphyton was
sampled in different hydrological
environments (according to velocity and water
depth), and  hydrological and physicochemical
parameters were measured. The number of
sampling points at a sampling site was
determined according to river bed width,
habitat structure, water depth, and current
velocity. A sampling site comprised a cross-
channel transect from the left to the right bank
and, in the case of stagnant water, the nearest
upstream and downstream pools.
Slika 1 . Odvzemna mesta v reki Soč i in v potoku Ušnica.
Figure 1 . Sampling points in the river Soč a and in the stream Ušnica.
PLAVE
ANHOVO
AJBA
DOBLAR
TOLMIN
USN
SOČ A
SOČ A
SO 3
SO 4
SO 2
UŠNICA
SO 1

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
68
Slika 2. Odvzemna mesta v reki Savi Dolinki, v reki Radovni in v potoku Završnica.
Figure 2. Sampling points in the river Sava Dolinka, in the river Radovna
and in the stream Završnica.
2.1 ZNAČ ILNOSTI HE MOSTE, HE
ZAVRŠNICA IN HE ZASIP
HE Moste obratuje kot prva več ja
elektrarna na reki Savi Dolinki. Betonska,
loč no-težnostna pregrada je s 60 m višine tudi
najvišja pregrada v Sloveniji. HE Moste je
akumulacijska elektrarna za proizvodnjo vršne
energije. Vtoč ni objekt leži ob levem boku
pregrade, od tam je speljan dovodni rov v
dolžini 840 m do strojnice. V dovodni rov so
speljane tudi zaledne vode iz potoka
Završnica. HE Moste sestavlja, skupaj s HE
Završnica na potoku Završnica, enoten
energetski sistem. V HE Moste so bili prvotno
vgrajeni trije agregati, s požiralnostjo 28.5
m
3
/s. Sistem je bil dograjen leta 1977 z
vgradnjo č etrtega agregata v strojnici HE
Moste, s požiralnostjo 6 m
3
/s in s priključ itvijo
dovodnega cevovoda HE Završnica. Č etrti
agregat obratuje v pogojih vršnega
obratovanja.
Obratovanje HE Moste je vezano na
količino dotoka vode v akumulacijo in
obratuje glede na potrebe energije v državi,
obič ajno v dnevnih urah. V primeru, da je
dotok vode v akumulacijo 14 m
3
/s, obratuje
HE Moste od 6. ure zjutraj do 22. ure zveč er,
in sicer z odvzemom vode 20 m
3
/s, razen v
2.1 CHARACTERISTICS OF THE
MOSTE, ZAVRŠNICA, AND ZASIP
POWER PLANTS
The Moste HPP is the first larger power
plant which was built on the  Sava Dolinka
River. The concrete arch-gravity dam, 60
metres high, is the highest in Slovenia. The
power plant  is a reservoir generating  peak
energy.  The intake structure is located on the
left side of the dam, where a 840-metre long
power tunnel leads  to the power station. The
Završnica Stream flows into the power tunnel.
Along with the Završnica HPP,  located on the
Završnica Stream, the Moste HPP constitutes a
uniform hydropower system. Initially, the
Moste HPP had three generators with a design
flow  of 28.5 m
3
/s. On completion of the
system in 1977, the power station of the Moste
plant was fitted with a fourth generator with a
design flow of 6 m
3
/s, and was connected with
the power channel of the Završnica HPP. The
fourth generator operates in peak energy
conditions.
The operation of the Moste HPP depends
on the quantity of the inflow into the reservoir.
It is operative according to electricity
requirements, usually during the daytime. If
inflow into the reservoir is 14 m
3
/s, the plant
operates from 6 a.m. to 10 p.m., with
abstractions of 20 m
3
/s, except from 1 p.m. to
SA 3
ZAVRŠNICA
SA 2
SA 1 SAVA DOLINKA
SA 5
He ZASIP
RADOVNA ZAV
SAVA BOHINJKA
HRUŠICA
JESENICE
BLED
SA 4
RAD

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
69
č asu med 1 3. in 1 8. uro z odvzemom vode od
4 do 10 m
3
/s. Na začetku obratovanja
elektrarne se v povpreč ju v č asu dveh minut
poveč a količ ina vode iz 0 na 1 0 m
3
/s oz. v
petih minutah iz 0 na 20 m
3
/s.
HE Moste v glavnem ne obratuje v sobotah
in nedeljah, ker se voda nabira v akumulacijo,
zato so pretoki na v.p. Blejski most takrat
najnižji. Obratovanje HE Moste povzroč a v
dolvodni strugi Save Dolinke, na odseku od
vtoka vode nazaj v Savo Dolinko do HE
Mavč ič e, hitro poveč evanje in zmanjševanje
pretokov.
Pod pregrado Moste se, zaradi zajezitve,
zbira le voda iz drenaž, del vode iz Završnice
in nekaj vode, ki se pretaka pod pregrado za
HE Zasip na Radovni. V primeru, da HE
Moste ne obratuje, doteka v strugo Save
Dolinke pred Piškotarjevim mostom le voda,
ki se pretaka pod pregrado HE Moste in
Radovna iz HE Zasip. Zaradi odvzema vode za
HE Moste je Sava Dolinka pod vplivom
odvzema vode na dolžini 2470 m.
Za HE Zasip  na reki Radovni je odvzem
vode iz Radovne v višini 7.5 m
3
/s. Zaradi
pušč anja jezu in zapornic se v strugi pretaka
nekaj deset litrov vode. Dolžina odseka
Radovne, ki je pod vplivom odvzema vode za
HE Zasip, je 21 75 m, dolžina Save Dolinke, ki
je pod vplivom odvzema za HE Zasip pa je
1625 m.
2.2 ZNAČ ILNOSTI HE DOBLAR, HE
AJBA, HE PLAVE
Soč a je bila energetsko zanimiva že v č asu
Avstro-Ogrske, ko so jo pričeli prvič intenzivneje preuč evati, z namenom izrabe
njene vodne moč i. Kasneje so tudi Italijani
nadaljevali s preuč evanjem Soč e in pritokov
ter zgradili tudi prve elektrarne (HE Log, HE
Plužna, 1 930-1 932). V letu 1 939 je bila
zgrajena HE Doblar in leta 1940 HE Plave. V
letih od 1971 do 1975 je bila zgrajena HE
Ajba na jezovnih zgradbah HE Plave, od leta
1984 pa je v pogonu tudi HE Solkan. Pod
pregrado Podsela do državne meje zaradi
energetske izrabe ni več naravnega pretoč nega
režima (Vrhovšek et al., 1 996a).
6 p.m. when abstractions amount to from 4 to
10 m
3
/s. When it starts to operate in the
morning, the abstraction increases, on an
average, from 0 to 10 m
3
/s in two minutes, or
from 0 to 20 m
3
/s in five minutes.
The Moste HPP is not in operation, as a
rule, on Saturdays and Sundays, when water
flows into the reservoir. Therefore, flows at
the Blejski most Gauging Station (g.s.) are
lowest at that time. The operation of the power
plant causes a rapid increase and decrease of
flows downstream of the Sava Dolinka River,
in the section from the inflow of water back
into the Sava Dolinka River to the Mavč ič e
HPP.
Due to damming, downstream of the dam
Moste, in the bed of the Sava Dolinka River,
water is collected from the draining s ystem,
part of the water from the Završnica Stream,
and some water flowing downstream of the
dam to the Zasip HPP on the Radovna River.
If the Moste HPP is not operational, then in the
river bed, before the  Bridge Piškotarjev most,
water flows from downstream of the dam for
the Moste HPP and from the Radovna River
for the Zasip HPP. Thus, a 2470 m long
section of the Sava Dolinka River is adversely
affected by abstractions for the Moste HPP.
For the Zasip HPP on the Radovna River,
there are abstractions of 7.5 m
3
/s. Due to gate
and sluice leakage, some tens of litres flow
into the river bed. The abstractions for the
Zasip HPP exert an effect on a 2175 m long
section of the Radovna River and on a 1625 m
long section of the Sava Dolinka River.
2.2 CHARACTERISTICS OF THE
DOBLAR, AJBA, AND PLAVE HPP
The Soč a River as a source of hydropower
was already considered interesting at the time
of the Austro-Hungarian Empire when this
aspect of its use was more intensely
investigated for the first time. Later, the
Italians continued to study the Soč a River and
its tributaries for this purpose, and thus the
first hydropower plants were built (Log,
Plužna, 1 930-1 932). The Doblar and Plave
power plants were constructed in 1939 and
1940 respectively. In 1971-1975, the Ajba
HPP was built by means of the Plave HPP
dams. The Solkan HPP has been operational
since 1984. As a consequence of power
utilisation, there is no natural flow regime
downstream of the  Podsela Dam to the Italian
border (Vrhovšek et al., 1996a).

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
70
Pregrada  Podsela za HE Doblar je
betonska, loč no težnostna in je s 55 m višine
druga najvišja pregrada v Sloveniji. Pregrada
Ajba leži 4.5 km dolvodno od elektrarne
Doblar. Odvzem vode med pregrado Podsela
in HE Doblar je na dolžini 4320 m, med
pregrado Ajba in HE Plave pa 7950 m.
Največ ji mogoč odvzem vode iz reke Soč e
na pregradi Podsela za potrebe HE Doblar je
96 m
3
/s; v primeru, da so pretoki vode višji in
se akumulacija ne polni, voda teč e preko
pregrade.
V letu 1 998 se je prič ela gradnja novih
hidroelektraren HE Doblar II in HE Plave II,
pri č emer  bo skupen inštaliran pretok vode
HE Plave I in II 180 m
3
/s, HE Doblar I in II
180 m
3
/s, HE Ajba, ki se nahaja v pregradi
Ajba, pa bo ukinjena.
V strugi reke Soč e pod pregrado Podsela se
pretaka le voda iz potoka Ušnica in majhne
količ ine vode, ki se precejajo skozi izpuste
zapornic pregrade Podsela. Levi pritok
Vogršč ek v sušnem obdobju nima vode, ker je
izrazito hudourniškega znač aja s kraškimi
znač ilnostmi.
Pod pregrado Ajba se skozi zapornico
spušč a pretok vode 0.5 m
3
/s, opredeljen v
vodnogospodarskem dovoljenju za HE Plave.
Na odseku od pregrade Ajba do izpusta vode
iz HE Plave so manjši hudourniški pritoki
(Vrhovšek et al., 1996a).
3. MATERIAL IN METODE DELA
3.1 Č AS VZORČ EVANJA
Vzorč evanje perifitonskih alg, določ anje
biomase perifitonskih alg in merjenje
hidroloških parametrov je potekalo v letih
1998 in 1999, v obdobju nizkih pretokov vode.
Na Soči smo vzorčevali dne 3.2.1 998,
20.5.1998, 25.8.1998 in 30.11.1998, na Savi
Dolinki pa 9.2.1998, 3.6.1998, 24.8.1998 in
7.1.1999. Linijski odvzem vzorca plavin smo
na Soč i opravili dne 1 9.7.1 999, na Savi
Dolinki pa dne 6.7.1999.  Meritve na območ ju
odvzema SA5 (Blejski most) v Savi Dolinki so
bile vedno izvedene v č asu, ko HE Moste ni
obratovala, torej ni bilo poveč anega pretoka
vode, izmerjenega gorvodno od pregrade
Moste.
The Podsela Dam for the Doblar HPP is a
concrete arch-gravity dam, 55 metres in
height, the second highest in Slovenia. The
Ajba Dam is situated 4.5 km downstream of
the Doblar HPP. The abstraction section from
the Podsela Dam to the Doblar HPP is 4320 m
long, and that from the Ajba Dam to the Plave
HPP is 7950 m long.
At the Podsela Dam, the highest possible
abstraction amount for the Doblar HPP is 96
m
3
/s. If flows are higher and the reservoir is
not being filled, water flows over the dam.
In 1998 the construction of the Doblar II
and Plave II power plants began. Joint design
flow for the Plave I and Plave II power plants
will be 180 m
3
/s, the same as the design flow
for the Doblar I and Doblar II power plants.
The Ajba HPP, situated within the  Ajba Dam,
will stop operating.
In the bed of the Soč a River, downstream of
the Podsela Dam, water flows from the Ušnica
Stream and small quantities of water trickle
through, due to gate leakage at the Podsela
Dam. In the dry season, the left Vogršč ek
Tributary dries up because of its distinctively
torrential character and karst features.
Downstream of the Ajba Dam, the flow
through the gate is 0.5 m
3
/s, according to the
water management operating licence for the
Plave HPP. In the section from the  Ajba Dam
to the discharge from the Plave HPP, there are
smaller torrential tributaries (Vrhovšek  et al.,
1996a).
3. MATERIAL AND METHODS
3.1 SAMPLING
A sampling of periphyton, determination of
periphyton biomass, and measurement of
hydrological parameters was carried out in the
period of low flows in 1998 and 1999. In the
Sava River, the sampling was conducted on
February 3, May 20, August 25, and
November 30, 1998, and in the Sava Dolinka
River, on February 9, June 3, August 24, 1998,
and on January 7, 1999. The Wolman Count of
sediment samples was performed in the Soč a
River on July 19, 1999, and in the Sava
Dolinka River on July 6, 1999. Measurements
conducted at sampling site SA5 (Blejski most
Gauging Station) in the Sava Dolinka River
were always carried out when the Moste HPP
was not in operation. So there was no increase
in flow measured upstream of the Moste Dam.

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
71
3.2 HIDROLOŠKI PARAMETRI
Hitrost vodnega toka in pretok vode smo
merili s hidrometrič nim krilom SEBA Mini
Current Meter MI. Na vseh odvzemnih mestih,
kjer smo vzorčevali, smo merili hitrost
vodnega toka 3 cm nad dnom. Povpreč no
hitrost v merskih vertikalah nad odvzemnimi
mesti smo izmerili na 0.4 globine vode,
merjeno od dna struge. Č as meritve v
posamezni toč ki je bil eno minuto.
Merjene hidrološke parametre ter podatke o
vodostajih, ki smo jih povzeli po MOP - HMZ,
smo obdelali z rač unalniškim programom
(VGI, 1992) na Vodnogospodarskem inštitutu
v Ljubljani.
Določ ili smo prispevno področ je (F) za
območja odvzema in s pomoč jo
računalniškega programa (VGI, 1 992)
izrač unali vrednosti sQs (srednji pretok - je
povpreč je srednjih dnevnih pretokov v m
3
/s za
vsako leto v obravnavanem obdobju), sQn
(srednji nizek pretok - je povpreč je najnižjih
pretokov v m
3
/s v letu v obravnavanem
obdobju), nQn (najmanjši nizek pretok- je
najnižji zabeležen pretok v m
3
/s v
obravnavanem obdobju), vQv (največ ji pretok
- je najvišji zabeležen pretok vode v m
3
/s v
obravnavanem obdobju), Q
300d
 (pretok, ki traja
300 dni na leto) in Q
347d
 (pretok, ki traja 347
dni na leto).
Cilj analize hidroloških podatkov je bila
določ itev hidroloških parametrov, ki kažejo
reč ni režim na odseku Soč e pod pregrado
Podsela in pod pregrado Ajba ter na odseku
Save Dolinke od pregrade HE Moste do
Blejskega mostu za posamezne hidrološke
prereze, za naslednje vodne režime:
1. brez odvzema – pretoki pridobljeni s
predpostavko, da na obravnavnem območ ju
ni odvzema vode za hidroelektrarno
2. z odvzemom – pretoki, ki so na
obravnavanem območju pri sedanjem
obratovanju hidroelektraren oziroma
odvzemih vode na Savi Dolinki, Završnici,
Radovni in Soč i.
3.2 HYDROLOGICAL PARAMETERS
Current velocity and flow were measured
with a SEBA Mini Current Meter MI. At all
the sampling points, the current velocity was
measured 3 cm above the bottom. The average
velocity was measured in measuring verticals
above the sampling points at 0.4 of water
depth from the bottom of the river bed. The
duration of individual measurements was one
minute per sampling point.
The results of the measurements of
hydrological parameters, and the data on water
levels according to the Ministry of
Environment and Physical Planning  w e r e
processed using a computer programme (VGI,
1992) at the Water Management Institute,
Ljubljana.
The catchment area (F) of sampling sites
was determined and the following values were
calculated using a computer programme (VGI,
1992): sQs (mean flow – the average of mean
daily flows in m
3
/s for every year in the
considered period); sQn (mean minimum flow
- the average of minimum flows in m
3
/s for
every year in the considered period); nQn
(minimum flow - the minimum flow in m
3
/s in
the considered period); vQv (maximum flow -
the maximum flow in m
3
/s in the considered
period); Q
300d
 (the flow lasting for 300 days a
year); and Q
347d
 (the flow lasting for 347 days
a year).
The intent of an analysis of the hydrological
data was to determine the hydrological
parameters characteristic to the Soč a River
regime in the section downstream of the
Podsela Dam and downstream of the Ajba
Dam, and that of the Sava Dolinka River, in
the section from the dam of the Moste HPP to
the gauging station at Blejski most, for
individual hydrological cross-sections under
the following water regime:
1. without abstractions – the flows were
determined on the supposition that there
were no abstractions for the power plant in
the sections  under consideration,
2. with abstractions – the flows were
determined for the present operation of
power plants or for abstractions in the Sava
Dolinka, Radovna, and Soč a rivers and the
Završnica Stream in the sections under
consideration.

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
72
3.3 ANALIZA PLAVIN
Analizo plavin smo opravili z linijskim
nač inom odvzema vzorca s programom ZPP,
napisanem v programskem okolju EXCEL
(Mikoš, 1999). Izdelali smo krivuljo zrnavosti
podlage in krovnega sloja s pomoč jo prerač una
linijske – številčne analize in togim
sestavljanjem s Fullerjevo zrnavostno krivuljo.
Iz vsotne zrnavostne krivulje je mogoč e
odč itati znač ilna zrna, kot so d
90
, d
84
 in d
16
.
Konč ni rezultat rač una v obliki preglednice je
bila določ itev aritmetič nega srednjega zrna
prodnatih plavin d
m
 in 90-odstotnega zrna
rinjenih plavin d
90
.
3.4 FIZIKALNI IN KEMIJSKI
PARAMETRI
Električ no prevodnost in temperaturo smo
merili z instrumentom MA 5950 (Iskra), pH z
instrumentom MA 5721 (Iskra), vsebnost
raztopljenega kisika in nasič enost s kisikom pa
z oksimetrom OM 8.
3.5 BIOLOŠKI PARAMETRI
3.5.1 VZORČ EVANJE PERIFITONSKIH
ALG IN OBDELAVA VZORCEV
Vzorce perifitonskih alg za kvalitativno
analizo smo pobirali tako, da smo postrgali
površino prodnikov, kamnov, skal, peska,
makrofitov in potopljenega lesa na območ ju
odvzema. Vzorce perifitonskih alg smo že na
terenu fiksirali tako, da je bila konč na
koncentracija formalina v vzorcih približno 5
odstotkov.
Vzorce za kvantitativno analizo perifitonske
združbe smo pobirali samo s plavin premera
50 do 200 mm. V laboratoriju smo ovrednotili
suho težo, organsko snov (suha teža brez
pepela) po metodiki APHA.AWWA.WPCP
(1992) in koncentracijo klorofila-a s
filtriranjem skozi Watman GF/C filtre ter z
ekstrahiranjem z vročim metanolom
(Vollenweider, 1974). Vrednosti biomase
perifitonskih alg smo prerač unali na m
2
 plavin.
3.3 SEDIMENT ANALYSIS
An analysis of the sediments was carried
out with the use of the Wolman Count of
samples with a ZPP  computer programme
prepared in the environment of EXCEL
(Mikoš, 1999). A grain-sized distribution
curve and a cover layer curve were designed
by means of the Wolman Count-numerical
analysis and a rigid combination with the
Fuller grain-sized distribution curve. The
cumulative grain-sized distribution curve
displays characteristic grains such as d
90
, d
84
,
and d
16
. The final result of the calculation, in
the form of a table, was the determination of
the mean grain of the gravel deposits, d
m
, and
90% of a bed load grain, d
90
.
3.4 PHYSICOCHEMICAL
PARAMETERS
Electrical conductivity and temperature
were measured with an MA 5950 (Iskra), and
the pH was measured with an MA 5721
(Iskra). The dissolved oxygen content and
oxygen saturation were measured using an
oxymeter OM 8.
3.5 BIOLOGICAL PARAMETERS
3.5.1 PERIPHYTON SAMPLING AND
PROCESSING
Periphyton samples intended for a
qualitative analysis were taken by scraping off
the surface area of pebbles, stones, rocks,
sand, macrophytes, and sunken wood found at
a sampling site. The samples were treated with
formaline in the field, so that the concentration
of formaline in the samples was around 5%.
Samples intended for a quantitative analysis
of the periphyton community were taken from
deposits 50 mm to 200 mm in diameter. Dry
weight and organic matter (ash-free dry
weight) were assessed in the laboratory using
the APHA.AWWA.WPCP technique (1992).
The chlorophyll-a concentration was
determined with the use of filtration through
Watman GF/C filters and extraction with hot
methanol (Vollenweider, 1974). The values of
periphyton biomass were calculated per square
meter of deposits.

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
73
V laboratoriju smo perifitonske alge
pregledali pod svetlobnim mikroskopom, s
fazno kontrastno optiko pri  poveč avah do
1000-krat. Pri pregledu vzorcev smo ocenili
pogostost posameznih taksonov (vrst)
perifitonskih alg (Grbović , 1 994).
3.6 STATISTIČ NE ANALIZE
Za posamezna območ ja odvzema smo
izrač unali Pantle - Buckov saprobni indeks.
Primerjavo združb perifitonskih alg med
odvzemnimi mesti in med območ ji odvzema
smo izvršili s pomoč jo podatkov vrstnega
sestava in relativne pogostosti prisotnih vrst.
Podobnost oziroma različnost združb
perifitonskih alg smo vrednotili z
multivariantno klastersko analizo (Bray -
Curtisov koeficient podobnosti) (Clarke in
Warwick, 1 990), s pomoč jo podatkovnega
sistema “DABA”.
4. REZULTATI IN DISKUSIJA
4.1 HIDROLOŠKI PARAMETRI
Rezultati hidroloških meritev in analiz so
pokazali na bistveno spremenjen hidrološki
režim na Soč i, pod pregradama Podsela in
Ajba, in na Savi Dolinki, pod pregrado Moste,
ki se odraža v zmanjšanju pretokov vode,
hitrosti vodnega toka in globini vode, nadalje v
spremenjeni krivulji trajanja pretokov vode ter
predvsem zastajanju in odlaganju plavin nad
pregradami ter s tem povzroč eno t.i. dolvodno
erozijo (Smolar-Žvanut, 2000). Vsi merjeni
hidrološki parametri so pokazali, da pod
pregradama Podsela in Moste niso bile
zagotovljene vrednosti Qes.
Do največ jih razlik v Savi Dolinki je prišlo
v vrednostih najmanjših nizkih pretokov vode
nQn na območ jih odvzema SA3 in SA4, saj je
voda tekla preko pregrade le nekaj dni na leto.
Manjše razlike v vrednosti sQs so bile
izrač unane na območ ju odvzema SA5, ker
vrednost ne kaže nihanja v pretoku vode zaradi
delovanja HE Moste in HE Završnica.
Območje odvzema SA5 je namreč izpostavljeno urnim in dnevnim spremembam
v pretoku vode, zaradi obratovanja HE Moste
In the laboratory, periphytic algae were
examined under a light microscope by means
of phase contrast optics for magnifications of x
1000 in order to assess the frequency of
individual  taxa (species) (Grbović , 1 994).
3.6 STATISTICAL ANALYSES
The Pantle-Buck Saprobic Index was
calculated for individual sampling sites. A
comparison of  periphyton communities within
individual sampling points and within
sampling sites was made with the use of data
on species composition and the relative
frequency of species found. Similarities and
differences among periphyton communities
were assessed by means of a multivariate
cluster analysis (Bray-Curtis coefficient of
similarity) (Clark and Warwick, 1990) and the
DABA data system.
4. RESULTS AND DISCUSSION
4.1 HYDROLOGICAL PARAMETERS
Results of the hydrological measurements
and analyses show substantial changes in the
hydrological regime of the Soča River
downstream of the  Podsela and Ajba dams,
and of the Sava Dolinka River, downstream of
the Moste Dam. The changes concerned
reduced flows, a decrease in current velocity
and, in water depth, an altered flow duration
curve, and, particularly, the stagnation and
deposition of sediments upstream of the dams,
resulting in erosion downstream (Smolar-
Žvanut, 2000). All the measurements suggest
that downstream of the Podsela and Moste
dams, the flow was not ecologically
acceptable.
In the Sava Dolinka River, the most
substantial differences were found in the
values of the minimum flow (nQn) at sampling
sites SA3 and SA4, since water was flowing
over the dam just a few days a year.  Less
substantial differences in the values of the
mean flow (sQs) were calculated at sampling
site SA5, since they show no fluctuations in
flows due to the operation of the Moste and
Završnica power plants. For the latter site is
subjected to hourly and daily changes in flow
induced by the operation of the power plants.

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
74
in HE Završnica. Zaradi odvzema vode za HE
Zasip na Radovni se je vrednost srednjega
nizkega pretoka (za obdobje od 1961 do 1995)
na območ ju odvzema RAD iz 1 .68 m
3
/s
zmanjšala na 0, oz. Radovna je zaradi
obratovanja HE Zasip obč asno presahnila
(preglednica 1).
Owing to abstractions for the Zasip HPP on
the Radovna River, the values of the mean
minimum flow (sQn) for the period 1961-1995
were reduced from 1.68 m
3
/s to 0 at sampling
site RAD; that is, the Radovna River
periodically dried up due to the operation of
the Zasip HPP (Table 1).
Preglednica 1. Glavni hidrološki parametri za Savo Dolinko in Radovno za obdobje od 1961 do
1 995 za vodni režim brez odvzema vode oz. z odvzemom vode.
Table 1. Hydrological parameters for the Sava Dolinka River and the Radovna River for the period
1961-1995 for water  regimes with and without water abstraction .
hidrološki prerez
Hydrological  cross-section
območ je
odvzema
Sampling
site
F
(km
2
)
sQs
(m
3
/s)
sQn
(m
3
/s)
nQn
(m
3
/s)
vQv
(m
3
/s)
Q300d
(m
3
/s)
Q347d
(m
3
/s)
Sava Dolinka v.p. Jesenice
Sava Dolinka River at g.s. Jesenice
SA1 257.6 10.65 4.12 2.46 261 5.65 4.43
Sava Dolinka pregrada Moste – brez
odvzema
Sava Dolinka River at the dam Moste -
without abstractions
/ 300.1 13.53 5.97 3.62 310 8.22 6.44
Sava Dolinka  pod Završnico – brez
odvzema
Sava Dolinka River downstream of the
confluence with the Završnica Stream -
without abstractions
SA3 325.9 14.70 6.48 3.93 337 8.94 7.01
Sava Dolinka pod Završnico – z
odvzemom
Sava Dolinka River downstream of the
confluence with the Završnica Stream -
with abstractions
SA3 325.9 0.63 0.11 0.048 337 0.17 0.13
Radovna izliv – brez odvzema
Outfall of the Radovna River -
without abstractions
RAD 170.4 8.03 1.68 1.02 113 2.77 1.90
Radovna izliv – z odvzemom
Outfall of the Radovna River -
with abstractions
RAD 170.4 3.47 0.00 0.00 113 0.0005 0.00
Sava Dolinka pod Radovno – brez
odvzema
Sava Dolinka River downstream of the
confluence with the Radovna River -
without abstractions
SA4 496.8 22.74 8.42 5.03 450 12.12 9.09
Sava Dolinka pod Radovno – z
odvzemom
Sava Dolinka River downstream of the
confluence with the Radovna River -
with abstractions
SA4 496.8 4.11 0.11 0.048 450 0.17 0.13
Sava Dolinka v.p. Blejski most – brez
odvzema
Sava Dolinka River at g.s. Blejski most -
without abstractions
SA5 505.4 22.96 8.47 5.06 453 12.20 9.18
Sava Dolinka v.p. Blejski most – z
odvzemom
Sava Dolinka River at g.s. Blejski most -
with abstractions
SA5 505.4 22.96 2.87 0.70 453 10.12 6.08

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
75
Preglednica 2. Glavni hidrološki parametri za Soč o in Ušnico za obdobje od 1 961 do 1 990 za vodni
režim, brez odvzema vode oz. z odvzemom vode.
Table 2. Hydrological parameters for the Soč a River and the Ušnica Tributary for the period 1 961 -
1995 for water  regimes with and without water abstraction.
hidrološki prerez
Hydrological  cross-section
območ je
odvzema
Sampling
site
F
(km
2
)
sQs
(m
3
/s)
sQn
(m
3
/s)
nQn
(m
3
/s)
vQv
(m
3
/s)
Q
300d
(m
3
/s)
Q
347d
(m
3
/s)
Soč a v.p. Kobarid
Soč a River at g.s. Kobarid
/ 434.7 34.1 7.96 4.59 664 12.10 8.96
Soč a pregrada Podsela
Soč a River at the Podsela Dam
/ 1244 80 16 10 2140 27.43 20.04
Ušnica pri pregradi Ušnik
Ušnica stream at the Ušnik Dam
USN 9.43 0.60 0.03 0.02 2140 / /
Soč a pod pregrado Podsela – brez odvzema
Soč a River downstream of the  Podsela Dam -
without abstractions
SO2 1254 80.6 16.03 10.0 2140 27.47 20.08
Soč a pod pregrado Podsela – z odvzemom
Soč a River downstream of the Podsela Dam -
with abstractions
SO2 1254 22.5 0.13 0.12 2140 0.64 0.25
Soč a pod pregrado Ajba – brez odvzema
Soč a River downstream of the Ajba Dam -
without abstractions
SO4 1345 86.2 17.8 10.5
>
2140
29.70 21.22
Soč a pod pregrado Ajba – z odvzemom
Soč a River downstream of the Ajba Dam -with
abstractions
SO4 1345 33.1 1.0 1.0
>
2140
1.41 1.12
Primerjava hidroloških parametrov za Soč o
za obdobje 1 961 -1 990 na območ jih odvzema
je pokazala, da je na območ ju odvzema SO2 in
SO4, zaradi odvzema vode za HE Doblar,
prišlo do zmanjšanja vrednosti sQn in nQn za
več kot 90 odstotkov (preglednica 2).
Merjeni pretoki Save Dolinke pod pregrado
Moste na območ ju odvzema SA3 in SA4 so v
č asu naših meritev zaradi odvzemov vode za
HE Moste, HE Završnica in HE Zasip dosegali
največ 5.9 % pretoka Save Dolinke, merjenega
na primerjalnem območ ju odvzema SA1 ,
medtem ko so bili pretoki na Soč i pod
pregrado Podsela vsaj za 97.6 % in pod
pregrado Ajba vsaj za 81 .3 % nižji od
pretokov na primerjalnem območ ju SO1 (Smolar-Žvanut, 2000). Posledič no so bile na
območ jih odvzema pod pregradami izmerjene
tudi nižje lokalne hitrosti ob dnu in povpreč ne
hitrosti vodnega toka. Zaradi nizkih pretokov
vode je voda pod pregradami tudi zastajala.
Vsi merjeni hidrološki parametri so
pokazali na zmanjšanje raznolikosti vodnih
habitatov za vodne organizme. Zaradi
odvzema vode je na odseku z zmanjšanim
pretokom vode prišlo do opaznega zmanjšanja
v velikosti in številu brzic, podobno kot na
reki Töss v Švici (Bundi et al., 1990).
Vrednotenje pretočnih hitrosti vode je
pomembno tudi kot del določ anja Qes (Mikoš,
1996).
    A comparison of hydrological parameters
for the Soč a River for the period 1 961 -1 990
shows a decrease in the values of the mean
minimum flow (sQn) and the minimum flow
(nQn) at sampling sites SO2 and SO4 by over
90%, which can be attributed to abstractions
for the Doblar HPP (Table 2).
In the Sava Dolinka River, flows measured
downstream of the Moste Dam at sampling
sites SA3 and SA4 attained, at the most, 5.9 %
of the flows measured at reference site SA1
due to abstractions for the Moste, Završnica,
and Zasip power plants. In the Soč a River, on
the other hand, flows measured downstream of
the Podsela Dam were at least 97.6 %, and
those measured downstream of the Ajba Dam
were at least 81.3 %, lower than flows
measured at reference site SO1 (Smolar-
Žvanut, 2000). Hence, lower local current
velocities at both the bottom and lower
average current velocitities were measured at
the above sampling sites downstream of the
dams. Owing to low flows, water stagnated
downstream of the dams.
All the hydrological parameters show a
decrease in the diversity of aquatic habitats for
water organisms. As a result of the
abstractions, a discernible decline in the size
and number of rapids occurred in sections with
reduced flow, as was also reported for the Töss
River, Switzerland (Bundi et al., 1990). Flow
velocity assessment is thus of importance to
EAF determination (Mikoš, 1996).

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
76
4.2 PLAVINE
Zajezitev in odvzem vode iz vodotoka
običajno povzroči značilno zmanjšanje
pretokov visokih voda dolvodno (Ward in
Stanford, 1995, Erskine et al., 1999), kar vodi
do zmanjšanega transporta plavin (Ward in
Stanford, 1995). Razlog za zmanjšanje
transporta plavin na Soč i in Savi Dolinki  je
predvsem v prekinitvi prodonosnosti, ne pa v
spremenjeni krivulji trajanja pretokov voda v
tistem delu, ki vpliva na prodni premik.
4.2 SEDIMENTS
The damming of watercourses and
abstractions usually give rise to a considerable
decrease in the flows of high waters
downstream (Ward and Stanford, 1995;
Erskine et al., 1999), which in turn leads to
reduced sediment transport (Ward and
Stanford, 1 995). In the case of the Soč a and
Sava Dolinka rivers, reduced sediment
transport may mainly be attributed to the
disruption of sediment transport, rather than to
changes in the flow duration curve at the
section influencing sediment transport.
Preglednica 3. Rezultat linijske-številč ne analize in togega sestavljanja s Fullerjevo zrnavostno
krivuljo v prostorninski vzorec za Savo Dolinko.
Table 3. Results of the Wolman Count-numerical analysis and rigid combination with the Fuller
grain-size distribution curve for a volume pattern of the Sava Dolinka River.
odvzemno mesto
Sampling point
d
16
(mm) d
84
(mm) d
90
(mm) d
m 
(mm) raztros zrnavosti
Grain-size
distribution
SA1P1 5 170 214 81 6
SA1P2 4 100 119 57 5
SA3P1 8 200 226 98 5
SA4P1 10 160 175 86 4
SA4P2 15 377 454 187 5
Preglednica 4. Rezultat linijske-številč ne analize in togega sestavljanja s Fullerjevo zrnavostno
krivuljo v prostorninski vzorec za Soč o.
Table 4. Results of the Wolman Count-numerical analysis and rigid combination with the Fuller
grain-size distribution curve for a volume pattern of the Soč a River.
odvzemno mesto
Sampling point
d
16
(mm) d
84
(mm) d
90
(mm) d
m 
(mm) raztros zrnavosti
Grain-size
distribution
SO1P1 4 125 138 59 5
SO1P2 5 163 183 72 6
SO2P1 7 184 219 92 5
SO2P2 14 324 359 155 5
SO3P1 11 280 301 134 5
SO3P2 6 165 210 84 5

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Po dolgih letih obratovanja HE se pod
pregrado izoblikuje stabilna struga, vendar
pride do poveč anja raznolikosti habitatov z
narašč anjem pretoka vode (Gore, 1 994). Na
Soč i, pod pregrado Podsela in Ajba, ter na
Savi Dolinki, pod pregrado Moste, so
pregrade prekinile normalen dotok plavin in
tako ustvarile nezasič eni vodni tok in tudi
bistveno okrnile pretok lebdeč ih plavin. To
je tudi razlog, da so pod pregradami Moste,
Podsela in Ajba prevladovale prodnate
plavine s precejšnjim deležem grobih zrn in
določ ili smo več je srednje aritmetič no zrno
plavin d
m
 kot nad pregradami (preglednica 3
in preglednica 4). Podobno je pod pregrado
na reki Fontauliere v Franciji, zaradi
sprememb v režimu premešč anja plavin, v
povezavi s spremenjeno hidravliko prišlo do
stabilne struge (Sear, 1995).
Rezultati so pokazali, da je bilo
povprečno zrno rinjenih plavin v Savi
Dolinki in Soč i na vseh območ jih odvzema
več je od povpreč nega srednjega zrna rinjenih
plavin v podobnih prodonosnih vodotokih v
Sloveniji, ki je od 35 do 40 mm. Vrednost d
m
nad 1 00 mm kaže na zelo grobo in zelo
sprano dno, kar kažejo rezultati pod
pregradami Moste, Podsela in Ajba.
4.3 FIZIKALNI IN KEMIJSKI
PARAMETRI
Spremenjene vrednosti fizikalnih in
kemijskih parametrov pod pregradama
Moste in Podsela so odraz prevelikega
odvzema vode, ki je v primerjavi s
primerjalnim mestom še posebej izraženo v
Soč i; merjene vrednosti kažejo, da pod
pregradama niso bile zagotovljene ustrezne
vrednosti Qes.
Poleti, ko je bila temperatura vode na
primerjalnem odvzemnem mestu SO1
13.5 ºC, je bila temperatura vode na odseku,
kjer je bil odvzem vode, višja za 6.7 ºC
(Smolar-Žvanut, 2000). Podobno so pokazali
rezultati raziskav na reki Schächenbach v
Švici (Bundi in Eichenberger, 1989), kjer je
na odseku odvzema vode prišlo do povišanja
temperature vode za 6 ºC. Do manjših razlik
If a hydropower plant has been in
operation for a number of years, then a stable
river bed is formed downstream of the dam,
but there is also an increase in the diversity
of habitats, along with an increase in flow
(Gore, 1 994). In the Soč a River, downstream
of the Podsela and Ajba dams, and in the
Sava Dolinka River, downstream of the
Moste Dam, the dams interrupted the normal
increase in sediments, creating an
unsaturated current, and substantially
reduced the transport of floating sediments.
This is also the reason why gravel deposits
with a high percentage of coarse grains
prevailed downstream of the Moste, Podsela
and Ajba dams,  and a larger mean grain, d
m
,
was determined here than upstream of the
dams (Tables 3 and 4). Similar findings were
reported for the Fontauliere River, France,
downstream of the dam, where changes in
the regime of sediment transport, combined
with altered hidraulics, gave rise to a stable
river bed (Sear, 1995).
Results of this study show that, at all the
sampling sites in the Sava Dolinka and Soč a
Rivers, the average bed load grain was larger
than the average mean bed load grain in
watercourses with a similar sediment
transport in Slovenia, that is 35-40 mm. The
value d
m
 of over 100 mm suggests a very
coarse and highly washed out bottom with
no fine grains, as is shown by the results
obtained downstream of the Moste, Podsela,
and Ajba dams.
4.3 PHYSICOCHEMICAL
PARAMETERS
The altered values of the physicochemical
parameters downstream of the Moste and
Podsela dams are the result of excessive
abstractions, which are particularly evident
in the case of the Soč a River, compared to
the reference site. The obtained values show
that downstream of the two dams,
appropriate EAF values were not assured.
In the summer, when the water
temperature at the  reference site SO1 was
13.5°C, water temperature in the abstraction
section was higher by 6.7°C (Smolar-Žvanut,
2000). Similar findings were reported for the
Schächenbach River in Switzerland (Bundi
and Eichenberger, 1989), where an increase
in water temperature of 6°C was found in the
abstraction section. Smaller differences in
water temperature among individual
sampling sites were observed in the Sava

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
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© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
78
v temperaturi vode med območ ji odvzema je
prihajalo v Savi Dolinki, kjer je temperaturni
režim takoj pod pregrado Moste določ al
pritok Završnica, nižje pa pritok Radovna.
Posledica odvzema vode je, da fizikalno
in kemijsko sestavo vode na odseku, ki je
pod vplivom odvzema vode, ne določ ajo več razmere v zgornjem delu poreč ja, temveč jo
določ ajo dotoki pod mestom zajetja (Bundi
in Eichenberger, 1 989), kar kažejo tudi naši
rezultati.
4.4 BIOLOŠKI PARAMETRI
4.4.1 VRSTNI SESTAV
V Savi Dolinki in Soč i je bila velika
raznolikost združbe perifitonskih alg, ki je v
primeru Save Dolinke s pritokoma Završnico
in Radovno vključ evala 1 28 taksonov, v
primeru Soč e in pritoka Ušnice pa 1 27
taksonov. V vseh vzorcih smo določ ili
največ je število vrst iz skupine kremenastih
alg, podobno kot pri drugih raziskavah alg v
slovenskih rekah (Kosi, 1988, Smolar, 1992,
1997, Vrhovšek et al., 1994, 1996a, 1996b).
Zaradi stabilnosti ekoloških dejavnikov
pod pregradami Moste in Podsela
(konstanten pretok in redko pojavljanje
visokih voda), nizkih do srednjih hitrosti
vodnega toka, ki omogočajo naselitev
zelenih alg, katere predstavljajo podlago za
naseljevanje kremenastih alg in dobri
osvetljenosti, smo določ ili več je število
perifitonskih alg kot nad pregradama.
Znano je, da je diverziteta perifitonskih
alg zelo majhna v vodotokih, kjer se
povišani pretoki vode pogosto pojavljajo
(Clausen in Biggs, 1997). Hiter vodni tok
namreč odtrga perifitonske alge od podlage,
mehansko premikanje več jih zrn plavin pa
privede do poškodb alg. Rod Oscillatoria
predstavlja slab substrat za kremenaste alge
zaradi majhne površine in izpostavljenosti
vodnemu toku (Koudelkova, 1999). To je
tudi eden izmed razlogov za manjšo
raznolikost perifitonskih alg v Savi Dolinki
nad pregrado Moste in v Soč i nad pregrado
Dolinka River, where the temperature regime
immediately downstream of the Moste Dam
is defined by the Završnica Tributary, and
further downstream by the Radovna
Tributary.
Due to abstractions, the physicochemical
composition of water in the section
influenced by the abstractions is no longer
defined by conditions in the upper reaches,
but by inflows downstream of the catchment
site (Bundi and Eichenberger, 1989). This
statement is supported by the results of the
present study.
4.4 BIOLOGICAL PARAMETERS
4.4.1 SPECIES COMPOSITION
The Sava Dolinka River and the Soč a
River are distinguished by a great diversity
of periphyton community. So 128 taxa were
determined in the Sava Dolinka River and its
tributaries, the Završnica and the Radovna,
and 1 27 taxa in the Soč a River and its
tributary, the Ušnica. In all the samples, the
highest number of species were found to
belong to Bacillariophyta, as was also
reported by other investigations of algae in
Slovenian rivers (Kosi, 1988; Smolar, 1992,
1997; Vrhovšek et al., 1994, 1996a, 1996b).
The stability of ecological factors
downstream of the Moste and Podsela dams
(constant flow and rare occurrence of high
waters), the low to moderate current
velocities which make possible the
colonisation of green algae,
a substratum of Bacillariophyta, and
adequate light, all of these factors result in
the fact that a greater number of periphyton
was determined here than upstream of the
dams.
It is known that periphyton diversity is
highly limited in watercourses with a
frequent increase in flow (Clausen and
Biggs, 1997). For periphyton will be torn
from substratum by fast flows, and damage
to algae will be caused by  the transport of
larger sediment grains. The genus
Oscillatoria is an inadequate substratum for
Bacillariophyta due to its small surface area,
and hence the exposure to the current
(Koudelkova, 1999). This is also one of the
reasons for the limited periphyton diversity
in the Sava Dolinka River upstream of the
Moste Dam, and in the Soč a River, upstream

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
The Role of Periphytic Algae in the Determination of Ecologically Acceptable Flow in Running Waters
© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
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Podsela. V obdobju pogostega pojavljanja
cianobakterij v poletnem č asu smo v Savi
Dolinki in Soč i nad pregradami Moste in
Podsela izmerili nižjo temperaturo vode,
medtem ko se zelene alge pogosteje
pojavljajo pri višjih temperaturah vode, ki so
bile izmerjene pod pregradami. Vpliv
odvzema vode na pojavljanje vrste Hydrurus
foetidus se je pokazal tako v Savi Dolinki
kot v Soč i. Množič no se je ta vrsta pojavljala
le v zimskem č asu na območ ju odvzema
SA1 v Savi Dolinki in območ ju odvzema
SO1 v Soč i ter na pritokih Radovna in
Završnica. To lahko pripišemo nizkim
zimskim temperaturam vode in
konstantnemu pretoku vode (Ward, 1974;
Valentin s sod., 1995; Smolar, 1997). Traaen
in Lindstrøm (1983) sta ugotovila, da se je
90 odstotkov alg Hydrurus foetidus
pojavljalo pri hitrostih, več jih od 80 cm/s
(hitrost, merjena 1 cm nad dnom), podobno
kot so pokazali rezultati naše raziskave.
Bray - Curtisov koeficient podobnosti
kaže kakovostne spremembe v strukturi
združbe in zagotavlja hiter in preprost
pregled podobnosti in različnosti med
združbami. Več ja podobnost v hidroloških in
fizikalno-kemijskih razmerah nad pregrado
Podsela in pod pregrado Ajba se je odražala
v več ji podobnosti med vzorci teh območ ij
odvzema. Torej lahko ugotovimo, da je
zaradi odvzema vode pod pregrado Podsela
prišlo do spremembe v vrstni sestavi in
pogostosti perifitonskih alg. Tudi v Savi
Dolinki je bila vidna krajevna odvisnost med
območ ji odvzema, in sicer je bila največ ja
podobnost v vzorcih med območ ji odvzema,
ki so bila pod vplivom odvzema vode za HE
Moste, v drugi skupini pa so bili vzorci iz
območ ij odvzema nad pregrado Moste (slika
3).
Velikost sprememb v združbi
perifitonskih alg pod pregrado Podsela in
pregrado Moste je dokaz, da pod pregradama
ni bil zagotovljen Qes.
of the Podsela Dam. At the time of the
frequent occurrence of Cyanophyta in the
summer, a lower water temperature was
measured in the Sava Dolinka River and the
Soč a River, upstream of the Moste and
Podsela dams, while green algae occured
more often at the higher water temperatures
which were measured downstream of the
dams. The effect of abstractions on the
occurrence of the species Hydrurus foetidus
was observed in the Sava Dolinka River as
well as in the Soč a River. The species
proliferated only in winter at sampling site
SA1 in the Sava Dolinka River, at sampling
site SO1 in the Soč a River, and in the
Radovna and Završnica tributiaries. This
may be ascribed to low water temperatures
in the winter and to constant flow (Ward,
1974; Valentin et al., 1995; Smolar, 1997).
Traaen and Lindstrom (1983) reported that
90 % of the algae Hydrurus foetidus
occurred at velocities of over 80 cm/s
(measured 1 cm above the bottom), which is
in agreement with the results of this study.
The Bray-Curtis coefficient of similarity
shows qualitative changes in the structure of
a community, providing a fast and simple
survey of similarities and differences among
communities. The hydrological and
physicochemical parameters measured
upstream of the Podsela Dam and
downstream of the Ajba Dam show closer
similarities among samples taken at these
locations. Thus, it can be concluded that
abstractions downstream of the Podsela Dam
gave rise to changes in species composition
and periphyton frequency. In the Sava River,
too, a local interdependence of abstraction
sections was evident. So the closest
similarities were found among samples taken
at locations influenced by abstractions for
the Moste power plant, while the second
group of samples comprised those taken at
locations upstream of the Moste Dam
(Figure 3).
The extent of changes in the periphyton
community downstream of the Podsela and
Moste dams provides convincing proof that
here the EAF was not assured.

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
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© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
80
Slika 3. Bray-Curtisov koeficient podobnosti za reko Savo Dolinko, reko Radovno in potok
Završnico, dne 3.6.1998.
Figure 3. Bray-Curtis coefficient of similarity  for the river Sava Dolinka, the river Radovna and
the stream Završnica, on 3
rd
 of June 1998.
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1
SA41J98
SA45J98
SA42J98
SA43J98
SA44J98
SA31J98
SA32J98
SA33J98
RADJ98
SA52J98
SA53J98
SA51J98
SA54J98
SA22J98
SA23J98
SA21J98
ZAV1J98
ZAV2J98
SA12J98
SA13J98
SA14J98
SA11J98

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© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
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4.4.2 PANTLE-BUCKOV SAPROBNI
INDEKS
Vrednost Qes mora zagotavljati tako
količ ino kot kakovost vode, da se vrednosti
Pantle-Buckovih saprobnih indeksov na
območju odvzema vode ne poveč ajo
(Smolar-Žvanut, 2000).
Razlog za nekoliko višje vrednosti Pantle
- Buckovega saprobnega indeksa na območ ju
odvzema pod pregrado Podsela na območ jih
odvzema SO2 in SO3 v Soč i (2. kakovostni
razred) je verjetno v manjši hitrosti vodnega
toka, ki se odraža v spremenjenih fizikalnih
in kemijskih razmerah v vodi in v poveč ani
onesnaženosti. Območ je odvzema SO1 smo
lahko v vseh obdobjih uvrstili v 1. oz. 1.-2.
kakovostni razred. Ker razmere v Savi
Dolinki pod pregrado Moste določ ajo pritoki
kot sta Završnica in Radovna, je bilo
onesnaženje pod pregrado manjše in
vrednosti Pantle-Buckovih saprobnih
indeksov pod pregrado Moste so bile v
več ini primerov nižje glede na vrednost
indeksov primerjalnega območ ja odvzema
SA1 (Smolar-Žvanut, 2000).
4.4.3 BIOMASA PERIFITONSKIH ALG
Vrednost Qes naj bi zagotavljala tako
količ ino kot kakovost vode, pri kateri naj, v
primerjavi s primerjalnim mestom ne bi
prišlo do bistvenega poveč anja biomase
perifitonskih alg, vendar rezultati kažejo
ravno to.
Vrednosti parametrov suhe teže in
organske snovi perifitonskih alg so bile v
Savi Dolinki in pritokih Završnica in
Radovna najvišje v predelih struge z
upoč asnjenim tokom vode. V č asu
konstantnega pretoka vode dosegajo
perifitonske alge obič ajno visoko biomaso na
velikih prodnikih in kamnih, posebej zaradi
majhne gibljivosti plavin na dnu vodotoka.
Visoka biomasa perifitonskih alg pa se lahko
razvije šele, č e je dovolj dolgo obdobje
stabilnosti habitata (Biggs, 1996). Nizki
pretoki vode, ugodne svetlobne razmere in
velikost plavin so bili dejavniki, ki so
omogoč ali tako bohotno rast alg v Savi
Dolinki in Soč i.
4.4.2 PANTLE-BUCK SAPROBIC INDEX
The EAF value should assure such
quantity and quality of water that the values
of the Pantle-Buck Saprobic Index do not
increase in the abstraction section (Smolar-
Žvanut, 2000).
The reason for the slightly higher values
of the Pantle-Buck Saprobic Index
determined in the Soč a River downstream of
the Podsela Dam, at sampling sites SO2 and
SO3 (2nd category of water quality) may
probably be lower current velocity, which
results in the altered physicochemical
conditions of water and in increased
pollution. Sampling site SO1 was classified,
in the whole investigation period, into the 1st
or 1st-2nd category. Since conditions in the
Sava Dolinka River, downstream of the
Moste Dam, are defined by tributaries such
as the Završnica Stream and the Radovna
River, the pollution downstream of the dam
was less severe and values of the Pantle-
Buck Saprobic Index were, in most cases,
lower, compared with those at reference site
SA1 (Smolar-Žvanut, 2000).
4.4.3 PERIPHYTON BIOMASS
In keeping with the EAF value, such
quantity and quality of water should be
assured that, in comparison with the
reference site, the periphyton biomass does
not increase considerably. Yet results of this
study show that this was what happened.
In the Sava Dolinka River and in the
Završnica and Radovna tributaries, the
values of dry weight and the organic matter
of the periphyton were the highest in
sections with a slower current. At the time of
constant flow, periphyton usually attains a
high biomass on large pebbles and stones,
particularly due to limited sediment transport
at the bottom of the watercourse. High
biomass of periphyton can develop only after
an extended period of habitat stability
(Biggs, 1996). Low flows, favourable light,
and appropriate sediment size were factors
that made the proliferation of algae possible
in the Sava Dolinka and Soč a rivers.

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
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© Acta hydrotechnica 19/30 (2001), 65-89, Ljubljana
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Preglednica 5. Vrednosti suhe teže, organske snovi in klorofila-a v Savi Dolinki,
Završnici in Radovni.
Table 5. Values of dry weight, organic matter, and chlorophyll-a for the Sava Dolinka
and Radovna Rivers, and the Završnica Stream.
suha teža (g/m
2
)
 Dry weight
organska snov (g/m
2
)
Organic matter
klorofil-a (mg/m
2
)
Chlorophyll-a
območ je
odvzema
Sampling
site
min
Min.
maks
Max.
povp
Average
min
Min.
maks
Max.
povp
Average
min
Min.
maks
Max.
povp
Average
SA1 12 139 56 5 37 19 17 398 107
SA2 54 356 139 5 91 34 58 379 179
ZAV 76 218 168 10 161 51 117 373 194
SA3 49 514 219 <1 144 56 21 243 118
RAD 37 388 153 16 71 35 9 166 64
SA4 29 413 208 27 103 48 19 342 121
SA5 38 182 78 13 66 32 45 579 207
Preglednica 6. Vrednosti suhe teže, organske snovi in klorofila-a v Soč i in Ušnici.
Table 6. Values of dry weight, organic matter, and chlorophyll-a for the Soč a River
and the Ušnica Stream.
suha teža (g/m
2
)
Dry weight
organska snov (g/m
2
)
Organic matter
klorofil-a (mg/m
2
)
Chlorophyll-a
območ je
odvzema
Sampling
site
min
Min.
maks
Max.
povp
Average
min
Min.
maks
Max.
povp
Average
min
Min.
maks
Max.
povp
Average
SO1 9 324 56 5 67 16 6 153 42
USN 28 45 38 8 22 14 34 147 91
SO2 5 352 85 2 72 24 24 283 89
SO3 14 283 114 4 84 40 25 260 123
SO4 12 76 37 5 21 13 11 130 57
Nizke vrednosti suhe teže in organske
snovi nad pregrado Moste na primerjalnem
območ ju odvzema SA1 (preglednica 5), a
relativno visoke vrednosti klorofila-a lahko
pojasnimo s tem, da je bilo zaradi velikih
hitrosti vodnega toka, manjše usedanje
organskih delcev in da je v združbi, zaradi
stalnega odnašanja odmrlih celic, več ji delež
živih celic. Zaradi vpliva drugih ekoloških
dejavnikov, je bilo veliko rast alg v Savi
Dolinki nemogoč e pojasniti le z nizkimi
pretoki vode, temveč tudi s količ ino
hranilnih snovi, svetlobo in strukturo
Low values of dry weight and organic
matter, but relatively high values of
chlorophyll-a were determined upstream of
the Moste Dam at reference site SA1 (Table
5). This may have been caused by the fact
that, due to high current velocities, fewer
organic particles settled at the bottom of the
river bed, and that there was a higher
proportion of living cells in the community,
since dead cells were constantly swept away.
Because of the effect of other ecological
factors, the proliferation of algae in the Sava
Dolinka River may be attributed, not only to
low flows, but also to the quantity of
nutrients, light, and sediment structure.

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usedlin. Hidrološke razmere vplivajo na
spremembe v biomasi perifitona, zato
priporoč ajo, da se pri raziskavah upoštevajo
prejšnje hidrološke razmere (Biggs in Close,
1989).
V poletnem obdobju smo na območ jih
odvzema SA3 in SA4 pod pregrado Moste
izmerili visoke vrednosti suhe teže in
organske snovi, kar lahko zaradi ugodnih
svetlobnih in temperaturnih razmer, nizkih
hitrosti vodnega toka, nizkih strižnih hitrosti,
negibljivosti podlage in redkega pojavljanja
povišanih pretokov voda, pripišemo
množič nemu pojavljanju alge Spirogyra sp.
Na območ ju odvzema SA5 pri Blejskem
mostu pa smo, tako v zimskem kot v
poletnem obdobju, izmerili nižje vrednosti
suhe teže in organske snovi in višje vrednosti
klorofila-a. Zaradi urnega spreminjanja v
vodostajih se odplavljajo vsi organski delci
in odmrle celice. Pri tem moramo upoštevati,
da je to območ je odvzema popolnoma
zasenč eno, kar ima lahko za posledico več je
količ ine klorofila-a v celicah. Na tem
območ ju odvzema sta se pogosto pojavljali
alga Hydrurus foetidus (zaradi nizkih
temperatur vode tudi poleti) in alga
Cladophora sp.
Z odvzemom vode iz Soč e je pod
pregrado Podsela prišlo do hidroloških,
fizikalnih in kemijskih sprememb v
vodotoku, kar se je odražalo v poveč ani
biomasi perifitonskih alg (Preglednica 6).
Prerašč anje dna vodotoka z nitastimi algami
je najbolj opazen vidni znak bioloških
sprememb na odseku odvzema vode in to
ima nadaljnje posledice za vodni živalski
svet (Bundi in Eichenberger, 1989).
Visoka biomasa perifitonskih alg,
izražena kot klorofil-a in organska snov, je
bila opažena takoj pod pregradami tudi
drugje (Lowe, 1979; Bundi in Eichenberger,
1989; Smolar, 1997; Koudelkova, 1999),
podobno kot v Soč i. Glavni razlog je lahko v
manjših nihanjih temperature vode, pretoku
vode brez več jega sezonskega nihanja in v
narašč anju koncentracije hranilnih snovi ter
njihovega prevzema v alge (Koudelkova,
1999) in v velikih negibljivih plavinah.
Poleg hitrosti vodnega toka je pogoj za
Hydrological conditions exert an influence
on changes in the periphyton biomass.
Therefore, it is recommended that former
hydrological conditions should be taken into
account when such investigations are
conducted (Biggs and Close, 1989).
In summer, high values of dry weight and
organic matter were measured at sampling
sites SA3 and SA4, downstream of the
Moste Dam. This may be ascribed to the
proliferation of the alga Spirogyra sp., as a
result of favourable conditions such as light
and temperature, low current velocity, low
shear velocity, substratum immobility, and
the rare occurrence of increased flow. At
sampling site SA5, at the gauging station at
Blejski most, lower values of dry weight and
organic matter, and higher chlorophyll-a
values were measured in the summer,
similarly as in winter. Due to hourly changes
in the water level, all organic particles and
dead cells were swept away. But it must be
taken into account that this abstraction
section is totally shaded, which may give
rise to higher quantities of chlorophyll-a in
the cells. At this location, Hydrurus foetidus
(due to low water temperatures in the
summer as well)  and Cladophora sp. were
often found.
Abstractions in the Soča River,
downstream of the Podsela Dam, resulted in
hydrological, physicochemical changes in
the watercourse, which in turn led to an
increased periphyton biomass (Table 6).
Biological changes were most strikingly
evident in the overgrowth of the bottom with
green algae at this location, which  will have
a further impact on the aquatic fauna (Bundi
and Eichenberger, 1989).
The high periphyton biomass, expressed
as chlorophyll-a and organic matter, found
immediately downstream of the dams was
reported by other studies as well (Lowe,
1979; Bundi and Eichenberger, 1989;
Smolar, 1997; Koudelkova, 1999). This may
be primarily attributed to minor fluctuations
in the water temperature, flows without more
distinct seasonal fluctuations, an increase in
the concentration of nutrients and their
absorption by algae (Koudelkova, 1999), and
to large immobile sediments. In addition to
current velocity, at locations with low

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84
veliko biomaso perifitonskih alg na območ ju
nizkih hitrosti vodnega toka, pomembna v
nezasenč enih vodotokih tudi kakovost vode,
ki je bila pod pregrado Podsela slabša. Alge
Cladophora glomerata, Mougeotia sp. in
Ulotrix zonata so prispevale velik delež k
biomasi spomladi in poleti na območ jih
odvzema SO2 in SO3 v Soč i pod pregrado
Podsela, medtem ko so bile v istem obdobju
na območju odvzema SO1 izmerjene
najnižje vrednosti biomase perifitonskih alg.
To je zaradi velikih hitrosti vodnega toka in
velike gibljivosti podlage.
Alga Cladophora je sposobna dosegati
veliko biomaso pri visokih hitrostih vodnega
toka ( v
v
 > 0.7 m/s) (Stevenson, 1996), v
Soč i pa je največ prispevala k biomasi
perifitonskih alg, pri nizkih hitrostih
vodnega toka pod pregrado Podsela ( v
v
 <
0.3 m/s).
Nobena izmed zelenih alg pa se ni
množič no pojavljala na območ ju odvzema
SO1 v Soč i nad pregrado Podsela, kar je
rezultat gibljive podlage, velikih hitrosti
vodnega toka, v pojavu visokih voda in
manjši onesnaženosti.
V primerjavi s Soč o je vpliv odvzema
vode na zelene alge v Savi Dolinki manjši,
kar lahko pripišemo dotoku manj onesnažene
vode pod pregrado in nižjim temperaturam
vode v poletnem č asu.
5. ZAKLJUČ EK
Rezultati vpliva odvzema vode pri že
zgrajenih HE Moste, HE Doblar in HE Ajba
so pokazali velike spremembe v hidroloških,
fizikalno-kemijskih in bioloških parametrih
pod pregradami, ki so posledica prenizkih
pretokov vode pod pregradami. Z
zagotavljanjem Qes do tako velikih
sprememb, posebej pod pregrado Podsela, ne
bi smelo prihajati.
Po svetu uporabljajo različ ne metode
določ anja Qes v tekoč ih vodah, vendar jih le
malo upošteva združbo perifitonskih alg kot
enakovreden parameter. Na podlagi pregleda
literature, rezultatov vpliva odvzema vode iz
Tržiške Bistrice (Smolar, 1 997), Soč e in
Save Dolinke lahko povzamemo, da je pri
current velocities in unshaded watercourses,
a high periphyton biomass also depends on
the water quality, which was of a lower
category downstream of the Podsela Dam.
The algae Cladophora glomerata,
Mougeotia sp. and Ulotrix zonata
contributed substantially to the biomass in
spring and summer at sampling sites SO2
and SO3 in the Soč a River, downstream of
the Podsela Dam, while in the same period,
lower values of periphyton biomass were
measured at sampling site SO1. This resulted
from high current velocities and a mobile
substratum.
The alga Cladophora can attain a high
biomass at high current velocities ( v
v
 > 0.7
m/s) (Stevenson, 1 996). But in the Soč a
River, the alga contributed most to the
periphyton biomass at low current velocities
downstream of the Podsela Dam ( v
v
 <  0.3
m/s).
No species of green algae  proliferated at
sampling site SO1 in the Soč a River,
downstream of the Podsela Dam, which is
the result of a mobile substratum, high
current velocities, the occurrence of high
waters, and less severe pollution.
Unlike the Soč a River, the abstractions do
not have such a noticeable effect on the
green algae in the Sava Dolinka River. This
may be attributed to less polluted inflowing
water downstream of the dam and to lower
water temperatures in summer.
5. CONCLUSION
The analysis of the effects of the
abstractions for the Moste, Doblar, and Ajba
hydropower plants shows substantial
changes in the hydrological,
physicochemical and biological parameters
downstream of the dams resulting from the
excessively low flows here. Such changes
would not have occurred if the EAF had
been assured.
To determine EAF in flowing waters,
different methods have been applied, but
only some investigations have taken into
account the periphyton community as an
equivalent parameter. Based on reports in the
literature and on the analysis of the effects of
the abstractions for the Tržiška Bistrica
(Smolar, 1 997), Soč a, and Sava Dolinka

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
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določ anju Qes nujno poznavanje združbe
perifitonskih alg, ker predstavljajo zač etek
prehranjevalne verige v tekoč ih vodah, hitro
odgovarjajo na spremembe v okolju ter
ponujajo podlago in zatoč išč e številnim
vodnim organizmom.
Rezultati naših raziskav in pregled
literature so pokazali, da so za razumevanje
pojavljanja perifitonskih alg med
hidrološkimi parametri pomembni: pretok
vode in njegova dinamika, nihanje vodne
gladine, lokalna hitrost vodnega toka nad
odvzemnim mestom, globina vode, velikost
in gibljivost plavin, med fizikalno-
kemijskimi parametri: temperatura, vsebnost
kisika, nasičenost s kisikom, vsebnost
hranilnih snovi ter onesnaženje in
morfologija vodotoka.
Pri določ anju Qes je potrebno poznavanje
vrstnega sestava in biomase perifitonskih alg
v različ nih tipih habitatov obravnavanega
odseka vodotoka v različ nih letnih č asih.
Vrednost Qes mora zagotavljati količ ino
in kakovost vode, da:
− - ne pride do prevelikega prerašč anja dna
s perifitonskimi algami in da se ne
pojavlja biomasa, neznačilna za tip
vodotoka,
− ne prevladuje le ena oziroma le nekaj vrst
perifitonskih alg,
− se vrstni sestav ne spremeni bistveno
glede na primerjalno mesto,
− ne pride do poslabšanja kakovosti vode,
− ohranimo diverziteto različnih tipov
habitatov (glede na globino vode, hitrost
vodnega toka, osenč enost, strukturo in
velikost plavin),
− ne pride do zastajanja vode (zagotoviti
moramo hitrost vodnega toka v
posameznih habitatih nad 30 cm/s),
− preprečimo nenehne spremembe v
pretoku vode, npr. zaradi vršnega
obratovanja vodnih elektrarn,
− se obč asno zagotavljajo pretoki visoke
vode (dovoljeno le ob naravnem nastopu
visokih voda)
− ne pride do prevelikih sprememb v
fizikalnih in kemijskih lastnostih vode,
takih, ki niso znač ilne za odsek vodotoka
pod vplivom odvzema vode.
rivers, it can be concluded that the
knowledge of the periphyton community is
vital for the EAF determination, since the
algae represent the beginning of the feed
chain in running water, respond quickly to
environmental changes, and act as substrata
and refuges for a number of aquatic
organisms.
The results of this study and a survey of
the literature indicate that the following
hydrological parameters, among others, are
of importance for an understanding of
periphyton occurrence: flow, flow
fluctuations, fluctuations in water level, local
current velocity above the sampling site,
water depth and size and mobility of the
sediments, along with the following
physicochemical parameters: temperature,
oxygen content, oxygen saturation, content
of the nutrients, pollution, and the
morphology of the watercourse.
To determine the  EAF, it is vital to have
a knowledge of species composition and the
periphyton biomass in different types of
habitats of the section under consideration in
different seasons.
The EAF value should ensure such
quantity and quality of water that
− the excessive overgrowth of the bottom
with periphyton and a biomass
uncommon for a particular type of
watercourse do not occur,
− merely one or just a few periphyton
species do not predominate,
− species composition does not change
substantially when compared with the
reference site,
− the water quality does not deteriorate,
− the diversity of different habitat types is
preserved (with regard to water depth,
current velocity, the extent of the shade
and the structure and size of the
sediments),
− the water does not stagnate (the current
velocity in individual habitats should be
over 30 cm/s),
− constant changes in flow, e.g. owing to
the peak operation of a hydropower plant,
are prevented,
− flows of high waters are occasionally
ensured (only if high waters occur
naturally), and that
− radical changes in the physicochemical
properties of the water do not occur; that
is, changes that are uncommon for the
section of a watercourse influenced by the
abstractions.

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
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Potrebne pa so nadaljnje raziskave, da
bomo lahko količinsko bolj podrobno
opredelili zgoraj naštete zahteve.
Rezultati naših raziskav so pokazali, da v
času konstantnega pretoka vode pod
pregradami dosegajo perifitonske alge
običajno visoko biomaso na velikih
prodnikih in kamnih, predvsem zaradi
majhne gibljivosti plavin v dnu vodotoka.
Zato je treba, poleg zagotavljanja Qes na
odseku pod pregrado za odvzem vode,
ohranjati naravno dinamiko pretokov visokih
voda na tem odseku in zagotavljati pretok
plavin v odsek pod pregrado.
6. ZAHVALA
Č lanek je povzetek doktorske disertacije.
Prof. dr. Danijelu Vrhovšku in
izr. prof. dr. Matjažu Mikošu se najlepše
zahvaljujem za mentorstvo, številne  nasvete
in strokovno pomoč pri izdelavi doktorske
disertacije. Zahvaljujem se Petru Mucku,
dipl. ing. gr. in Darku Burji, univ. dipl. ing.
gr. za nasvete in pomoč s področ ja
hidrologije, Darku Anzeljcu, univ. dipl. ing.
gr. za pomoč pri obdelavi hidroloških
podatkov ter vsem, ki so mi pomagali pri
izvedbi naloge.
Zahvaljujem se tudi Soškim elektrarnam
Nova Gorica, d.o.o. in Savskim elektrarnam
Ljubljana, d.d. za posredovanje podatkov.
Further research is needed to define
quantitatively, in more detail, the above
statements.
Results of the study show that, at the time
of the constant flow downstream of a dam,
periphytonic algae usually attain a high
biomass on large pebbles and stones,
primarily owing to the limited mobility of
sediments  at the bottom of a watercourse.
Therefore, it is vital - in addition to ensuring
EAF downstream of the dam intended for
abstractions - to preserve the natural
dynamics of the flows of high waters at this
location, and to ensure sediment transport
into the section downstream of the dam.
6. ACKNOWLEDGEMENTS
This study is a summary of a doctoral
dissertation. The author is most grateful to
Professor Danijel Vrhovšek, Ph.D., and to
Associate Professor Matjaž Mikoš, Ph.D.,
for their supervision, counselling, and
professional assistance in the preparation of
her thesis. Grateful thanks are due to Mr.
Peter Muck, BCE. and Mr. Darko Burja,
BCE., for their valuable advice and
assistance in the field of hydrology, Mr.
Darko Anzeljc, BCE., for his assistance in
the processing of hydrological data, and to
all who assisted the author in the preparation
of her thesis.
Thanks are also due to the Soč a
Hydropower Stations, Nova Gorica Ltd., and
to the Sava Hydropower Stations, Ljubljana
Ltd.  for imparting the data.

Smolar-Žvanut, S.: Vloga perifitonskih alg pri določ anju ekološko sprejemljivega pretoka vode v tekoč ih vodah -
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Naslov avtorja - Author's Address
dr. Nataša SMOLAR-ŽVANUT
Limnos, Skupina za ekologijo voda - Limnos, Group for water ecology
Podlimbarskega 31
SI - 1000 Ljubljana
E-mail: natasa@limnos.si