Sava River Basin Management Plan

Background paper No. 4 Hydromorphological alterations in the River Basin

March 2013

This document has been produced with the financial assistance of the European Union. The contents of this document are the sole responsibility of the beneficiaries and can under no circumstances be regarded as

reflecting the position of the European Union.

Sava River Basin Management Plan

Table of contents 1. Introduction ...... 1

2. Methodology of assessment of modification of river morphology ...... 2

2.1 List of hydromorphological features to be assessed in the SR basin...... 2 2.2 Classification of water bodies by five classes ...... 11 2.3 Methodology of risk assessment ...... 11 3. Results of assessment ...... 12

3.1 River and habitat continuity interruption ...... 12 3.2 Disconnection of adjacent wetlands/floodplains ...... 16 3.3 Hydrological alterations - impoundment, water abstraction, ydropeaking ...... 16 3.4 Morphological alterations ...... 17 3.5 Risk assessment - hydromorphological alterations ...... 19

List of Tables Table 1: Protocol of assessment of selected hydromorphological features ...... 3 Table 2: Classification terms for five classes of modification of river morphology...... 11 Table 3: Overview of the number of river continuity interruptions 2010 and 2015 restoration measures and exemptions according to the WFD Article 4(4) for each Sava country ...... 13

List of Figures Figure 1 : Interruptions of river continuity in the Sava River Basin (in numbers) ...... 12 Figure 2: Types of interruptions of river and habitat continuity in the SRB ...... 13 Figure 3: The length of impoundments in the Sava RB (in km) ...... 17 Figure 4: Classes of modification of morphology of river water bodies on the Sava River Basin (in %) ...... 18 Figure 5: Classes of modification of morphology of river water bodies on the Sava River (in %) ...... 18 Figure 6: Risk assessment – hydromorphological alterations (figures in columns represent number of relevant water bodies) ...... 19

Background paper No.4: Hydromorphological alterations in the Sava River Basin

Sava River Basin Management Plan

1. Introduction Taking into account, that all main drivers, namely hydropower, navigation, flood protection, urban development and agriculture are present (affect) Sava River Basin, hydromorphological (HYMO) alterations were considered as significant water management issue (SWMI) in the Sava River Basin Analysis Report (SRBA Report, 2009). It is in line with the SWMIs defined in the River Basin Management Plan, where hydromorphological alterations are one of four SWMIs apart from organic pollution, nutrient pollution and pollution caused by hazardous substances. Since the Sava River Basin is one the most significant tributaries of the Danube, its SWMIs reflect the SWMIs of the whole Danube. Identification of hydromorphological alterations was performed on the basis of two out of three main hydromorphological pressure components, which have been identified in the analysis reports for both the Danube and Sava River Basins: - Interruption of river and habitat continuity - Hydrological alterations Regarding disconnection of adjacent wetland/floodplains, it was decided by Sava HYMO national experts not to consider it as a hydromorphological pressure for the Sava RB. Taking into account that there is only one site (floodplain) with potential for reconnection, this pressure was considered as non-relevant for Sava River basin-wide scale. However, lateral connectivity of river and floodplain is taken into account into proposed integral component - modification of river morphology. It allows assessing the extent of floodplain not allowed to be flooded regularly due to engineering, but not the potential for reconnection. The use of a new hydromorphological pressure component - modification of river morphology - was agreed at the PEG RBM meeting on 27-28 September 2010. The final list of hydromorphological pressure components in the Sava RB: - Interruption of river and habitat continuity - Hydrological alterations - Modification of river morphology

Background paper No.4: Hydromorphological alterations in the Sava River Basin 1

Sava River Basin Management

2. Methodology of assessment of modification of river morphology

2.1 List of hydromorphological features to be assessed in the SR basin Modification of the river morphology is integrated pressure, which includes assessment of many man-caused changes. Based on the expert judgments and availability of the data in the Sava RB the following parameters were selected from the list of hydromorphological features mentioned in the EN 15843:2010:

1. River geometry (river in sinuosity meandering for one channel rivers or cut- off side /secondary arms for braided river) Man-caused changes in natural meandering of the water body have a clear negative effect to ecological status of water body because it increases the flow in the main channel and changes local habitats.

2. Subtract/sediment composition (e.g. assessment of gravel extraction) Sediments define type of habitat for biological quality elements (BQEs). Changes in them lead to changes in composition of BQEs, which are the key parameters for ecological status assessment.

3. Large woody debris in the water body Large woody debris in water also provides habitat for biological quality elements (BQEs). Therefore their removal negatively affects the ecological status of water body.

4. Bank structure (assessment of bank enforcement) Non-natural bank enforcement also negatively affects environmental status of the water bodies because it causes significant erosion at the banks.

5. Lateral connectivity of river and floodplain The floodplain connected ensures the development of self-sustaining aquatic populations, flood protection and reduction of pollution in the entire river basin.

6. Riparian zone vegetation structure/type (land use in the riparian zone) According to the national legislations, land use in the riparian zone is limited.

7. Floodplain cover (land use in the river corridor beyond the riparian zone) Non-natural land use in the floodplain such as recreational and high intensity agricultural grassland, cultivated land, urban areas etc. have a negative impact on the ecological status of the water body.

The assessment of the selected hydromorphological features was done according to the standard EN 15843:2010 (see Table 1).

Background paper No.4: Hydromorphological alterations in the Sava River Basin 2 Sava River Basin Management

Table 1: Protocol of assessment of selected hydromorphological features Score band A Features Score band B – Examples of suitable # Description – Guidance assessed Qualitative methods/data use Quantitative

In this context, "planform" both to 1 = 0 % to changes in 5 % of reach channel 1 = Near-natural length with sinuosity and planform. changed to changes in Consult maps and compare historical Changes in planform. channel with present-day sinuosity braiding or to planform where (meanderin multiple changes have resulted g) for one channels. from engineering, etc. channel If possible, use (Includes loss of rivers or absolute or braiding, etc.) (1/2). cut-off side 2 = > 5 % to 3 = Planform recorded /secondary 15 % of reach changes amounts of arms for length with throughout part of change rather braided changed the reach. than estimates river planform. from variety of sources. Channel 1 geometry 3 = > 15 % to 35 % of reach length with changed planform.

Quantitative 4 = > 35 % to 5 = Planform Where a river (in %) 75 % of reach changed in has some assessment length with majority of reach, artificial Engineering of reduction changed or reach sinuosity, but construction and of the river planform. completely, or has lost its maintenance work length and / almost natural records (1/2). or completely, meandering, qualitative straightened. assign score 5. description 5 = > 75 % of or reach length qualitative with changed description planform. of the cut-off works

Quantitative 1 = 0 % to 1 = Near-natural. Local/management (in %) 5 % of reach No, or minimal, assessment length with personnel/expert change in cross- assessment (2). of river changed and/or long- width and channel

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Score band A Features Score band B – Examples of suitable # Description – Guidance assessed Qualitative methods/data use Quantitative

depths section. section. changes or qualitative description 3 = Moderately

within altered. Channel changed partially affected channel 2 = > 5 % to by one or more of section 15 % of reach the following: Survey data (e.g. length with regrading, evidence of regrading, Channel changed reinforcement, structures installed longitudi channel culvert, berm, or (e.g. deflectors) (2).

nal section. clear evidence of section 2 dredging causing and some changes in cross- width/depth ratio. sections* 3 = > 15 % to 35 % of reach length with changed 5 = Greatly channel altered. Channel section. predominantly affected by one or 4 = > 35 % to more of the 75 % of reach following: Knowledge of changes length with regrading, to width/depth ratios changed reinforcement, (2). channel culvert, berm, or section. clear evidence of dredging causing 5 = > 75 % of major change in reach length width/depth ratio. with changed channel section.

1 = No, or Quantitative 1 = 0 % to minimal, presence User assesses Hydromorphological (in %) 1 % artificial of artificial how the survey information. assessment material. channel of artificial material. Substrate subtract and sediment is not 3 / 3 = Small to natural (e.g. / or 2 = > 1 % to sediment moderate increased Observations made by qualitative 5 % artificial presence of walk-over surveys. description material. siltation, gravel artificial material. compaction/ of natural cementation). subtract 3 = > 5 % to 5 = Extensive Local/management alterations 15 % artificial presence of personnel/expert

Background paper No.4: Hydromorphological alterations in the Sava River Basin 4 Sava River Basin Management

Score band A Features Score band B – Examples of suitable # Description – Guidance assessed Qualitative methods/data use Quantitative

and / or material. artificial material. assessment qualitative assessment 4 = > 15 % to Observations made 30 % artificial during biological material. sampling. (Includes evidence of sediment running off fields; 5 = > 30 % boulders installed for artificial fish, compaction of material. gravels, etc.)

Note that the score 1 = Near-natural for management of amount and size woody debris can be of woody debris; affected by no active removal management within or addition. the reach or upstream from the reach.

Qualitative 3 = Amount and assessment size of woody Large of removal Feature not debris slightly to 4 woody of debris scored. moderately Although scores are debris** from altered; occasional given only for woody riverbed active removal or debris, the presence addition. of other organic debris (e.g. leaf packs) 5 = Amount and is important and size of woody should be noted debris greatly where it occurs. altered; regular active removal or addition.

a. Bank 1 = Banks not, or reinforceme 1 = Banks If modified only minimally, nt by soft affected by bank materials affected by hard materials 0 % to 5 % are "natural" Local/management/e artificial (biodegrada hard, or 0 % (e.g. willow ngineering materials, or ble material: to 10 % soft, spilling) personnel/ expert moderately 5 Bank brushwood, artificial maximum assessment. affected by soft structure reed, materials. score is 3. materials. and willow) modificat ion b. Bank 2 = Banks 3 = Banks slightly Assessment of Hydromorphological reinforceme affected by or moderately extent of bank and walk-over

nt by hard > 5 % to 15 % affected by hard affected is surveys. materials hard, or artificial based on

Background paper No.4: Hydromorphological alterations in the Sava River Basin 5 Sava River Basin Management

Score band A Features Score band B – Examples of suitable # Description – Guidance assessed Qualitative methods/data use Quantitative

(concrete, >10 % to materials, or predominant sheet piling, 50 % soft, greatly affected by material bricks) artificial soft materials. present (may materials. be a mix of two

types).

3 = Banks c. affected by Constructio > 15 % to ns (groyne, 35 % hard, or spike, > 50 % to

embankmen 100 % soft, t artificial Bank materials. structure and 5 = Majority of Data from both 4 = Banks modificat banks composed banks are affected by Air photos. ion Quantitative of hard artificial combined for > 35 % to assessment materials the assessment. 75 % hard (in %) of artificial length of materials. bank affected and 5 = Banks / or affected by qualitative > 75 % hard assessment artificial materials.

Is over-bank Need to know flooding likely Is over-bank historical Use whatever engineering to occur (or flooding likely to extent of information allows an construction likely to have occur (or likely to floodplain – e.g. assessment of the s (dikes, occurred have occurred some may now extent to which impounding historically) historically) be lost to urban natural flooding is / drainage) naturally in naturally in the development controlled: Lateral the reach? reach? Yes/No. (include all, not connecti Yes/No. just recent, vity of development 6 river and Quantitative that has floodplai reduced the assessment Land use in n If No – N/A. If No – N/A. natural (in %) of floodplain. floodplain inundation of

and / or the floodplain). qualitative assessment Land cover Controlling structures of extend of If Yes, score: If Yes, score: may be a guide (e.g. flood banks, floodplain – grassland, flood walls). not allowed wet woodlands

Background paper No.4: Hydromorphological alterations in the Sava River Basin 6 Sava River Basin Management

Score band A Features Score band B – Examples of suitable # Description – Guidance assessed Qualitative methods/data use Quantitative

to be and other flooded wetlands more regularly likely to be due to flooded than

engineering arable/cultivat ed and urban land.

1 = 0 % to 5 % reaches affected by 1 = None, or

flood banks or minimal amount, NOTE: Area other of reach affected data should be Engineering records

measures by flood banks or used where (e.g. deepening, impeding other measures available; if resectioned banks, flooding of impeding flooding not, use % two-stage channel). Lateral floodplain of floodplain (e.g. length of reach. connecti (e.g. channel deep dredging). vity of and bank river and regrading,). floodplai n 3 = Moderate amount of reach 2 = > 5 % to affected by flood Indicative floodplain 15 % as banks or other maps. above. measures impeding flooding Any flooding of floodplain. deliberately allowed as 3 = > 15 % to flood storage 35 % as under the EC Local knowledge. above. Floods 5 = Majority of Directive 4 = > 35 % to reach affected by should not be Hydromorphological 75 % as flood banks or taken as surveys/assessments. above. other measures natural. impeding flooding Aerial photos. of floodplain. 5 = > 75 % as Walk-over surveys. above. Historical maps.

Background paper No.4: Hydromorphological alterations in the Sava River Basin 7 Sava River Basin Management

Score band A Features Score band B – Examples of suitable # Description – Guidance assessed Qualitative methods/data use Quantitative

Overall aim is to record the naturalness of the vegetation

in the riparian zone (the strip of vegetation 1 = 0 % to 1 = No, or only adjoining a 5 % non- minimal, areas of May combine reach- river channel), natural land the riparian zone scale and site-based where cover in with non-natural information from: naturalness is riparian zone. land cover. based on land cover as a surrogate, thus not requiring the expertise of professional botanists.

Non-natural land use 2 = > 5 % to 3 = Moderately This standard 15 % non- large areas of the does not (recreationa Hydromorphological Riparian natural land riparian zone with specify any l and high surveys. zone intensity cover in non-natural land fixed width for 7 vegetatio agricultural riparian zone. cover. the riparian n grassland, zone. However, structure cultivated users should / type land, urban state (with areas etc.) reasons) the width of the riparian zone

used for each reach assessed. The width may 3 = > 15 % to be a fixed value 5 = Non-natural 35 % non- (e.g. 1 m, 5 m, land cover is natural land 20 m) or be Local knowledge. dominant in the cover in related to the riparian zone. riparian zone. width of the river (e.g. 1,5 x). Abrupt changes in land cover could indicate the boundary

between the riparian zone and the

Background paper No.4: Hydromorphological alterations in the Sava River Basin 8 Sava River Basin Management

Score band A Features Score band B – Examples of suitable # Description – Guidance assessed Qualitative methods/data use Quantitative

floodplain.

Non-natural land cover classes include: Riparian 4 = > 35 % to recreational zone 75 % non- and high vegetatio natural land intensity Databases. Quantitative n cover in agricultural assessment structure riparian zone. grassland, (in %) of / type cultivated land, bank urban areas, covered by etc. non-natural land use and Near-natural Also use: / or land cover qualitative classes include Aerial photos. assessment 5 = > 75 % natural non-natural wetland, land cover in alluvial riparian zone. forest/natural Walk-over surveys. woodlands, moorland.

1 = 0 % to This feature 5 % non- includes the May combine reach- Non-natural natural land 1 = No, or floodplain scale and site-based land use cover beyond minimal, areas of where one information from: the riparian the river corridor exists. zone. beyond the riparian zone with Floodplai Quantitative non-natural land Overall aim is 8 n land assessment cover (e.g. to record the cover (in %) of 2 = > 5 % to dominated by naturalness of floodplain 15 % non- near-natural the vegetation beyond the natural land vegetation and/or in the river Hydromorphological riparian cover beyond features such as corridor surveys.

zone the riparian ox-bows, remnant beyond the covered by riparian zone, zone. channels, bogs). non-natural where land use and naturalness is / or based on land

Background paper No.4: Hydromorphological alterations in the Sava River Basin 9 Sava River Basin Management

Score band A Features Score band B – Examples of suitable # Description – Guidance assessed Qualitative methods/data use Quantitative

qualitative cover as a assessment surrogate, thus of not requiring naturalness the expertise of

of professional vegetation botanists.

Non-natural land cover 3 = Moderately classes include: 3 = > 15 % to large areas of the recreational 35 % non- river corridor and high natural land beyond the intensity Local knowledge. cover beyond riparian zone with agricultural the riparian non-natural land grassland, zone. cover. cultivated land, urban areas,

etc. Floodplai n land Near-natural land cover cover 4 = > 35 % to classes include 75 % non- 5 = Non-natural natural natural land land cover is wetland, Databases. cover beyond dominant in the alluvial the riparian river corridor forest/natural zone. beyond the woodlands, riparian zone (e.g. moorland. near-natural vegetation and/or Floodplain Also use: features such as features 5 = > 75 % ox-bows, remnant Remote sensed data include non-natural channels, bogs) (e.g. aerial photos, remnant land cover mainly or totally satellite imagery, channels, bogs, beyond the absent). especially for large and artificially riparian zone. rivers). created open- water habitats. Walk-over surveys.

Background paper No.4: Hydromorphological alterations in the Sava River Basin 10 Sava River Basin Management

2.2 Classification of water bodies by five classes The assessment of modification of river morphology has been performed using five classes (Table 2 2).

Table 2: Classification terms for five classes of modification of river morphology Score Class Description Map colour

1 to < 1.5 1 Near-natural Blue

1.5 to < 2.5 2 Slightly modified Green

2.5 to < 3.5 3 Moderately modified Yellow

3.5 to < 4.5 4 Extensively modified Orange

4.5 to 5.0 5 Severely modified Red

The names used to describe each class (e.g. "near-natural") have been deliberately chosen to be different from terms used in the WFD (e.g. "high", "good") to emphasize that classifications using standard EN 15843:2010 are unrelated to classifications of ecological status for the WFD. Although the five colours listed for reporting hydromorphological modification are the same as those in the WFD, they are also used routinely for reporting other (non-WFD) aspects of environmental quality.

2.3 Methodology of risk assessment The final goal is to distribute all delineated water bodies into three groups based on the risk criteria (risk of failure to achieve the environmental objectives):

1. Not at risk 2. Possibly at risk 3. At risk The first group includes water bodies, which do not have any significant (see criteria in Table 2) hydromorphological alterations (barriers, impoundments, water abstraction, hydropeaking) and its class of modification of river morphology is 1st “near-natural” or 2nd “slightly modified”. Water bodies of this group should be considered as natural river water bodies (not heavily modified). The second group includes water bodies, which do not have any significant (see criteria in Table 2) hydromorphological alterations (barriers, impoundments, water abstraction, hydropeaking) and its class of modification of river morphology is 3rd “moderately modified”. This group is temporary, because decision whether these water bodies should belong to category “provisional HMWB” cannot be done and needs additional data and investigation. The third group includes water bodies, which have one or more significant (see criteria in Table 2) hydromorphological alterations (barriers, impoundments, water abstraction, hydropeaking) or its class of modification of river morphology is 4th (extensively modified) or 5th (severely modified). Water bodies of this group should be considered as

Background paper No.4: Hydromorphological alterations in the Sava River Basin 11 Sava River Basin Management provisionally heavily modified (pHMWB). According to the ICPDR approach, final decision on designation of HMWB should be done using high confidence biological data. Using this methodology, objective and integrated assessment of hydromorphological pressures is done, which gives the following important information for Sava RBMP:

- Classes of hydromorphological quality (as a supportive element of the ecological status assessment) - Based on the analysis of the scores of hydromorphological features assessed, the relevant actions to improve the hydromorphological class can be identified, which can be further included in the program of measures - List of water bodies with risk / possible risk / no risk of failure to achieve the environmental objectives (p HMWB, HMWB). It allows to define which water bodies are subject to archiving of good ecological status and which – good ecological potential. 3. Results of assessment 3.1 River and habitat continuity interruption The key driving forces causing river and habitat continuity interruption in the Sava RB are mainly hydropower (77%), water supply (10%), and flood protection (7%) (Figure 1).

Figure 1 : Interruptions of river continuity in the Sava River Basin (in numbers)

In the Sava RB there are 30 barriers1 (SI -6; HR - 7, BA – 9, ME – 2, RS - 8) on the Sava River itself 7 barriers and 23 on the tributaries. Out of the 30 barriers, 27 are dams, 2 are ramps and one of the barrier is classified as “other type of interruption” (Figure 2).

1 Both BA and RS included in their lists HE Zvornik and Bajina Basta, located on transboundary river .

Background paper No.4: Hydromorphological alterations in the Sava River Basin 12 Sava River Basin Management

Figure 2: Types of interruptions of river and habitat continuity in the SRB

Three barriers (HPP Blanca on the Sava river in Slovenia, Kolubara (vodozahvat TE Veliki Crljeni) and Drina river (HE Zvornik) in Serbia, trans-boundary with ) are equipped with functional fish passes. HPP Mavčiče and HPP Vrhovo on the Sava in Slovenia are not passable by fish. HPP Krško on the Sava River in Slovenia is under construction now and is still passable by fish. Gate Trebež (HR) on Lonja River has a sluice with limited connectivity. The key migration route of migratory fish species in the Upper Sava (between 42,9 and 189,7 km from the river source) is interrupted, impacting the development of self-sustaining populations. Fish migratory routes are also interrupted on the tributaries, e.g. dams on tributaries: Sotla/Sutla, Kolpa/Kupa, Dobra, , , Pliva, Lasva, Spreča, Bosut (gate), Drina, Ćehotina, Piva, , and Lim.

Table 3: Overview of the number of river continuity interruptions 2010 and 2015 restoration measures and exemptions according to the WFD Article 4(4) for each Sava country Country Barriers Passable by River continuity Fish passes to River Exemptions Measures 2010 fish 2010 interruptions be constructed continuity WFD 4(4) indicated 2010 interruptions by 2015 SI 6 1 5 1 4 0 4 HR 7 1 6 0 6 0 0 BA 9 1 8 0 8 0 0 RS 8 2 6 0 6 0 0 ME 2 0 2 0 2 0 0 Total2 30(32) 4(5) 26 (27) 1 25 (26) 0 4 Sava 7 2 5 1 4 0 4

2 Both BA and RS include in their lists HPP Zvornik and Bajina Bašta, located on the trans-boundary river Drina.

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Slovenia Name/Location Barriers Passable by River Fish passes to be River Exemptions Measures 2010 fish 2010 continuity constructed continuity WFD 4(4) indicated interruptions interruptions 2010 by 2015 HPP Moste* Yes No Yes No Yes No Yes HPP Yes No Yes No Yes** No Yes Mavčiče** HPP Yes No Yes No Yes No Yes Medvode* HPP Yes No Yes No Yes** No Yes Vrhovo** HPP Boštanj Yes No Yes Yes No No --- HPP Blanca Yes Yes No No No ------HPP No Yes No Yes No ------Krško*** * Combination of measures foreseen in national RBMP, based on the fact, that current assessment of ecological potential does not include fishes yet due to the lack of data ** Fish catch and transport' measure, extent of the measure will be based on research study, as foreseen in national RBMP *** Under construction

Croatia

Name/Location Barriers Passable by River Fish passes to River continuity Exemptions Measures 2010 fish 2010 continuity be interruptions by WFD 4(4) indicated interruptions constructed 2015 2010 HE Ozalj Yes No Yes No Yes No No Akumulacija Yes No Yes No Yes No No Vonarje HE Lešće Yes No Yes No Yes No No Pregrada Yes No Yes No Yes No No Lipovac Akumulacija Yes No Yes No Yes No No Bukovnik Ustava Yes No* Yes --- Yes No --- Trebež Pregrada TE Yes Yes No --- No No ---- TO Zagreb * Limited connectivity (depending on water regime of the Sava River and on manipulation of the Trebež gate during flood events)

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Bosnia and Herzegovina Name/Location Barriers Passable by River Fish passes to River continuity Exemptions Measures 2010 fish 2010 continuity be interruptions by WFD 4(4) indicated interruptions constructed 2015 2010 HE Bočac Yes No Yes No Yes No No HE Zvornik Yes Yes No --- No ------HE Bajina Yes No Yes No Yes No No Bašta HE Višegrad Yes No Yes No Yes No No HE_Jajce II Yes No Yes No Yes No No HE_Jajce I Yes No Yes No Yes No No HE_Kostela Yes No Yes No Yes No No Modrac Yes No Yes No Yes No No MHE_Vitez1 Yes No Yes No Yes No No

Serbia Name/Location Barriers Passable by River Fish passes to River continuity Exemptions Measures 2010 fish 2010 continuity be interruptions by WFD 4(4) indicated interruptions constructed 2015 2010 HE Zvornik Yes Yes No --- No ------Bajina Bašta Yes No Yes No Yes No No Kokin Brod Yes No Yes No Yes No No Uvac Yes No Yes No Yes No No Radoinja Yes No Yes No Yes No No Potpeć Yes No Yes No Yes No No Vodozahvat Yes Yes No ------TE Veliki Crljeni Ustava Bosut Yes No Yes No Yes No No

Montenegro Name/Location Barriers Passable by River Fish passes to River continuity Exemptions Measures 2010 fish 2010 continuity be interruptions by WFD 4(4) indicated interruptions constructed 2015 2010 HE Piva Yes No Yes No Yes No No HE Otilovići Yes No Yes No Yes No No

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3.2 Disconnection of adjacent wetlands/floodplains Sava River has lost much of its floodplains, however, along the lower courses there are still some major important floodplains. The Sava River still hosts the second largest active floodplains (1,900 km²) after the Danube (without the Delta some 5,000 km²). According to estimates, out of the total length of the Sava River (945 km), 78% of floodplain is lost (8,592 km2)3. Lateral connectivity of river and floodplain is included as one of the features of morphological alterations assessment. The results of the assessment showed that more than 2/3 of water bodies at the Sava tributaries have no more than 15% of dikes and other hydrotechnical constructions limiting inundation of floodplain during regular floods. Respectively for remaining 1/3 the length of the dike is more than 15% of their total length.

3.3 Hydrological alterations - impoundment, water abstraction, hydropeaking Hydrological alterations refer to pressures resulting from impoundment, water abstraction and hydropeaking. Hydrological alterations are often of local importance and do not necessarily result in basin-wide transboundary effects. However, the cumulative effect of water abstractions may become significant in the transboundary context.

The main pressure types in the Sava River Basin causing hydrological alterations4, are 27 impoundments5, one case of water abstraction (Otilovići on Ćehotina river in ) and one case of hydropeaking with water level fluctuation >1m/day (on Piva river) and six cases of altered flow regime.

Impoundments are the major hydrological pressure type in the Sava River Basin. Impoundment leads to alteration/reduction in flow velocity in the water body. Hydropower is the main driving force. There is a significant impoundment at 27 water bodies, leading to changes in water body category. Length of impoundment in different countries is presented at the Figure 3.

3 Assessment of the restoration potential along the Danube and main tributaries, Vienna, July 2010 http://assets.panda.org/downloads/restpotwwf_dcpofinal08072010.pdf.

4 According to criteria, as given by the ICPDR HYMO TG impoundment is significant when impoundment length during low flow conditions is longer than 1 km; water abstraction is significant is flow below dam < 50% of mean annual minimum flow of a specific time period (comparable with Q95), hydropeaking is significant if water level fluctuation is higher than 1 m /day. 5 The location of impoundments corresponds to longitudinal interruptions. See Annex 7.

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Figure 3: The length of impoundments in the Sava RB (in km)

4.5 17.5

Slovenia 163 226 Croatia Bosnia and Herzogovina 43.5 Montenegro Serbia

Water abstraction for urban, industrial, agricultural and other uses, including seasonal variations and total annual demand, and the loss of water in distribution systems, leads to an alteration in the quality and discharge in the water body. The significant water abstraction reported for one water body is causing changes to the water body category.

Hydropeaking leads to alteration of flow variation/discharge changing along the river. The main driver is hydropower. There is a significant hydropeaking at one water body, causing changes in water body category.

3.4 Morphological alterations The main drivers causing morphological alterations in the Sava river basin are flood protection, navigation, hydropower, and urbanization. Based on the methodology of river morphological alterations assessment described in Chapter 2, 130 water bodies have been assessed) (Figure 4). Morphological alterations have been assessed only for non-HMWBs.

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Figure 4: Classes of modification of morphology of river water bodies on the Sava River Basin (in %)

1 1 8 Near-natural 30 Slightly modified 60 Moderately modified Extensively modified Severely modified

On the Sava River itself, 14 water bodies have been assessed the results are shown in Figure 5.

Figure 5: Classes of modification of morphology of river water bodies on the Sava River (in %)

28 36 Near-natural Slightly modified Moderately modified

36 Extensively modified Severely modified

90% of the assessed water bodies within the Sava RB belong to the first and second class, but for the Sava River water bodies this figure is only 64%.

The main causes of the morphological alterations (3rd, 4th and 5th classes of morphological quality) are changes in channel geometry, channel longitudinal section and cross-sections, substrate/sediment, bank structure, lateral connectivity of river and floodplain.

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3.5 Risk assessment - hydromorphological alterations Water bodies classified as “not at risk” are those which do not have any significant hydromorphological alterations (barriers, impoundments, water abstraction, hydropeaking) and are classified as 1st “near-natural” or 2nd “slightly modified” class with regard to the modification of river morphology. Within the Sava RB 83% of water bodies belong to this category however for the Sava River itself this figure amounts to 60% only. Water bodies “possibly at risk” include water bodies, which do not have any significant hydromorphological alterations and belong to the 3rd class of modification of river morphology “moderately modified”. There are 16 and 40% of such water bodies in the Sava River Basin and in the Sava River, respectively. Water bodies “at risk” include water bodies, which have one or more significant hydromorphological alterations or its class of modification of river morphology is 4th (extensively modified) or 5th (severely modified). 1% of such water bodies in the Sava River Basin fall in this category (Figure 6).

Figure 6: Risk assessment – hydromorphological alterations (figures in columns represent number of relevant water bodies)

1 100% 16 90% 40 80% 70% at risk 60% possibly at risk 50% 83 40% not at risk 60 30% 20% 10% 0% Total Sava

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