Case study:LIFE 06 NAT/SLO/000069 Intermittent Lake Cerknica

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Location: 45° 44' 33", 14° 21' 48"
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Project overview

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Status Complete
Project web site http://life.notranjski-park.si/eng/index.shtml
Themes Habitat and biodiversity, Hydromorphology, Land use management - agriculture
Country Slovenia
Main contact forename Tanja
Main contact surname Vasilevska
Main contact user ID
Contact organisation Notranjski regijski park
Contact organisation web site http://life.notranjski-park.si/eng/index.shtml
Partner organisations
This is a parent project
encompassing the following
projects
RESTORATION OF THE GORIŠKI BREŽIČEK STREAM, RESTORATION OF THE TRESENEC STREAM
The regulated bed of Goriski Brezicek stream before restoration (Photo: Notranjski regijski park, http://life.notranjski-park.si/eng/project_threats.shtml)

Project summary

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In 2006 Notranjska Regional Park acquired financial support from European programme LIFE – Nature for project LIFE 06. The purpose of this project was the establishment of appropriate conditions for protection and conservation of animal and plant species and their habitats on Lake Cerknica. Factors that threaten the biodiversity on Lake Cerknica are modified watercourses, abandoning of meadow mowing and deficient knowledge of nature and its conservation.

With the intention of maintaining biodiversity on Lake Cerknica efforts were oriented to following actions:

  • Restoration of watercourses, that would contribute to higher water ground level and retaining of overall water level on Lake Cerknica
  • Composition of a Management plan, which serves as groundwork for managing the project area and is orientated towards conservation of natural and cultural heritage of Lake Cerknica
  • Mapping of habitat types with the intention of conserving the endangered ones
  • Land managing including buying, late mowing and mulching on the permanently protected land.
  • Popularization of the project and education of the youth on the importance of nature conservation.

The aim of the project was the restoration of former meanders and by doing so retaining the water longer in the dry period and increasing the groundwater level in wetland areas. It was expected that in this way the ecological conditions of the wetland areas, and thereby the living conditions for flora and fauna, improve. Inženiring za vode d.o.o. produced the project documentation, based on a review of the situation on the terrain and examining the location of riverbeds as they were before the regulating operations began. More than 12 km of watercourses in the Cerknica area are included in this study.

Re-instatement of the old course and creation of backwater and water retention areas to encourage groundwater level rise and slower runoff of low waters.

Community Involvement - education of the youth on the importance of nature conservation.

                         RESTORATION OF THE GORIŠKI BREŽIČEK STREAM: 

By restoring former meanders of the Goriški Brežiček stream it was intend to raise the groundwater level in the area of the Dujce fen which ranks among the qualifying habitats for determining the Natura 2000 areas, and thus restore appropriate conditions for sustaining this bog. The company TGM Bizjak, Dušan Bizjak s.p. completed the restoration works on approximately 500 m long section of upper stream and on 200 m in its lower part at the confluence with the Lipsenjščica stream.

Expected results of this restoration:

  • slower runoff of low waters from the area of the intermittent lake,
  • ground water level rise,
  • retention of water in depressions and stream branches, consequently higher constant ground water level height and change in the soil – water rate.

Restoring Goriški Brežiček stream was planned for the entire section, from the mill at the source, to its mouth in Lipsenjščica River, but only a part has been realized. The entire length of the stream has been straightened in the past, but given the terrain and vegetation, the original stream channel is still clearly visible. Restoring the original layout consisted of its deepening. Average width of the planned channel section was from 3.0 to 6.0 m. Excavation has been exercised in the form of U, with banks sloping 1:2, but it was planned that the transition slope of stream bank and terrain on majority of the length is carried out in a vertical slope and then let the water itself create a stable bank. It was assumed that the stability would be provided primarily by turf and partly by the riparian vegetation root system. Deepening of the stream bed at the juncture with the primary bottom at the upstream side has been protected by the small wooden weir (a small weir with the top corners at the bed level or just above it, which is not noticeable under normal hydrological conditions). Where possible, multiple channels with lower spills/overflows between the excavated meanders were predicted. Spills/overflows has been fortified with small wooden weirs (wooden piles, tree trunks) to prevent uncontrolled deepening of the spills/overflows. Spills/overflows were carried out above medium water level and they were covered with turf. At the appropriate locations at the contact of the current and planned section have also been carried out coves or bays, which are designed by keeping part of the current channel or in the area of inactive tributaries.

                         RESTORATION OF THE TRESENEC STREAM:

The restoration of the former riverbed of Tresenec stream from its source in the direction of Levišča sinkholes was undertook in order to raise the level of groundwater and thus enable the sustenance of characteristic water and river-bank plant communities. The Tresenec stream is also of great importance to the animal world since it is the only watercourse in the Lake Cerknica area that never runs dry and as such offers refuge for the water animals in the times of drought. On its banks you can still find elusive Otter’s (Lutra lutra) footprints. GRADBINKO d.o.o. enterprise completed the restoration on 650 m long section of the Tresenec stream.

By increasing length of stream, restoring former branches and meanders, the water surface of the stream increased, which will have a positive effect on the conservation of aquatic, riparian and wetland habitats.

Monitoring surveys and results

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Lessons learnt

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Image gallery


Lake Cerknica in autumn (Photo: Notranjska Regional Park archive)
The Goriški Brežiček stream during the rainfall, January 2007. Straightened, regulated channel is seen in the foreground, while primary channel is seen in the background (Photo: Rok Fazarinc).
Restoring the old riverbed of Goriški Brežička (Photo: Notranjska Regional Park archive).
The Goriški Brežiček stream after restoration, partly flooded, during higher water surface (March 2010) (Photo: Rok Fazarinc).
Restored meanders of Goriški Brežiček stream (Photo: Notranjska Regional Park archive).
Restored old riverbed of the Tresenec (Photo: Notranjska Regional Park archive).
Tresenec in upper flow (Photo: Notranjska Regional Park archive).
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Catchment and subcatchment

Catchment

River basin district Danube River Basin District
River basin Danube

Subcatchment

River name Sava River
Area category 100 - 1000 km²
Area (km2)
Maximum altitude category 200 - 500 m
Maximum altitude (m) 270
270 m
0.27 km
27,000 cm
Dominant geology
Ecoregion Dinaric Western Balkan
Dominant land cover Wetland
Waterbody ID



Other case studies in this subcatchment: HPP Blanca


Site

Name Goriški Brežiček stream, Trstenc stream
WFD water body codes SI141VT2
WFD (national) typology
WFD water body name VTJ Cerkniško jezero (Cerknica lake)
Pre-project morphology Straight
Reference morphology Sinuous
Desired post project morphology
Heavily modified water body No
National/international site designation
Local/regional site designations Ramsar, Special Protection Area, Special Area of Conservation
Protected species present Yes
Invasive species present No
Species of interest
Dominant hydrology Ephemeral, Quick run-off
Dominant substrate Silt, Sand, Gravel
River corridor land use Wetland, Extensive agriculture, Grassland, Woodland
Average bankfull channel width category
Average bankfull channel width (m)
Average bankfull channel depth category
Average bankfull channel depth (m)
Mean discharge category
Mean annual discharge (m3/s)
Average channel gradient category
Average channel gradient
Average unit stream power (W/m2)


Project background

Reach length directly affected (m)
Project started January/2007
Works started
Works completed
Project completed
Total cost category 1000 - 5000 k€
Total cost (k€) 1840
1,840 k€
1,840,000 €
Benefit to cost ratio
Funding sources Notranjska Regional Park, Municipality of Cerknica, Ministry of Environment and Spatial Planning

Cost for project phases

Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname
Investigation and design
Stakeholder engagement and communication
Works and works supervision
Post-project management and maintenance
Monitoring



Reasons for river restoration

Mitigation of a pressure
Hydromorphology straight channel
Biology Quantity & dynamics of flow, Channel pattern/planform, Structure & condition of riparian zones
Physico-chemical
Other reasons for the project


Measures

Structural measures
Bank/bed modifications Weir construction, Bank reprofiling
Floodplain / River corridor Local deepening, Coves and bays construction, Construction of the overflows between individual meanders
Planform / Channel pattern Re-instatement of old course, Creation of backwater
Other
Non-structural measures
Management interventions late mowing and mulching on the permanently protected land, mapping of habitat types
Social measures (incl. engagement) Student Education
Other popularization of the project, Information provision


Monitoring

Hydromorphological quality elements

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative
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Biological quality elements

Element When monitored Type of monitoring Control site used Result
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Physico-chemical quality elements

Element When monitored Type of monitoring Control site used Result
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Any other monitoring, e.g. social, economic

Element When monitored Type of monitoring Control site used Result
Before measures After measures Qualitative Quantitative


Monitoring documents



Additional documents and videos


Additional links and references

Link Description
http://archive-si.com/si/n/notranjski-park.si/2012-10-05 373223/ project archive

Supplementary Information

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REFERENCES

LAYMAN’S REPORT Project LIFE 06 NAT/SLO/000069, Intermittent Lake Cerknica, Notranjska Regional Park, Cerknica, december 2009. Availabe at: http://ec.europa.eu/environment/life/project/Projects/index.cfm?fuseaction=home.showFile&rep=file&fil=LIFE06_NAT_SI_000069_LAYMAN.pdf

Smolar-Žvanut N., Fazarinc R., Perič B., Blumauer S., Kavčič I. 2011. The restoration of tributaries of Cerknica Lake and Škocjan Caves Park. Seminar: Forging Targets and Solutions for Rivers and Water Ecosystem Restoration. Ljubljana, 16-18 November 2011.