D E U TSCHLA N D. ILL Catchment area. Bregenz. Rhein. V orarlberg. T irol. Alfenz. Ill. Litz S WITZERLAND

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1 T irol D E U TSCHLA N D ILL Catchment area Bregenz Rhein V orarlberg Ill Alfenz Litz S WITZERLAND 9

2 Measures in the Ill catchment area Bregenz Rhein V orarlberg Dabaladawehr T irol Ill Rodund Alfenz Braz Litzfassung Litz N Restill/ Partenen Inn km River portrait of Ill catchment area The Ill is a 72 km long south-eastern tributary of the Rhine and is located entirely in Vorarlberg, the most Western province of Austria. Its two source streams the Ochsentalerbach and Klostertalerbach are fed by the effluent of three glaciers: the Vermunt glacier, the Ochsentaler glacier and the Schneeglocken glacier, all three of them situated in the Silvretta group in the Eastern Alps. The source region of the Ill is located at 2,240 metres above sea level and is surrounded by the Dreiländerspitze (3,197 m), Piz Buin (3,312 m) and Silvrettahorn (3,244 m), which are all higher than 3,000 metres. From this source at the national border between Austria and Switzerland, the Ill flows through the Ochsental valley and is dammed up in the Silvretta reservoir before it flows OESTERREICHS ENERGIE HYDROPOWER 10

3 onwards to the northwest through the Montafon region where it picks up its two longest tributaries: the Litz near Schruns and the Alfenz near Bludenz. The further course of the Ill takes it through the Walgau region and carries it below Feldkirch, until the so-called Illspitz, its confluence with the Rhine. Actually, the river basin of the Ill at the most westerly border of Austria accounts for the 4% of Austrian national territory that does not drain into the Black Sea via the Danube, but rather to the North Sea via the Rhine. Alongside its course of 72 km, the Ill surmount more than 1,800 m. By being fed from multiple glaciers and due to its numerous small to medium-sized tributaries, the water levels along the Ill change significantly over the course of the year reaching their highest altitudes in July and August. With an average water flow of 65.5 m³/s, the Ill is the largest tributary of the Alpine Rhine. Fish fauna The Ill follows the typical zoning of a water course with a high Alpine source, continuing its way to more gently sloping valleys and valley floors via steep gradients and canyons. Following the decreasing elevation and flow rates, the changing topography, fauna, flora, oxygen content, temperature and riverbed composition, the following fish regions typical for Alpine water bodies are also to be found in the Ill in descending order: the trout region (epirhithral), the grayling region (hyporhithral) and the barbel region (metapotamal). Rainbow trout, grayling and bullhead are among the respective predominant fish species in the course of the different river sections of the Ill. The target species on the Ill River in the Brown trout, i.e. all dimensions of the fish passage facilities are calculated according to the size and swimming performance of this species (see photo). Photo: VERBUND AG OESTERREICHS ENERGIE HYDROPOWER 11

4 Fish pass by the Restill/Partenen catchment Partenen catchment before construction of the fish pass Fish pass Partenen with a view downstream OESTERREICHS ENERGIE HYDROPOWER 12

5 Company Water body Water body number River kilometre Vorarlberger Illwerke AG Ill Aim of measure Creation of ecological connectivity Type of measure Construction of a fish pass Description of measure Vorarlberger Illwerke AG constructed a fish pass by the Restill-Pertenen catchment with the objective of restoring the connectivity of the Ill in the area of the Restill-Partenen catchment. This makes it possible for the fish and other benthic invertebrates living in the water to negotiate the dam of the Restill/Partenen catchment. The vertical slot fish pass made of reinforced concrete overcomes a height difference of 92 cm. It consists of 12 pools that are each 1.90 m long and 1.20 m wide. The height difference of the individual pools is ca. 7 cm. Individual stones were built into a 10 cm thick, structured layer of concrete in the bottom of the pools. A bottom substrate with an average minimum grain diameter of 60 mm was poured loosely into the pool. A natural light supply could not be ensured for all pools of the fish pass; therefore, window openings were installed in three pools for an adequate light supply. There is still no natural light in 2 pools. Just in case experience shows that artificial light is required for the fish pass, the possibility of an electrical connection was created for these pools as a precaution. In addition, a catwalk was built for maintenance of the pools. The ecological discharge for the fish pass is adapted to the hydrological conditions on a monthly schedule: 3 months 150 l/s, 3 months 200 l/s, 6 months 300 l/s. A fish trap was installed in the fish pass for approximately two months in autumn 2011 for a functional check during the expected spawning migration. It was checked twice daily. Trapped fish were measured and then released again above the fish pass. It was possible to confirm the functionality of the fish pass and fulfilment of the criteria of the guideline. Period of construction/implementation (without monitoring) to Financial expenditures Total investment in 240,000.- Of which UFG funding 0.- (Expected) monitoring expense in 5,600.- (Expected) operating expense in /year 7,000.- Generation losses in MWh/year 7,314 MWh/year (voluntary ecological flow release) OESTERREICHS ENERGIE HYDROPOWER 13

6 Fish pass in the Litz catchment Old dam barrier before the beginning of construction at river kilometre 2.95 New fish pass with ecological flow release via controllable slider OESTERREICHS ENERGIE HYDROPOWER 14

7 Company Water body Water body number River kilometre Montafonerbahn AG Litz Aim of measure Creation of ecological connectivity Type of measure Removal of a transverse structure and construction of a fish pass Description of measure With the project, the existing migration barriers in the area of the Litz catchment were removed and ecological connectivity was created through removal of the old dam barrier at river kilometre 2.95 of the Litz and the construction of a fish pass at the dam at river kilometre Regarding the functional capability of the fish pass, a study of variations was carried out before preparation of the documentation to be submitted with the involvement of the official fish biology and limnological experts. Due to the existing infrastructure and the related very tight spatial conditions in the area of the existing water catchment, a rough channel pool-type fish pass along the desander emerged as the best variation. The fish pass is fed with 150 l/s year round and the head pond level is kept constant except for surplus water situations. The further dynamised residual water is delivered at up to 550 l/s at the downstream water of the fish pass via a metering slider with magneto-inductive flow measurement. Regarding its connection to the downstream water, the fish pass is very easy to find. Due to the water body geometry and runoff conditions that prevail here, there is only a single migration corridor that is passable to fish to the pool of the fish pass. The discharge fraction of the fish pass of the total residual water drainage lies between 21% and 100%. Due to the existing channel geometry and connection of the fish pass in the area of the mainstream of the body of water, it is practically excluded that the fish could swim past the fish pass. Hence, monitoring by means of pit tag detection verified an adequate number of all studied size classes of the brown trout. Downstream of the fish pass, in connection with the removal of an old dam barrier that was not passable to fish, which made it flush to the riverbed, the depth of the riverbed was increased and also a low-water channel was designed. Period of construction/implementation (without monitoring) to Financial expenditures Total investment in 895,000.- Of which UFG funding 223,750.- State funding 89,500.- Miscellaneous 250,000.- (Expected) monitoring expense in 3,016.- (Expected) operating expense in /year 3,000.- Generation losses in MWh/year None No generation loss is to be expected. The measures for connectivity were part of further optimisation measures on the catchment. Residual water for the fish pass is handled without increasing the current ecological discharge. OESTERREICHS ENERGIE HYDROPOWER 15

8 Fish pass in the Ill/Rodund catchment Fish pass Rodund with a view downstream General overview of the Rodund fish pass OESTERREICHS ENERGIE HYDROPOWER 16

9 Company Water body Water body number River kilometre Vorarlberger Illwerke AG Ill Aim of measure Creation of ecological connectivity Type of measure Construction of a fish pass Description of measure Vorarlberger Illwerke AG constructed a fish pass by the Ill/Rodund catchment. Through this structure, connectivity of the Ill was created in the area of the Ill/Rodund catchment. This makes it possible for the fish and other benthic invertebrates living in the water to negotiate the dam of the Ill catchment. The Rodund Ill catchment is designed as an outside curve. This ensures that the bed load is kept away from the catchment inlet. The water supply to the fish pass was designed so that it remains free of bed load. Making use of the existing attraction flow, the first pool of the fish pass was placed directly at the discharge of the residual water channel. The vertical slot fish pass runs over the existing support wall from the residual water channel up to the gravel flushing channel. The vertical slot fish pass runs along the gravel flushing channel wall above the gravel flushing sluice. The pools were designed as prefabricated sections in the area of the gravel flushing channel wall. Altogether, the vertical slot fish pass overcomes a height difference of more than 4 m. It consists of 30 reinforced concrete pools that are each 1.90 m long and 1.20 m wide. The height difference of the individual pools is 13 cm. An average minimum grain diameter of 60 mm was poured loosely into the pools as a bottom substrate. The fish pass has a constant residual flow of 300 l/s. A fish trap was installed in the fish pass for approximately two months in autumn for a functional check during the expected spawning migration. Since the trapping results were poor for several seasons, it was decided to carry out a pit tag trial. To do this, 40 brown trout were caught from an Ill section at a higher location, individually marked and then released again below the dam. It was assumed that territorial brown trout would attempt to find their original territory once again. With the success of the test, it was possible to demonstrate the full functional capability of the fish pass. Period of construction/implementation (without monitoring) to Financial expenditures Total investment in 200,000.- Of which UFG funding 0.- (Expected) monitoring expense in 18,000.- (Expected) operating expense in /year 10,000.- Generation losses in MWh/year 3,311 MWh/year (ecological flow release) OESTERREICHS ENERGIE HYDROPOWER 17

10 Fish pass at the Braz power plant Einlauf Fischwanderhilfe Dotierwasserabgabe mit Regelung Wehranlage Auslauf Fischwanderhilfe (Restwasserstrecke) Overview drawing of the fish pass at the Braz power plant Fish pass outlet OESTERREICHS ENERGIE HYDROPOWER 18

11 Company Water body Water body number River kilometre ÖBB-Infrastruktur AG Alfenz Aim of measure Creation of ecological connectivity Type of measure Construction of a fish pass Description of measure ÖBB-Infrastruktur AG constructed a fish pass at the dam system of the Braz power plant in the year A so-called vertical slot pass was built with an additional, parallel running, controllable ecological flow release. The ecological flow release facilitates the correct delivery of the required water despite a fluctuating water level in the inlet area of the fish pass. The water inlet of the fish pass was constructed in the area of the existing dam pool. The water outlet is directly below the dam system. 26 individual pools were planned and built to overcome the height difference (downstream water to head pond) of ca. 3.9 m. The individual pools are connected with vertical slots with a slot width of 15 cm. The water flows through these slots from one pool to the other at a speed that is compatible for fish. That way the energy of the water is reduced gradually with the respective pool size. In contrast to other types of construction, this vertical slot pass has a high level of self-cleaning force and therefore requires less maintenance. This is confirmed by the operating experience. A fish trap was installed in the top pool of the fish pass on In the subsequent monitoring over approximately one month, there were daily checks. In the process, it was possible to demonstrate the function of the fish pass. Period of construction/implementation (without monitoring) to Financial expenditures Total investment in 343,018.- Of which UFG funding 68,604.- State funding 17,151.- (Expected) monitoring expense in 10,000.- (Expected) operating expense in /year 5,000.- Generation losses in MWh/year 6,000 MWh/year OESTERREICHS ENERGIE HYDROPOWER 19

12 Renaturation of the Dabalada dam Condition of the Dabalada dam before reconstruction in 2012 Dispersed riverbed ramp after reconstruction in 2013 OESTERREICHS ENERGIE HYDROPOWER 20

13 Company Water body Water body number River kilometre Wasserverband Ill- Ill Walgau Aim of measure Creation of ecological connectivity Type of measure Removal of the transverse structure through a dispersed riverbed ramp Description of measure Until 2013, the Dabalada dam was the first impassable hurdle for fish upstream of the entry of the Ill into the Rhine and was the only migration obstacle before the subsequent renaturation stretch. To create the connectivity, a decision was made for the variation with a dispersed riverbed ramp with a length of approximately 50 m and a fall height of approximately 2 m. The existing transverse structure of the bottom sill was replaced by a riverbed ramp in the trough-step-pool system and covers the entire width of the water body. With this structure, there is unrestricted possibility for the fish to ascend. In addition, the dispersed ramp does not constitute a barrier for the specific sediment dynamics. Period of construction/implementation (without monitoring) to Financial expenditures Total investment in 990,000.- Of which UFG funding 0.- State funding 660,000.- Miscellaneous 330,000.- (Expected) operating expense in /year 0.- Generation losses in MWh/year None OESTERREICHS ENERGIE HYDROPOWER 21