Altusried test case
| Fact box: Altusried | |
|---|---|
| Country | Germany |
| River | Iller |
| Operator | LEW |
| Capacity | 4 MW |
| Head | 9 m |
| Inter-annual discharge | 46.5 m3/s |
| Turbine(s) | 2 Kaplan turbines |
| Detailed report | Click for pdf |
Contents
Introduction
The river Iller is located in the far south-western part of Germany. It flows into the river Danube near the city Ulm. The river Iller originates from the confluence of the three rivers Stillach, Breitach and Trettach near the city Oberstdorf in the “Allgäuer Alps”, south Germany.
It’s catchment area has a size of 2152 km². The HPP Altusried is the first HPP after the source of the river Iller. The last HPP of the BEW is near Memmingen. In the downstream area of the BEW HPP chain there are an additional 8 HPPs.
The hydrology of the Iller is characterized by a sustained flows in winter, high water levels in spring due to snow melting and low water period from August to October. At Altusried, the main Test Case HPP at the Iller, the mean interannual discharge is estimated to be 46.6 m3/s.
About the hydropower plants
The HPP at Altusried is a run-of-river HPP with an installed capacity of 4 MW and a mean annual output of 30 million kWh. The HPP has two Kaplan turbines, each with a flow rate of 50 m³/s and a drop height of 9 m. The hydropeaking operation mode has been minimized since 2014.
Layout
There is a big reservoir in the upstream area of the Hydropower plant. In the downstream area of the HPP the river Iller is still flowing. After a free flowing area of round 1500 the root of the next reservoir starts. The BEW has built a fish bypass channel around the HPP in 2015. It is 700 m long and has a mean flow of 1 m³/s.
The Operator: LEW Wasserkraft GmbH (LEW)
The LEW is a 100 % subsidiary of the Lechwerke AG. It runs and maintains 36 HPPs at the rivers Danube, Günz, Lech and Iller and is thereby one of the leading HPP operator in Bavaria, Germany. The company produces over 1 billion kWh energy out of regenerative hydropower per year. [Read more.]
Pressures on the water body's ecosystem
Several dams with different purposes upstream and downstream of the two HPPs pose a problem for the continuity of the water body and thereby for fish migration. The native fish species are in decline and several alien species are appearing and/or increasing in number. The flow is highly regulated for irrigation and hydropower uses and there are a lot of artificial lentil habitats due to the presence of dams, which has an effect on the hydrology. There is a heavy agricultural use in the area with a significant use of agrotoxins, which leak into the water. Several dams block the sediment transport, especially since there is no law that enforces an improvement of the situation.
Test case topics
Fish population
The river is dominated by small and medium size reophilic native cyprinids like Iberian barbel (Luciobarbus bocagei), northern straight-mouth nase (Pseudochondrostoma duriense), Northern Iberian chub (Squalius carolitertii) and Pyrenean gudgeon (Gobio lozanoi). All of them are suffering a decrease in their populations (specially nase, wich is an endemic species) and allien species are increasing their presence (mainly Alburnus alburnus)
Migration devices
The Bragado weir does not have a fish pass for either upstream or downstream fish migration. Such device was considered unnecessary by the Portuguese authorities since the HPP is placed in a reach of the Avelames River with reduced natural longitudinal connectivity, due to the occurrence of natural falls. Furthermore, migratory fish species requiring long distance movements to reproduce do not occur in this river.
Upstream migration
The main facilities for upstream migration are the fishways built on each dam (all native species are potamodromous). At Guma, it is a pool and weir fishway, with submerged notch with bottom orifice. It has a slope of 8.77 % and covers a trial height of 8.85 m. Vadocondes has a vertical slot fish pass with a trial height of 3.75 m. Both have supplementary attraction flow into the fishway entrance.
E-flow
Due to the hydropower plant type (over the dam and run-of-river type), there is no legal requirement for ecological flow. Nonetheless, fishways always must have enough flow for operating and therefore the downstream by-pass of the river always maintains a minimum flow of 0.25-0.50 m3/s.
Research objectives and tasks
This hydropower plant type (run of river) is quite common on the main Spanish river basins. The work at the Test Case sites aims at improving the knowledge on the impacts this type of HPP has on fish migration and location of ascent paths. Different flow configurations through the turbines and fishway-attraction flow will be tested to maximize the relationship between fish upstream movement and hydropower production. Also, fish passage through turbines and their survival using different turbine configurations will be an important result about HPP management and impact.
Research tasks
The research tasks and field studies conducted at Guma and Vadocondes are:
- Population and habitat analysis
- Analysis of the conceptual solutions and facilities for fish migration
- Assessment and improvement of fish mortality in the turbines
- Spawning areas and hydro-morphology to attain self-sustainable populations
- Migration facilities and attraction flow
- Hydraulic modelling of attraction flow
