Restoration for wide response in ecological quality and for complex needs of use

 

Restoration of eutrophic temperate lakes by biomanipulation

Control of aquatic invasive species in Ireland, CAISIE

Re-watering of a drained large lake in Greece

Planning the multi-purpose use of a reservoir

 

Restoration of eutrophic temperate lakes by biomanipulation

Biomanipulation can reduce ecological, economic and health nuisances caused by blooms of cyanobacteria in lakes and increase biodiversity in wetlands and small water bodies. Mass removal of cyprinids and/or favouring of piscivorous species  has been successfully used in Denmark, Finland, Czech Republic, the Netherlands and other European countries for more than two decades in restoration of eutrophic lakes. However, less successful cases or failures are also known.

Biomanipulation has been an important research object in freshwater ecology for decades. It has been particularly useful in lakes with slow improvement in water status after sewage diversion. An intensive intervention can usually be carried out in 2 - 3 years, in small lakes even in less than one year. In addition to other water status improvements, a successful biomanipulation also results in better fish stocks, adds value of lakes for recreation and fishing and benefits protection of waterfowl habitats.

The Danish experience has shown that a successful biomanipulation may have an impact also in highly eutrophic lakes. Methods of cost effective fish removal have been developed in Finland since the 1990s and today they are routinely used even in larger lakes (>100 km²). Biomanipulation is not a onetime intervention.  Both in Denmark and Finland the needs for catchment management and other long-term actions are emphasised.

More information:  Finnish Environment Institute, Finland and Alleroed Municipality, Denmark

 

Control of aquatic invasive species in Ireland, CAISIE

CAISIE is an EU Life+ funded programme which has contributed to the understanding and control of aquatic invasive species in Ireland. Aquatic invasive species are a major threat to biodiversity in Irish freshwaters most particularly Lough Corrib in the West Region and their adverse effect will continue to increase unless effective eradication and control methods are developed. CAISIE focuses on researching and implementing control and eradication methods (through jute matting and the use of V-Blades) combined with a marketing campaign to increase awareness and stakeholder engagement.

Lagarosiphon major was first identified in Lough Corrib in 2005 and is capable of growing in inland waters up to 6 meters deep. It is native to southern countries of Africa and once established it strongly outcompetes other native species. Advantage of the control is that this aggressive invasive weed has been stopped from colonising and establishing sustainable populations in lower Lough Corrib, which is a significant achievement as the shallow character of this large water body makes it highly amenable to invasion.  A large submerged weed infestation here could exacerbate future flooding events in the Corrib catchment by restricting the normal drainage of water through the system. In addition any infestation would degrade the current high ecological status of the lower lake. The successful weed control operations undertaken during the Life+ project have reopened previously overgrown areas of the lake for angling and boating. Moreover, the native charophyte dominated habitat that is vital to maintain a healthy wild brown trout population has been naturally rehabilitated.

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More information:  West Regional Authority, Ireland

 

Re-watering of a drained large lake in Greece

Restoration of Lake Karla (originally 144 km², fluctuation 40 – 180 km²) is the largest restoration of a drained natural large lake by re-watering in Europe. The whole experience in technical, hydraulic, environmental and management issues is a valuable example. Karla was a lake since ancient times and it had a high local socio-economic value. In the late 1950s, constant floods and a growing need for cultivated land led to a decision to drain the lake. It was drained completely by 1962, without reservoir control. Approximately fifty years later, aquatic and environmental degradation such as decline of the aquifer of the City of Volos, lowering of ground water level, ground cracking and changes in microclimate, indicated need for construction of reservoir control. Socio-economic and environmental needs demanded plans for re-watering the lake area. The activity was launched in the early 2000s. The restoration was implemented since 2009 and the area of the reservoir is now ca. 38 km². It has facilitated management of water resources for water supply and irrigation. Lacustrine fauna and flora have reappeared. Eutrophication and difficulties in water balance call for further management to improve the status of the water body. The experience will be used in restoration of other Greek lakes drained without reservoir control. 

More information:  Pelion Development Company S.A., Greece

 

Planning the multi-purpose use of a reservoir

The Plastiras reservoir was created with the construction of a dam in late 1950s. Filling of the reservoir started in 1959. The initial objectives of the construction were contribution to the electrification of the country and the watering of a big part of Thessaly plain. The above purposes were achieved. Half of Karditsa plain, a big part of Larissa plain, the city of Karditsa and the city of Sofades with other 35 communities are irrigated by the reservoir. Since the 1990s a tourist attraction with ecological and aesthetic interests has been developed in EU funded development projects.

In one decade (1991-2001) the population of the adjacent municipalities of Plastiras Lake increased by 19% and incomes nearly doubled while the neighbouring regions were declining. The Plastiras Lake is a special example of socio-economic progress for all Greek natural and artificial lakes. An example of effort to apply the practice of Lake Plastiras is the development of the artificial Lake of Smokovo.

More information:  Pelion Development Company S.A., Greece

 

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