A total of over one thousand dams have been counted on Estonian rivers, of which close to 75% are insurmountable for fish. Researchers are studying the mobility of fish and the possibilities for removing migration obstacles, on the high potential northeastern Estonian rivers.
All the dams in the area were evaluated in 2019, according to the project application and 14 priority dams were selected, on 8 bodies of water. The selection of dams, foremost took into consideration the effects of the dam and the fish potential of the river, the location of the migratory obstacle on the river (the dams were preferred, which were the first insurmountable migratory barrier on the river), technical feasibility and the cost of the solution.
The monitoring of the fish will be performed in the next phase, on the selected water bodies, as well as the services and their values that the given bodies of water offer, will be assessed. An evaluation methodology is being developed for assessing the services of the ecosystems of the river. Talks will also continue to take place, with dam owners and activities continued on those dams, where the owner is ready to be cooperative, as well as where the solutions offered, ensure the fish free mobility, both upstream and downstream.
Preliminary projects will be compiled for eight dams, according to the results, as well as six migratory obstacles will be removed, within the framework of the project. The preferred solution is the demolition of the dam, but solutions may also be different types of fish ladders.
The following are part of the initial broader selection of dams and barrier structures, resulting from the survey, the removal of which or the possibility of establishing fish ladders and solutions, will be considered in the second phase:
Loobu River – Undla Dam
Võsu River – Võsu (Mere) and Võsu (Metsa) Dams
Ala River – Tamme Dam
Purtse River – Püssi Dam and the Lohkuse Dam
Pada River – Unukse Dam and Unnukse-Mahu highway culverts
Selja River – Varangu Dam, Päide I and II Dams
Kunda River — Aravuse Dam and Kunda IV (Kunda Manor) Dam
Udriku Brook – Udriku (Mäo) 2 and dam in the Mäo village, near the Jõekääru Farm
The best solution to ensure the free movement of fish would be to remove the dams, however this is not always possible. A fish ladder is established by the dam, in such cases, if it is technically possible, reasonable and ensures the desired result. Fish ladders are divided into natural and artificial. Natural fish ladders are artificial rapids, rock ramp fish ladders, a cascade of ponds etc. Artificial fish passes are for example, by-pass fish ladders, fish elevators etc.
The LIFE IP CleanEST project will evaluate, if previously established fish ladders, function or not. The effectiveness of the fish ladders, established in the framework of the project will also be assessed. The effect on fish, of the replaced road culverts on the Toolse River, will also be assessed, in addition to the fish ladders.
There are in total 15 fish ladders established in the region of the project, of which 13 are located in Lääne-Viru County and 2 in Ida-Viru County. Hereby the Lohkuse fish ladder has also been taken into consideration, which has not been established as a fish ladder and has not been accounted for as a fish ladder, but in the framework of the project will be assessed, if the current solution is functional or not. The Metsa Dam located on the Võsu River, has also been taken into consideration, into which an opening has been created, for fish that ensures their access.