Dam
A dam is construction works that prevents the flow of water and has a damming effect for water. If a dam is to be built for damming a water body, the local government must first approve the design specifications of the dam and the draft building permit with the Environmental Board. The purpose of approval of the design specifications is to provide the applicant with first information on the need to ensure the fish pass. Once the approvals have been received, an environmental permit can be applied for the construction of the dam and damming a water body. In practice, new dams are generally not built and the existing ones are used.
Damming
Damming means raising the natural water level by more than 0.3m. As a rule, a water body is dammed on the existing dam. Damming of a water body and use of hydro-electric energy require an environmental permit, including the existing damming.
An environmental permit for damming gives the right to dam the water body, i.e. to keep the water level above the natural level. An environmental permit for damming can be applied for if the dam (construction works) already exists.
No environmental permit is required if the natural level of a watercourse is raised by up to one meter, unless the damming takes place in the water bodies that need protection as spawning areas or habitats of salmon, brown trout, salmon trout or grayling, or sections of such water bodies, included in the list established under the Nature Conservation Act. This provision frees the owner of a dam from applying for an environmental permit for damming, but not from the environmental permit necessary for the construction of a new dam. It is also possible to lower the water level of damming to a level that does not require water permit any more. Registration of activities involving risk to aquatic environment must be submitted for this.
Use of hydro-electric energy
Hydro-electric energy, or water energy, is a potential or kinetic energy of water. A hydroelectric power plant or water power plant is a complex of buildings and equipment through which the energy of a water flow is converted into electricity.
An environmental permit is always required for the use of hydro-electric energy. As of 1 June 2021, 28 hydroelectric power plants operate in Estonia on the basis of an environmental water permit.
Reservoir
A reservoir is an anthropogenic water body on a river or stream where the dam is located. A reservoir is not a permanent water body. This means that if the owner of the dam is no longer interested in continuing damming or it is not possible to issue the necessary environmental permit, the reservoir will also disappear upon elimination of damming.
If a river and stream generally do not require maintenance, then a reservoir significantly changes the characteristics and natural processes of a watercourse, and therefore it is necessary to maintain it.
When a reservoir is built, the flow rate and mode of the water body changes, which is why particles of sand, clay, mud and plant residue moving along the river settle to the bottom of a reservoir. Over the years, a thick layer of sediment is formed, which can fill a large part of the reservoir together with the plant residues that have formed on the site. A thick layer of sediment implies an abundance of nutrients, which periodically causes a massive proliferation of vegetation and algae. In reservoir and in the river parts downstream, this is accompanied by pollution from organic substances, which are extremely negative from the point of view of the river's fish and bottom fauna. Therefore, it is necessary to maintain reservoirs and remove sediment. If this is not done, then with time, such reservoirs silt and grow full, which means that the reservoir will disappear.
Liquidation of damming
Liquidation of damming means restoration of lowering the water level in the dammed part of the river to the level before damming. Depending on the situation, the area of the former reservoir must be cleaned up after liquidation of damming – to clean up the litter, to design the shore areas and the riverbed. In order to liquidate damming, registration of activities involving risk to aquatic environment is required. It is also necessary to submit the position of the local government together with registration application.
The damming has been liquidated for a variety of reasons. For example, some have been liquidated at the request of the owner because they do not need or do not want to apply for the necessary environmental permit. In some cases, the management of a dam, together with the establishment of fish pass, has proved to be too complicated and expensive. Liquidated damming provides natural living conditions for all aquatic biota.
Registration of activities involving risk to aquatic environment is required for liquidation of damming.
Fish pass
A dam prevents the movement of fish. Fish pass is a facility or part of a fixed riverbed, with a favourable flow rate, necessary for fish to cross the dam. In Estonia, mainly bypasses and artificial rapids have been built at the dams. Between 2009 and 2020, the migration conditions of fish improved at 113 dams.
Building a fish pass requires an environmental permit or registration of activities involving risk to aquatic environment, depending on the type of fish pass and the volumes of activity. If an environmental permit has been issued for damming, an application for amendment of the environmental permit or registration of activities involving risk to aquatic environment must be submitted for building a fish pass.
Last updated: 16.12.2022
