Tidal Power Plants as opposed to thermal power stations do not emit greenhouse gases and other pollutants into the atmosphere, do not flood the surrounding territories, do not require expenditure on melioration, do not pose the threat of disasters when the dam bursts and do not present any potential threats as opposed to nuclear power stations. Tidal power has these main ecological advantages that it prevents emissions of pollutants into the atmosphere, accumulation of ash heaps, radioactive and thermal waste during the mining, transport and utilization of fuels and prevents the reduction of oxygen content in the atmosphere.
It is clear that the ecological “purity” of Tidal Power Plants is only relative since their construction and operation, as any other human intrusion into nature, cannot remain without consequences. However, tidal power is characterized by the fact that these consequences are minimal compared to other power stations and can be considered as marginal. These consequences display positive features as well by creating recreational conditions, defending the shoreline from wave erosion, reduction in the turbulence of water flows and causing beneficial influence on the fauna and flora. Apart from that the flotation method of construction allows to remove the main works from the uninhabited region of the fragile wild nature to the existing maritime industrial center and prevent the ruinous cessation of the water exchange between the sea and the basin. Besides, the developed in Russia and world recognized model of a one basin Tidal Power Plant does not disturb the natural pace of energy production.
Studies of the influence of the Kislaya Guba Tidal Power Plant on the environment was conducted by the Murmansk Marine Biology Institute, the Institute of Fishing and Oceanography of the Polar Region, the Southern Seas Biology Institute and the Moscow State University. Ecological studies regarding the Rance Tidal Power Plant in France and the expert assessment of the following projects under consideration: Fundy (Canada), Severn and Mersey (UK), Tugur and Mezen (Russia) were analyzed as well.
The studies of the isolated by the dam basin of the Kislaya Guba Tidal Power Plant showed that under the free water exchange regime the water level fluctuations in the basin generally repeat that of the water level fluctuations in the sea but with a 2-3 hours phase shift. The water exchange depends on the mode of operation of the Tidal Power Plant. During the procedure of “basin cleaning” the water exchange diminishes and electricity production is reduced to one fifth of that during the natural mode of operation. The water exchange reduction leads to the restructuring of the bottom ecosystem of the bay. The length of this process was approximately ten years since the commissioning of the Kislaya Guba Tidal Power Plant and this has to be taken into consideration in the analysis of the ecological consequences of any similar project.
The ecological monitoring of the Kislaya bay that started in 1924 allowed to collect extremely valuable data for the substantiation of ecological safety of large tidal power projects both in Russia and abroa
Tidal Power Plant - Fishing Grounds Monitoring
The Tidal Power Plant dam complicates the passage of fish from the sea into the basin. However, theoretical data and tests conducted by the “Sevryba” Trust at the Kislaya Guba Tidal Power Plant (fish passage through the station dam and subsequent harvesting) showed that trade fish with the width of up to 25 cm (99% of the total) pass though the blades of the directing device and the low pressure operating wheel of the capsule type turbine with a diameter of 3,3, m rotating at 72 turns/sec. Apparently with the increase of the turbine wheel diameter to 5,3 -10 m the passage of fish will not have any restrictions whatsoever. Apart from that the uninhibited passage of fish through the dam should be through the water passage openings that are intended for the filling up of the basin in each tidal cycle (2-2,5 hours). The totally uninhibited passage of fish will be made possible through the currently developed orthogonal hydro turbines (already installed and successfully operating). These turbines will idle for water passage as the idling orthogonal turbine has the highest transfer capability. In addition, the Tidal Power Plants dams usually have openings for the passage of fish. According to the data on the operations of Tidal Power Plants at Rance in France and Tcjanzansan in China these are beneficial for the local marine fauna leading to increased diversity of species and fish population number in the basin.
The noted similarity of species types and biomass of the plankton in the basin and the adjacent sea at stable (design) water exchanges through the dam indicates the identity of the marine fauna in these two areas. As opposed to that differences in the composition and quantities of zooplankton in the basin and the adjacent see area were detected in the basin of Kisloguskaya Tidal Power Plant. These were caused by the significant reduction in the design water exchange through the Tidal Power Plant in the beginning of the 1980-decade. With the subsequent restoration of the water exchange the plankton biomass in the basin was restored.
The Monitoring of Erosion, Sedimentation and Icing Regimes
It was established that sharp changes in the operation of the Tidal Power Plant lead to the erosion of the bottom (up to 2-3 cm a day). However, following the designed operation regimen for 2 years all the processes stabilize, come into a dynamic equilibrium and erosion ceases. It was also shown that on average a somewhat smaller amount of sedimentation is brought into the basin, the activity of dynamic processes diminishes and no bottom deformation has been detected.
Studies show that the presence of a Tidal Power Plant results in softening of the icing regime in its basin and practically eliminates storms in it.
Monitoring of Water Salinity
Water salinity is one of the main factors determining the ecological state of the marine fauna. Monitoring of water salinity indicated that if in natural conditions fluctuations in water salinity are around 0,7%, with a Tidal Power Plant present they drop to 0,3% so as to be practically invisible. However, a Tidal Power Plant may lead to increased water stratification in the basin. The difference between the salinity of the surface water and that of the layer deeper may increase by 0,2-0,3%. This means that the stratified waters will move from their current position towards the sea but this apparently will have no practical influence.