3.2. History and the Current Status of Small Hydropower in the Baltic States
The first written evidence of the existence of the watermills in the Baltic States dates as early as the 11th century. Together with windmills, they are the oldest industrial objects in these countries. The power of water via the waterwheels was used to operate grain mills, sawmills, wool carding mills, paper mills, and other industrial objects. The first road systems were linked with watermills, as dams were also used as bridges [
36].
It is difficult to determine the exact number of watermills that were operating at the end of the 19th century, when the first hydropower plants were built in Lithuania, Latvia, and Estonia. It is known that, in Lithuania and Latvia, there were approximately 640 and 700 watermills. The reconstruction of these watermills, replacing the waterwheel with the turbine and connecting it to the generator, thereby, transforming the watermills into small or micro hydropower plants, stared the era of hydropower in these three countries.
Before World War II, small hydropower became one of the main sources of electricity in the rural areas, and this forced the development of the local electricity grids. There were 96 small hydropower plants in Lithuania in 1935 with a total installed capacity of 1.9 MW [
37]. In Latvia in 1926, there were 26 SHP plants with a total installed capacity of 1.5 MW [
38]. At that time, Estonia had the most developed network of hydropower plants, because, in 1940, there were 921 operational waterwheels and hydroturbines, while the total installed capacity of the hydropower plants was 9.3 MW [
39].
During World War II, the majority of SHP plants were destroyed; however, after the war, the restoration work began immediately together with the construction of new plants. The status of small hydropower grew together with the number of plants. In 1949 in Latvia, there were 60 SHP plants with the installed capacity of 5.8 MW [
40], while, in Lithuania in 1958, there were already 104 SHP plants producing 19 GWh annually [
37].
The decline of small hydropower started in 1954 with the beginning of construction of the joint electricity grid. After the construction of large hydro, nuclear, and thermal power plants, the SHP plants became unprofitable and were eliminated from the grid. By 1977, there were no SHP plants operating in Latvia [
38] and Estonia [
39], while, in Lithuania in 1981, there were only 13 still operating [
37].
Small hydropower was rediscovered in Lithuania, Latvia, and Estonia after 1990 when all three Baltic States regained independence. Many old SHP plants and watermill sites were rebuilt and began to produce electricity once again. The growth in the number of SHP plants in the Baltic States from 1990 is presented in
Figure 5.
The year 1990 started with Lithuania with 10 SHP plants and Latvia and Estonia with none. Six years later in Latvia, there were already more SHP plants than in Lithuania, and, as can be seen from
Figure 5. Latvia became and still is the biggest developer of small hydropower in the Baltic States. In 2017 in Latvia, there were 147 small hydropower plants, while, in Lithuania, there were 95 and in Estonia, 47.
The impressive growth of the number of SHP plants in Latvia until 2002 was related to favourable state support policies for all renewables due to the lack of electricity generators. At that time in Latvia, approximately 50% of the consumed electricity in the country was generated locally. Lithuania still had its Ignalina nuclear power plant, and Estonia had its oil shale power plants, which meant that surplus capacities were available in these countries. Therefore, there was no need for such exclusive support. The sharp decline in the development of small hydropower in all three Baltic States starting from 2002 is clearly visible in
Figure 5. This was due to the stringent adopted environmental laws that stopped further development.
Interestingly, a large number of SHP plants in Latvia did not respond in terms of the actual electricity generation. Although, in Lithuania, there are nearly 1.5-times less SHP plants and, by the same amount, less total volume of water in the rivers than in Latvia, the electricity generation at the SHP plants is much higher (
Figure 6). During the period from 1990 to 2017 at SHP plants in Lithuania, a total of 1437 GWh, in Latvia a total of 1180 GWh and in Estonia a total of 429 GWh of electricity was generated. This also reflects in normalised electricity generation evaluations for the same period (
Figure 6).
As it was mentioned, the Baltic States reached their targets of the share of energy from renewable sources in the final energy consumption set for 2020 ahead of schedule. On the other hand, these targets were reached with minimal input from the development of hydropower. From the hydropower perspective, the targets of the NREAPs looked discouraging (
Figure 7). Estonia did not foresee the development of small hydropower after 2011 and still the targets for small hydropower were never reached. Lithuania’s target was the rapid development of small hydropower, when, in reality, those targets were also never reached, and, according to the 2016 figures, the lag from the target was quite large—6 MW. Only Latvia, not only exceeded its target for small hydropower already in 2013 but also, by doing this, at the same year reached the target for 2020 regarding the installed capacity of SHP plants. Unfortunately, the foreseen growth in the installed capacity in Latvia for SHP plants for the period from 2005 to 2020 was only 3 MW, when, for example in Lithuania for the same period, the same growth was foreseen as 13 MW.
For comparison, the installed capacity and electricity generation of other renewables are juxtaposed with the NREAP goals in
Table 2. The renewables that are presented in
Table 2 are wind power (land and sea), sun power (photovoltaic), and biomass (solid).
Estonia in
Table 2 is represented only by wind power. This is because Estonia has no target in its NREAP for solar power and, at the same time, no solar power plants. Estonia, in its NREAP, also does not show goals for the installed capacity of biomass power plants, only goals for electricity generation using biomass. The goal in 2018 was to generate 346 GWh of electricity using biomass in Estonia, yet the development exceeded expectations, and the actual generation was steadily increased. In 2018, the electricity generation using biomass and waste was more than three-times higher. Perhaps this, and the fact that Estonia reached the target for the share of energy from renewable sources in final energy consumption set for 2020 in 2015, affected the suspension of wind power growth that can be seen in
Table 2. It is clear that Estonia will not reach the NREAP target for wind power. Estonia does not currently have any installed wind power capacity in the sea, although it was foreseen in the NREAP.
Latvia, according to the NREAP prevision, began the development of sun power, although currently the electricity generated from this type of power plant does not reach the planned values (
Table 2). As with Estonia, Latvia targeted wind power plants installations in the sea, but did not manage to install any, consequently, falling behind its target for wind power. The only reached and exceeded target, except for small hydro, which was foreseen in NREAP for Latvia was the installed capacity and electricity generation from biomass power plants (
Table 2).
In contrast to the other Baltic States, Lithuania reached and exceeded its NREAP targets for the installed capacity from sun and wind power but did not reach the target foreseen for power plants that use biomass (
Table 2). All of Lithuania’s wind power plants are on land. On the other hand, offshore wind power installations were not foreseen in Lithuania’s NREAP.
The important aspect is that, regardless of reaching the targets of the NREAPs or not, in Estonia, Latvia, and Lithuania, growth in the installed capacity and electricity generation of other renewables, except for hydropower, is apparent. The development of hydropower is suspended through strict environmental-oriented laws. However, even bearing in mind that the Baltic States are lowland countries, a small hydropower there is a more favourable form of renewable energy than wind or solar energy.
Solar and wind power are commonly recognised as sources of intermittent electricity. Thus, the amount of available electricity is directly dependent on the availability of the source. Therefore, there will always be a favourable years or unfavourable years for wind or solar power. On the other hand, the recurring dry and wet years directly influence the availability of water for hydroturbines. This corresponds to the variations in the capacity factor values of all three renewable energy sources in the Baltic States. The available annual national statistics [
30,
31,
33] revealed that, during favourable years, the capacity factor for wind energy in Lithuania reached 30%, in Latvia, 23%, and in Estonia, 28%. During wet years, the small hydropower capacity factor in Lithuania and Latvia reached 45%, while in Estonia, 62%. The meaningful statistics for solar energy could be calculated only in Lithuania. There during favourable years, the capacity factor for this renewable energy source reached only 12%.
3.4. Historic and Currently Nonpowered Dam Sites in the Baltic States
3.4.1. Number of Sites
The initial total number of historic and nonpowered dam sites used in this study was 1539 (
Table 4). If such sites would be retrofitted with hydroturbines, generally they would be counted as small hydropower sites. Yet, in this paper, we used a more detailed breakdown in capacity, and, as will be proven later, the vast majority of such sites can be classified as micro-hydro sites. Therefore, this description will be further used in this paper.
In terms of the quantity, historic watermills represent almost 54% (835 sites) of all micro-hydro sites all over the Baltic region. Lithuania, with a total of 739 micro-hydro locations, is a clear leader among the Baltic countries and represents 48% of the total number in the Baltic States.
Table 4 summarises the data used for further analysis.
The total average of the density of micro-hydro sites in the Baltic region was 8.8 per 1000 km
2. The highest density of micro-hydro sites was identified in Lithuania, followed by Estonia and then Latvia (
Table 4).
The historic watermills prevailed in Estonia (254 sites) and Latvia (367 sites) and varied from 73% to 81% of all recorded micro-hydro sites existing in the country. The largest amount of nonpowered dam sites was identified in Lithuania (524) and represented almost 71% of all micro-hydro locations in the country. A small fraction of micro-hydro sites (12 unknown sites) was not identified as watermills or dams and was not used in the analysis.
3.4.2. Potential Capacity and Electricity Generation
Old watermill sites were typically of low height (an average of 2 to 3 m). Large reservoirs were not created also; therefore, people could construct such mills even in smaller rivers and streams. This is clearly seen in the potential capacity of old watermill sites in the Baltic States (
Figure 8). In
Figure 8 all watermill sites used in this study are arranged in descending order according to their potential capacity.
This is a clear indication of why a more detailed breakdown in capacity was needed. A total of 74% of all old watermill sites’ potential capacity were attributed to micro-hydro in Lithuania. In Latvia and in Estonia, this number is even higher—87% and 98%, respectively. Only four such sites were attributed to small hydro in Latvia, and none of the sites were attributed to small hydro in Estonia and Lithuania. The total potential capacity of all old watermill sites in Latvia, Lithuania, and Estonia was 26,281, 16,538, and 3558 kW, respectively. The total potential electricity generation in Latvia was 105.1 GWh/year; in Lithuania, 66.3 GWh/year; and in Estonia, 14.2 GWh/year.
A similar situation was found for nonpowered dam sites. The potential capacity of such sites in the Baltic States is presented in
Figure 9. Similarly, as in
Figure 8, in
Figure 9 all nonpowered dam sites used in this study are arranged in descending order according to their potential capacity.
The number of dam sites that were attributed to micro-hydro is even higher—98% in Lithuania, 97% in Estonia, and 92% in Latvia. Only one dam site was attributed to small hydro across three Baltic States, and this site is located in Latvia. The total potential capacity of all existing dam sites in Lithuania, Latvia, and Estonia was 8963, 4371 and 1513 kW, respectively. The total potential electricity generation in Lithuania was 35.9 GWh/year; in Latvia, 17.5 GWh/year; and in Estonia, 6.1 GWh/year.
3.4.3. Sites in Environmentally Sensitive Areas
Environmental policy documents recommend first to upgrade existing hydropower plants or use existing in-stream structures—dams, weirs, etc.—before proceeding with new developments [
45,
46]. This can be viewed as a wise approach, as many of the costs and environmental impacts during dam construction have already been incurred at these sites and may not be significantly increased by the incorporation of new energy production facilities. A possibility of using existing dams and old water mill sites could be one of the means for a sustainable hydropower development. Still, a considerable drawback for this idea is that a large number of historic sites are located in environmentally sensitive areas. More than 51% (428 sites) of all watermills in the Baltic States and analysed in this study are in restricted areas, meaning that they are in nationally protected areas, Natura 2000 areas, or are located in river stretches that are listed as under restriction (“no go areas”) (
Figure 10).
Almost 22% (180 sites) of watermills in the Baltic States are in Natura 2000 areas. As far as individual countries are concerned, the greatest number of watermills in Natura 2000 areas was identified in Lithuania, followed by Estonia, and then Latvia.
Approximately 30% (252 sites) of all watermills in the Baltic States are located in nationally designated areas. The greatest number of such mills was identified in Latvia, followed by Estonia, and then Latvia.
Finally, almost 29% (241 sites) of watermill sites are located in rivers under restriction (“no go areas”). Overwhelmingly in this case, the leader is Latvia. In Lithuania, after the amendment of the Water Law in 2019, currently, there are no such “no go areas”.
In total, the greatest number of watermills located in environmentally sensitive areas is in Latvia (230 sites). This is followed by Estonia (110 sites) and then Lithuania (88 sites). There are multiple watermills identified in overlapping areas, meaning that, in Latvia and Estonia, there are 31 and 21 watermill sites, accordingly, that are located in the area that is a jointly nationally protected area, Natura 2000 area, and “no go area”. Similarly, in Lithuania, there are 58 watermill sites that are located in the area that is designated as nationally protected and Natura 2000.
Considerably less—almost 15% (103 sites)—of all existing nonpowered dams in the Baltic States are in environmentally sensitive areas (
Figure 11).
The largest number of existing nonpowered dams, almost 11% (75 sites) are in nationally designated areas. Unsurprisingly, as the largest number of such dams were identified in Lithuania, the largest number of them located in nationally designated areas, is also in Lithuania, followed by Estonia, and then Latvia.
Less such dams are in the Natura 2000 areas—7% (50 sites). As far as individual countries are concerned, the leader was again Lithuania, followed by Latvia, and then Estonia.
Only slightly more than 5% of the existing nonpowered dams in the Baltic States are in rivers under restriction (“no go areas”). This number was reduced by the change of laws in Lithuania. Currently, the largest number of dams that are in rivers or river stretches that are in “no go areas” are in Latvia. Again, the fact that a considerable number of nonpowered dams are in the overlapping environmentally sensitive areas must be taken into account.
A visualisation of the distribution of historic watermills and nonpowered dam sites is presented in
Figure 12. This also includes mapping on how many of these sites falls within the boundaries of protected areas in the Baltic States, according to the International Union for Conservation of Nature (
Figure 12a) [
47], as well as within each category of Natura 2000 sites (
Figure 12b) [
27] and within rivers or river stretches designated as “no go areas” (
Figure 12c). Additionally, historic watermill and nonpowered dam sites that are in overlapping environmentally sensitive areas are categorised as follows: historic sites that fall under one restriction are marked with 1; the sites that fall under two restrictions are marked with 2; and if sites fall under all restrictions considered in this study, they are marked with 3 (
Figure 12d). Therefore, in
Figure 12d, we present the final view of the distribution of historic watermills and currently nonpowered dam sites that are and are not under restriction for hydropower development in the Baltic States.
3.4.4. Share of the Potential Hydropower Generation of Historic Sites in the Remaining Small Hydropower Potential
This large number of old watermills and nonpowered dam sites in environmentally sensitive areas inevitably decreases the available potential for hydropower development in these historic sites. The share of possible hydropower generation with and without constraints in historic sites in the remaining small hydropower potential is presented in
Table 5.
Environmental constraints indeed limit the use of historic sites for hydropower development, and the largest limitations were observed in Latvia and Lithuania (
Table 5). In total, across all three Baltic States, the possible electricity generation from watermills and nonpowered dams’ sites that are located in environmentally sensitive areas was 152.8 GWh/year. This number reduces the share of the historic sites in the remaining small hydropower potential in the Baltic States quite dramatically. The remaining share was 21.6%, which still can be considered a large number. However, for plans to retrofit any of the historic sites for electricity generation, the capacity of the future hydropower plant would be an important factor in the majority of cases. Therefore, the issue would inevitably be that the majority of historic sites with the highest capacity are in environmentally sensitive areas. For example, for the 20 watermill sites with the highest capacity (from 1853 kW to 34 kW) in each country, 18 are in environmentally sensitive areas in Latvia, 17 in Lithuania, and 12 in Estonia. The situation is better with nonpowered dams; however, a considerably larger part of the existing dams is attributed to micro-hydro compared to watermills (
Figure 9).