Volume 6 hydro power 6 11 – evolution of hydropower in spain

6.11

Evolution of Hydropower in Spain

A Gil, Hydropower Generation Division of Iberdrola, Salamanca, Spain
F Bueno, University of Burgos, Burgos, Spain
© 2012 Elsevier Ltd. All rights reserved.

6.11.1
6.11.1.1
6.11.1.2
6.11.1.3
6.11.1.4
6.11.1.5
6.11.2
6.11.2.1
6.11.2.2
6.11.2.2.1
6.11.2.2.2
6.11.2.2.3
6.11.2.3
6.11.2.3.1
6.11.2.3.2
6.11.2.4
6.11.2.4.1
6.11.2.4.2
6.11.2.4.3
6.11.2.5
6.11.2.5.1
6.11.2.5.2
6.11.3

6.11.4
References

Hydroelectric Power in Spain
Electric Power and Hydroelectric Power
The Strategic Importance of Hydroelectric Power
Hydrology, River Network, and Hydroelectric Development
Power Plants and Main Developments
Producing Companies
Evolution of Schemes and First Developments
Periods in the Evolution of Development
The 1890–1940 Period
First steps of electricity in Spain
The electricity sector in the first decades of the twentieth century
Main hydropower developments
The 1940–60 Period
The electricity after the civil war
Main hydropower developments
The 1960–75 Period
The electricity sector
The golden age of dam engineering in Spain
Main hydropower developments
The Last Three Decades
The electricity sector
Main hydropower developments
A Representative Case: The Duero System and Its Evolution
The Future of Hydroelectric Power in Spain

309

309

310

311

313

315

315

315

317

317

318

318

323

323

324

327

327

328

329

333

333

333

336

339

341


6.11.1 Hydroelectric Power in Spain
6.11.1.1

Electric Power and Hydroelectric Power

In the first years of hydroelectric power development in Spain, at the end of the nineteenth century, it was the thermal plants that
covered most of the electric power demand. With the general use of alternating current and transformer stations this changed, and in
the first four decades of the twentieth century hydraulic power increasingly became the main source of supply, reaching 93% of the
total supply in 1936.
With slightly lower values, this relevance was maintained until, from the first years of the 1960s, a large number of classic
thermal power plants started operating, and nuclear power plants started from the beginning of the 1970s, which meant that in

1975 hydroelectric production was only 35% of the total. In this century, the construction of combined cycle power plants and wind
farms has led to the current situation, in which the installed hydroelectric power is 20% of the total and the coverage of demand is
around 12% in an average year.
Thus, the installed hydroelectric power at the end of 2008 was 18 700 MW, from which 16 700 corresponded to the ordinary
production system and 2000 to mini power plants under the special production system, over an installed total of all types of energy
of 96 000 MW. Combined cycle power plants are those that provide the highest installed power to the group, whereas wind power is
practically the same as hydroelectric power (Figure 1).
As for energy produced, hydroelectric power accounted for 26 000 GWh in 2008, from which 21 500 corresponded to the
ordinary system and 4500 to the special system, compared to the nearly 295 000 GWh of the system’s total net generation
(Figure 2). These values are below average, the average being 35 000 GWh, as 2008 was a dry year.
The pluviometric irregularity that characterizes the Spanish territory results in irregularity of superficial runoff and, as a
consequence, affects hydroelectric production. In 1979, good hydraulicity resulted in attaining an absolute maximum hydroelectric
production of 47 473 GWh, which meant 45% of the total. On the contrary, the drought in 1992 resulted in the energy produced
only reaching 20 750 GWh, which meant 13% of the total.

Comprehensive Renewable Energy, Volume 6

doi:10.1016/B978-0-08-087872-0.00610-7

309


310

Hydropower Schemes Around the World

Combine cycle
24%

Special regime

32%

Hydraulics

18%


Wind
17%

Hydraulics
2%
Other renewable
5%
Nonrenewable
8%
Nuclear
8%
Coal
13%

Fuel/gas
5%

Figure 1 Installed electrical power at the end of 2008.

Combine cycle
32%

Wind

11%
Special regime
24%

Hydraulics

8%


Hydraulics
2%
Other renewable
3%
Nonrenewable
8%

Nuclear
20%
Coal
15%

Fuel/gas
1%

Figure 2 Electric power production in 2008.

6.11.1.2

The Strategic Importance of Hydroelectric Power

Hydroelectric power has a series of important qualities that make it one of the most strategically important energies from the
technical, economic, and environmental points of view. From a technical point of view, due to its high degree of use in comparison
to its potential, as the high efficiency of the turbines and alternators must be added to the low load losses in intake and return pipes,
achieving a global efficiency of the plants between 85% and 90%, which has never been achieved in any other type of power plant.
From the economic point of view, the cost of the raw material is very low or nil, which affects the total generation costs very
favorably. From an environmental point of view, its main characteristic is in the nonemission of greenhouse gases. Each hydro­
electric kWh avoids the emission of up to 1 kg of CO2, 7 g of SO2, and 3 g of NOx. The average production in Spain is equivalent to
not emitting 35 million tons of CO2.
In addition, the developments related to regulation reservoirs and pumping provide a high quantity and guarantee electrical
energy supply, facilitating load curve management and the regulation of frequency and voltage. They are also an installed power
reserve in view of possible unavailability of other types of generation.


Evolution of Hydropower in Spain

311

Besides, hydroelectricity is a source of energy in itself, an important fact in a country and high energy dependence. National
hydroelectric production in an average year is equivalent to that obtained with 6 billion cubic meter of natural gas, 13.2 million tons
of coal from abroad, or 9.3 million tons of fuel in plants that consume these fuels. The cost of avoided imports may amount to
nearly €1100 million in the case of gas, €680 million in that of coal, or €1900 million in that of fuel.

6.11.1.3

Hydrology, River Network, and Hydroelectric Development

The average annual precipitation in Spain is around 650 mm and is characterized by its irregularity, both spatial and temporal.
Spatial irregularity results in two differentiated areas: Wet Spain and Dry Spain (Figure 3). Temporal irregularity of precipitations
results in that for any considered period – multiannual, annual, or seasonal – the gap between the maximum and minimum values
is very big. To this we need to add a high evapotranspiration, which makes the average value of runoffs around one-third of

precipitation. From the 330 000 hm3 of precipitation, only around 110 000 become runoff.
All this results in the natural regulation level in Spain being close to 6–8%. The current regulation level is around 40–42%, for
which it has been necessary to build more than 1300 large dams. Without them, economic and social development in Spain
throughout the twentieth century would have been impossible (Table 1).
The Spanish hydrographic network is characterized, in a first approach, by the existence of rivers with two types of structure,
some with a well-developed river network (considerably long tree-shaped riverbeds with a large number of tributaries) and others
with rather parallel riverbeds and short in length.
Among the first we find the Miño, Duero, Tajo, Guadiana, and Guadalquivir that flow into the Atlantic Ocean, and the Ter,
Llobregat, Mijares, Ebro, Júcar, Turia, and Segura that flow into the Mediterranean Sea. The second type are characterized for flowing
in a perpendicular direction between the Cantabrian mountain ranges and the Cantabrian Sea in the north of the peninsula, and
between the Andalusian mountain ranges and the Mediterranean Sea in the south. The proximity of these mountain ranges with the
coast give these rivers characteristics of short lengths, steep slopes, perpendicularity to the sea, and the nonconnection between them
despite being close to each other (Figure 4).
From the river network structuring point of view, in the first type not only has the full use of the main rivers with their tributaries
been possible, but also in some cases full use of both has been possible. This layout of the river network has favored a higher use of

70−300
300−600
600−900
900−1200
1200−1600
>1600
100

Figure 3 Spatial distribution of precipitation in the peninsula.

0

100

200

km


312

Hydropower Schemes Around the World

Table 1

Basin
Norte I
Norte II
Norte III
Duero
Tajo
Guadiana I
Guadiana II
Guadalquivir
Sur
Segura
Júcar
Ebro
C. I.
Cataluña
Galicia
Costa
Total

Natural regulation and artificial regulation by hydrographic basins

Natural resources
(hm3 yr−1)

Natural regulation
(hm3 yr−1)

Natural
regulation
(%)

Reservoir
capacity
(hm3)

Available
resources
(hm3)

Available
resources
(%)

12.689
13.881
5.337
13.660
10.883
4.414

1.061
8.601
2.351
803
3.432
17.967
2.787

916
1.146
251
742
490
44
7
208
18
192
771
1.819
190

7
10
6
6
5
1
1
3

1
25
28
11
11

3.040
559
122
7.667
11.135
8.843
776
8.867
1.319
1.223
3.349
7.702
772

3.937
1.837
353
6.095
5.845
1.922
228
2.819
359
626

2.095
11.012
791

31
16
8
49
54
47
23
35
26
83
76
64
46

12.250

426

6

688

1.223

18

110.116

7.219

8

56.063

39.175

41

Figure 4 Spanish hydrographic basins.


Evolution of Hydropower in Spain

313

some of the tributaries, fed by high and medium-height mountains, than those of the main rivers, whose middle sections are less
steep and whose use has been destined to irrigation. In the rivers of the second group, hydroelectric use has followed classic steep
development schemes.
Hydroelectric development of the rivers in Spain has been conditioned by competition with other uses: that of supply and
especially that of irrigation. Currently, 70–75% of the consumptive uses of water are destined to irrigation, which occupy the center
of the Atlantic river basins and the lower sections of the Mediterranean rivers, with the consequential need of regulation reservoirs at
the headwaters of its tributaries, on mountain fringes. The development of irrigation began in the early twentieth century, at the
same time as the origins of hydroelectric development, being direct competitors in some lands.

6.11.1.4

Power Plants and Main Developments

There is a great variety of hydroelectric plants, both regarding the size and the facilities characteristics. In 2004, there were more than
1500 plants, including mini power plants under the special system. There were nearly 900 power generation units under the
ordinary system.
There are five power stations with more than 500 MW and 21 with more than 200 MW, which represent more than half the
installed power. Another 14 power stations exceed 100 MW and represent 12% of the power; those that exceed 50 MW represent
14% and those with less than 50 MW, including mini power plants, the rest (Table 2 and Figure 5).
The largest plants are those of Aldeadávila I and II, with 1243 MW, Jose M. de Oriol with 933 MW, Cortes-La Muela with
915 MW, Villarino I and II with 810 MW, and Saucelle I and II with 520 MW. The first, fourth, and fifth are located in the Duero
System, the second in the Tajo river, and the third in the Júcar river.

Table 2
100 MW

Hydroelectric power plants in Spain with an installed capacity of more than

Hydro plant

Turbining capacity

River

Aldeadávila I and II
José María Oriol
Cortes – La Muela
Villarino
Saucelle I and II
Estangento – Sallente
Cedillo

Tajo de la Encantada
Aguayo
Mequinenza
Puente Bibey
San Esteban
Ribarroja
Conso
Belesar
Valdecañas
Moralets
Guillena
Bolarque I and II
Villalcampo I and II
Castro I and II
Azután
Los Peares
Ricobayo I and II
Tanes
Frieira
Torrejón
Salime
Cofrentes
Cornatel
Tavascán Superior
Castrelo
Gabriel y Galán
Canelles
Cíjara I and II

1.243

934
915
825
520
451
500
360
362
324
316
265
263
270
258
250
221
210
246
227
194
200
168
328
126
154
133
160
124
132
120

130
111
108
102

Duero
Tajo
Júcar
Tormes
Duero
Flamisell
Tajo
Guadalhorce
Torina
Ebro
Bibey
Sil
Ebro
Camba
Miño
Tajo
Nog. Ribagorzana
Ribera de Huelva
Tajo
Duero
Duero
Tajo
Miño
Esla
Nalón

Miño
Tajo – Tiétar
Navia
Júcar
Sil
Lladore-Tabascán
Miño
Alagón
Nog. Ribagorzana
Guadiana

Pumping capacity
(MW)
Pure 435
Pure 635
Mixed 825
Pure 451
Pure 360
Pure 362
Mixed 316

Mixed 270

Pure 221
Pure 210

Mixed 126
Mixed 133

Mixed 111

Figure 5 Location of Spain’s main hydroelectric power plants.


Evolution of Hydropower in Spain

315

Approximately 10 000 MW have a high seasonal regulation, of which 2500 MW are equipped with pumping. There are around
2350 MW in important power systems but with scarce regulation, and around 1300 MW in developments at the base of a dam. The
rest of the hydroelectric facilities consist of small power plants, many of run of rivers.
Spain’s hydroelectric potential is estimated at around 162 000 GWh yr−1, of which a little over 64 000 GWh are technically
usable. Taking into account that average yearly power production is around 35 000 GWh yr−1, there is still technical margin
available. The economically viable potential is estimated at 37 000 GWh, in accordance with the most recent data, not including
the pumping plants. This means that Spain is close to the economically acceptable ceiling. However, some clarifications must be
made. On the one hand, this ceiling is moveable, as it depends on the economic conditions not only of the jumps themselves but
also, and especially, of the power production strategies at national level, which depend on the degree of dependence, on power
vulnerability, on petrol and gas prices, or on the consideration of other types of plants’ environmental costs, among others. On the
other hand, power production is far from this level in the last few years, partly due to low rainfall. Exploitation during these dry
years may be increased by building new facilities or improving the existing ones.

6.11.1.5

Producing Companies

The large electric utilities that have hydroelectric power stations in Spain are Iberdrola, Endesa, Gas Natural SDG, Acciona, E.ON
España, and HC Energía. The last two concentrate their hydroelectric activity mainly in the north part of the peninsula, while the
others distribute their facilities over greater areas of the national territory. A high number of other small companies must be added
to these large ones, including those that have mini power plants with less than 50 and 10 MW and that are subject to the special

electric production system. The Administration is also the owner of a high number of toe of dam schemes, most of these in dams
intended for regulation for irrigation or integral regulation of rivers.
Iberdrola is the result of a merger in 1991 between Iberdrola and Hidroeléctrica Española and owns 9187 MW. Iberduero had its
origins in Hidroeléctrica Ibérica, founded in 1901, and in Saltos del Duero, founded in 1918 with the purpose of exploiting the great
hydroelectric potential of the Duero System. They were merged in 1944, soon after joined by Saltos del Sil, born to exploit the great
hydroelectric site of the Sil river and its tributaries. Hidroeléctrica Española was founded in 1907, with its origins also being some of
the schemes and concessions of Hidroeléctrica Ibérica. The main hydroelectric development of Hidroeléctica Española took place in
the Júcar and Tajo basins.
Endesa, with a current installed hydroelectric power of 4511 MW, was created with public funding in 1944 with the
purpose of helping the private sector in hydroelectric development. In 1983 the Endesa group was created, with the
acquisition of some electricity companies such as Enher or Gesa, among others, from the National Institute of Industry.
In the 1990s it acquired Electra del Viesgo, the historical Sevillana de Electricidad, Hidroeléctrica de Cataluña, and Fuerzas
Eléctricas de Cataluña.
Unión Fenosa was the result of the merger between Unión Eléctrica and Fuerzas Eléctricas del Noroeste (FENOSA) in the year 1982.
The first had its origins in 1889, with the creation of the Compañía General Madrileña de Electricidad, which after several groupings
became Unión Eléctrica Madrileña in 1912. The second was created in 1943 to exploit several hydroelectric schemes in Galicia, in the
northeast of Spain. Recently, Unión Fenosa has merged into Gas Natural as Gas Natural SDG has a hydroelectric power of 1860 MW.
Acciona acquired Energía Hidroeléctrica de Navarra and assets from Endesa, Saltos del Nansa among them, to achieve the 857
hydroelectric MW.
The presence of E.ON. is more recent, as it dates back to 2007 through its renewable energies affiliate and to 2008 as a market
unit and as E.ON España, with 668 MW. This presence is due to the acquisition of assets from Ente Nazionale per L’Energia Elettrica
(ENEL), who in turn had acquired the old Electra de Viesgo from Endesa, one of the Spain’s historical companies created in 1906.
The historical Hidroeléctrica del Cantábrico has merged into the EDP group (Electricidade do Portugal) in the last few years
under the name HC Energía. It has 433 MW of hydroelectric power.

6.11.2 Evolution of Schemes and First Developments
6.11.2.1

Periods in the Evolution of Development

The demand of electric energy has been increasing from the first days until today, with variable rates according to economic growth
in general and the industrialization level in particular. The relationship between the industrialization and electric energy demand
has always been similar. This demand has been met throughout the twentieth century with different types of power plants, among
which hydroelectric power plants have had varied importance.
The distribution of generation to satisfy such demand between the different stations has depended on several factors, among
which we must mention the hydroelectric potential and its level of exploitation, the cost of produced power and the environmental
problems of the different power plants, or the strategic decisions to protect different sectors of the national economy, just to
mention some of the main ones. The political and economic situation was also important in Spain in certain periods as it conditions
the availability of equipment and building technology, as we will see later on. From a technical point of view, the main factors were
those corresponding to the state of the art of the technologies available for those elements that affect hydroelectric developments:
turbines, turbo pumps, or generators, as well as hydraulic engineering, dam engineering, and tunnel engineering, essential elements
in Spain’s hydroelectric development.


316

Hydropower Schemes Around the World

(a) 1800
1600

Hydropower

1400

Thermal power
Total installed power

MW

1200
1000
800
600
400
200
0
1880

1890

1900

1910

1920

1930

(b)
4000
3500
Hydro

3000

Thermal
MWh

2500

Total generation

2000
1500
1000
500
0
1880

1890

1900

1910

1920

1930

Figure 6 (a) Installed power in Spain between 1880–1940 period. (b) Generated power in Spain between 1880–1940 period.

All these factors have contributed to the variation of the development and the hydroelectric use systems and their importance in
the electricity sector in Spain throughout the twentieth century, with clearly different characteristic periods.
The first period goes from the first steps of electrical energy in Spain to the civil war (1890–1940), characterized by an important
increase of installed power and of produced energy, especially since 1910. After some years during which thermal power plants
supplied most of the energy, with the new century it was the hydroelectric power plants that began to absorb most of the demand. In
1940, the installed hydroelectric power was 78% of the total and the generated power was 93% (Figures 6(a) and 6(b)).
The 1940–73 period is characterized by the importance of hydroelectric production, which represented more than half the total
electric production. From 1973, the increase of thermal production in classic and nuclear power plants made hydroelectric power

stop being the main source, and has from then on lost relative importance in terms of energy (Figure 7).
If we take other factors into account, we can clearly distinguish two different phases within this period. One is from 1940 to the
second half of the 1950s, characterized by the use of building equipment already used before the civil war, as a result of the autarchic
politic and of Spanish isolation, which meant a certain continuation of previous productions.
The second period begins with the change of decade from the 1950s to the 1960s, during which the confluence of several factors
allowed for the great development of hydroelectric power. The great development of dam engineering, the development of
reversible power units, and the cost reduction in the construction of all types of works – hydraulic, underground, mechanical,
and so on – due to the availability of new equipment, are the reason for the quick evolution in the development schemes. On the
other hand, the more constructive and economic facility in underground works allowed for a greater flexibility in hydroelectric
schemes, making it possible to build developments unthinkable just a few years before. From then, the construction of underground
power plants and reversible power plants were commonplace.
From the middle 1970s, the increase of installed power continued increasing, but less than the classic thermal or nuclear power
plants, despite of which the produced power stagnated to previous levels, with the exception of very favorable years in hydrological


Evolution of Hydropower in Spain

(a)

317

80
70
Biomass
60

Mini hydro
Wind

50

GW

Cogeneration
40

Nuclear
Gas turbines

30

Thermal
Hydro

20
10
0
1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
(b)
300

250

Biomass
Mini hydro

TWh

200

Wind

Cogeneration

150

Nuclear
Gas turbines

100

Thermal
Hydro

50

0
1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Figure 7 (a) Installed power in Spain between 1940–2008 period. (b) Generated power in Spain between 1940–2008 period.

terms. From 1990, the increase of installed power has been very little mainly due to electric system regulation installations and
power increases in already existing plants (Figures 7(a) and 7(b)).
In the last decade of the past century, a construction process of small plants and the renovation of others that were not in use began.
In the origins of this process we find, on the one hand, the development of more and more reliable power units and the remote control
and/or centralization of operations, with the corresponding reduction of maintenance and operation costs and, on the other hand, the
inclusion from 1997 of these plants in the special electricity production system, whose purpose is the promotion of renewable energy.
In each one of these periods, hydroelectric power and hydroelectric developments have had clearly different characteristics.

6.11.2.2
6.11.2.2.1

The 1890–1940 Period

First steps of electricity in Spain

The first reference to the practical application of electricity in Spain dates back to 1852, when the pharmacist Domenech lit up his
premises in Barcelona with a method invented by him. That same year lighting tests were carried out in several public spaces using
galvanic cells. From then on, and with a higher intensity in the 1870s, certain areas of some cities began to be lit up, generally using
dynamos powered by steam engines.
The production of electrical energy in important quantities for that time began in the mid-1870s, using thermal power units
powered by coal and low-quality gas. The first electricity supply contract dates back to 1876, Sociedad Española de Electricidad was the
first Spanish electricity company. In 1878, several squares, streets, and important buildings in Madrid were lit up, and at the beginning
of the next decade in cities such as Valencia and Bilbao. Increasing demand in the last two decades of the nineteenth century resulted in
several companies being established with the only purpose of supplying electricity, both for public and private use.


318

Hydropower Schemes Around the World

In the last few years of the nineteenth century and in the beginning of the twentieth century it was supplied as direct current,
which forced the power plants to be located near the consumption centers, which in turn limited the building of hydroelectric
schemes and favored the use of thermal power plants. With the first use of alternating current in the last few years of the century and
its great development in the first decade of the twentieth century, the limitations of the location of hydroelectric power plants
disappeared, making the boom that took place during the second decade of the century for this type of energy possible.
In 1901 there were 861 electric power plants in Spain, with a total installed capacity of nearly 100 MW. Around 65% of them were
thermal and 35% were hydroelectric, 650 mostly dedicated to public services, and the rest for private use. More than half of the total,
around 510, produced in direct current and the rest in alternating current. The uses of this energy were around 87 000 incandescent
lamps and 1500 arch lamps for public lighting, and 1 240 000 incandescent lamps, 2800 arch lamps, and 2036 engines for private use.

6.11.2.2.2

The electricity sector in the first decades of the twentieth century

In the 1901–30 period, the total electric power was multiplied by 12, reaching 1200 MW, which became 1600 MW in 1936, a
number that slightly dropped at the end of 1939 as a result of the civil war destructions, which paralyzed the development of the
Spanish economy. This big increase of installed power resulted in there being a small excess of installed production over
consumption during this period. Increase in demand was variable: 8% between 1901 and 1922, 10% up to 1930, and 5% up to
1936, very similar values to those of economic and industrial growth.
If in 1890 installed hydroelectric power in Spain was 30% of the total electric power, this percentage went up to 69% in 1910 and
77% in 1920. This percentage would become stable until 1936, the year the civil war paralyzed electric development. As far as production
is concerned, these percentages were even more favorable for hydroelectric power plants due to a higher amount of operation hours than
those of thermal power plants. So, in 1929, 81% of production was hydroelectric. This percentage rose to 93% in 1936 (Figure 6).
Apart from the general use of alternating current, the origins of this development lie in the fewer total costs of hydroelectric
power despite a higher initial investment, this was not only due to the zero cost of water but also to the increase in the cost of coal,
gas, and petroleum products throughout these first few decades.
The construction of hydroelectric schemes of considerable size was generalized from the last years of the century’s first decade to
cope with the demand, which involved high economic investments. This was only possible due to the creation of a large number of
electricity companies intended for production and distribution, which was led by private initiatives and with important participa­
tion of the banking sector.

6.11.2.2.3

Main hydropower developments

Between 1901 and 1902, the first large (for that time) hydroelectric plants began operating, among which we must mention those of
Molino de San Carlos, near Zaragoza, Navallar, on the Manzanares river, the first to supply this type of power to Madrid, and San
Román, on the Duero river near Zamora.
The Navallar power plant, with 1750 CV installed in four power units was the first of series of facilities that supplied power to the
capital city from the rivers located to the north of it (Figure 8). The source of the scheme was the first dam of Manzanares el Real,
with a height of 10 m and which was raised in 1906. A canal flowed from the dam which, apart from feeding the plant’s surge
chamber, served as a reservoir from which water was pumped to the city of Colmenar. It was one of the first important dams
destined for hydroelectric and multiuse purposes.

The San Román power plant, which had an installed capacity of 5000 CV and took advantage of a long meander of the Duero river,
with a 6 m-high dam and a 15 m head meant an important leap in terms of installed capacity, superior to those built until then.
Until 1910, a large number of similar schemes were built, most of them with installed capacities of 1500–2000 kW and located in
medium river watercourses. Most of them were characterized by their diversion schemes, with a weir, a canal which was not too long
and flowing parallel to the river, a small surge chamber and one or more horizontal configuration power units with Francis turbines.
In 1909, the Salto de Molinar, on the Júcar river, was inaugurated. It was the most remarkable hydropower project built in Spain
until then. The development has been historically considered as one of the best and most profitable in Spain. It was projected for a
production of 70 GWh, when Madrid’s consumption was 30 GWh. Three 4500 kW power units were initially installed, in the
following year an additional power unit was installed, achieving an installed capacity of 22 500 kW. If the development was

Figure 8 Navallar power plant (1902). Cross-section and inside the power plant.


Evolution of Hydropower in Spain

319

Figure 9 Molinar power plant (1909).

important for its singular technical characteristics, it was also important for the transport line, 250 km long with a voltage of 60 kV,
which supplied power to Madrid. This line was Europe’s most important one at that time (Figure 9).
For similar purposes, the Villora project meant another leap in hydroelectric development in Spain. Located on a tributary of the
Júcar river, the Cabriel river, it had an installed capacity of 12 000 kW. The scheme comprised a dam, a tunnel that crossed the
watershed with a tributary of the Cabriel, and a power plant that hosted two horizontal axis power units. A second dam that
regularized the turbined waters completed the system. In 1925, the increase in demand in the Madrid area made it necessary to
install a new unit that doubled the installed capacity, which was the first vertical axis power unit installed in Spain. A new power
unit, similar to the previous one, was installed in 1945, after the war, with the purpose of collaborating in relaunching the battered
Spanish economy (Figure 10).

Figure 10 Villora power plant. In the foreground are the two vertical power units, one of them the first of this type in Spain. Behind and at a lower level

are the two initial horizontal axis power units.


320

Hydropower Schemes Around the World

In the same Júcar–Cabriel system as the previous ones, in 1928 the Millares project works began, inaugurated in 1933 with two
20 000 kW vertical power units, those with the highest installed capacity in Spain until then, to which others were added in 1933
and 1942, achieving an installed capacity of 80 MW in 1942, which were very important at that time.
The power supply to Madrid had, apart from those already mentioned and several others, the Bolarque project, which was put
into operation in 1910. Its scheme, even though it was also a bypass, was different from the others as it had a more regulated
reservoir and a short high capacity canal of 60 m³ s−1. The connection line with Madrid was important, to which it supplied electric
power, with a length of 78 km and a voltage of 50 kV. After completing in 1952, a rise with which the dam went from being 26 m
above the riverbed to being 37 m above it, a power plant was built at the base of the dam, with pressure intakes, taking better
advantage of the regulation and height. A pumping station was also installed to safeguard the watershed between the Tajo basin and
the headwaters of the Tajo-Segura water diversion canal, with a north to south course crossing a large area of the eastern part of the
peninsula, taking water for supply and irrigation purposes to an important part of the Mediterranean basins (Figure 11).
The first important hydroelectric development in Catalonia was that of Salto de Capdella, built from 1910 to 1914 in the
Pyrenees, which supply power to the city of Barcelona. It uses the waters of the upper watercourse of the Flamisell river, a tributary of
the Noguera Pallaresa river, in turn one of the main tributaries of the Ebro river. Collection and regulation takes place in 28 glacial
reservoirs interconnected by means of canals and tunnels, all of them located between 2140 and 2534 m above sea level. Nine of
these reservoirs were raised with 10–20 m-high dams. The lower reservoir, which collects the waters of all the others, is that of Estany
Gento, from which nearly 5 km canal flows to feed two pipes that supply the water to the turbines. Four power units with Pelton
turbines of 8500 CV each were initially installed.
Along with the singularity of collection and regulation, due to its height, we must mention the head of 836 m, the highest in
Spain and one of the highest in Europe at that time (Figure 12).

Figure 11 The Bolarque power station and dam are in the foreground, the power plant is at the base of the dam. At the back is the pumping station for the
Tajo-Segura diversion.

Figure 12 Capdella power plant: Diagram of the scheme and photograph of the power plant.


Evolution of Hydropower in Spain

321

Figure 13 Evolution of development schemes in the middle watercourse of the Noguera Pallaresa.

Downstream from the Capdella power plant, three other power plants turbined the waters coming from it and from its own
basins, one of them, that of Molinos, with a head of 273 m and an installed capacity of 13 500 kW. The system of these schemes was
the same as interconnected bypass jumps, so they did not need a dam.
The next step in the exploitation of the Noguera Pallaresa did not follow this scheme. For the middle section of the river, between
the confluence of the Flamisell and its confluence with the Segre, the first phase of the studies planned the construction of two
diversion schemes with parallel canals near to the riverbed. The next phase of the studies was carried out after the unification of both
concessions, both from the administrative and from the technical points of view. This solution seemed to be a complex one and it
was decided that the first section was to be exploited with a dam and a station at its base: the Talarn power plant. The advantage of
this solution was the achieved regulation, which would exploit more efficiently downstream (Figure 13). This type of evolution was
commonplace during the first two decades of the century.
In 1916 the construction of the Talarn dam and power plant ended, which acted as the primary regulation of the Noguera
Pallaresa river. It was the first large reservoir of hydroelectric use in Spain, with more than 200 hm³ achieved, thanks to the
86 m-high dam, which was the highest at that time and one of Spain’s dam engineering milestones. The power house is located half
way down the slope on the left margin and initially had four Francis power units with a total power of 30 000 kW (Figure 14). With
this record, in 1920 the construction of the Camarasa dam ended. It was 103 m high and with spillway capacity for 2000 m³ s−1. Like
its predecessor, this dam also established a height record in Spain and was a new milestone in our country’s dam engineering. The
power station was equipped with four Francis power units, with a total power of 56 000 kW (Figure 15).
These two schemes of the Noguera Pallaresa were the beginning, wherever possible, of new way of conceiving hydroelectric
exploitation of the rivers by means of their integral exploitation, which included the regulation with dams and reservoirs and steep

Figure 14 Talarn dam and power plant.


322

Hydropower Schemes Around the World

Figure 15 Camarasa dam and power plant.

schemes in large river sections by means of power plants at the base of the dams. In rivers with medium flow rates and in winding
orography, this solution proved economically competitive in comparison to the classic diversion schemes, which, on the other
hand, carried on being viable and were the best solution in many other cases.
Integral exploitation studies of basins and rivers began to be carried out from the 1920s. The most representative example is the
one carried out by José Orbegozo for the exploitation of the lower watercourse of the Duero river and its tributaries in Spain, from
the Esla to the Agueda (see Section 6.11.3). The construction of the 97 m-high Ricobayo was finished in 1935, with a reservoir, that
exceeded 1000 hm3 and an installed capacity of 133 MW. All these numbers were new milestones in Spain’s hydroelectric
development.
In the western Pyrenees, important projects were also built in the 1920s and 1930s. The most important ones had the same
scheme: a medium regulation dam and high heads. Among these we must mention Lafortunada-Cinca-Pineta, with a 475 m head;
Lafortunada-Cinqueta, with a 375 m head; Barrosa-Avellaneda, with a 205 m head; and Urdiceto, with a 426 m head. All these
jumps were equipped with Pelton turbines.
In the Guadalquivir river basin and some of its tributaries, more projects stand out, more due to the characteristics of the dams than
for the importance of the power plants. That is the case of the Cala power plant, which began being operational in 1927, with a
53 m-high dam, a maximum power of 13 000 kW and a 193 m head. One of the most beautiful dams built in Spain was built on
the Jándula river in 1932. With a height of 90 m, its aesthetic characteristics are due to its neat plant and the location and design of the
hydroelectric power station, which adhered to the downstream wall, anticipating designs that in the future the great André Coyne
would use in his Dordogne dams and that would be adopted in the Grandas de Salime and Contreras dams in Spain (Figure 16).
On the Guadalquivir itself and during this period, three projects were built. These were Mengibar, El Carpio, and Alcalá del Río,
in 1916, 1922, and 1930, respectively, with head created by barrages (gated dams) in each one. The meticulous designs and
execution of the plants were a common characteristic of these projects. Mengibar was the first gated dam built in Spain (Figure 17).

They were all part of the ‘Channelling and exploitation of the Guadalquivir’s power between Córdoba and Seville Project’, and the
ambitious project included 11 installations between both cities, each one with a power plant, a lock and a gated dam. Finally,
navigability was discarded, and from the 11 installations, only four dams with their respective power plants were built.
In the Sur river basins, the El Chorro power plant and dam were built on the Guadalhorce river, in an abrupt location ending in
an impressive gorge. Soon after, in 1927 the construction of the Gaitanejo dam and power station ended, a little downstream from
the previous reservoir. It supplied power to the city of Málaga from the time after it began operating. The dams were the main
elements of both developments: the first, 80 m high with a large regulation reservoir, and the second, of smaller dimensions was
20 m high, and very singular in design, with the power station included in it and the spillway above it (Figure 18).

A-Rejilla protectora
B-Compuerta-ataguia plana
C-Llave de mariposa
D-Llave esférica
EyF-Válvulas de cierre de la galeria
G-Pozo de equilibrio
H-Galeria de comunicacion

Figure 16 Jándula Dam. View during construction and cross-section.


Evolution of Hydropower in Spain

323

Figure 17 Mengibar power station and dam.

CORTE TRANSVERSAL DE LA PRESA POR EL
EJE DEL SALON DE MAQUINAS Y PROYECCION

SECCION TRANSVERSAL POR A-B

Y PROYECCION

Figure 18 Gaitanejo dam: Cross-section and photo.

Next to the previous one and near the city of Ronda we find the Montejaque dam, which was a 84 m-high first modern arch dam
built in Spain. It was finished in 1924, and was the top of a hydroelectric scheme which had to be abandoned soon after, as the
reservoir could not be filled due to the high leakage through the calcareous basin.

6.11.2.3
6.11.2.3.1

The 1940–60 Period
The electricity after the civil war

After the civil war, the situation in Spain was characterized by the economic isolation from abroad, in turn a consequence of two
situations that fed each other. On the one hand, the international embargo and, on the other hand, the desire of the regime to
become a self-sufficient autarchy, aside from the international economy. To this we need to add the state of the economy after the
physical destruction of industries and facilities, and the disappearance of the emerging industrial infrastructure and, in the first
years, the consequences of the Second World War resulting in generalized poverty in Europe.
All of this resulted in having to use the same building equipment as that used in the previous decades, a lot of which was in poor
condition and needed to be repaired; despite this they carried on using them and achieved good results.
During the years of war (1936–39), the energy production capacity stalled, although some power plants continued to be operative,
others were damaged or destroyed. After this period there was a severe drought, from 1944 to 1946, which resulted in a considerable
decrease of hydroelectric production. In this way the production capacity excesses of the previous decade turned into important
production deficits versus demand, whose growth values in that decade were very high due to the logical reconstruction needs.
The installed capacity went from 1731 to 2553 MW in the 1940–50 period, due to the new hydroelectric facilities. In the
1950–60 period, it rose to 4600 MW. In this case from the 2000 MW installed, 1300 belonged to thermal plants, which especially


324

Hydropower Schemes Around the World

occurred in the second half of the decade. The application of a new rate system, which allowed companies to initiate new
investments, influenced the higher increase of this decade. With this, the usual restrictions began to disappear, and totally did so
from 1958 (Figure 7).
The end of the international embargo and a certain economic liberalization gave way to the 1959 Stabilization Plan, which was
enforced by the international economic institutions to provide assistance. With this assistance, the two development plans
established in the following decade allowed for the Spanish economy’s big take off.

6.11.2.3.2

Main hydropower developments

As a result of what has been previously mentioned, Spanish hydroelectric development can be considered as a continuation of the
previous periods. However, this continuation was optimized due to the experience acquired in previous decades and to the Spanish
engineers’ know how. With few means they were able to build remarkable constructions for that time. As an example we must
mention Villalcampo, Castro, and Saucelle projects, the second phase of the building of the Duero System, that were put into
operation between 1949 and 1956 with capacities of 206, 190, and 240 MW, respectively. Those projects were built in difficult
execution conditions, both in economic and in technical terms (see Section 6.11.3).
Important hydroelectric systems began to be developed during this period, which in some cases meant the integral exploitation
of basins. This is the case of the Sil System, whose first steps were taken during these years and which was completed from 1960 with
more complex and advanced installations. Between 1952 and 1960, nine power plants were built in it, with seven dams (Figure 19)
and a total installed power of around 450 MW, from which more than half corresponded to the power station at the base of the San
Esteban dam, with 266 MW.
The dams were an important part of these first power plants of the Sil System. Seven of them have heights between 22 and 42 m
and functions of forebay, with small or medium regulation for diversion schemes. The other two are more important, that of San
Esteban and that of Chandreja, with relatively small reservoir capacities for height, and whose main purpose is to create height head
in order to locate the power plants at their toe. That of San Esteban is a 115 m-high arch-gravity dam, and the most modern means
began to be used. We could say that it is a transition dam between this period and the next. That of Chandreja is an 85 m-high

buttress dam. This type of dam was used frequently in Spain during that period, due to the lesser need of the scarce concrete and the
higher manpower, which were abundant and cheap in those years (Figure 20).
There are numerous power plants and dams of both types from this period in Spain especially with small and medium height
dams, and diversion schemes of all types. Those located in high plateaus in the Pyrenees stand out. This is the case of the Baños power
plant, fed by several dams built between 1942 and 1961 in plateaus located between 2100 and 2550 m above sea level, or that of
Moncabril, fed by several reservoirs raised by means of dams in glacial lakes in Sanabria (Figure 21) with a net head of 514 m.
The first important dam in that period was the Grandas de Salime, located on the Navia river in the north of Spain. It was built
between 1946 and 1955 in abrupt terrain, and is 128 m high, creating an important scheme of 160 MW. This dam was a milestone in
Spanish dam engineering at that time due to how quickly it was built despite the rather inefficient construction means they had,
reaching a European record for daily and weekly concrete laying. The location of the power plant stands out, at its base and under

PERFIL ESQUEMATICO

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EN CONSTRUCCION

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Figure 19 Saltos del Sil diagram, situation in 1961.

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Evolution of Hydropower in Spain

325

Figure 20 San Esteban and Chandreja dams.

1644,50

Garandones


Sistema TERA

Puente Porto

Lagunas represadas

Canal de Trasvase
Pocillo de
Garandones

Playa

1570

Cardena
Galeria Cabril

Rio Cárdena
Rio Segundera

1582,43
Vega de
Conde

Canal
Moncalvo

T

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B

E

R

I

A

F
O
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A
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Rio Tera

MONCABRIL
1014,50

Lago de
Sanabria

Figure 21 Diagram of Salto de Moncabril in Sanabria and inside the power plant.

the spillway designed for a flow of 2000 m3 s−1. This arrangement, contrary to the hydraulic interests of flood outflow, required
several model tests, achieving an effective design (Figure 22).
In the Pyrenean Noguera Ribagorzana, parallel to the Noguera Pallaresa, we find, among others, the power plants of Escales and
Canelles, both with an underground power house near them, the first important ones of this type. The first is a 125 m-high gravity
dam with a 118 m head. The turbined waters of this power plant also make use of the Puente Montañana power plant, which, in
turn, makes use of the necessary compensating reservoir located downstream. Downstream we find the 150 m-high Canelles dam,
built between 1958 and 1961. It is a peculiar arch dam due to its irregular shape, located in a narrow calcareous area and practically
entirely designed by means of structural tests on models. Once it was finished, important injection screens had to be carried out on
the left hillside in order to stop the important water leaks from the basin (Figure 23), as well as a great reinforcement on the right
side as a result of new studies carried out due to the breaking of the Malpasset dam. The power plant is a cavern on the left side and

has an installed power of 108 MW. With this one and the other two previous power plants, the Noguera Ribagorzana river is totally
regulated from the hydroelectric point of view.


326

Hydropower Schemes Around the World

Figure 22 Grandas de Salime power plant and dam.

Figure 23 Canelles jump power plant and Canelles dam.

There are two other arch dams that we must mention: La Cohilla, 116 m high, whose purpose is the general regulation of the
Nansa river for the power plants located downstream (Figure 24), and Eume, the first modern Spanish arch dam, with a 103 m
height and a 55 MW power plant downstream with a 245 m head. The first was built with very scarce means. The second stands out
for its design and for being the first arch projected with modern criteria and parameters (Figure 24).
The hydroelectric development of the middle-lower section of the Ebro, the main Spanish river, dates back to this period,
although the last of those projects was built in the 1960s. The Flix power plant was built in 1948, next to the barrage (gated dam) of
the same name, which is 26 m high. The plant has a power of 40 MW, despite the small 12 m head, thanks to a maximum flow of
400 m3 s−1, exploited with four vertical axis Kaplan power units.
The study of the section located upstream of the latter was performed over the first few years of the 1950s, with the building of
the Mequinenza dam at the end of the decade and that of Ribarroja at the beginning of the next decade, with the object of staggering
the construction of the complex. The conception of the schemes can be considered as classic, far from the criteria that would have
been followed in the following decade.
These are two gravity dams in two wide enclosures that allowed for a ‘comfortable’ design, as the power plant could be placed at
the toe of the dam, as well as the large spillways suitable for draining floods of 11 000 and 8500 m³ s−1. In both cases, the
transformer stations are located on the vast banks. The Ebro’s large flow rate allowed for high power plants, 324 and 256 MW,
respectively, with Francis turbines in the first and Kaplan turbines in the second (Figure 25).
The construction of supply systems to towns and cities was important in these two decades. This is the case of the improvement
of Bilbao’s water supply by means of the interbasin diversion from the Zadorra, a tributary of the Ebro, and the construction of two

Evolution of Hydropower in Spain

327

Figure 24 La Cohilla dam during construction and Eume dam.

Figure 25 Mequinenza power plant and dam.

dams. The diversion of the waters, with a very constant flow, is turbined to the Barázar power plant, of 83 MW, taking advantage of a
330 m height variation levels, resulting in an average power production of 170 GWh yr−1.
In many of the rivers where dams and power plants were set up before the war, they continued building during this period by
making use of the existing regulation and infrastructures.

6.11.2.4
6.11.2.4.1

The 1960–75 Period
The electricity sector

The 1959 Stabilization Plan, which established a stable framework for growth, the First Development Plan of 1964 and the opening
to the ‘outside world’, which favored incoming currencies and commercial exchange, was the source of the great Spanish economic
development from 1960. The electricity sector was an active collaborator in this development, quickly adapting to the demand. The
previous existence of a fairly large and comprehensive supply network and its extension throughout these years was a decisive factor.
In these years they achieved to electrify practically the entire national territory.
The installed power rose from 6600 MW in 1960 to 18 000 MW in 1970 and to 25 500 in 1975, hence four times as much in
15 years. Production also rose from 18 600 GWh in 1960 to 56 500 in 1970 and to 82 515 in 1975, five times as much in the same
period of time.
During these years, hydroelectric power units were greatly developed, from 4600 MW installed to 12 000. However, the high increase

was due to the building of new thermal plants, both conventional fuel oil plants in a context of low oil prices, and nuclear power plants,
with the start up of José Cabreras in 1968, of 160 MW, Garoña in 1971, with 466 MW, and Vandellós I in 1972, with 500 MW (Figure 7).
In 1973, the first oil crisis took place, which multiplied the source price by six, despite that the important fleet of thermal power
plants under construction used this fuel. Spain only reacted to this in 1975, when the National Energy Plan was passed, but effective
measures were not taken to change the energy model, which was indeed done one decade later, in 1983, with the II National Energy
Plan.


328

Hydropower Schemes Around the World

6.11.2.4.2

The golden age of dam engineering in Spain

Since the Roman times the construction of dams in Spain has been common, due to the semiarid nature of a good part of the
territory and the temporal irregularity of precipitation and runoffs. Since then, and throughout all the periods, dams have been
essential in social and economic development. Dam engineering has always been level with the world’s best with important and
numerous constructions, even during unfavorable periods, as previously mentioned. This important and continuous experience
reached its climax from 1960 with the conjunction of all the mentioned factors, which favored the building of important dams with
different purposes. We can therefore affirm that the 1960s and 1970s were the golden age of dam engineering in Spain. From all the
dams of this golden age, those built for hydroelectric purposes stand out, most of them among the highest dams built in Spain
(Table 3). This golden age of dam engineering was so especially in the construction of arch dams in general and double-curvature
dams in particular, but also with a few important examples of buttress dams and embankment dams.
In the Duero System the arch-gravity dam of Aldeadávila, 140 m high, and the double-curvature dam of Almendra, 202 m
high, were built in this period. The first was finished in 1963 and is located in an impressive granite canyon formed by the Duero
river. A double-curvature dam was the first selection, but the high floods made them opt for the arch-gravity type. It is one of the
most beautiful Spanish dams, not only for the surroundings but also for the dam itself. In 1970, the Almendra double-curvature
dam was finished, the highest in Spain, which rises beyond the closed topography, thanks to two gravity abutments on which it

is supported. For the closure of the lateral troughs, a buttress dam and an embankment dam with a bituminous concrete face
were built (see Section 6.11.3).
In the Sil Sytem, the construction of the Santa Eulalia ended in 1967. It had the slimmest and most curved double-curvature dam
ever built in Spain (Figure 26). Most of the building equipment that was later used to build the great Almendra dome was fine tuned
here. In the same system, the Las Portas double-curvature dam was finished in 1975, with a height of 141 m, which was the third
highest hydroelectric dam (Figure 26).
The Belesar dam, on the Miño river and 132 m high, and the Valdecañas dam, on the Tajo river, 78 m high with a singular
arrangement, with the power station at the base of the dam, protected by a small arch cofferdam and with spillways in tunnels on
both sides (Figure 27), were built in 1963 and 1964. Other double-curvature dams built during these years included La Jocica
(1964), 87 m high and very narrow, and that of La Barca (1966), 74 m high, over the Cantabrian Narcea river. The Susqueda dam
(1968) was built over the Ter river, with a height of 135 m.
Among the buttress dams we must mention that of José María de Oriol (1969), associated to the Alcántara reservoir, with a
height of 130 m and a double-buttress or ‘Marcello’ type, which was a world record for its height in this type of dam until the Itaipu
dam was built. This dam changed the single-buttress dam type used in profusion throughout the 1950s and 1960s by hydroelectric
companies. It was also the last important dam of this type built in Spain (Figure 28).
Gravity dams continued to be the most used for lower heights, while embankment dams were used to a lesser extent, of which
that of Portodemouros (1967), 91 m high, stands out. Among the gated dams, we must mention those of Velle, Castrelo, and Frieira,
all over the Miño river, with heights in the 25–35 m range and built in the 1960s.

Table 3

Main hydroelectric dams in Spain

Dam

Height
(m)

Typology

Year

River

Location

Reservoir capacity
(hm3)

Almendra
Canelles
Portas, Las
Aldeadavila
Susqueda
Belesar
José María de Oriol
Escales
Salime
Cohilla, LA
Cortes II
Matalavilla
San Esteban
Bao
Eume
Ricobayo
Doiras
Tanes
Peares, Los
Portodemouros

202
151
141
140
135
132
130
125
125
116
116
115
115
107
103
99
95
95
94
91

VA
VA
VA
VA-PG
VA
VA
CB
PG
PG

VA
VA-PG
VA
VA-PG
PG
VA
PG
PG
PG
PG
ER

1970
1960
1974
1963
1968
1963
1969
1955
1956
1950
1988
1967
1955
1960
1960
1934
1934
1978

1955
1967

Tormes
Noguera Ribagorzana
Camba
Duero
Ter
Miño
Tajo
Noguera Ribagorzana
Navia
Nansa
Jucar
Valseco
Sil
Bibey
Eume
Esla
Navia
Nalon
Miño
Ulla

Salamanca
Huesca
Ourense
Salamanca
Gerona
Lugo

Caceres
Huesca
Oviedo
Santander
Valencia
Leon
Ourense
Ourense
Coruña, A
Zamora
Oviedo
Oviedo
Lugo
Coruña, A

2.649
687
535
114
233
654
3.162
153
266
12
118
65
213
238
123

1.150
96
33
182
297


Evolution of Hydropower in Spain

329

Figure 26 Santa Eulalia and Las Portas dams, in the Sil System.

Figure 27 Valdecañas dam.

6.11.2.4.3

Main hydropower developments

From a technical point of view, the important hydroelectric development in this period was based on three cornerstones: the
construction of large dams, the construction of underground power plants, and the development of pumping installations. The first
enabled the creation of higher heads and a higher regulation. The second, due to the development and availability of building
equipment and building techniques, enabled a higher flexibility in the arrangement of development schemes without the technical
or environmental conditionings of surface locations. The third enabled for the development of electric power storage schemes in the
way of potential hydraulic power. This was an important factor in an electricity system such as the Spanish one which was beginning
to generate more through thermal plants. The pumping installations of that time continued to be used for decades and are actually
still in use, although with different criteria.
At present, and as explained further on, we need pure pumping facilities that allow us to supply very concentrated peaks and with
a relatively low number of operative hours. In the 1960s and 1970s pumping was understood as a storage means, by means of
pressure diversions, in lateral basins of the main riverbeds, where the reservoir capacity and the flow availability did not coincide

geographically. With the change of generating model, this concept changed toward the pure pumping facilities in the 1980s with the
purpose of serving as system regulation and to be able to supply the strong peaks. This does not mean that both approaches are
different, but complementary, when not coincidental.
The main pumping developments carried out in this period are connected to three of the main Spanish development schemes:
the Duero System, the Sil System, and the Tajo Inferior Development. The first development was carried out from the first decades of
the twentieth century, and was continued during the 1940s and 1950s with classic schemes, while the second began its development


330

Hydropower Schemes Around the World

Figure 28 JM de Oriol Dam.

after the war, as we have already pointed out. But the definite boost during this period in both of these was, to a great extent, due to
the application of pumping. The third, that of the Tajo, was developed in a concentrated manner between 1960 and 1975, and had
pumping as its main element from the start.
The Sil System takes advantage of the waters of the Sil river, as well as of most of its tributaries. It currently has an installed power
in generation of 1270 MW and in pumping of 400 MW, with 19 power plants, 45 power units, and 17 large dams, all built between
1952 and 1994. It has the highest concentration of hydroelectric developments in Spain (Figure 29).
There are three pumping stations in the system: Camba-Conso, Bao-Puente Bibey, and Santiago-Jares. The first (1975) is the
main one, with an installed power of 230 MW, a flow of 120 m3 s−1 and a 230 m head between the power house and the large
multiannual Las Portas reservoir, which confers a great power reserve for all the power plants located downstream, among which is
that of Bao (1964), with one of the four pumping units with a ternary arrangement. This station, along with that of Aldeadávila I,
built at the same time, were the first step in the application of the modern underground excavation techniques applied in
hydroelectric power plants and galleries in Spain (Figure 30).
The analysis of the study phases of the Tajo Inferior Development is interesting, as it highlights the change in the design of
hydroelectric systems that took place in only a few years. Downstream from Toledo, the Hidroeléctrica Española concession allowed
for the exploitation of the river itself, with a total height variation of 280 m (Figure 31). The top 40 m were exploited with a
conventional power plant in accordance with the existing easements, fundamentally agricultural and for town use.

For the lower 240 m there were three solutions. The first was a conventional scheme, with four development steps by means of
dams and power plants at their base. Subsequently, the inclusion of the exploitation of one of its tributaries, the Tiétar, was

Figure 29 Current schematic plan and profile of the Sil System.


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331

Figure 30 Bao power plant. Cross-section, in which the difference between the three generation units and the pumping-generation unit are shown.

Figure 31 Scheme of the Tajo project, situation in 1964.

considered. And finally, soon after the previous one, the possibility of including pumping was considered, which was indeed done
in two of the power plants.
On the basis of the need to create a large regulation reservoir, it was situated as far upstream as possible, resulting in the
Valdecañas dam. In order to create a minimum head of 50 m, a volume of 270 hm3 was sacrificed, while the oscillation between a
height of 50 and 75 m created a regulated water reserve of 1275 hm3, not excessive if we take into account that, although it is one of
the main ones in Spain, it has annual irregularities of 1–6 and monthly of 1–140. As downstream the Tajo river did not receive
important contributions, the construction of more regulation reservoirs was not considered, using the following step, of 46 m, with
a second dam, that of Torrejón, with a power plant at the toe of the dam.
This scheme was considered as satisfactory until the mid-1950s, with two power plants, one of 225 MW in Valdecañas and the
other of 130 MW in Torrejón, plus another two to be exploited later on. The expected productivity of this scheme in the first two
power plants was 550 GWh in the first and 345 GWh in the second, that is, a total of 895 GWh, but with strong oscillations, from
1 to 4 in annual values.


332

Hydropower Schemes Around the World

On the other hand, a group of power plants at the base of dams fed by an important regulating reservoir such as that of
Valdecañas was considered as ideal to supply the connection load peaks. In this way, first the partial exploitation of the Tiétar river’s
resources was considered, being a tributary of the Tajo downstream from the projected Torrejón jump, and second the large-scale
adoption of pumping with reversible power units in both sites.
The final result was the construction of the Valdecañas power plant, at the toe of the dam, with a power of 250 MW and pumping
from the lower reservoir, that of Torrejón. The incorporation of the Tiétar to the scheme immediately presented the convenience of
also using its contribution, for which the possible pumping from it to the Tajo in the Torrejón reservoir was considered. For this
purpose a power house was built to serve both reservoirs, that of Torrejón and a new one on the Tiétar, in an area in which they are
both very close to each other, upstream from their confluence. Both reservoirs have a difference in height of 20 m. This power plant
was designed to have a great operational flexibility between both rivers, in such a way that Tajo-Tajo and Tiétar-Tajo turbination is
possible, as well as Tajo-Tajo, Tiétar-Tajo, and Tajo-Tiétar pumping. In this way, the expected productivity was 710 and 420 GWh,
respectively, with a total of 1130 GWh, with a minimum improvement of 26% and only a 1–2 variation (Figure 32).
The scheme continued with the construction of the José M. de Oriol power plant, which was initially expected for a power of
600 MW and finally achieved 935 MW, being Spain’s second largest today. The last phase of the development was the construction
of the Cedillo power plant, located at the point where the Tajo enters Portuguese territory, in the confluence of the Tajo and Sever
rivers. The power house is located in the dam with the same name, between two large spillways, one per river. Its installed power is
500 MW (Figure 33).

Figure 32 José M. de Oriol power plant. Tiétar-Tajo pump operation.

Figure 33 Cedillo power plant and dam.


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333

Many other developments were built over this period of strong hydroelectric expansion. The schemes used in most of them were

those with power plants at the toe of dams and those with diversion schemes, both in areas with strong height variations such as in
the century’s first decades, and in lesser height variations and more important flows in more regulated river sections.

6.11.2.5
6.11.2.5.1

The Last Three Decades
The electricity sector

At the end of the 1970s and beginning of the 1980s, several coal (both national and imported) power plants began to operate. In
addition, the nuclear program continued and between 1983 and 1988 seven power plants began operating, with a total installed
power of more than 7000 MW.
The quick fuel plant replacement process and the development of the nuclear program had a double effect on the electricity
sector: The strong indebtedness of the electricity companies and the overcapacity made it necessary for a Legal and Stable Framework
to be established in 1988, which stabilized the sector and in the 1990s enabled the electricity companies to reorganize, mainly in
two large groups: Endesa and Iberdrola, which also began to expand internationally.
In 1995, the Law for the Regulation of the National Electricity System was enacted, and in 1996, the EU Council passed the
Directive concerning common rules for the internal market in electricity. As a result, in 1997 the Electricity Sector Law was enacted,
introducing the most important regulatory changes in this sector’s history, in the line of a liberalization of the electricity market and
of the separation of the generation, transport, distribution, and marketing activities. Subsequently, the figures of the Market
Operator, whose purpose was the market’s economic management, and that of the System Operator, whose purposes were to the
system’s technical management and the management of the transport network, were created.
At the beginning of this century, the Spanish electricity sector was characterized by a low reserve of installed power, as a transport
network with congestion problems in certain areas, and an important increase in demand, a result of the strong economic growth.
All this was the cause for an important development in the construction of new power plants: on the one hand, combined cycle
plants, and on the other hand, renewable energy plants in general and wind farms in particular, under the shelter of favorable laws
for this type of energy and of the social concern in the ambit of environmental protection.

6.11.2.5.2

Main hydropower developments

From 1985 the economically exploitable hydroelectric potential was practically used, so from then on the developments have been
of four types. Among the medium and great power developments, the pumping plants stands out, especially pure pumping plants,
and those built as an extension of relatively important power plants, under the shelter of the gradually greater regulation upstream
with reservoirs of all uses throughout time. Two types stand out among the small power developments: small power plants built
under the special production system and those that exploit the existing regulation hydraulic installations, such as the irrigation or
supply regulation dams.
Among the pure pumped storage we must mention those of Aguayo, with an installed power of 362 MW; Estangento-Sallente,
with 450 MW; Guillena, with 210 MW; La Muela, with 635 MW; Moralets, with 222 MW; and Tajo de la Encantada, with 360 MW;
2240 MW in total, built in these last few decades, to which we must add the 112 MW from the Gabriel y Galán and the 126 MW of
the Tanes mixed pumped storages.
To complete the pumping power plant overview in Spain, we would have to add the over 2600 MW of installed power of mixed
pumping plants built before 1975, in the aforementioned Saltos del Sil, Tajo System, Duero System, and others with less power.
Total power installed in reversible power units is, in terms of turbination power, of the order of 5100 MW. This capacity will be
increased in the coming years with the installations being built and those being projected.
The first pure pumping plant built in Spain was that of Guillena, in the Guadalquivir basin near the city of Seville in 1970.
Between 1983 and 1984, the reversible power plant of Aguayo became operative in the Cantabrian mountain range, whose lower
reservoir was formed by raising the existing Alsa dam (Figure 34). This reservoir is also part of the Ebro-Besaya interbasin diversion.
Between 1986 and 1989, the Moralets pumping plant was built at the headwaters of the Noguera Ribagorzana river. The location
of the Tajo de la Encantada pure pumping plant is rather singular, with the building inside the reservoir (Figure 35).
The pure pumped storage of Estangento-Sallente, Spain’s second largest in terms of power, is located at the highest watercourse
of the Capdella river, and uses as its upper water tank the lake which was raised with the Estangento dam, which has been
mentioned previously (Figure 11). The initial dam has the same purpose as that of the beginning of the twentieth century, which is
to collect the waters for the power station, while the rise is used to regulate the pumping. The lower tank was formed by building a
90 m-high embankment dam (Figure 36).
The most important pure pumped-storage plant in Spain is that of La Muela, located near the Cofrentes Nuclear plant,
on the Júcar river. This pumping plant is currently being enlarged, which will make it Spain’s most powerful plant
(Figure 37).
The schemes of the two mixed power plants built in this period are interesting. That of Tanes is part of the supply system to the

central region of Asturias and is located between two reservoirs, Tanes and Rioseco, and has the particularity that the power plant is
located near the middle point of the hydraulic circuit. The Gabriel y Galán mixed pumping plant is part of a development built in
the 1980s and of which the Guijo de Granadilla dam is also part. Both the power plant and the dam are located between two dams
built in the 1960s for irrigation purposes; the upper dam, Gabriel y Galán, is a regulation dam, and the lower dam, Valdeobispo, acts