Some people believe that History and Geography are two wholly unrelated fields…whereas the first deals with time, the second one rules over space, but somehow, through the hard work of researchers, these two sciences come together and complete each other. Today’s story is written in the pages of history, geography, or, as a hydrologist would say, it is to be read is the waves of a river. Valea Mare is a successful hydroelectric power station which has stood the test of time!
“With the help of God and the people from C.H.E. Motru and the Tg-Jiu Hydrological Station, we were able to build this power station. Water is our strength!” This is the statement with which the power station, located near Padiș, Gorj County, at the foothills of the Vulcan Mountains, greets us. While the Iron Gorge dams were being built, engineers began to study the possibility of harnessing waters from the Cerna, Motru and Tismana rivers, and gradually, this perspective grew until it became certitude. The taming of waters began in 1972, and in 1978 Cerna became the first of the three rivers to have a power station and, until 1987, Motru and Tismana got their own stations (with three lakes and associated work colonies: Clocotiș, near Stadionul cel Vechi, Coșbuc on the valley of Tismana and Tismănița, close to the north-eastern slopes of Cioclovina). The energy produced by this system of dams and lakes, connected by underground canals, would be fed into the national electricity grid during hours of peak demand. 
According to statistical data, the energy generated by this chain of hydroelectric stations grew, between 2008 and 2010, from less than 400GWh to around 600GWh, due to increased demand for electricity in Gorj County, both for domestic consumers and industrial purposes. The Motru Hydroelectric station, on the left slope of Motru Valley, upstream from its junction with Valea Mare River, is the first to harness Cerna’s energy and the water is next carried through pipes towards the Tismana River power station.
Valea Mare is one of the tallest dams in Romania, and it dominates the surrounding landscape. The powerful generator, with a capacity of 500 W, is fed with water through a pipe descending from a higher altitude in the Cerna Basin, more precisely from the Valea lui Iovan Lake, located perpendicularly in the Cerna Valley, between the Mehedinți and Godeanu mountains. The central building of the power station is a massive reinforced concrete box, buried 17 meters deep in the rock base and traversed by the waters of Motru, which then flow from the Motru reservoir into the Tismana reservoir through a massive culvert with a 300 meter level difference.
Due to the triangular shape of the electricity catchment and generation system used in the Motru hydroelectric power station (the second element in a chain of 3 stations and 5 reservoirs), the water’s energy is collected in a different way compared to other dams. This mechanical energy manifests itself through its two components: potential energy, created by the level difference between the reservoir (situated in this instance at a lower altitude) and the power station (located upstream from the lake), and the kinetic energy of moving water, which is continuously increased by the alternation of stationary and flowing positions, due to the triple junction of the rivers – Cerna, Motru and Tismana. Located inside Romania’s largest natural park, Domogled – Cerna Valley, this hydroelectric power station fulfills multiple roles, including tourism, the supply of potable water, flood control, whereas the production of electricity is not permanent, but only required when the national electricity grid experiences increased demand. Its Francis-type turbines are unique in Romania, and they spin at 750 rotations per minute. The generation of electricity on the Motru River is made possible by the Cerna reservoir, with a useful volume of 125 million m3, channeled towards the turbines by an 8000 meter long underground pipe connecting the valleys of Motru and Tismana.
In order to fit within the environmental plans for energy production and to reduce the technological waste of water and the infiltrations in the power station, 50.000 euros were spent on modernizing several installations. The technological upgrade continues to this day at the Motru power station, and, over the last two years, the installations powering the spherical valves and the speed and tension regulators have been repaired, and the place was embellished by the addition of a fountain, (decorated with excerpts from the 91st Psalm and a fresco depicting a typical Carpathian landscape, with a group of wild deer drinking from a spring) and the creation a space for the selective gathering of waste products. The idea of using water for human needs dates back to the times of the Roman Empire, when the first mills, used for processing ores and wool appeared on the Tismana River. The famous “barrel mills” from Sohodol have their origins in the dawn of time, and each passing generation has improved and replaced them with better creations. 
If you have the chance to visit the Valea Mare Hydroelectric station, make sure to admire it from all angles. The success of this project to harness to power of one of the largest rivers in the Danube-Jiu region is illustrated by a fresco on the wall of a fountain at the entrance of the station, which reminds us of the traditional Romanian society, which has used water in many ways, but has always maintained a correct balance between its needs and all the elements of the biosphere.
http://www.hidroelectrica.ro/Details.aspx?page=45
http://primariatismana.sapte.ro/hidroel.htm
Article written by Gabriela Morosanu and translated by Mihail Mitoșeriu.
