Why are the lakes in Romania shrinking and drying up more and more. The worrying phenomenon, visible on more and more waters
Several reservoirs set up in the past decades have gone through extensive transformations, increasingly visible in recent years, caused by alluvium, clogging, but also by dry periods. The locals complain about the condition of the lakes, but the phenomenon can hardly be stopped.
Lake Cinciș from Hunedoara upstream. Photo: Daniel Guță. TRUTH
Lake Cinciș in Hunedoara was developed in the early 60s in the Cerna valley, after the construction of its concrete dam, about ten kilometers from the municipality of Hunedoara.
The accumulation, with a capacity of almost 30 million cubic meters of water, spread over more than 250 hectares, occupying the hearths of several villages in the Forest Land, which would be swallowed by the waters.
Lake Cinciș “entered the water”
In recent years, Lake Cinciș has gradually changed its appearance in the upstream area, located 7-8 kilometers from the Cinciș-Cerna dam. Located on the shore of the lake, the ruined church, over two centuries old, of the former village of Baia Craiului, which disappeared when the lake was developed, is a landmark of the transformations in the area.
“In the past, we used to take a boat to the church and even go inside the place with it. You can still see the traces of the church flood, left by the moisture. In some periods, the waters reached almost two meters inside it. For several years, however, the waters no longer reach the church at the tail of the lake, and in the area where the lake's sheen covered almost everything around it, we now see the Cerna water line, which flows a little above the the place where it flowed before Cinciș was developed”, says a local from Toplița, a locality located upstream from Lake Cinciș.
Every year, land gains more and more ground in the area at the “tail” of the reservoir. The alluvium brought by the Cerna River initially formed a marshy area, from which, in dry years, small islands of fine sand emerged. Over time, the upstream islands widened and became permanent, some joining the land, and vegetation gradually settled on them: first reeds and marsh plants, then shrubs and clumps of meadow trees. The valley covered in the past by the sheen of the water, where the locals had set up their pontoons and places where they tied the boats, gradually reforested, and the dry land expands by several hectares every year, outlined by the threads of the Cerna and the forests on the slopes.
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The church on the shore of Lake Cinciș Photo Daniel Guță THE TRUTH jpg
Wild boars, deer and many birds were attracted to this habitat, finding shelter in places crossed by boats and steamers in the past. Until the middle of the last century, the area shaped by the alluvium collected for decades was occupied by the houses, churches, cemeteries and former smelters of Baia Craiului village, which still preserve some ruins on the shore of the reservoir.
Lake Trei Ape, smaller and smaller
In the 60s, the Trei Ape reservoir was built, in the Semenic Mountains, located in the vicinity of the villages of Gărâna and Brebu Nou. Its dam, located at an altitude of 850 meters, was the first to be built in Romania from clay core deposits, local materials being used for the construction that would collect the waters of the Grădiște, Semenic and Brebu streams, which form the Timișul, one of the longest rivers in western Romania.
Like Cincișul, in the past decades since its construction, Trei Ape lake has been an attractive destination for tourists. The leisure area around it was sought after by the families of workers from the Banatul Montan, by the people of Timisoara and even by the Serbs.
“I remember the summers when, from the shore of the lake to the pastures of Brebu Nou, it was full of people who pitched their blankets and tents, some right behind our house, our village being right on the edge of the lake. Year by year, the village became more and more deserted, and the number of tourists decreased, the lake being more and more dry.” says a local woman from Brebu Nou.
Drought years and alluvium have caused the waters of Lake Trei Ape to recede and the dry land to gain more and more hectares around the water shine. Some locals and guesthouse owners in the area have complained about the “emptying” of the lake, demanding an explanation from the authorities. But the phenomenon affects most reservoirs in Romania, some at a slower pace, others faster, depending on their size, geology and relief of the area.
Why are reservoirs shrinking?
A study published by the Technical University of Constructions in Bucharest, entitled “Clogging of accumulations”, shows that the creation of reservoirs changes the natural regime of rivers and favors the deposition of alluvium, especially in the area at the tail of the lakes, where solid transport is slowed down. The process gradually leads to clogging, and in the case of shallow lakes, it can even favor the formation of deltaic areas.
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Lake Trei Ape Photo Daniel Guță THE TRUTH (7) jpg
“Small reservoirs are prone to the phenomenon of clogging, as a result of bank erosion, a phenomenon induced by waves in areas with erodible slopes or with a slope greater than the natural one”, shows the study published by UTCB.
The research carried out by Laurențiu Mihai Lungu shows that the lakes in the hilly areas and on the lower courses of the rivers are affected by clogging, where erosion and the torrential nature of the runoff favors the rapid deposition of alluvium.
“The slowest silting of lakes occurs in mountain regions, where erosion-resistant rocks predominate. This can be seen in alpine lakes, whose age exceeds 10,000 years and where the sediment thickness is not yet particularly high. At the opposite extreme are the lakes of the Subcarpathian regions and the Moldavian Plateau, where many small lake basins have sometimes been silted after a single flood“, notes the study.
The siltation process is influenced by both natural conditions and human interventions such as deforestation, land use change, urbanization and infrastructure development.
“Approximately 50 percent of the annual volumes of alluvium drain in less than a month, when floods are recorded. The rapid clogging process is explained by the energetic action of eroding the bed, favored by the following factors: the geological nature of the formations in the hydrographic basin; the torrential nature of the flows; the pulsating nature of the flows discharged on the river by the operation of the upstream plant, with values higher than in the natural regime”note the authors of the research.
In Romania, some dam lakes have been functional for centuries, the oldest being at Oravița, in the Banat Mountains, and at Roșia Montană, in the Metaliferi Mountains, but other lakes have been clogged in just a few years.
“In an average period of 15 years, about 200 million cubic meters of alluvium were deposited in the dam lakes on the inland rivers, almost half of which only in the lakes on the Argeș and Olt rivers. Small rates of clogging are recorded in the large lakes: Izvorul Muntelui – 0.03% and Vidraru – 0.04%, which ensures their millennial operation, if no situations intervene unpredictable”the research shows.
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The conditions of the relief and drainage of the rivers did not offer much chance for the construction of large lakes and dams, such as Vidraru, Vidra, Siriu or Gura Apelor. Almost 90 percent of reservoirs in Romania have capacities below 200 million cubic meters, and of these, half have capacities below 20 million cubic meters.
How can the clogging of lakes be stopped
Another study published by the UTCB in 2021 shows that climate change is leading to increased torrential downslope runoff, the activation of torrents on watercourses that are usually free of flows, and the emergence of increasingly large flash floods.
“For reservoirs, the phenomenon is extremely unfavorable, leading to their accentuated clogging. The immediate effect is a decrease in volume, affecting both the use of raw water supply and the ability to mitigate floods, for the protection of the downstream. A situation often easily overlooked is the clogging at the tail of the lake. Over time, veritable alluvial dams are produced, intensely vegetated, sometimes even forested, which prevent access of high water in accumulation. The flood can bypass the lake, with a direct effect on the safety of the dam, but especially with catastrophic effects for the localities located in the vicinity or downstream of the dam”. show the authors of the research with the title “River basin management plans in the context of climate change”.
According to the study, reducing the clogging of reservoirs can be done by limiting the alluvium that reaches the lake, by transiting the sediments so that they are deposited as little as possible, and by eliminating what has already been deposited, i.e. by unclogging.
“To maintain the volume of the accumulation, the optimal solution, when possible, consists in transiting the alluvium through the lake. The discharge must be done in a regime as close as possible to the natural one, and if the exploitation is done in this way from the first years of use, it is expected that the deposits from the lake will be partially carried downstream and no significant deposits will be created.” shows the research carried out by Elena Țuchiu and Corina Boscornea.
On the other hand, the evacuation of the accumulated sediments is the most expensive measure and has an adverse impact on the environment.
