Retezat Biosphere Reserve - Romania

The tectonic, lithology and morphologic conditions of the Retezat Mountains, correlated with the positioning of the crests in relation with the advection of the oceanic air masses, make the massif be the area with the highest humidity and draining in the Romanian Carpathians.
The abundant hydrographic network drains in two directions:

Northwards, towards the Strei River (the Mures hydrographic basin), which collects all the waters from the west, north and northeast of the massif.
Southwards, towards the West Jiu river (the Jiul Romanesc Hydrographic basin).
The density of the river network is higher in the Strei hydrographic basin (0.8- 1.0 km/ km 2) than in the one of the Jiu (0.7- 0.8 km / km 2). According to the altitude, one can notice that the maximum density corresponds to the sub- alpine level and the minimum one to the alpine level.
The values of the specific medium drain increase proportionally to the altitude: from 14.3 l/s/ km 2 between 600 ?800 m, at over 40 l/s/km 2 at altitudes higher than 2400 m. During the year, the maximum drain is usually reported in May- June, due to the snow melting and heavy rainfalls. The minimum drain takes place in the winter months, when the extremely low temperatures and precipitations do not offer the optimal conditions of maintaining the draining process. The winter drain conditions are stable and the summer drain is two times higher.
The average temperature of the rivers decreases proportionally with the altitude. It is around 4 0 at 1600 m and around 20C at 2200m .The maximum temperatures of the rivers arise in July- August (12 to 22 0 C) and the minimum ones in December- March (?20C to 00C).
The most important watercourse is Lapusnicul Mare, having an annual average flow of 12.9 m 3 /s. Waterfalls can be found on any brook within the Park.
The relic natural lakes play an important role in characterizing the hydrologic network of the Park. Their genesis was determined by the optimal conditions for the accumulation and transformation of the snow into glaciers, at altitudes higher than 1700 m, during the Superior Pleistocene. Over 37.8% of the Romanian glacial lakes are situated within the Retezat National Park. Located at the bottom of the glacial basins, ranged in tires, aligned, isolated or grouped in complexes, they represent a main attraction, not only for tourists, but also for the scientist who come to these places.
The morphometric elements of the lakes oscillate within large limits, some of them breaking the country records: Bucura- the largest glacial lakes, Zanoaga- the deepest. The surface of the lakes is between 300m 2 (Stanisoara I) and 88612m 2 ( Bucura) and the maximum depth is between 0,3 m (Stanisoara I & II) and 29 m (Zanoaga). The volume of the lakes varies between 90.3 m 3 (Galesul II) and 693.152 m 3 (Zanoaga).
Although they have relatively small surfaces, the glacial lakes have a highly important role in the natural regularization of the draining of the rivers in the Retezat Mountains. 58 permanent glacial lakes exist in the entire massif, located between 1700 and 2300 m. Some bibliographical sources mention the existence of over 80 glacial lakes.
As a result of the 20th century anthropic interventions, the regularization of the river draining started to be controlled also by means of the dam lakes (artificial lakes), which are built on Rau Mare. The building of the Gura Apei reservoir lake, at the junction of Lapusnicul Mare, Lapusnicul Mic and Ses rivers, started in 1975 and was finalized in 2000. Two subterraneous feed pipes, collecting the water from the Rausor and Nucsoara rivers were built for supplementing the water capacity of the dam. The hydro- technique buildings have generated, due to the absence of water on several hundreds of meters of the Raul Mare riverbed, upstream of the Tomeasa dam, ecologic modifications, which have been studied to a little extent, mainly on the Raul Mare Valley. .
The swamps frequently appear in the Park in the surrounding area of some springs, alpine brooks or as the result of the partial clogging of some glacial lakes (the Judele glacial valley, the Negru pool, Lia, Bucura and Taul Rasucit lakes). These are the propitious areals to the water loving species. .
The shallow underground waters (phreatic waters), are mainly situated within the alteration crest at the bottom of the detritus areas (where important water reserves are located) and in the calcareous deposits area from the superior basin of the West Jiu river.