Limnology of the Red Lake, Romania

Limnology is one of the most important disciplines of hydrology. It studies inland waters and all other standing waters (natural or artificial), including hydrologic phenomena, physical or chemical, in relation to the environment (chemism, thermals, dynamics, development capabilities of the flora and fauna associations, etc.), as well as the way they are valorized by man. From a historical point of view, limnology is only approximately one century old and the founder of limnology is considered to be François A. Forel from the University of Lausanne (Switzerland). It is very important to make a clear distinction between similar terms, such as “lake” and “pool” and define a clear terminology. Out of the grand total of 1 million lakes, distributed all around the world, in Romania, there are currently about 3,450 lakes. There are many types of lakes and numerous classifications are based on several factors, such as: the origin of the lacustrine basin, hydric regime, thermal regime, mineralization degree, trophic potential, geographic position, nature (natural vs. anthropic). The anthropic category is devised into smaller types, depending on the size (the amount of the water reservoir), or on the purpose (hydro-energetic, drinking or industrial water supply, irrigations, pisciculture, recreation, balneotherapeutic, residue cleaning, wet concentration, etc.). The Red Lake is a natural dam lake, which was formed after a huge landslide blocked the Bicaz Valley in 1837. Here, the objective is emblematic, because it is the most well-known natural barrage lake in Romania.

The Red Lake is situated in the Central Group of the Eastern Carpathians, within the Hăghimaş Mountains (Hăşmaşu Mare). The Hăghimaş Mountains are part of the Moldavian-Transylvanian Carpathians group. They correspond to the southern sector of the External Marginal Syncline, with a median position between a volcanic chain in the west and a flysch chain in the east (Cristea in Munţii Hăşmaş şi Staţiunea Lacu Roşu. Sport-Turism Publishing House, Bucharest, 1978; Mihăilescu in Carpaţii Sud-estici. Scientific Publishing House, Bucharest, 1963; Niculescu and Oancea in Munţii Giurgeului şi Curmăturii. Geografia României, vol.III. Romanian Academy Publishing House, Bucharest, 1987). The name “red” comes from the fact that, at sunrise, the sun rays fall directly on the reddish clays of the western slope (Piciorul Licoş), which are reflected in its relatively clear waters. The most important tributaries are the Oaia brook (also known as Oii) and the Sec brook on the right side; on the left, there are the Vereşcheu, Licoş and Suhard brooks.

The Red Lake is part of the Bicaz Gorges-Hăghimaş National Park. It is situated in the Group of Giurgeului and Hăghimaş Mountains (Curmăturii or Hăşmaş) within the Moldavian-Transylvanian Carpathians (Romanian Carpathians and Transylvanian Depression 1987). It must be mentioned that the delimitation of mountain units has been an intensely disputed subject within the past few years, the reason for which the limits of the Hăghimaş Mountains or even its name are still being questioned. The Bicaz Gorges-Hăghimaş National Park has objectives related to hydrology, hydrogeology, flora, fauna, archaeology and to the geologic substrate. Besides the lake basin being occupied by the Red Lake and by karstic forms dominated by the Bicaz Gorges, there are also numerous geologic sites such as fossil-bearing points with a biostratigraphic and paleontologic value, a series of petrographic outcrops with paleogeographic significance and some structural perimeters that help to decipher retro-tectonic aspects. Along with the geologic sites, there are several physical-geographic sites, such as The Licaş Swallow Hole, The Melekviz intermittent sources and the Izvorul Rece site and there are also archaeological objectives, such as with the Bardos-Bicaz Gorges. The vegetal sector is very well represented, through monuments of nature (Taxus baccata, Gentiana lueta, Leontopodium alpinum, Cypripedum calceolus); rarities (Juniperus sabina, Nigritella rubra, Daphne cneorum, Larix decidua ssp. carpatica) or endemisms (Aconitum toxicum, Campanula rotundifolia ssp. calcicolum, Centaurea melanocalathia).

The central-longitudinal area of the Eastern Carpathians belongs to the Crystalline-Mesozoic unit. This area, known as the Carpathians, belongs to the Crystalline-Mesozoic unit, whose sector is known as the Moldavian Compartment (the Tisa-Ciuc Compartment) (Grasu C, Miclăuş C, Brânzilă M, Baciu DS (2010) Munţii Hăşmaşului. Monografie geologic şi fizico-geografică. “Al.I.Cuza University” Publishing House, Iaşi; Mutihac V (1990) Structura geologică a teritoriului României. Technical Publishing House, Bucharest). To the east, the Mesozoic sedimentary is known as the External Marginal Syncline. It is separated into two compartments: the Hăghimaş syncline in the south and Rarău in the north. The Hăghimaş Mountains, which also comprise the Red Lake lacustrine basin, correspond to the Mesozoic syncline, located between Frumoasa-Ciuc in the south and Bistricioara in the north (Grasu C, Miclăuş C, Brânzilă M, Baciu DS (2010) Munţii Hăşmaşului. Monografie geologic şi fizico-geografică. “Al.I.Cuza University” Publishing House, Iaşi). The Red Lake was formed in the summer of 1837, when, after heavy rainfalls, a landslide diluvium fell from the Ghilcoş (Ucigaşu) Mountains and blocked the stream of the Bicaz brook. The Ghilcoş-Hăghimaş-Mezinul Crest is located in the northern compartment of the central unit within the Eastern Carpathians. The most frequent rocks within the Red Lake hydrographic basin are the following: limestones and dolomites (Triassic), limy sandstones (Lias-Dogger), sandstones and conglomerates (Barremian-Albian) and crystalline schists (Maastrichtian). There are five sedimentation cycles: the first comprises sequences of conglomerates, sandstones, loam and limestones; the second is associated with Lias limestones; the third is represented by conglomerates, calcareous sandstones and Dogger-Portlandian grey limestones; the fourth mostly comprises Neocomian whitish grey limestones; and the last one comprises conglomerates (along the Bicăjel valley, at the contact with the slopes) with loam and sandstone intercalations (the bottom of the Bicăjel valley).

The tectonics of the erosive substrate (composed of limestones and conglomerates) is highly fragmented and represents an important factor in the morphology and morphometry of the landscape. The hydrographic basin is individualized by a series of variables, from which the most important are: rocks; soil layer and vegetal layer. The morphometric parameters for the Red Lake hydrographic basin were determined through the computer-based cartography programs TNTMips (Microimage) and ArcGis (ESRI). Out of these, the most important are: basin length, width, drainage network length and frequencies, basin surface, landform orientation, slope exposure etc. The Horton-Strahler hierarchy of the hydrographic network was also assembled, in order to point out the maximum order number of the basin river system and make a statistical analysis on the Red Lake tributaries of each Horton-Strahler river order. A detailed analysis (from both a spatial and a statistical point of view) was made on different hydrographic basins, according to the corresponding river’s Horton-Strahler order. The lake basin parameters were measured with state of the art equipment (LEICA TCR 1201 total station, together with LEICA GPS 1200; Valeport Midas Surveyor echo sounder), which was used to obtain a bathymetric map of the lake and the morphometry of the surrounding areas. The bathymetric map was used to generate transects, which would later be used in silting analysis and other detailed analyses.

The sediment discharge that ends up in the Red Lake is important, mostly given that the last decades have been characterized by intense deforestations. These have accelerated the erosion and the silting of the lake basin, as well. In order to correctly assess the source areas of the sediments, from the drainage basin, satellite imagery has been used, to accurately identify the areas that have suffered from deforestation in the last decades. Through deforestation, the slopes are severely destabilized, being vulnerable to landslides, high-water waves, etc. Several silt samples from the bottom of the lake were taken in 17 points covering the whole surface of the lake. The thickness of the lacustrine sediments varies extremely, reaching a maximum of over 6 m in the spillway sectors of the two important brooks: Oaia (Oii) and Suhard. The silting process was also measured by comparing bathymetrical transects between the measurements taken by Pişotă and Năstase in 1957 and the measurements taken in 2010 with specialized equipment. Therefore, the silting rate is a very important parameter, associated with numerous processes both natural and anthropic. Silting has also been studied with the help of gravity core samples. Several USLE models have been made, to emphasize the difference between natural erosion and accelerated erosion, due to illegal deforestation. Silting analysis is very important, because, by using different methods, predictions on future silting rates can be made and we can estimate the lifespan of the lake.

The area of the Red Lake and the Hăghimaş Mountains is included in a mountain thermal climate, with great diurnal and seasonal variations. There are no meteorological and hydrologic posts in the area of the Red Lake hydrographic basin and data were taken from expeditionary measurements made by Ghenciu (Yearbook Museum Nat Sci Piatra Neamţ, Geol-Geogr, 3:313–319, 1976) in 1968–1970 or they came from interpolation (Apăvăloaie 1971, 1980; Mihăilescu in Observaţii microclimatice expediţionare în uvala Terkö (Piatra Crăpată), Pângăraţi, p 7, 1980 and Apăvăloaie 1980). The specific winds are mountain-valley breezes: from the peak towards the valley in the evenings and the other way around during the day. The big difference in the relative altitude makes the breezes frequent and relatively strong. In the evenings, during the mountain-valley breezes, a strong smell of resin—from the high-altitude pines—fills the air. The relatively cold climate is determined by the appearance of thermal inversions. They are frequent in the winter and they make the ice bridge that occurs on the lake, very long-lasting. Though the Red Lake is situated in a mountain area, there have been examples of temperatures above freezing in winter (4.3 °C in February 1968, 1.1 °C in December 1970, or 0.4 °C in December 1969). For a mountain area, with frequent thermal changes, especially in the winter, the values are not surprising. The climate of the Red Lake area is typical for the surroundings and it is a representative example of the mountainous climate of the Oriental Carpathian mountain range.

In order to have a complete picture of the limno-ecological conditions, 17 measuring and sampling points were chosen. The points chosen covered the whole of the bathymetric and morphological spectrum of the lake. The measurements were carried out on the surface and from meter to meter as far as the bottom and they were repeated in every season; spring, summer, autumn and winter. The pH of the water is found to be slightly alkaline throughout the year with a range of 7.5–8.0 (Fig. 8.5). Very rarely, in certain conditions, the pH value falls within the circum-neutral category. The existence of dissolved oxygen is essential for the water table. Even given this, the Red Lake is not the object of extraordinary biological diversity, which follows from the fact that its existence is relatively recent. All these parameters are important because, at their junction, they define the vegetal and animal life conditions that the Red Lake has to offer. The geographic location of the lakes in Romania, in distinct landform units (mountains, hills, and plains, littoral) creates different environments for the manifestation of trophicity. According to the value of the nutrients, the greatest parts of the lakes (wetlands) are situated in the mesotrophic, meso-eutrophic, eutrophic, eutro-hypertrophic and hypertrophic categories.

The chapter concerning the vegetation and fauna of the Red Lake (except for the wetlands) is based upon data taken from the scientific literature. From this perspective, the ecologic succession of the lacustrine system may be divided into three phases: open water with an oligotrophic lake regime; invasion of the lake with aquatic macrophytes, with an oligotrophic-mesotrophic lake regime; and, in the end, mesotrophic; senescence, with a mesotrophic-eutrophic lake regime (Ghenciu Trăsături hidrofizice, hidrochimice şi hidrobiologice ale Lacului Roşu, 1972). The vegetation within the hydrographic basin is dominated by pine forests: spruce (Picea excelsa); silver fir (Abies alba); white pine (Pinus silvestri); larch (Larix decidua), etc. On the mountain pastures and on the alpine empty crests, graminaceous plants are predominant: red fescue (Festuca rubra); matgrass (Nardus stricta); rosy vanilla orchid (Nigritella rubra) etc., while hydrophyte and helophyte vegetation is present through the following associations: Carocetum inflatovesicariae; Caricetum appropinquatae; Equisetum limosi etc. The fauna of the hydrographic basin comprises a great variety of species, many of them rare and protected. Among the mammals the following should be mentioned: the brown bear (Ursus arctos); the common wild boar (Sus scrofa); the red Carpathian deer (Cervus elaphus carpaticus); the roe deer (Capreolus capreolus); the wolf (Canis lupus); the lynx (Felis lynx); the wildcat (Felis silvestris); the chamois (Rupicapra rupicapra), etc. The fish fauna is specific to the upper salmon area. As it contains dry residue, organic substance, nitrates, phenols, etc., the water provides satisfying conditions for the fish culture.

Systemic analysis—mainly the analysis of interactions between elements of a system and the study of the changes between the systems—has become important for current scientific research, known as global or holistic research. Analysis of the “earth-water” system functioning shows the fact that transfers are regulated through transition areas between terrestrial and aquatic environments, known as wetlands (Romanescu et al. 2009, 2010). The wetlands and deep waters of the mountain units within the Eastern Carpathians have suffered fewer transformations compared to those situated in the lower sectors of the Romanian landform. At the level of the entire country, the morphometric characteristics and the climatic conditions allowed the installment of a large variety of wetlands and their conservation has been sustained by conditions preventing drainages or reduced inhabitation density. The most important argument in conserving and rehabilitating wetlands is represented by the roles they have been playing: regulating the hydrologic cycle; increasing the biodiversity; reducing soil erosion; improving the microclimate; reducing the floods; ensuring natural life conditions for numerous species of plants and animals; tourist destination, etc. (Hurt and Carlisle 2001).

The Red Lake has started to be very influenced by human activity, due to the usage of water bodies for touristic purposes. From this point of view, there are several activities, such as deforestation, inappropriate tourist activities, pollution etc. that intervene in the natural erosion, transport and accumulation cycles, causing an increase of the silting rate, a phenomenon that will eventually lead to the disappearance of the Red Lake. For this reason, water management is a very important subject to bear in mind, when trying to adopt political or administrative decisions that involve landscape modifications in the drainage basin of the lake. The administration of the Red Lake—Bicaz Gorges Reservation monitors, on a daily basis, the tourist activity and ensures an ecological behavior. In order to conserve the hydrologic balance and to reduce clogging, the following actions are taken into account: catchment of deep underground waters and reducing the samplings directly from the tributary brooks of the Red Lake; stopping the deforestations of the hydrographic basin and eliminating over-pasturing. Other effective actions would be the hydro-technical management of the torrents and stopping the business activities incompatible with the National Park status; building a retention pond on the Suhard brook, etc. The measures foreseen consider the preservation of wetlands as areas of biodiversity and alluvium blockage.

Although most of the lakes in Romania are anthropic, there are relatively numerous standing waters, but the actual natural lakes, according to the universal definition, are rare. The north-eastern part of Romania is characterised by a lack of water, because of which many ponds were built as early as the 14th century. There are numerous types of lakes, natural dam lakes (Red (Roşu), Cuejdu, Ştiol, etc.); volcanic (Saint Anne); fluviatile limans (Ostrov, Mârleanu, Vederoasa, etc.); lagoons (Razim, Sinoie, Siutghiol, etc.), of subsidence (Movila Miresii) etc. The best-known natural dam lake is the Red Lake (10.5 meters deep) formed in 1837, in the Haghimaşul Mare Mountains. The Red Lake catchment basin has a surface of 40.59 km2, and it is drained by typical, high mountain rivers, such as Suhard, Licoş, Vereschiu, Oaia etc. A detailed morpho-metric analysis of the hydrographic basin has been conducted, in order to emphasise the main ecologic elements. Using modern equipment (eco-drill, topometric total station, high precision multi-parameter, etc.), detailed measurements have been taken for the morph-bathymetric elements and for the physical–chemical parameters of the water. Therefore, the main cartographic results obtained refer to slope value and orientation, hypsometry, river classification according to Horton Strahler system etc. Deforestations have accelerated the erosion rate, contributing to the silting process of the Red Lake. The largest deforested surfaces were registered between 1989 and 2001. The maximum clogging rate has reached 1.5 – 1.6 meters (2.8 – 3 cm/year), mostly between 1957 and 2010. All physical–chemical parameters of the water have fluctuations depending on seasons and morpho-bathymetric layers. From a trophic point of view, the Red Lake is included in the meso-eutrophic (nutrients) and ultra-oligotrophic (biologic) categories. The Red Lake has existed for a very long time. The current silting rate is relatively low, which contributes by rising the lifespan of the lake. Several structural and non-structural measures have been applied, to reduce silting, and the most recommended ones refer to lowering soil erosion inside the hydrographic basin, which would also be adopted to maintain biodiversity and the general landscape of this area.