Nature park Rilski manastir: Abiotic factors
The Nature Park Rila Monastery is a part of the highest massif on the Balkan Peninsula – Rila. The park’s territory includes the upper reaches of the Rila River’s watershed and the entire watershed of The Illeena River. The park’s total area is 2,730.7 hectares.
In terms lithography and geology The Nature Park Rila Monastery is endowed with considerable diversity. The majority of the park’s bedrock and surface rocks are of the metamorphic type – the oldest rock type found in Bulgaria. Besides these rocks, several types of intrusive geologic formation are to be found at the park’s surface, especially granite. Sedimentary geologic deposits from the Paleolithic, Pleistocene and Quaternary periods are to be found here but mainly at the park’s periphery.
The contemporary morphological processes and complexes present in the Rila Massif show well defined altitudinal zoning. Based upon this observation, there are three clearly independent mountain zones – high, middle, and low.
The high mountain zone includes all territory above 2,200 meters. At these elevations the predominate feature is denuded alpine peak. Below these peaks are deeply incised cirques. Within the park’s territory there are 34 peaks with an elevation greater than 2,200 meters. In this high zone the intense effects of alpine weathering and the Rila massifs considerable gravitational force, lead to typical alpine features such as scree and talus slopes. During the winter, conditions are ripe for avalanches and their flows lead to characteristic alpine phenomena such as deep avalanche banks and avalanche cones.
The middle mountain zone includes all territory between 2,200 meters and 1,500 meters elevation. The defining characteristics of this middle zone are the considerable remnants of older denuded geological strata with deeply sunken and eroded valleys, within which are found alluvial deposits.
The low mountain level includes all park territory below 1,500 meters elevation. At this level especially well expressed are the many sudden twists and turns of river beds and the presence of alluvial deposits.
Due to the action of glaciers during the Quaternary geologic period, there now is a considerable number of glacial lakes at the higher elevations of this region. Just within the boundaries of the park there are 28 lakes, several of which serve as the source of the alpine rivers and streams that flow through the park. The largest of these rivers are: The Rila, The Illeena, The Devils’ Waters, and The Drooshluovitsa. Of these lakes, the highest is the first of the so called Devils’ Lakes (Dyavolskite ezera – elevation 2,445 meters) and the lowest is the Dry Lake (Soohoto ezero – elevation 1,892 meters). Additionally, the largest alpine lake on the Balkan Peninsula is found in the park – The Smradleevo Lake, with a surface area of 212 decares and a maximum depth of 24 meters.
According to the climatic zoning of Bulgaria, the territory of Nature Park Rila Monastery falls almost entirely (with small exceptions on the western peripheral area) within the alpine climatic zone (for terrain at or above 1,000 meters elevation) and borders between the temperate-continental climatic region and the transitional-Mediterranean climatic region.
The local climate is influenced by the following factors of relief and topography: vertical segmentation; aspect and elevation above sea level. The shapes and orientations of the valleys and the barriers in between them influence the circulation of air masses and therefore the temperature, winds and amount and frequency of precipitation. At elevations above 1,500 meters the aspect of a given slope directly determines that slopes precipitation regime. The differences in temperature between northern and southern-aspected slopes are considerable. On the northern-aspected slopes drastic temperature inversions frequently occur – for every 100 meters of elevation gained, the temperature falls approximately 0.7 degrees Celsius.
Generally, the average annual precipitation increases as elevation increases. This is only true, however, up until around 2,300 – 2,400 meters elevation. Above this level, average annual precipitation tends to diminish with a corresponding rise in elevation. For the highest elevations of The Nature Park Rila Monastery, the average annual precipitation is between 1,050 and 1,200 millimeters, while for the lowest elevations of the park the figure is between 700 and 800 millimeters. During the winter, precipitation on the northern slopes is less that that experienced by the southern slopes. Lasting snowpacks at the lower elevations begin to form on northern slopes after the middle of December and on the southern slopes towards the end of December. The maximum average snowpack thickness for lower elevations occurs during February and reaches a value of between 20-30 centimeters, and for the higher elevations (above 2,000 meters elevation) this occurs during March and attains between 70 – 80 centimeters thickness. At the highest elevations in the park the snowpack can reach up to 240 centimeters thickness.