**2.1 Geological and geomorphological features**

According to Micevski (2000), the Ohrid-Prespa region is characterised by fairly complex geological-tectonic structures with rocks from the oldest Paleozoic formation to the youngest Neogene and Quaternary sedimentary rocks.

Prespa Valley is surrounded by the mountains of Petrinska Planina, Galichica, Suva Planina, Ivan Planina and Suva Gora. Both mountains and the valley are mainly composed of rocks varying in their age, mineralogical composition and origin. The calcareous rocks are dominant and to a small extent are distributed between magmatic rocks and Grano-Diorites. Syenites are present at the higher elevation areas, but Triassic carbonate rock masses are also present in many areas. Different types of Quaternary sediments, such as alluvial, fluvioglacial, proluvial, organogenic-marsh and diluvial sediments, are dominant in the valley, especially at the riverbeds. The depth of those sediments varies between 100 and 200 m.

Since the carbonate rocks dominate the geology of Prespa Valley and it is of principal importance for the arguments presented in this chapter, the geomorphological features of Galichica Mountain (located on the North-West side of the valley – Fig. 2) will be presented in more details.

According to its morphometrical characteristics (hypsometry, exposition, inclination), Galichica Mountain exhibits a profound tectonical character (a horst) elevated between two

Macedonia and Greece. The Ohrid Lake again belongs partly to the Republic of Macedonia and partly to Albania. The Micro and Macro Prespa Lakes are connected by a small natural channel here referred to as the Isthmus of Koula. Since 1969/70 the water level of the Micro Prespa has been controlled by a regulating weir structure to limit the maximum water level.

Fig. 1. Google map of the Prespa and Ohrid Lakes system, and the position of the

According to Micevski (2000), the Ohrid-Prespa region is characterised by fairly complex geological-tectonic structures with rocks from the oldest Paleozoic formation to the

Prespa Valley is surrounded by the mountains of Petrinska Planina, Galichica, Suva Planina, Ivan Planina and Suva Gora. Both mountains and the valley are mainly composed of rocks varying in their age, mineralogical composition and origin. The calcareous rocks are dominant and to a small extent are distributed between magmatic rocks and Grano-Diorites. Syenites are present at the higher elevation areas, but Triassic carbonate rock masses are also present in many areas. Different types of Quaternary sediments, such as alluvial, fluvioglacial, proluvial, organogenic-marsh and diluvial sediments, are dominant in the valley, especially at the riverbeds. The depth of those sediments varies between 100 and 200 m.

Since the carbonate rocks dominate the geology of Prespa Valley and it is of principal importance for the arguments presented in this chapter, the geomorphological features of Galichica Mountain (located on the North-West side of the valley – Fig. 2) will be presented

According to its morphometrical characteristics (hypsometry, exposition, inclination), Galichica Mountain exhibits a profound tectonical character (a horst) elevated between two

investigated area in the map of Europe.

in more details.

**2.1 Geological and geomorphological features** 

youngest Neogene and Quaternary sedimentary rocks.

lake basins (Fig. 3). Resulting from its geological composition (almost totally presented by Triassic carbonate rocks), hypsometrical features (only 7.19 km2 of its surface is above 2.000 m elevation) and climate (or more its fluctuations in the past), the dominant morphogenetic processes that have caused and created modern relief on this mountain are karstic, glacial and periglacial. These processes have been intermingled (supplemented), changed in intensity and duration or fully stopped over the time due to climatic changes.

Fig. 2. Geological map of Prespa Lake (Macedonian part only).

Fig. 3. Galichica Mountain – a horst between two lakes, Prespa Lake on the left and Ohrid Lake on the right.

Environmental Changes in Lakes Catchments

Fig. 5. Periglacial landscape on Galichica Mountain.

sediments into the lake, due to:

aquifers;

rocks;

**2.2 Hydrology** 

with clay material.

as a Trigger for Rapid Eutrophication – A Prespa Lake Case Study 67

the rock masses. Often the above mentioned fractures and cracks are closed and filled up

Similarly the granites, granodiorites and syenites are characterised with low water permeability, with yield of 0.1 – 0.5 L cm\*s-1 (Pelister, Ilinska mountain, Stogovo, etc.).

Having this kind of natural geomorphology in a lake's catchment means that any significant change in the land cover would result in massive washout of nutrients, minerals and



The Prespa catchment area includes two lakes: Micro and Macro Prespa, and permanent or seasonal streams, which discharge into the two lakes. The major contributing rivers to Macro Prespa Lake are Golema, Brajcinska and Kranska Rivers in the Republic of Macedonia and Aghios Germanos River in Greece. There is no major source of surface water input from Albania to Mikro Prespa. Together with the Ohrid Lake, the Prespa Lakes form a unique ensemble of water bodies in the Balkan regions. The Prespa Lakes form the deep points of an inner-mountainous basin that has no natural surface outflow. Drainage is only provided through karstic underground links by which water of the Macro Prespa Lake (approximately 845 m asl) drains westwards towards the Ohrid Lake lying approximately


The *karstic features* are the dominant genetic type of relief forms on Galichica Mountain, which is a typical karstic area where the Triassic massive and banked limestone layers lie over the crystal shales. These surfaces have been exposed for a long time to the influence of external factors which have strongly initiated the process of karstification. Micro and macro relief karstic forms, such as *karrens*, numerous karst *sinkholes* and karstic *dry flows,* as well as *karstic fields,* are frequent. From the underground karstic forms, a dozen caves and two chasms have been registered.

Fig. 4. The peak Magaro (2.254 m), the karstic field Lipova Livada and the glacial cirque between them.

Mountain Galichica's altitude and its favourable morpho-plasticity enabled the accumulation of snow and ice during Pleistocene resulting in glacial relief formation. Aside from the two cirques (Fig. 4), a small number of cribs can also be found, but the dominant landscape is formed by the *periglacial* processes resulting in *stony horseshoes, slided blocks, grassy terraces, loose glacial residues* etc. (Fig. 5).

In relation to water transport and balance, such a complex geomorphology based on karstic fundaments has created the only possible type of aquifer in the mountain region – the *fractured type of aquifer* with medium or low water permeability (yield between 0.1 and 5.0 L\*s-1). The most presented rocks in this aquifer are Paleozoic schists with a low degree of crystallisation (chlorite, sericite, quartz schist and quartzite) Less presented are gneiss, micaschist and amphibole schist, as well as intrusive rocks (gabbro, granite, syenite, diorite, diabase, quartz-porfire, andesite, etc.).

All those rock masses are rugged with faults, fractures and cracks, which generally cannot accumulate larger reserves of groundwater. These rocks have a very low coefficient of filtration (kf ≤ E-4 cm\*s-1) and different intensity of fissuring. Local fissuring is very important due to the presence of intense subsurface fissuring and surface to sub-surface weathering (locally over 20 m depth), which influence the hydro-geological characteristics of the rock masses. Often the above mentioned fractures and cracks are closed and filled up with clay material.

Fig. 5. Periglacial landscape on Galichica Mountain.

Similarly the granites, granodiorites and syenites are characterised with low water permeability, with yield of 0.1 – 0.5 L cm\*s-1 (Pelister, Ilinska mountain, Stogovo, etc.).

Having this kind of natural geomorphology in a lake's catchment means that any significant change in the land cover would result in massive washout of nutrients, minerals and sediments into the lake, due to:


#### **2.2 Hydrology**

66 Studies on Environmental and Applied Geomorphology

The *karstic features* are the dominant genetic type of relief forms on Galichica Mountain, which is a typical karstic area where the Triassic massive and banked limestone layers lie over the crystal shales. These surfaces have been exposed for a long time to the influence of external factors which have strongly initiated the process of karstification. Micro and macro relief karstic forms, such as *karrens*, numerous karst *sinkholes* and karstic *dry flows,* as well as *karstic fields,* are frequent. From the underground karstic forms, a dozen caves and two

Fig. 4. The peak Magaro (2.254 m), the karstic field Lipova Livada and the glacial cirque

Mountain Galichica's altitude and its favourable morpho-plasticity enabled the accumulation of snow and ice during Pleistocene resulting in glacial relief formation. Aside from the two cirques (Fig. 4), a small number of cribs can also be found, but the dominant landscape is formed by the *periglacial* processes resulting in *stony horseshoes, slided blocks,* 

In relation to water transport and balance, such a complex geomorphology based on karstic fundaments has created the only possible type of aquifer in the mountain region – the *fractured type of aquifer* with medium or low water permeability (yield between 0.1 and 5.0 L\*s-1). The most presented rocks in this aquifer are Paleozoic schists with a low degree of crystallisation (chlorite, sericite, quartz schist and quartzite) Less presented are gneiss, micaschist and amphibole schist, as well as intrusive rocks (gabbro, granite, syenite, diorite,

All those rock masses are rugged with faults, fractures and cracks, which generally cannot accumulate larger reserves of groundwater. These rocks have a very low coefficient of filtration (kf ≤ E-4 cm\*s-1) and different intensity of fissuring. Local fissuring is very important due to the presence of intense subsurface fissuring and surface to sub-surface weathering (locally over 20 m depth), which influence the hydro-geological characteristics of

chasms have been registered.

between them.

*grassy terraces, loose glacial residues* etc. (Fig. 5).

diabase, quartz-porfire, andesite, etc.).

The Prespa catchment area includes two lakes: Micro and Macro Prespa, and permanent or seasonal streams, which discharge into the two lakes. The major contributing rivers to Macro Prespa Lake are Golema, Brajcinska and Kranska Rivers in the Republic of Macedonia and Aghios Germanos River in Greece. There is no major source of surface water input from Albania to Mikro Prespa. Together with the Ohrid Lake, the Prespa Lakes form a unique ensemble of water bodies in the Balkan regions. The Prespa Lakes form the deep points of an inner-mountainous basin that has no natural surface outflow. Drainage is only provided through karstic underground links by which water of the Macro Prespa Lake (approximately 845 m asl) drains westwards towards the Ohrid Lake lying approximately

Environmental Changes in Lakes Catchments

and 30.0 m3/s respectively.

elevation

843.00 844.00 845.00 846.00 847.00 848.00 849.00 850.00 851.00 852.00 853.00 854.00

**2.3 Soils** 

growing.

as a Trigger for Rapid Eutrophication – A Prespa Lake Case Study 69

become a tributary of Istocka River which inflows into the lake. The total catchment area of

During the last century the Macro Prespa Lake experienced a significant water level fluctuation. After its last peak in June 1963, the level generally dropped to its last low by approximately 8 metres up until 2002 (Fig. 7). This signifies a loss in water volume, with a loss of water surface maybe being even more significant. The major tributary of Macro Prespa Lake, the Golema River, shows high variations of the discharge during that time. It has been noticed that for the series of the minimal discharges it is typical that in some years, during the summer period, the river has very low water discharges or even no water at all. Floods have been registered in 1962 and 1979 with maximal discharge of Q max=33.4 m3/s

the Golema River is F=182.9 km2, the length of the river is L=26.1 km.

Fig. 7. Water level decrease of Macro Prespa Lake during the 1951-2008 period.

Depending on the various pedogenetic factors in the region, there are several soil types presented on the soil map (Fig. 8). Dominant soils in the Prespa Valley are *alluvial soils* (fluvisols) located in the lowest region. These soils are formed over the sediments by the rivers. On the other hand, on the central region of the Ezerani protected area, as well as within the band closest to the lakeshore – *hydric soil* formation is ongoing, which leads to the formation of *gleysols* in different stages of evolution. Around the fluvisols, *colluvial soils* are well developed. These soils are formed above thicker sediments and are being created by the rivers and torrents in the area. On a significant part in the valley and hills on the western side, *chromic luvisols* have been formed and these soils are mainly used for agriculture. On the mountain region various types of *cambisols* have been formed. On the Baba Mt., *eutric* and *district cambisols* are dominant. Natural vegetation adapts to the soils and on the eutric cambisols there are oak stands, whilst on the district cambisols beech compositions stand. R*ankers* (humus-accumulative soils) with various phases of development are formed on the highest altitude in the subalpine and alpine areas. On these soils only grass vegetation is

1950 1970 1990 2010

**Water Level of Prespa Lake (1951-2008)**

Time [year]

150 metres below. The Macro Prespa and the Ohrid lakes are separated by the Galichica Mountain, where a surface drainage network is almost absent due to the karstic nature of that mountain chain. The karstic mountains of Mali i Thate (Dry Mountains) in Albania and Galicica in are highly porous, resulting in high capacity for water transport.

Fig. 6. Soil erosion risk map for the Prespa Lake watershed (Macedonian part only).

The karstic connection of the Prespa Lake and Ohrid Lake is evidenced by spring observations. The Saint Naum spring and Tushemisht springs on the south coast of the Ohrid Lake originate from the Prespa Lake. Lake Ohrid has a surface outflow to the Crni Drim River. Since 1962 the outflows of the Ohrid Lake have been controlled in the City of Struga by means of a weir. Operation of the weir is governed by the needs of downstream hydropower plants and the need to maintain the lake's water level within optimal levels (maximal water level is 693 m and the minimum water level is 691.65 m).

The Micro and Macro Prespa Lakes are connected in Greece via a small natural channel. From the North and East of the catchment, several small and mostly ephemeral watercourses flow into the Macro Prespa Lake.

The main tributary of Prespa Lake is the Golema River. Two springs which are situated on the slopes of Plakenska and Bigla Mountains form the water courses of the Leva and Bukovska Rivers that join into the Golema River. Elevations of the Golema River springs are at 1440.00 m asl, while it inflows into the lake at 850.00 m asl. Larger tributaries of Golema River flow on the left side of the catchment. These are Krivenska, Celinska and Sopotska. Bolnska River used to inflow into the Golema River in the past, while at present it has become a tributary of Istocka River which inflows into the lake. The total catchment area of the Golema River is F=182.9 km2, the length of the river is L=26.1 km.

During the last century the Macro Prespa Lake experienced a significant water level fluctuation. After its last peak in June 1963, the level generally dropped to its last low by approximately 8 metres up until 2002 (Fig. 7). This signifies a loss in water volume, with a loss of water surface maybe being even more significant. The major tributary of Macro Prespa Lake, the Golema River, shows high variations of the discharge during that time. It has been noticed that for the series of the minimal discharges it is typical that in some years, during the summer period, the river has very low water discharges or even no water at all. Floods have been registered in 1962 and 1979 with maximal discharge of Q max=33.4 m3/s and 30.0 m3/s respectively.

Fig. 7. Water level decrease of Macro Prespa Lake during the 1951-2008 period.

#### **2.3 Soils**

68 Studies on Environmental and Applied Geomorphology

150 metres below. The Macro Prespa and the Ohrid lakes are separated by the Galichica Mountain, where a surface drainage network is almost absent due to the karstic nature of that mountain chain. The karstic mountains of Mali i Thate (Dry Mountains) in Albania and

Galicica in are highly porous, resulting in high capacity for water transport.

Fig. 6. Soil erosion risk map for the Prespa Lake watershed (Macedonian part only).

(maximal water level is 693 m and the minimum water level is 691.65 m).

watercourses flow into the Macro Prespa Lake.

The karstic connection of the Prespa Lake and Ohrid Lake is evidenced by spring observations. The Saint Naum spring and Tushemisht springs on the south coast of the Ohrid Lake originate from the Prespa Lake. Lake Ohrid has a surface outflow to the Crni Drim River. Since 1962 the outflows of the Ohrid Lake have been controlled in the City of Struga by means of a weir. Operation of the weir is governed by the needs of downstream hydropower plants and the need to maintain the lake's water level within optimal levels

The Micro and Macro Prespa Lakes are connected in Greece via a small natural channel. From the North and East of the catchment, several small and mostly ephemeral

The main tributary of Prespa Lake is the Golema River. Two springs which are situated on the slopes of Plakenska and Bigla Mountains form the water courses of the Leva and Bukovska Rivers that join into the Golema River. Elevations of the Golema River springs are at 1440.00 m asl, while it inflows into the lake at 850.00 m asl. Larger tributaries of Golema River flow on the left side of the catchment. These are Krivenska, Celinska and Sopotska. Bolnska River used to inflow into the Golema River in the past, while at present it has Depending on the various pedogenetic factors in the region, there are several soil types presented on the soil map (Fig. 8). Dominant soils in the Prespa Valley are *alluvial soils* (fluvisols) located in the lowest region. These soils are formed over the sediments by the rivers. On the other hand, on the central region of the Ezerani protected area, as well as within the band closest to the lakeshore – *hydric soil* formation is ongoing, which leads to the formation of *gleysols* in different stages of evolution. Around the fluvisols, *colluvial soils* are well developed. These soils are formed above thicker sediments and are being created by the rivers and torrents in the area. On a significant part in the valley and hills on the western side, *chromic luvisols* have been formed and these soils are mainly used for agriculture. On the mountain region various types of *cambisols* have been formed. On the Baba Mt., *eutric* and *district cambisols* are dominant. Natural vegetation adapts to the soils and on the eutric cambisols there are oak stands, whilst on the district cambisols beech compositions stand. R*ankers* (humus-accumulative soils) with various phases of development are formed on the highest altitude in the subalpine and alpine areas. On these soils only grass vegetation is growing.

Environmental Changes in Lakes Catchments

as a Trigger for Rapid Eutrophication – A Prespa Lake Case Study 71

Fig. 9. Climatic types and isohyetic map of Macro Prespa Lake (Macedonian part only).

The vegetation varies from submerged aquatic formations and reed beds to shrublands of junipers and oaks to forests of oak, beech, mixed broadleaves to alpine grassland. In total, there are 1,326 plant species in Prespa, 23 freshwater fish species, 11 amphibian and 21 reptile species, more than 42 mammal species, among which are the brown bear, the wolf,

**2.5 Flora and fauna** 

the otter and the chamois, and over 260 bird species.

Fig. 8. Soil map of Macro Prespa Lake (Macedonian part only).

## **2.4 Climate**

Being close to the Mediterranean seas (Adriatic and Aegean), it could be expected that the influence of the Mediterranean climate on the location of Prespa Valley would be significant. But the high mountains surrounding the valley mark the existing highland properties of the climate. The specific orographic conditions that have an impact on the dynamic factors of the climate, as well as the impact of geographical and local factors, create three different types of climate throughout the whole watershed (Fig. 9). The whole region of the Prespa Lake watershed belongs to the Eco-region 6 – Hellenic Western Balkan.


Fig. 8. Soil map of Macro Prespa Lake (Macedonian part only).

Lake watershed belongs to the Eco-region 6 – Hellenic Western Balkan.

1,300 m and from 1,300 m to 1,650 m altitude, respectively,

1,100 m altitude, respectively,

respectively.

Being close to the Mediterranean seas (Adriatic and Aegean), it could be expected that the influence of the Mediterranean climate on the location of Prespa Valley would be significant. But the high mountains surrounding the valley mark the existing highland properties of the climate. The specific orographic conditions that have an impact on the dynamic factors of the climate, as well as the impact of geographical and local factors, create three different types of climate throughout the whole watershed (Fig. 9). The whole region of the Prespa

• Warm and cold sub-Mediterranean climatic area, from 600 to 900 m and from 900 to

• Sub-mountainous and mountainous sub-Mediterranean climatic area, from 1,100 m to

• Sub-alpine and alpine climatic area from 1,650 m to 2,250 m and above 2,250 m altitude,

**2.4 Climate** 

Fig. 9. Climatic types and isohyetic map of Macro Prespa Lake (Macedonian part only).

#### **2.5 Flora and fauna**

The vegetation varies from submerged aquatic formations and reed beds to shrublands of junipers and oaks to forests of oak, beech, mixed broadleaves to alpine grassland. In total, there are 1,326 plant species in Prespa, 23 freshwater fish species, 11 amphibian and 21 reptile species, more than 42 mammal species, among which are the brown bear, the wolf, the otter and the chamois, and over 260 bird species.

Environmental Changes in Lakes Catchments

as a Trigger for Rapid Eutrophication – A Prespa Lake Case Study 73

*Parameter Unit Value*  Inhabitants person **20,792** 

BOD5 g/**PE**\*d 60 COD g/PE\*d 110 TSS g/PE\*d 70

N (as TKN) g/PE\*d 8.8

**Calculation for Wastewater Quantity and Quality: 1**

**Flow (Q)=(People\*Q per capita)/1000** m3/d 3,118.8

BOD5 kg/d 1,247./5

 *mg/l 400*  COD kg/d 2,287.1

 *mg/l 733.3*  TSS kg/d 1,455.4

 *mg/l 466.7*  N kg/d 183

 *mg/l 58.7*  P kg/d 37.4

*mg/l 12* 

per person.

accordance with the WFD (2004).

Table 1. Calculations for 20,792 people (together with 3,967 tourists), based on average loads

1 Based on German ATV 131A Standard (May, 2000) and German Wastewater Ordinance (2004) for assessing wastewater load, approved by Guidance for the Analysis of Pressures and Impacts in

P g/PE\*d 1.8

*m3/year 1,138,362* 

kg/year 455,344.8

kg/year 834,798.8

kg/year 531,235.6

kg/year 66,783.9

kg/year 13,660.3

Qwater per capita l/d\***P**eople **E**quivalent 150

A shelter for over 90 species of migratory birds, Prespa Lakes are also home to tens of species that have been officially registered as critically endangered or vulnerable. Among them is the Dalmatian Pelican, one of the largest flying birds in the world, who seeks secluded wetlands to build nests and to hatch chicks in what is its largest breeding colony worldwide.

Fig. 10. Dominant reed bed flora and the Dalmatian Pelican (*Pelicanus crispus*) on Macro Prespa Lake.

From the phytocoenological point of view, the presence of endemic plant community *Lemneto-Spirodeletum polyrrhize aldrovandetosum* is the most important.
