**Environmental Changes in Lakes Catchments as a Trigger for Rapid Eutrophication – A Prespa Lake Case Study**

Svetislav S. Krstić *Faculty of Natural Sciences, St.Cyril and Methodius University, Skopje, Macedonia* 

### **1. Introduction**

62 Studies on Environmental and Applied Geomorphology

 URL: http://eusoils.jrc.it/ESDB\_Archive/eusoils\_docs/esb\_rr/n11\_ita\_er06.pdf ISPRA Servizio geologico d'Italia (2011). Cartografia Geologica d'Italia alla scala 1:50.000

URL: http://www.apat.gov.it/site/it-IT/Servizi\_per\_l%27Ambiente/Carte\_geolog

ISPRA (2006). La lotta alla desertificazione in Italia: stato dell'arte e linee guida per la

URL: http://www.apat.gov.it/site/it-IT/APAT /Pubblicazioni /Manuali\_ e\_linee

Lavecchia G., Boncio N., Creati N. and Brozzetti F. (2004). Stile strutturale e significato

Märker M., Angeli L., Bottai L., Costantini R., Ferrari R., Innocenti L., Siciliano G. (2008).

Miccadei E., Barberi R., Cavinato G.P. (1999). La geologia quaternaria della Conca di

Miccadei E., Paron P. and Piacentini T. (2004). The SW escarpment of the Montagna del

Mitasova H., Hofierka J., Zlocha M., Iverson L.R. (1996). Modeling topographic potential for erosion and deposition using GIS. International Journal of GIS, 10, pp. 629–641. Parotto M. Praturlon A., (2004), 'The southern Apennine arc. In: Geology of Italy', Special Volume of the Italian Geological Society for the IGC 32 Florence, pp. 53-58. Patacca E., Scandone P. (2007). Geology of the Southern Apennines. Boll. Soc. Geol. It. Spec

Pizzi A. (2003). Plio-Quaternary uplift rates in the outer zone of the central Apennines foldand-thrust belt, Italy. Quaternary International, 101-102C: pp. 229-237. Vezzani L., Ghisetti F. (1998). Carta Geologica dell'Abruzzo, scala 1:100.000. Regione

Southern Tuscany, Italy. Geomorphology, 93, pp. 120–129.

Sulmona (Abruzzo, Italia centrale). Geol. Romana, 34, pp. 58-86.

front. Geografia Fisica e Dinamica Quaternaria, 27, pp. 55-87.

Abruzzo, set. Urbanistica-Beni Ambientali e Cultura.

Luxemburg, pp. 28.

(Progetto CARG).

ISBN 88-448-0213-9.

Soc. Geol. It., 123, pp. 111-125.

Issue CROP-04, 7, pp. 75-119.

\_guida/Documento /manuale\_2006\_41.html

iche/

Office for Official Publications of the European Communities Luxembourg,

redazione di proposte progettuali di azioni locali. Manuali e linee guida - 41/2006.

sismogenetico del fronte compressivo padano-adriatico: dati e spunti da una revisione critica del profilo Crop 03 integrata con l'analisi di dati sismologici. Boll.

Assessment of land degradation susceptibility by scenario analysis: a case study in

Morrone (Abruzzi, Central Italy). geomorphology of a faulted-generated mountain

Elucidating upon and/or separating the natural processes of eutrophication from the anthropogenically induced ones in a lake's history have proven to be a formidable task. The nature and patterns of the eutrophication processes, their overall impact on the ecosystem and biota, as well as the possible management practices to be introduced to reverse or slow down the accelerated eutrophication have been in focus only very recently mainly due to imposed EU legislation such as the WFD. Another important and also very demanding task that greatly influences management plans, costs and activities is the detection of the reference conditions for every particular water body. Among various suggested approaches, we have concluded that the best way is to reveal the past changes of the lake's environment by conducting paleo-ecological research (the so called *state change approach*) using core sample analyses of as many parameters as possible and relate them to the biota, algae in particular. In that regard, under the comprehensive River Basin Management Plan developed for the Prespa Lake catchment (the part that belongs to Macedonia), the most wide-ranging 12 month surveillance monitoring has been conducted in order to reveal the present ecological situation and the past changes during the last 10 ka period. The results of these investigations are presented in this chapter.

#### **2. Investigated area**

The Prespa Lake has been chosen as a part of the complex Prespa-Ohrid-River Crni Drim system which is thought to be more than 3-5 million years old, and as a pilot project as its catchment is relatively small. Nevertheless, obtaining the research objectives was far from simple, since the Prespa region includes two inter-linked lakes, namely the Micro Prespa and Macro Prespa, surrounded by mountainous ecosystems. These two lakes together form the deep points of an inner-mountainous basin that has no natural surface outflow. Drainage is only provided by means of underground links by which water of the Macro Prespa Lake (approximately 845 m asl) drains towards the west to the approximately 150 metres lower Ohrid Lake. On its northern shore, in the town of Struga, the Ohrid Lake has a natural outlet into the Crni Drim River. The Micro Prespa Lake is shared between Greece and Albania, while the Macro Prespa Lake is shared between Albania, the Republic of

Environmental Changes in Lakes Catchments

as a Trigger for Rapid Eutrophication – A Prespa Lake Case Study 65

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).

Lake on the right.

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

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 investigated area in the map of Europe.
