Aim of the study:
Thrace Region is the most important geographical regions of Turkey in terms of agricultural and industrial production. Meriç – Ergene River Basin is the main watershed of this significant region and there are many streams feeding the basin. In the current research, water qualities of fluvial ecosystems of Thrace Region were evaluated by using some ecological and statistical indicators.

Material and methods:
For each water sample, 27 physical and chemical limnological parameters (EC, TDS, turbidity, NO3, NO2, SO4, F, COD, BOD5, As, Se, Cu, Zn, Cd, Sb, Ba, Pb, B, Na, Mg, Cr, Mn, Al, K, Ca, Fe, Ni) were analysed and all the investigated parameter values were used to develop the Water Quality Index (WQI). Furthermore, Cluster Analysis (CA) were applied to detected data in order to classify the investigated locations and also Geographic Information System (GIS) was used to provide a visual summary of contamination levels in the basin components.

Results and conclusions:
The results show quite high WQI coefficients of COD (20.773), Se (9.667) and BOD5 (9.216) parameters in fluvial components of Thrace Region. The WQI values of the fluvial habitats of Thrace Region ranged from 33.91 – 329.84 and Çorlu Stream and Ergene River were determined as the most contaminated fluvial ecosystems. According to the results of applied CA, 2 statistically significant clusters were formed, which were named as “High Contaminated Zones” and “Low Contaminated Zones”.