The intercalibration of the Hellenic Evaluation System for Mediterranean rivers of type R-M1 and R-M2 at Northern and Central Greece

The present paper deals with the intercalibration of the Hellenic Evaluation System (HESY) boundaries for the ecological quality of Greek rivers (Northern and Central Greece) [small size and mid altitude (type R-M1) and medium size and low altitude (type R-M2)] with the officially quality boundaries set by the European Commission and the quality boundaries of the multimetric indices STAR_ICMi and ICMi7RM based on the Mediterranean Guadalmed benchmark database. Benthic macroinvertebrates were used as biological elements for the HESY and the multimetric indices STAR_ICMi and ICMi7RM. The Hellenic dataset of benthic macroinvertebrates came from previous data of the Laboratory of Zoology, Department of Biology (Aristotle University of Thessaloniki), consisting of 129 samples (41 reference samples) from Northern and Central Greece. Both the multimetric indices performed well against the stressor gradient and indicated strong relationship to the Hellenic Evaluation System. Therefore, they could both be used for the intercalibration process and the assessment of the ecological quality in Northern and Central Greece. Moreover, the use of the HESY in Greek territory (a) can produce comparable results to the STAR_ICMi, which is also used by the Central European and Baltic GIG, assessment method and (b) may be considered reliable in other river types (e.g. R-M3) for which there has not been an intercalibration process or even intercalibration metrics in Europe, due to the lack of reference conditions.