Geologic component of river typology of lake Sevan catchment (Armenia)

The purpose of the study is to develop a geological typology of the main rivers in the catchment of Lake Sevan. Research methods. The methodological foundation was European Union Water Framework Directive (EU WFD). According to EU WFD assessment and monitoring of the ecological status of surface waters should be type-specific. There are two widely acceptable systems for the classification of river types, System A and System B. However, geology was overlooked in both in Armenia. Following the distribution of sampling sites within state hydrobiological monitoring system in Lake Sevan basin, the geological features of the rivers Masrik, Karchaghbyur, Vardenis, Argichi, Gavaraget, and Dzknaget have been studied. Geologic typology from the System A was used and assessment was made based on GIS analyses of hydromorphological parameters of catchments, literature analysis of rock structures as well as hydrochemical parameters derived within the fieldworks. Research results. The results show that in frames of the existing sampling sites’ network there are four main geologic types such us mixed, calcareous, siliceous, and organic. The most frequent is silicius type while organic exist only in the lower course of the Masrik River and calcareous type is only in the lower course of the Gavaraget River. Mixed type is typical for the lower course of the Dzknaget River, the entire length of the Argichi River, and the middle course of the Masrik River. Conclusions. The study shows that geological factors exert a significant influence on the typology of the main rivers within the Lake Sevan basin according to the EU WFD System A classification. Taking into consideration that up to now all the rivers in the Sevan basin were hypothetically classified into siliceous type, new results can significantly alter the existing tools for the assessment of ecological status in the basin.

Drainage basin · Geological survey · Structural basin · Typology · Water Framework Directive · Groundwater and Watershed Analysis · Soil and Environmental Studies · Water Resources and Management