Groundwater around Lake Sevan, Armenia: Insights from stable isotopes of water and nitrate
2 Helmholtz Centre for Environmental Research – UFZ, Department of Catchment Hydrology, Germany
3 Ministry of Environment, Hydrometeorology and Monitoring Center, Armenia
4 Deutsche Gesellschaft für Internationale Zusammenarbeit – GIZ, Armenia; National Academy of Sciences, Institute of Geological Sciences, Armenia
P 3.4 in Earth System Science and Reconstruction
Lake Sevan (at 1900 m a.s.l., approx. 1280 km²) is of paramount importance for Armenia, for economic and ecologic reasons (water supply, fishing, recreation, tourism, biodiversity, etc.). Due to a number of environmental problems, incl. eutrophication, the lake received quite some attention over the last years, but this does not apply to the surrounding groundwater. Thus, aspects such as groundwater quality, prevailing residence times, recharge mechanisms, and eventually the role of groundwater in the lake’s water budget are not well understood.
In a recent survey, we found isotopically depleted groundwaters, with δ18O values mostly ranging between -14 and -9 ‰ V-SMOW. These values are lower than the amount-weighted mean precipitation signal of a monitoring station at the lakeshore, which reflects a seasonal recharge bias (snowmelt season) and an elevation effect. 3H concentrations range from below detection limit to several TU, indicating a modern recharge component. Partly even artesian wells show 3H, which suggests a certain groundwater vulnerability. The latter is supported by elevated nitrate concentrations (up to 130 and 44 mg/l in non-artesian and artesian wells, respectively). δ15N and δ18O of groundwater nitrate show limited scatter (4.9 to 9.7 ‰ AIR and 0.1 to 4.6 ‰ V-SMOW, respectively) and hence point towards a uniform but hitherto unidentified source.