Stable isotope composition of event-based and monthly composite precipitation collected between 2003 and 2009 in the south-western sector of Lake Balaton (Hungary)

Abstract Stable isotope parameters (δ 2 H, δ 18 O, d exc ) of event-based and monthly composite precipitation collected between 2003 and 2009 in the south-western sector of Lake Balaton displayed the normal seasonality typical for mid-latitude continental sites. Fluctuation in δ 2 H and δ 18 O values of monthly composite precipitation in the SW Balaton Region closely followed the monthly values reported from the surroundings, especially Zagreb (Croatia) situated ∼150 km southwest-ward. The amount-weighted annual mean isotope parameters of precipitation ranged from −8.30 to −7.25‰ for δ 18 O-ann, from −58.8 to −52.2‰ for δ 2 H-ann: and from 5.7 to 7.7‰ for d exc -ann depending on which observation site and 12-month subperiod is selected in the SW Balaton region between March 2008 and November 2009. The Local Meteoric Water Line (LMWL) was determined using ordinary least squares-, reduced major axis-, and precipitation-weighted least squares regressions. A preliminary estimate for precipitation-weighted LMWL based on monthly composite data of the 2006–2009 period in the SW Balaton Region is δ 2 H = 7.35(±0.16) × δ 18 O + 2.14(±1.41) is practically identical with the LMWL determined with the same methodology for Zagreb in an overlapping period reinforcing the isotope hydrometeorological similarity between these regions. This linearized approximation of the δ 2 H–δ 18 O covariance can be used as a benchmark for modern precipitation in isotope hydro(geo)logical studies in the SW Balaton Region.