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The STUDIA UNIVERSITATIS BABEŞ-BOLYAI issue article summary
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Abstract: Here we present the results of oxygen isotopic analyses carried out on water samples
from Budzisławskie Lake (Central Poland). The lake has neither tributaries nor
outflows, being supplied most probably only by precipitation waters (no evidence for
groundwater supply). For several years a serious decrease in water level has been
observed in this lake (e.g., in the hydrological year 2003/2004 the water table has
lowered with about 0.3 m). The total annual rainfall of the year 2003 was as low as
344 mm, and in the year 2004 it raised to 440 mm – this area shows a significant
water deficit (average annual precipitation in Poland is about 550 mm).
Our study was aimed at determining the possible reasons for the observed water loss.
The oxygen isotopic analyses of the water have been done in order to estimate the rate
of evaporation from the lake’s surface and its direct catchment. The water samples of
Budzisławskie Lake have been collected on 3rd October 2005 from 3 sampling points
and from 3 different depths at each sampling point (9 samples analyzed). The δ18O
values vary between -2.36‰ and -1.78‰ (an extremely high value compared to typical
δ18O values for lake waters in Poland, averaging -9‰, or to precipitation waters
averaging -10.1‰). Such a large enrichment in heavy oxygen isotopes in the
Budzisławskie Lake is, in our opinion, due to intensive evaporation. Using the
Rayleigh distillation model we calculated that 56% of the water supplied by
precipitation evaporated from the lake and from its direct catchment. We assumed
that water from precipitations (falling directly into the lake and coming through its
direct catchment) is the only water supply for the lake and that there is no outflow
(e.g., to groundwater). Consequently, it can be calculated that the evaporation was
responsible for an up to 6 m decrease of the water level of Budzisławskie Lake. |
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