Abstract
The water balance of lake Pavin is not closed with superficial inputs only, so sublacustrine inflow(s) were invoked in order to complete the budget. But until now both superficial inputs and outputs were themselves poorly constrained, and so the derived budget was not reliable. The aim of this paper is to improve the knowledge of the water budget of this lake. New and numerous data, which were acquired from May 2006 to February 2008 for 12 streams feeding the lake, lead to a mean annual input of 2160 ± 300 m3 d-1. Most of the superficial inputs (> 90 %) are located in the South-East shore of the lake. Moreover, the chemical composition of the superficial inflows (17 streams or springs) allows to distinguish at least 3 kinds of water inputs corresponding to 3 subterranean reservoirs. The surface water outflow (North shore), which was determined from a limnigraphe data set, is estimated to a mean value of 5720 ± 500 m3 d-1. New 14C data (for dissolved inorganic carbon) allow to assess a mineral water input at c. a. 68 m depth. The modeling of the oxygen isotope composition (δ18O) of the water column gives a corresponding inflow estimated to 150 m3 d-1 and an evaporation rate to 300 m3 d-1. Moreover, temperature show some artifacts on some vertical profiles that can be attributed to a cold sublacustrine intrusion of superficial water type, from 53 m depth to 35 m depth depending on the period. A water discharge coming from the upper monimolimnion zone is identified, but its outflow is negligible. All these data allow to propose a global water budget. The water residence time in the monimolimnion is calculated to be about 90 years. A global modeling of the water column shows that the observed steady state of the deep layer can be achieved in more than two centuries. In addition, chemical budget is given for some dissolved elements.
Published Version
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