Water exchange processes estimation in a temperate shallow lake based on water stable isotope analysis

QUIROZ LONDOÑO, ORLANDO MAURICIO; ROMANELLI, ASUNCIÓN; MARTÍNEZ, DANIEL EMILIO; MASSONE, HÉCTOR ENRIQUE

ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES

TAYLOR & FRANCIS LTD

Año: 2020 vol. 56 p. 465 - 479

1025-6016

The estimation of lake hydrological characteristics such as evaporation/inflow ratios and water residence time become necessary for understanding cycling and potential retention of natural and anthropogenic substances into the lake. The aim of this work was to estimate the evaporation loss and the water residence time of a temperate shallow lake based on the water isotopic mass balance approach. One representative freshwater shallow lake from the Pampa Plain (Argentina), surrounded by intensive agriculture activity and complex socio-economic conditions, was selected. Groundwater, lake and stream samples (N=56) were collected for δ2H-H2O and δ18O-H2O determinations. Moreover, water level fluctuations of the lake and its inflow stream were recorded with data-loggers. Both the δ2H and δ18O relationship and d-excess of lake water indicated evaporation. Water isotopes and daily stream flow data recorded in the inflow stream evidenced groundwater contribution to Los Padres stream. Monthly E/I estimations of the lake water indicated that about 20 - 25 % ±12 lake water was lost through lake surface evaporation and revealed that hydrologic balances were regulated mainly by changes in water inflow rather than evaporation in both wet and dry seasons. A mean residence time of 1.11 year ± 0.65 was also calculated.