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

ABSTRACT

The estimation of lake hydrological characteristics such as evaporation/inflow ratios and water residence time becomes 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 isotope mass balance approach. One representative freshwater temperate shallow lake from the Argentinian Pampa Plain 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 evaporation as a fraction of inflow 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. A mean residence time of 1.11 ± 0.65 year was also calculated. This lake hydrological information is relevant for the region and crucial to improve water management plans.

KEYWORDS:

• Argentina
• evaporation loss
• groundwater
• hydrogen-2
• isotope hydrology
• Pampean shallow lake
• oxygen-18
• residence time

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors would like to acknowledge the financial support of the Agencia Nacional de Promoción Científica y Tecnológica (Fondo para la Investigación Científica y Tecnológica; PICT 2019), Consejo Nacional de Investigaciones Científicas y Técnicas – CONICET [PIP 0350], Universidad Nacional de Mar del Plata [EXA 514/10; EXA 606/12], Argentina, and the IAEA’s Coordinated Research Project F30059 entitled ‘Assessment of Groundwater Resources at Local/National Scales’.