thumbnail

The use of stable isotope to evaluate water mixing and water use by flood plain trees along the Garonne valley

Isotopes in Environmental and Health Studies

By:
, , and
DOI: 10.1080/10256010310001621100

Links

Abstract

Before the confluence of the Tarn, the Garonne valley was the driest area in the entire south-west of France, due to the relatively low rainfall and low summer discharge of the Garonne River and its tributaries. The natural abundance of the stable isotope of oxygen (18O) and ionic charge of surface and ground water were used to estimate the water source for the Garonne River and phreatic subsurface water. We also measured these constituents in the sap of trees at several flood plain sites to better understand the source of water used by these trees. 18O signatures and conductivity in the Garonne River indicated that the predominance of water was from high altitude surface runoff from the Pyrenees Mountains. Tributary inputs had little effect on isotopic identity, but had a small effect on the conductivity. The isotopic signature and ionic conductivity of river water (??18O: -9.1??? to -9.0???, conductivity: 217-410??S/cm) was distinctly different from groundwater (??18O: -7.1??? to -6.6???, conductivity: 600-900??S/cm). Isotopic signatures from the sap of trees on the flood plain showed that the water source was shallow subsurface water (<30cm), whereas trees further from the river relied on deeper ground water (>1m). Trees at both locations maintained sap with ionic charges much greater (2.3-3.7x) than that of source water. The combined use of 18O signatures and ionic conductivity appears to be a potent tool to determine water sources on geographic scales, and source and use patterns by trees at the local forest scale. These analyses also show promise for better understanding of the effects of anthropogenic land-use and water-use changes on flood plain forest dynamics.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
The use of stable isotope to evaluate water mixing and water use by flood plain trees along the Garonne valley
Series title:
Isotopes in Environmental and Health Studies
DOI:
10.1080/10256010310001621100
Volume
39
Issue:
4
Year Published:
2003
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Isotopes in Environmental and Health Studies
First page:
301
Last page:
310
Number of Pages:
10