Issue |
Annls Limnol.
Volume 10, Number 3, 1974
|
|
---|---|---|
Page(s) | 275 - 309 | |
DOI | https://doi.org/10.1051/limn/1974002 | |
Published online | 16 June 2011 |
Écologie d'un torrent Pyrénéen de haute montagne II. — Caractéristiques chimiques
The ecology of a high mountain stream in the Pyrenees II. — Chemical conditions
Laboratoire d'Hydrobiologie, Univ. P. Sabatier, 118, route de Narbonne, 31077 Toulouse Cedex
Les caractéristiques chimiques du torrent d'Estaragne et de ses affluents, sont étudiées en relation avec les conditions géographiques générales.
Les bicarbonates et le calcium forment plus de 90 % du contenu ionique des eaux. Les teneurs en fer total, Ca++, HCO3-, SO4-, PO4 —P, NO3 —N, Mg++, K+, diminuent entre l'amont et l'aval. Les concentrations en Na+, Cl- et SiO, restent constantes ou s'accroissent légèrement le long du cours. La conductivité passe de 114 µmhos à 80 µmhos, entre la source et l'embouchure. L'évolution de la composition chimique de l'eau est liée au passage de roches altérables et nues, à des roches cristallines couvertes de pelouse.
La plupart des caractéristiqus présentent des corrélations significatives avec les débits. Ces relations ont permis d'évaluer – avec des limites de confiance – les quantitiés de matériel transporté. Lors des deux années d'étude, le torrent a déversé en moyenne 470 t/an d'éléments dissous, dans le lac d'Orédon ; 65 % de ce charriage s'effectue à la fonte des neiges.
Abstract
The chemical features of the river Estaragne and its tributaries were studied in relation to general geographical conditions.
Bicarbonates and calcium formed more than 90 % of the ionic content of the water. The amounts of total iron, Ca++, HCO3-, SO4-, PO4—P, NO3—N, Mg++, K+ decreased from the source of the river to its mouth. Concentrations of Na+, Cl- and SiO, remained constant or increased slightly down the length of the river. Conductivity changes from 114 µmhos to 80 µnhos between the source and the mouth of the river. The changes in the chemical composition of the water are related to the changes in the stream bottom from an unstable and naked bedrock to a crystalline bedrock covered with plants.
Most of the chemical features showed some significant correlations with flow. It has therefore been possible to estimate (with confidence limits) the quantifies of material transported down the stream during the two years of this study. The river discharged into Lake Oredon a mean of 470 t/year for dissolved elements, 65 % of this material is carried down the river when the snow melts.
© Masson, 1974
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