Hydrograph Separation of the Amazon River Using 18o as an Isotopic Tracer

Abstract

The 18O content of rain and river waters was used as an isotopic tracer in order to carry out the hydrograph separation of the Amazon river, during the 1973-1974 hydrological years, and to estimate the contributions of the surface runoff (event water) and baseflow (pre-event water) components to the total river flow. The average surface runoff and baseflow contributions were 30.3 and 69.7% respectively. At peak discharge, the mean contribution of the baseflow was about 57%. The results of the isotopic separation model were compared with the filter-separation autoregressive method, showing similar behavior and magnitude.<br>Os teores de 18O em águas de chuva e amostras de água de rio foram utilizados como traçadores num modelo isotópico de separação de hidrógrafas do rio Amazonas durante o período 1973-1974, com o intuito de se estimar as contribuições do escoamento superficial rápido e escoamento de base para o escoamento total da bacia de drenagem. As contribuições médias desses reservatórios foram de 30,3 e 69,7% respectivamente. Durante o período de pico de cheia, o fluxo de base contribuiu com cerca de 57% do volume total de água escoada. Os resultados do modelo de separação isotópico foram comparados com o método estatístico de filtros auto-recursivos, mostrando comportamentos similares

Analyzing relationships among water uptake patterns, rootlet biomass distribution and soil water content profile in a subalpine shrubland using water isotopes

“…We applied this method to characterizing water dynamics among soils and plant roots and stems. Generally, the stable isotope ratios of hydrogen and oxygen in water samples can identify water sources and water dynamics in watersheds [30,43] Previous studies using dD tracers have shown that sugar maple trees can absorb water from groundwater through the root system [44] and that the shrub Artemisia ordosia takes advantage of deeper soil water recharged by large rain events in arid regions [6]. In our study, comparison of the similarity in the relationship between dD vs. d 18 O of soil and stem water indicated that stem water of our subalpine shrubs originated primarily from soil water with a depth of 0e50 cm.…”

Characteristics of water isotopes and hydrograph separation during the wet season in the Heishui River, China

“…In hydrograph separation analysis, the two-component model was widely used to compute the contributions of different components of river water. Mortathi et al (1997) reported that the average surface runoff and baseflow (pre-event) contributions were 30.3% and 69.7%, respectively, in the Amazon River. Kendall (1993) believed that surface water and subsurface water contributions were 38% and 62%, respectively, in northeastern China, based on stable isotope oxygen data.…”

The Guianese paradox: How can the freshwater outflow from the Amazon increase the salinity of the Guianan shore?

“…With regard to the deuterium excess over the Amazon basin, the isotopic signals of the river water depend on the recharge process (rainfall) as well as two additional factors: the amount effect and the recirculation of the water into the forest (Mortatti et al, 1997). As high deuterium excesses are generally found (10 or more and a slope close to eight), this suggests that equilibrium conditions obtain between the condensation and evapotranspiration processes.…”