Tracer methods

Environmental and artificial tracers are used to understand flow and transport processes in hydrology. The most ideal environmental tracers are stable isotopes of water. As being part of the water molecule, oxygen and hydrogen isotopes provide a tracer signal with every precipitation event over a certain space. Due to fractionation effects, stable isotopes of water have a seasonal distribution in precipitation with more depleted values in winter (colder season) and more enriched values in summer (warmer season). This seasonality can be followed in the hydrological cycle to get information about water transit times, flow paths and transport processes.

Within WATERAGRI, partners will assess water fluxes, residence times and groundwater recharge rates, which are parameters that cannot be directly measured in wetlands or the subsurface, by advancing tracer methods for the analysis of stable isotopes of water in the pore water of soils. This method is currently generally working, but there are limitations requiring substantial improvement. Advanced water-vapour equilibration techniques will allow measuring the isotopic composition of pore water in high-resolution soil cores. Corresponding data will be used to quantify water fluxes and improve the calibration of the subsurface models (soil and groundwater), thus reducing their predictive uncertainties. 

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