Porous cup samplers and drainage samplers are two of the broadly used techniques to monitor soil water for agronomical studies. This study provides further insight into the sample signification of these two sampling techniques. For that purpose, temporal variations of soil water δD and δ¹⁸O values collected by these two techniques have been monitored for an experimental field studied by INRA. The stable isotope data acquired provide further evidence that soil water samples collected by these two techniques are not equivalent and correspond to different water dynamics in soils: 1) quick infiltration along preferential flow paths for drainage (short residence time) and 2) water with longer residence time for porous cups. This implies that stable isotopic tools could be useful to provide additional information to “classical” monitoring of soil water. This could be of particular interest to estimate the residence time of soil water and could be relevant to follow the effectiveness of agricultural pressure reduction programs on natural water ecosystems.