4152 20190221073103.0 CTALK-2019-0100 Delforge, D. Hydrological connectivity from causal analysis of time series in the Lhomme Karst System, Belgium 2019 2019-04-08 The hydrological behaviour of karstic systems is difficult to theorize holistically because of their specificheterogeneities leading to distinctive nonlinear processes. Karstified systems present great opportunities for fieldexploration and hydrogeological monitoring of the vadose zone through its network of caves and conduits. Theseunique but explorable environments are predisposed to an inductive scientific approach where transfer processesassociated with hydrological connections are directly inferred from the data.This is done conventionally using dye tracing from which connections and transfer times are undeniably revealed.However, single tests do not allow appreciating the dynamic character of the hydrological connections. Nowadays,several data analysis methods aim at the detection of causal relationships between time series allowing theinvestigation of dynamics and interactions. Some are designed for linear systems as the simple cross-correlationmethod or the Granger causality, while others are suitable for nonlinear interactions, such as the Convergent CrossMapping method.Here, these methods are applied in order to draw up causal maps and compare short-term (up to 2 days) interactionsin the Lhomme Karst System in Belgium. The Lhomme Karst System has been monitored since 2013 and manytime series are available: meteorological data, soil moisture, drip discharges in the caves, piezometric levels, andlocal gravimetric time series. In addition, dye tracing experiments revealing connections and characteristic transfertimes were conducted. The different causal maps are compared and causal interactions are appreciated throughthe current knowledge of the system and discussed in relation to the question: can we infer true hydrologicalconnections and processes from the empirical determination of causal relationships between hydrological timeseries? FRIA/ FRIA/ FRIA NO Karst Rochefort Causal analysis Non-linear system Van Camp, M. Vanclooster, M. Hallet, V. Kaufmann, O. Poulain, A. Watlet, A. EGU, Vienna michel.vancamp@observatoire.be Contributed CTALKCONT