Monitoring and modelling vapor flux in dune sediments using a precision meteo-lysimeter

The contribution shows data of a high precision meteo-lysimeter since 2015, installed in a coastal dune of the Doñana Natural Reserve SW Spain to quantify water and energy fluxes and to estimate its dependence on regional climate trends. The weighing lysimeter contains an undisturbed soil sample of 1 square meter surface, 1.50 m height with a weighing resolution of 10 g. Furthermore, the site is equipped with 2 automatic meteorological stations, 1 Hellmann pluviometer and six calibrated TDR sensors installed outside the lysimeter at 6 different depths until 3 m below surface. Environmental humidity conditions at the lysimeter bottom were maintained by a peristaltic pump controlled by two tensiometers installed inside and outside of the lysimeter and the volume of the drained water was analyzed continuously. A total of 11 meteorological and soil water parameters were recorded in 10 and 1 minute intervals, respectively. Intrinsic noise in lysimeter data was reduced by smoothing through the AWAT filter (Peters et al. 2014). Precipitation and drained water from the lysimeter was analyzed for mayor ions and stable isotopes of water. Additionally relevant physical and retention curve parameters of the sediment were analyzed and the individual fluxes were quantified using lysimeter observations. Results show important amounts of daily vapor adsorption and evaporation between0.3-0.5 mm. Isotope signatures of the drained water are different compared to precipitation which may indicate a different source of water originated by vapor condensation. Energy fluxes as well as liquid and gas phase of water and air fluxes were modelled and calibrated based on monitored data. The calibrated model reproduces well the monitored data and is used to estimate the impact of vapor flow on groundwater recharge, a crucial aspect in semi-arid and arid environments subjected to global change.