Uncertainty in the modelling of spatial and temporal patterns of shallow groundwater flow paths: the role of geological and hydrological site information

摘要: Summary Understanding the hydrological and hydrogeochemical responses of hillslopes other small scale groundwater systems requires mapping velocity direction flow relative to controlling subsurface material features. Since point observations materials head are often basis for modelling these complex, dynamic, three-dimensional systems, considerable uncertainties inevitable, but rarely assessed. This study explored whether piezometric data measured at high spatial temporal resolution over six years a hillslope research site provided sufficient information determine paths that transfer nitrate leached from soil zone through shallow saturated into nearby wetland stream. Transient were modelled using MODFLOW MODPATH, with patterns hydraulic conductivity in three layers being estimated by regularised pilot calibration PEST, constrained slug test estimates several locations. Subsequent Null Space Monte Carlo uncertainty analysis showed this was not definitively pattern site, although water table dynamics matched heads acceptable accuracy space time. Particle tracking predicted similar throughout year as rose fell, aligned either ground surface or contours; indeed layers, having relatively properties, appeared have little effect on site. Flow path that, while accurate could be determined available alone, origin well samples contour still broadly deduced. highlights both challenge collecting suitably informative field which characterise hydrology, power modern techniques assess systems.