Methodology and results
The overall project result is the methodology for assessing the minimum scale at which a model with a given data input potentially has predictive capability. It is based on the recognition that it will never be possible to obtain sufficiently detailed data to deterministically describe the geological heterogeneity. Instead we have to rely on geostatistical approaches, including generation of plausible geological models. To assess the minimum scale with predictive capabilities we will use the RES approach. This implies that we carry out numerical modelling studies using the stochastically generated heterogeneous geologies and sample results from an increasing number of grid cells (from 'small' scale to 'large' scale) until the results among samples become stable.
This is illustrated in the figure below in the right column assuming that new geophysical data from MiniSkyTEM and MRS are available (first step). The second step is then to construct a geological model and characterise the heterogeneity so that several plausible geological models can be generated by use of TProGS in the third step. These models will all have to justify the geophsyical data. In the fourth step a hydrological catchment model including nitrate leaching, transport and reduction is then run for each geological realisation. The output from this fourth step is nitrate reduction (between the bottom of the root zone and the river/lake system) calculated spatially distributed with a resolution corresponding to the model grid size. Here different model realisations result in different nitrate reduction at different locations within the catchment. In the last step resulting in the RES graph the differences between the model realisations are characterised in terms of standard deviations, initially calculated at model grid size basis and subsequently aggregated to larger and larger area. With a given acceptable level of uncertainty the scale of potential model predictability (RES) can be found. In case of less data (case denoted "existing data") the same procedure will result in larger uncertainty and hence a larger RES value. In this way the value of acquiring additional data in terms of improved accuracy or potential use at smaller spatial scales can be assessed.
See large fig
The project work is organised in five work packages (WP), four of these being technical WPs and one dealing with dissemination and co-ordination. The content of the four technical WPs can be found below.
WP1 - Geophysical techniques
WP2 - Field work and geological modelling
WP3 - Hydrological modelling (water flow + nitrate)
WP4 - Water management