Author(s): Luis Ribeiro; Ana Rita Lopes
Linked Author(s):
Keywords: Groundwater; Karstic Hydrogeology; Factorial Kriging; Variogram
Abstract: Factorial Kriging Analysis is used here to study the main spatial-temporal variations in the groundwater levels observed for a long period of time which reflects the zones of water circulation of the karstic aquifer system. This is based on the following conceptual model of interpretation of piezometric variograms: under natural flow conditions the experimental variogram computed on the piezometric spatial data exhibit an idiosyncratic non stationary behaviour, which reflects the groundwater flow gradients. If an external process is the cause of modification of the shape of the variogram, we may detect the particular spatial correlation at a specific scale. This is the case of a recharge phenomenon preferentially actuating in an aquifer region or a depletion situation caused by pumping. Therefore two structures can be deduced: a short-range one, mostly reflecting the variability of the local actions and a long-range one, more related with the regional groundwater flow gradients. In a first step Factorial Kriging technique will be used to analyse the spatial variability of the 2 regionalized factors for 2 time periods, October and March. The resulting maps will enhance the areas with similar (or opposite) groundwater flow behaviours: for instance the ones more related with the recharge phenomenon. This is analysed according to the precipitation temporal patterns. In a second step, the time horizons relationships are introduced, in order to better estimate areas with poor monitoring. A method combining Factorial Kriging Analysis with simple linear regression was used for this purpose. The tool was baptised as Factorial Kriging with Quality Weighting The area under study is the groundwater karstic system of Querenca-Silves, located in Central Algarve, Portugal.
Year: 1999