ABSTRACT
In the Manawatu region of New Zealand, a regional scale aquifer medium model was derived from well-driller’s reports. These reports provide the only consistent database describing the aquifer medium over the entire study area. The phreatic surface, that represents the top of the aquifer, was treated as a spatially distributed continuous variable and modeled using water level data from more than 1100 bores. Well-driller’s descriptions of the aquifer medium below the phreatic surface were then encoded. The various media encountered were assigned to the following grain size classes: gravel, gravel and sand, sand, or fine medium. These descriptions were treated as “point” estimates for input to a spatially distributed model. Field checking of the model indicates a strong agreement between actual and modeled aquifer medium vulnerability ratings.
