Testing in-class variability of groundwater systems: local upland systems

The objective of this paper is to assess the extent that information can be transferred between hydrogeologically similar catchments, by investigating in detail one set of similar catchments. In particular, five examples of a class of deeply weathered, fractured rock aquifers were used as the basis for this assessment. This catchment type was chosen because of its prominence in salinized regions in southeastern Australia. The catchments chosen encompass a wide variety of scales. gradients, and climatic zones. The five catchments were modelled using FLOWTUBE. Catchment parameter values, catchment response to incremental reductions in recharge and the similarity of the catchments were compared. The results suggest that there is a considerable range in parameter values, but that this is smaller than the range for all aquifer types. However, given the sensitivity of the models to transmissivity and specific yield, the range of values was too high to allow the transfer of 'averaged' values to other hydrogeologically similar catchments with confidence. Evaluation of a dimensionless similarity parameter G for each of the five catchments indicates that the parameters of transmissivity, specific yield, length and head may be interrelated. The implications of this are: (1) that the range in catchment responses might not be as great as suggested by standard sensitivity studies; (2) surrogate parameters may exist, which would enable aquifer parameters to be transferred to other hydrogeologically similar catchments with greater confidence. Copyright (C) 2003 John Wiley Sons, Ltd.