The eigenvalue approach to groundwater modelling for resource evaluation at regional scale

A conference paper presented at ModelCARE 2002, 4th International Conference on Calibration and Reliability in Groundwater Modelling, Prague, Czech Republic, 17-29 June 2002.The dynamic response of piezometric head at any location in an aquifer to time variation of regional land surface recharge and abstraction can be expressed as a linear system comprising only a few conceptual water storages. Model structure and parameters are related to aquifer characteristics and spatial pattern of recharge by the eigenvalues and eigenfunctions of a general analytical solution to the linearised Boussinesq equation. The model is implemented as a stochastic ARMA difference equation, independently for each location. This modelling approach is demonstrated for an aquifer of 2000 km² area, yielding additional information about unobservable recharge and aquifer boundaries.Development of methodology was funded by the Foundation for Research, Science and Technology. Demonstration results are from a water resource study for Environment Canterbury, Ministry for the Environment and Ministry of Agriculture and Forestry, New Zealand