An overview of complex behaviour in the groundwater compartment of catchment systems and some implications for modelling and monitoring

An understanding of non-causal relationships between processes in the air, soil and water compartments of the environment is fundamental to sustainable integrated management. This paper provides an overview of the groundwater sub-compartment and asserts that it exhibits many characteristics of a complex system, especially in relation to a wide range of non-linearities, although not all groundwater phenomena should be regarded as reflecting system complexity. Analysis of the groundwater compartment based on concepts such as emergence has been hindered by a long history of deterministic conceptualisation, while other aspects of complex systems such as self-organised criticality are difficult to investigate in the groundwater context due to problems of obtaining appropriate data. Despite this, conceptualising the groundwater compartment as a complex system would enable groundwater processes to be more fully integrated in a systems understanding of the environment. Some of the implications of complex behaviour for groundwater resource modelling and monitoring are briefly noted.