Sustainable groundwater resources development implies use of groundwater as a source of water supply, on a long term basis, in an efficient and equitable manner sustaining its quality and environmental diversity. An understanding of the behaviour of a groundwater system and of its interaction with the environment is required to formulate a sustainable management plan. Mathematical models supported by field information play a key role in assessing the future behaviour of a system to stresses and to find effective operating conditions for sustainable development and management of groundwater resources. Basic principles for sustainable development are stressed and a brief review of two case studies is provided to illustrate how a systems approach and its computational framework of mathematical models can be used in addressing the main issue of water allocation satisfying some of the technical and environmental constraints.