Abstract
This paper concentrates on the hydrologic underpinnings of sustainable yield and points out how hydrologic fundamentals can be used to develop a sound water-use planning policy for stream-aquifer systems. The transition curves of all major aquifer systems from groundwater storage depletion to induced recharge of surface water need to be identified, and stream-aquifer numerical models are advocated for this purpose. The paper also addresses the more general concept of sustainability from the systems perspective and outlines our still-evolving ideas on environmental sustainability. The Kansas waterresources management experience and its evolution towards achieving sustainability are then outlined. This experience includes the establishment of local Groundwater Management Districts and their water-management policies, minimum streamflow and TMDL (total maximum daily load) standards, conjunctive stream-aquifer policies, integrated resource planning, subbasin waterresources management, and other programs. "Safe yield" rules, such as pumping the natural recharge, are shown to lead to degradation of streams, springs, wetlands, and water-dependent ecosystems. Because of the interdependence of surface water and ground water, operations on one have consequences for the other. Therefore, the importance of integrated resource planning and management harmonizing environment and society is stressed. The paper concludes with suggestions to move forward in sustaining water resources, stressing, among other things, precautionary principles and the need for long-time education supported by research and technical assistance, as well as improved communications, so that people become more conscious of the complexities and constraints involved in water-resources management.