Most current issues regarding water availability and water quality in agriculture have arisen due to increasing competition for limited resources and changes in public preferences regarding the environment. Demand for water has increased in recent decades with increases in population and income levels. Water supply has remained largely fixed due to natural conditions and a declining rate of investment in new water supply facilities. Investment has slowed as the cost of developing new sites for dams and reservoirs has increased, and as public preferences have shifted toward greater concern for protecting the environment and sustaining the use of natural resources. Public agencies and legislatures have responded to the shift in public preferences by implementing new environmental standards that require changes in agricultural and industrial production methods. The two primary issues that must be resolved by public officials in the future are: determining the best ways to allocate limited water supplies in an era of increasing demands by agriculture, industry, cities, and the environment, and determining the best ways to define and achieve state and national water quality objectives, while not constraining desirable economic growth and development. Many smaller issues are described within the context of these primary issues.