Problem Background

To establish agricultural water management as a priority subject for national policy attention, this report first examines the historical context, present situation, and quantitative significance of selected water resource problems in the United States. This chapter is organized by following the mass flow of water from source to use to discharge:

• Sources--Surface water and groundwater, the two most significant water sources for agriculture, are described along with national usage trends and implications for specific regions of the country.
• Uses--Irrigation, the primary use of water withdrawn for agricultural production, is quantified and the potential for increases in efficiency is discussed.
• Discharges--The fate of agricultural water supplies is examined with regard to quantity loss and pollution contributions.

Before an analysis of these areas, it is important to understand the degree to which a national water balance can be quantified. By understanding the difficulties involved with modeling the water cycle and using this data to project future water trends, policy makers will be better prepared to appreciate and to act on the information contained in this report.