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003!~') INTRODUCTION The Bureau of Reclamation {Reclamation) is the West's primary water resources management agency, Reclamation operates more than 350 storage darns, delivering about 30 million acre-feet of water each year, It serves the needs of approximately 25 million people, provides irrigation water to an average 10 million acres of land each year, and generates an average 45 billion kilowatt- hours of hydroelectric energy, annually, In addition, Reclamation provides recreation, fish and wildlife, water quality, and other water-related benefits to the citizens of the West, The amount of water available to meet these purposes varies from year to year. Water supply largely depends upon the pattern of winter snowfall; summer precipitation is negligible in most areas of the West, During winters with average or high snowfall (and with temperatures cold enough to accumulate a snowpack), 5pring runoff is sufficient to fill reservoirs for the season's demands, However, when winter weather is too dry or too warm to accumulate mountain snowpack, reservoirs may not filL In many Reclamation reservoirs, one winter of deficient snowpack may be insignificant. These reservoirs were designed to account for such variable weather conditions; thus, sufficient carryover storage from the previous year is available. Other reservoirs were sized to meet the demand for water even if three consecutive years of inadequate snowpnck occur. However, some older Reclamation reservoirs were not designed to meet this requirement, And, for most reservoirs, carryover storage is no longer available when drought conditions extend beyond three years, That condition-four years of consecutive drought-has now occurred in some areas of the West. Based on current water supply conditions, it is possible that we are entering the fifth year of water shortages in some of the West's most populous regions, The demand for water has steadily increased, placing greater stress on water supplies even under normal conditions, Population growth and a national consensus about the importance of water for other values, such as instream uses, have increased demands. New burdens have been placed on some water supplies that were, unti.l recently, adequate to fulfill all needs, The water supply requirements of southern California are a particular example, where potential water shortages are possible even in normal water years, Water users in some areas of the West are jointly dependent on surface water and ground-water resources, In years of drought, users are more likely to depend on ground water, Such use places more demand on aquifers at a ti.me when less recharge is occurring due to dry surface conclitions, Although the relationship between ground water and surface water is important, this document only