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groundwater storage is one part of the water supply and reliability component under consideration by the CALFED Bay-Delta program. CALFED, a consortium of state and federal agencies, has been charged with determining the best possible physical solution to the Bay-Delta's problems of levee instability, ecosystem restoration, water quality and water supply reliability. A preferred alternative is to be selected in late 1998. But as conjunctive use evolves from a local option into a statewide option for evening out the disparities between wet and dry years, the strategy takes on the controversies of more traditional water supply projects. In particular, Sacramento Valley communities that rely on groundwater to meet urban and agricultural needs are wary that plans to restore the Delta with conjunctive use will result in additional water exports that could diminish local supplies. Some believe the pressures to better coordinate surface water and groundwater will increase pressures for uniform statewide regulation of groundwater. Others believe that as all water sources become more valuable, landowners who previously resisted efforts to determine groundwater rights will find it in their best interest to see those rights defined. While groundwater management in the past has focused on limiting pumping or recharging aquifers, increasingly management means protecting the groundwater from contamination and cleaning up supplies so they can continue to be used to quench California's growing thirst. ~ acre-foot - 325,851 gallons, or enough water to cover an acre of land 1 foot deep. An acre-foot can supply the annual needs of one to two average California households. artificial recharge - the purposeful addition of surface water to a groundwater basin by human activity. aquifer - a geofogic formation that stores, trans- mits, and yields significant quantities of wa- ter to wells or springs. confined aquifer - an aquifer that is bound above and below by dense layers of soil or rock. extraction - the process of withdrawing ground- water from storage by pumping or other controlled means. groundwater - water stored underground in pore spaces within rocks and other alluvial materials and in gaps between fractured hard rock. hydrologic cycle - the natural recycling process powered by the sun that causes water to evaporate into the atmosphere, condense, and return to the earth as precipitation. impermeable - having a texture that does not permit water to move through quickly. 10 overdraft - intentional or inadvertent withdrawal of water from an aquifer in excess of the amount of water that recharges the basin over a period of years. percolation - the movement of water through small openings within a porous material. permeability - the capability of soil or rock to transmit water. recharge - flow to groundwater storage from pre- cipitation, irrigation, spreading basins and other sources of water. saturated zone - the area below the water table in which the soil is completely saturated with groundwater. sea water intrusion - the movement of sea water into fresh water coastal aquifers. subsidence -lowering or sinking of the land sur- face due 10 a number of factors, of which groundwater extraction is one. surface water - water that remains on the earth's surface in rivers, lakes, reservoirs or oceans. unsaturated zone - the subsurface zone, usually starting at the land surface and ending at the water table, that includes both water and air in spaces between rocks.