This glossary presents simplified definitions of technical terms used in this report. Alluvium: Clay, silt, sand, gravel, or similar detrital material deposited by running water. Andesitic: Pertaining to a dark-colored, fine-grained, volcanic rock. Aquifer: A formation, group of formations, or part of a formation that contains sufficient saturated permeable material to yield water to wells and springs. Aquifer system: A heterogeneous body of intercalated permeable and poorly permeable material that functions regionally as a water-yielding hydraulic unit. Artificial recharge: Recharge at a rate greater than natural, resulting from man's activities. Base line and meridian: A pair of coordinate axes, one east-west (base line) and the other north-south (meridian), from which township, range, section, and quarter-section corners are established in the U.S. Public Land Survey system. (There are three pairs of coordinates in California.) Basement complex: The undifferentiated complex of rocks that underlies the rocks and unconsolidated deposits of interest in an area. Basin spreading (artificial recharge): Impounding water in natural or manmade depressions behind levees, dikes, or dams. Breccia: A coarse-grained rock, composed of angular broken rock fragments held together by a mineral cement or in a fine-grained matrix; the fragments have sharp edges and unworn corners. Claypan: A dense, heavy, relatively impervious subsurface soil layer that owes its hardness to a relatively higher clay content than that of the overlying material. It is usually hard when dry and plastic when wet. Confined aquifer: An aquifer containing confined ground water. Confined ground water: Water under pressure significantly greater than atmospheric; its upper limit is the bottom of a bed of distinctly lower hydraulic conductivity than that of the material in which the confined water occurs. Glossary V Type (soil): A division of soil series. Unconfined aquifer: An aquifer in which the upper surface of the saturated zone, the water table, is at atmospheric pressure and is free to rise and fall. Unconfined ground water: Water that is in an unconfined aquifer. Water table: The upper surface of the zone of saturation in an unconfined aquifer. Well canvass: A systematic field examination of wells.

County Land Co., and to their engineers, who supplied information on pumpage, pumping-plant efficiency tests, agricultural power, and agri cultural power usage. The writers are grateful for the cooperation and assistance received from city and county officials and other federal and state agencies.

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