The lower Mesilla Valley extends southward from the vicinity of Anthony, Tex., to the gorge of the Rio Grande north of El Paso and westward from the Franklin Mountains to the east edge of La Mesa. The increase in the use of ground water for the public water supply of El Paso and for supplemental irrigation, when the surface-water allotments were inadequate, emphasized the need for an investigation of the ground-water resources of the lower Mesilla Valley.