Thick deposits of alluvium generally are not present. The depth to groundwater varies greatly. Water levels measured between 1990 and 1992 near the International Boundary were less than 30 feet below land surface and up to 42 feet above land surface in the flowing wells. The direction of groundwater flow generally is from the mountains toward the central part of the valley and then south toward the International Boundary and into Mexico. No current data are available on the water-bearing characteristics of the alluvial aquifer.
Few wells withdraw water from the alluvial aquifer.
There is no major irrigation likely because of the lavas and pyroclastics that cover most of the basin floor.