The KID service area overlays the Raymond Basin, a vast underground water storage aquifer bounded on the north by the San Gabriel Mountains, on the south and east by the Raymond Fault, and on the west by the San Rafael Hills. Water from rainfall and mountain snow percolates or soaks into the underground basin where it is stored in soils and rocks. Because of its natural formations and barriers, the Raymond Basin is replenished by surface water flows from the San Gabriel Mountains.

KID's customers use approximately 700 acre-feet of water per year, which equates to 228 million gallons.

KID's water is supplied from two deep wells, the Wilcox Well and the K-3 well. These wells range in capacity from 550 to 760 gallons-per-minute. Additional water is supplied from five horizontal wells (water tunnels) ranging in capacity from 25 to 170 gallons per minute. This water is stored in ten reservoirs with capacity of between 125,000 to 1,250,000 gallons.  The KID only provides water from these local sources and does not use water from other agencies or water imported from the Colorado River or from Nothern California.