Average annual rainfall varies across the region. In Lubbock, Texas, the average annual rainfall is 18 inches per year. The region is characterized by a semi-arid climate and persistent winds, which results in high evaporation rates. The average annual evaporation rate in Lubbock is about 80 inches per year. Natural recharge to the Ogallala Aquifer occurs primarily through the percolation of precipitation through the formation to the water table.
Recent studies reveal that playa lakes also play a significant role in recharge.
One recent study indicates natural recharge from playa basins ranging from 0.5 to 3.24 inches per year per surface acre. Another study indicates that natural recharge to the aquifer averages about 0.35 of an acre-inch per surface acre per year. Natural recharge for the land surface area outside the playa basins is possible and probably occurs in rare events when precipitation events occur while the top four or five feet of soil is wet to field capacity by irrigation or unusual precipitation. Also, water can move from the surface into the aquifer through micropores created by worms, animal burrows, and decayed plant roots. Early settlers believed the water supply that lay beneath them was inexhaustible.