Secondary Recovery of Water

Abstract

Injection of air into the vadose zone has made water available for recovery by conventional means at two test sites on the High Plains of Texas. The cost of this water, exclusive of research costs, is estimated to be about $50 per acre‐ft. Large quantities of water may be available for recovery in aquifers which have experienced long term water level declines, and where a layer of low permeability material is available to prevent rapid escape of the injected air. A possible explanation of the mechanism of removal is examined, and the conclusion reached that movement occurs because of unbalanced pressure forces on the capillary water. These forces are caused by the flow of the injected air past the pore water.